ctivity的四种启动模式：

standard、singleTop、singleTask、singleInstance

为了打印方便，定义一个基础Activity，在其onCreate方法和onNewIntent方法中打印出当前Activity的日志信息，主要包括所属的task，当前类的hashcode，以及taskAffinity的值。之后我们进行测试的Activity都直接继承该Activity

  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.content.Intent
    import android.os.Bundle
    import android.view.MenuItem
    import androidx.appcompat.app.ActionBar
    import androidx.appcompat.app.AppCompatActivity
  4.  
  5. open class BaseActivity : AppCompatActivity() {
        lateinit var actionBar: ActionBar
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
  8.  
  9.         actionBar = supportActionBar!!
            actionBar?.setDisplayHomeAsUpEnabled(true)
  10.  
  11.         printTaskInfo(this, "onCreate")
            dumpTaskAffinity(this)
        }
  12.  
  13.     override fun onNewIntent(intent: Intent?) {
            super.onNewIntent(intent)
            printTaskInfo(this, "onNewIntent")
            dumpTaskAffinity(this)
        }
  14.  
  15.     override fun onRestart() {
            super.onRestart()
            printTaskInfo(this, "onRestart")
        }
  16.  
  17.     override fun onStart() {
            super.onStart()
            printTaskInfo(this, "onStart")
        }
  18.  
  19.     override fun onResume() {
            super.onResume()
            printTaskInfo(this, "onResume")
        }
  20.  
  21.     override fun onPause() {
            super.onPause()
            printTaskInfo(this, "onPause")
        }
  22.  
  23.     override fun onSaveInstanceState(outState: Bundle) {
            super.onSaveInstanceState(outState)
            printTaskInfo(this, "onSaveInstanceState")
        }
  24.  
  25.     override fun onStop() {
            super.onStop()
            printTaskInfo(this, "onStop")
        }
  26.  
  27.     override fun onDestroy() {
            super.onDestroy()
            printTaskInfo(this, "onDestroy")
        }
  28.  
  29.     override fun onOptionsItemSelected(item: MenuItem): Boolean {
            when (item.itemId) {
                android.R.id.home -> onBackPressed()
            }
            return super.onOptionsItemSelected(item)
        }
    }

此处还需要另一个Kotlin文件

  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.content.Context
  4. import android.content.Intent
  5. import android.content.pm.PackageManager
  6. import android.util.Log
  7. import androidx.appcompat.app.AppCompatActivity
  8.  
  9. fun printTaskInfo(activity: BaseActivity, methodName: String) {
  10.     log("$methodName: ${activity.localClassName} taskId: ${activity.taskId} hashCode: ${activity.hashCode()}")
  11. }
  12.  
  13. fun log(message: String, tag: String = "LaunchMode") {
  14.     Log.i(tag, message)
  15. }
  16.  
  17. fun dumpTaskAffinity(activity: BaseActivity) {
  18.     val info = activity.packageManager.getActivityInfo(
  19.         activity.componentName,
  20.         PackageManager.GET_META_DATA
  21.     )
  22.     log("taskAffinity: ${info.taskAffinity}")
  23. }
  24.  
  25. /**
  26.  * @param T 目标 Activity
  27.  */
  28. inline fun <reified T : AppCompatActivity> Context.toActivity() {
  29.     startActivity(Intent(this, T::class.java))
  30. }

一、standard——标准模式（默认模式）

　　这个模式是默认的启动模式，即标准模式，在不指定启动模式的前提下，系统默认使用该模式启动Activity，每次启动一个Activity都会重新创建一个新的实例，不管这个实例存不存在，这种模式下，谁启动了该模式的Activity，该Activity就属于启动它的Activity的任务栈。这个Activity它的onCreate()，onStart()，onResume()方法都会被调用。

配置形式：

  1.  
  1. <activity
        android:name=".StandardActivity"
        android:launchMode="standard" />

使用案例：

　　StandardActivity

　　对于standard模式，android:launchMode可以不进行声明，因为默认就是standard。 
　　StandardActivity 的代码如下，入口Activity中有一个按钮进入该Activity，这个Activity中又有一个按钮启动StandardActivity。

  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_standard.*
  4.  
  5. class StandardActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_standard)
  8.  
  9.         btn_self.setOnClickListener {
                toActivity<StandardActivity>()
            }
        }
    }

　　进入StandardActivity，然后再点击两次“启动自身”按钮。

输出的日志如下：

  1. 2020-04-29 16:07:32.235 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40477 hashCode: 32430795
    2020-04-29 16:07:32.236 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:07:32.259 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40477 hashCode: 32430795
    2020-04-29 16:07:32.262 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40477 hashCode: 32430795
  2.  
  3. 2020-04-29 16:07:34.490 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40477 hashCode: 32430795
    2020-04-29 16:07:34.518 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: StandardActivity taskId: 40477 hashCode: 90465235
    2020-04-29 16:07:34.518 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:07:34.527 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: StandardActivity taskId: 40477 hashCode: 90465235
    2020-04-29 16:07:34.532 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: StandardActivity taskId: 40477 hashCode: 90465235
    2020-04-29 16:07:34.867 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40477 hashCode: 32430795
    2020-04-29 16:07:34.869 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40477 hashCode: 32430795
  4.  
  5. 2020-04-29 16:07:35.423 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: StandardActivity taskId: 40477 hashCode: 90465235
    2020-04-29 16:07:35.448 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: StandardActivity taskId: 40477 hashCode: 139304006
    2020-04-29 16:07:35.449 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:07:35.455 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: StandardActivity taskId: 40477 hashCode: 139304006
    2020-04-29 16:07:35.458 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: StandardActivity taskId: 40477 hashCode: 139304006
    2020-04-29 16:07:35.780 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: StandardActivity taskId: 40477 hashCode: 90465235
    2020-04-29 16:07:35.782 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: StandardActivity taskId: 40477 hashCode: 90465235
  6.  
  7. 2020-04-29 16:07:36.215 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: StandardActivity taskId: 40477 hashCode: 139304006
    2020-04-29 16:07:36.240 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: StandardActivity taskId: 40477 hashCode: 102119413
    2020-04-29 16:07:36.241 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:07:36.246 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: StandardActivity taskId: 40477 hashCode: 102119413
    2020-04-29 16:07:36.249 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: StandardActivity taskId: 40477 hashCode: 102119413
    2020-04-29 16:07:36.576 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: StandardActivity taskId: 40477 hashCode: 139304006
    2020-04-29 16:07:36.578 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: StandardActivity taskId: 40477 hashCode: 139304006

可以看到日志输出了三次StandardActivity的和一次MainActivity的，从MainActivity进入StandardActivity一次，后来我们又按了两次按钮，总共三次StandardActivity的日志，并且所属的任务栈的id都是40477，这也验证了谁启动了该模式的Activity，该Activity就属于启动它的Activity的任务栈这句话，因为启动StandardActivity的是MainActivity，而MainActivity的taskId是40477，因此启动的StandardActivity也应该属于id为40477的这个task，后续的两个StandardActivity是被StandardActivity这个对象启动的，因此也应该还是40477，所以taskId都是40477。并且每一个Activity的hashcode都是不一样的，说明他们是不同的实例，即“每次启动一个Activity都会重新创建一个新的实例”。

二、singleTop——Task栈顶单例模式（栈顶复用模式）

　　此模式下，如果新的activity已经位于栈顶，那么这个activity不会被重新创建，同时他的onNewIntent方法会被调用，此时这个activity的onCreate()，onStart()方法没有回调，onResume()方法会被回调，所以这个activity没有发生改变，还是同一个activity。通过此方法的参数我们可以获取当前请求的信息。如果栈顶不存在该activity的实例，则情况与standard模式相同。

配置形式：

  1.  
  1. <activity
        android:name=".SingleTopActivity"
        android:launchMode="singleTop"
        android:taskAffinity="com.lyf.test.singleTop" />

使用案例：

SingleTopActivity

　

  1.  
  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_single_top.*
  4.  
  5. class SingleTopActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_single_top)
  8.  
  9.         btn_self.setOnClickListener {
                toActivity<SingleTopActivity>()
            }
  10.  
  11.         btn_other.setOnClickListener {
                toActivity<OtherTopActivity>()
    //            toActivity<MainActivity>()
            }
        }
    }

OtherTopActivity

  1.  
  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_other_top.*
  4.  
  5. class OtherTopActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_other_top)
  8.  
  9.         btn_top.setOnClickListener {
                toActivity<SingleTopActivity>()
            }
        }
    }

1、和standard启动方式一样，先启动SingleTopActivity，然后点击两次“启动自身”按钮

　　输出日志如下：

  1. 2020-04-29 16:10:38.177 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40478 hashCode: 264932
    2020-04-29 16:10:38.178 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:10:38.194 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40478 hashCode: 264932
    2020-04-29 16:10:38.197 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40478 hashCode: 264932
  2.  
  3. 2020-04-29 16:10:39.872 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40478 hashCode: 264932
    2020-04-29 16:10:39.902 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:39.903 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:10:39.916 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:39.920 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:40.261 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40478 hashCode: 264932
    2020-04-29 16:10:40.263 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40478 hashCode: 264932
  4.  
  5. 2020-04-29 16:10:42.664 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:42.666 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:42.667 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:10:42.669 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40478 hashCode: 246478133
  6.  
  7. 2020-04-29 16:10:44.706 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:44.707 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTopActivity taskId: 40478 hashCode: 246478133
    2020-04-29 16:10:44.709 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:10:44.712 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40478 hashCode: 246478133

从日志可以看出，除了第一次进入SingleTopActivity这个Activity时，输出的是onCreate方法中的日志，后续的都是调用了onNewIntent方法，并没有回调onCreate、onStart方法，回调了onResume方法，并且三个日志的hashcode都是一样的，说明栈中只有一个实例。这是因为第一次进入的时候，栈中没有该实例，则创建，后续的两次发现栈顶有这个实例，则直接复用，并且调用onNewIntent方法。

那么假设栈中有该实例，但是该实例不在栈顶情况又如何呢？

我们先从MainActivity进入到SingleTopActivity，然后点击“启动另外一个activity”启动OtherTopActivity，再从OtherTopActivity调回SingleTopActivity，再从SingleTopActivity跳到SingleTopActivity。日志如下：

  1. 2020-04-29 16:12:26.281 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40479 hashCode: 213102559
    2020-04-29 16:12:26.282 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:12:26.295 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40479 hashCode: 213102559
    2020-04-29 16:12:26.298 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40479 hashCode: 213102559
  2.  
  3. 2020-04-29 16:12:28.257 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40479 hashCode: 213102559
    2020-04-29 16:12:28.283 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTopActivity taskId: 40479 hashCode: 178327198
    2020-04-29 16:12:28.284 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:12:28.292 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTopActivity taskId: 40479 hashCode: 178327198
    2020-04-29 16:12:28.296 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40479 hashCode: 178327198
    2020-04-29 16:12:28.627 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40479 hashCode: 213102559
    2020-04-29 16:12:28.628 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40479 hashCode: 213102559
  4.  
  5. 2020-04-29 16:12:30.413 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTopActivity taskId: 40479 hashCode: 178327198
    2020-04-29 16:12:30.441 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: OtherTopActivity taskId: 40479 hashCode: 135729268
    2020-04-29 16:12:30.441 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:12:30.447 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: OtherTopActivity taskId: 40479 hashCode: 135729268
    2020-04-29 16:12:30.450 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: OtherTopActivity taskId: 40479 hashCode: 135729268
    2020-04-29 16:12:30.767 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleTopActivity taskId: 40479 hashCode: 178327198
    2020-04-29 16:12:30.769 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleTopActivity taskId: 40479 hashCode: 178327198
  6.  
  7. 2020-04-29 16:12:31.873 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: OtherTopActivity taskId: 40479 hashCode: 135729268
    2020-04-29 16:12:31.900 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTopActivity taskId: 40479 hashCode: 148854986
    2020-04-29 16:12:31.900 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:12:31.909 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTopActivity taskId: 40479 hashCode: 148854986
    2020-04-29 16:12:31.912 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40479 hashCode: 148854986
    2020-04-29 16:12:32.244 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: OtherTopActivity taskId: 40479 hashCode: 135729268
    2020-04-29 16:12:32.246 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onStop: OtherTopActivity taskId: 40479 hashCode: 135729268
  8.  
  9. 2020-04-29 16:12:35.347 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTopActivity taskId: 40479 hashCode: 148854986
    2020-04-29 16:12:35.348 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTopActivity taskId: 40479 hashCode: 148854986
    2020-04-29 16:12:35.349 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:12:35.351 11953-11953/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTopActivity taskId: 40479 hashCode: 148854986

我们看到从MainActivity进入到SingleTopActivity时，新建了一个SingleTopActivity对象，并且task id与MainActivity是一样的，然后从SingleTopActivity跳到OtherActivity时，新建了一个OtherActivity，此时task中存在三个Activity，从栈底到栈顶依次是MainActivity，SingleTopActivity，OtherActivity，此时如果再跳到SingleTopActivity，即使栈中已经有SingleTopActivity实例了，但是依然会创建一个新的SingleTopActivity实例，这一点从上面的日志的hashCode可以看出，此时栈顶是SingleTopActivity，如果再跳到SingleTopActivity，就会复用栈顶的SingleTopActivity，即会调用SingleTopActivity的onNewIntent方法。这就是上述日志的全过程。

对以上内容进行总结 
       standard启动模式是默认的启动模式，每次启动一个Activity都会新建一个实例不管栈中是否已有该Activity的实例。 
singleTop模式分3种情况

  1. 当前栈中已有该Activity的实例并且该实例位于栈顶时，不会新建实例，而是复用栈顶的实例，并且会将Intent对象传入，回调onNewIntent方法
  2. 当前栈中已有该Activity的实例但是该实例不在栈顶时，其行为和standard启动模式一样，依然会创建一个新的实例
  3. 当前栈中不存在该Activity的实例时，其行为同standard启动模式

standard和singleTop启动模式都是在原任务栈中新建Activity实例，不会启动新的Task，即使你指定了taskAffinity属性。

那么什么是taskAffinity属性呢，可以简单的理解为任务相关性。

  • 这个参数标识了一个Activity所需任务栈的名字，默认情况下，所有Activity所需的任务栈的名字为应用的包名
  • 我们可以单独指定每一个Activity的taskAffinity属性覆盖默认值
  • 一个任务的affinity决定于这个任务的根activity（root activity）的taskAffinity
  • 在概念上，具有相同的affinity的activity（即设置了相同taskAffinity属性的activity）属于同一个任务
  • 为一个activity的taskAffinity设置一个空字符串，表明这个activity不属于任何task

很重要的一点taskAffinity属性不对standard和singleTop模式有任何影响，即时你指定了该属性为其他不同的值，这两种启动模式下不会创建新的task（如果不指定即默认值，即包名）

指定方式如下：

  1. <activity
  2.     android:name=".SingleTopActivity"
  3.     android:launchMode="singleTop"
  4.     android:taskAffinity="com.lyf.test.singleTop" />

三、singleTask——Task栈内单例模式（栈内复用模式）

这个模式十分复杂，有各式各样的组合。在这个模式下，如果栈中存在这个Activity的实例就会复用这个Activity，不管它是否位于栈顶，复用时，会将它上面的Activity全部出栈，并且会回调该实例的onNewIntent方法。其实这个过程还存在一个任务栈的匹配，因为这个模式启动时，会在自己需要的任务栈中寻找实例，这个任务栈就是通过taskAffinity属性指定。如果这个任务栈不存在，则会创建这个任务栈。

配置形式：

  1. <activity
        android:name=".SingleTaskActivity"
        android:launchMode="singleTask" />

使用案例：

SingleTaskActivity

  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_single_task.*
  4.  
  5. class SingleTaskActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_single_task)
  8.  
  9.         btn_self.setOnClickListener {
                toActivity<SingleTaskActivity>()
            }
  10.  
  11.         btn_other.setOnClickListener {
                toActivity<OtherTask1Activity>()
    //            toActivity<MainActivity>()
            }
        }
    }

OtherTaskActivity

  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_other_task.*
  4.  
  5. class OtherTaskActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_other_task)
  8.  
  9.         btn_task.setOnClickListener {
                toActivity<SingleTaskActivity>()
            }
        }
    }

现在我们先不指定任何taskAffinity属性，对它做类似singleTop的操作，即从入口MainActivity进入SingleTaskActivity，然后跳到OtherTaskActivity，再跳回到SingleTaskActivity，然后再启动一次SingleTaskActivity。看看整个过程的日志。

  1. 2020-04-29 16:25:02.985 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40489 hashCode: 184844997
    2020-04-29 16:25:02.986 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:03.004 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40489 hashCode: 184844997
    2020-04-29 16:25:03.009 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40489 hashCode: 184844997
  2.  
  3. 2020-04-29 16:25:05.158 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40489 hashCode: 184844997
    2020-04-29 16:25:05.188 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:05.188 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:05.200 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:05.204 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:05.550 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40489 hashCode: 184844997
    2020-04-29 16:25:05.551 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40489 hashCode: 184844997
  4.  
  5. 2020-04-29 16:25:06.739 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:06.770 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onCreate: OtherTaskActivity taskId: 40489 hashCode: 191707012
    2020-04-29 16:25:06.771 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:06.777 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStart: OtherTaskActivity taskId: 40489 hashCode: 191707012
    2020-04-29 16:25:06.781 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: OtherTaskActivity taskId: 40489 hashCode: 191707012
    2020-04-29 16:25:07.108 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:07.110 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleTaskActivity taskId: 40489 hashCode: 259974370
  6.  
  7. 2020-04-29 16:25:08.044 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onPause: OtherTaskActivity taskId: 40489 hashCode: 191707012
    2020-04-29 16:25:08.056 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.057 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:08.058 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onRestart: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.058 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.060 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.400 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onStop: OtherTaskActivity taskId: 40489 hashCode: 191707012
    2020-04-29 16:25:08.401 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onDestroy: OtherTaskActivity taskId: 40489 hashCode: 191707012
  8.  
  9. 2020-04-29 16:25:08.950 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.951 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:08.953 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:08.955 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40489 hashCode: 259974370
  10.  
  11. 2020-04-29 16:25:10.130 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:10.132 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTaskActivity taskId: 40489 hashCode: 259974370
    2020-04-29 16:25:10.134 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:25:10.136 13514-13514/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40489 hashCode: 259974370

当我们从MainActiviyty进入到SingleTaskActivity，再进入到OtherTaskActivity后，此时栈中有3个Activity实例，并且SingleTaskActivity不在栈顶，而在OtherTaskActivity跳到SingleTaskActivity时，并没有创建一个新的SingleTaskActivity，而是复用了该实例，并且回调了onNewIntent方法。并且原来的OtherTaskActivity出栈了，具体见下面的信息，使用命令adb shell dumpsys activity activities可进行查看

  1. TaskRecord{e5a85ca #40489 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=2}
        Run #2: ActivityRecord{2a5292c u0 com.lyf.launchmodektdemo/.SingleTaskActivity t40489}
        Run #1: ActivityRecord{f9f926b u0 com.lyf.launchmodektdemo/.MainActivity t40489}

　　可以看到当前栈中只有两个Activity，即原来栈中位于SingleTaskActivity 之上的Activity都出栈了。

我们看到使用singleTask启动模式启动一个Activity，它还是在原来的task中启动。其实是这样的，我们并没有指定taskAffinity属性，这说明和默认值一样，也就是包名，当MainActivity启动时创建的Task的名字就是包名，因为MainActivity也没有指定taskAffinity，而当我们启动SingleTaskActivity ，首先会寻找需要的任务栈是否存在，也就是taskAffinity指定的值，这里就是包名，发现存在，就不再创建新的task，而是直接使用。当该task中存在该Activity实例时就会复用该实例，这就是栈内复用模式。

　　这时候，如果我们指定SingleTaskActivity 的taskAffinity值。

  1. <activity
  2.             android:name=".SingleTaskActivity"
  3.             android:launchMode="singleTask"
  4.             android:taskAffinity="com.lyf.test.singleTask" />
  1. 　　这时候，如果我们指定SingleTaskActivity 的taskAffinity值。
  1. 2020-04-29 16:49:33.424 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onRestart: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:49:33.429 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:49:33.437 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40512 hashCode: 240024050
  2.  
  3. 2020-04-29 16:49:36.714 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:49:36.781 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:36.781 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleTask
    2020-04-29 16:49:36.794 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:36.798 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:37.336 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:49:37.337 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40512 hashCode: 240024050
  4.  
  5. 2020-04-29 16:49:39.118 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:39.147 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: OtherTaskActivity taskId: 40515 hashCode: 176277901
    2020-04-29 16:49:39.148 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:49:39.155 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: OtherTaskActivity taskId: 40515 hashCode: 176277901
    2020-04-29 16:49:39.158 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: OtherTaskActivity taskId: 40515 hashCode: 176277901
    2020-04-29 16:49:39.479 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:39.481 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleTaskActivity taskId: 40515 hashCode: 60225666
  6.  
  7. 2020-04-29 16:49:42.322 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: OtherTaskActivity taskId: 40515 hashCode: 176277901
    2020-04-29 16:49:42.332 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:42.333 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleTask
    2020-04-29 16:49:42.333 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onRestart: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:42.334 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:42.335 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:42.679 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: OtherTaskActivity taskId: 40515 hashCode: 176277901
    2020-04-29 16:49:42.680 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onDestroy: OtherTaskActivity taskId: 40515 hashCode: 176277901
  8.  
  9. 2020-04-29 16:49:44.245 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:44.245 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleTaskActivity taskId: 40515 hashCode: 60225666
    2020-04-29 16:49:44.246 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleTask
    2020-04-29 16:49:44.249 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40515 hashCode: 60225666

我们看到SingleTaskActivity所属的任务栈的TaskId发生了变化，也就是说开启了一个新的Task，并且之后的OtherActivity也运行在了该Task上 。
打印出信息也证明了存在两个不同的Task：

  1. TaskRecord{babe221 #40515 A=com.lyf.test.singleTask U=0 StackId=1 sz=1}
        Run #2: ActivityRecord{c1d7e91 u0 com.lyf.launchmodektdemo/.SingleTaskActivity t40515}
    TaskRecord{eb83944 #40512 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=1}
        Run #1: ActivityRecord{94299af u0 com.lyf.launchmodektdemo/.MainActivity t40512}

如果我们指定SingleTaskActivity的taskAffinity属性与MainActivity一样，又会出现什么情况呢？

配置形式：

  1. <activity
  2.     android:name=".SingleTaskActivity"
  3.     android:launchMode="singleTask"
  4.     android:taskAffinity="com.lyf.test.launchmodedemo" />

没错，就是和他们什么都不指定是一样的。 
这时候，就有了下面的结论 
singleTask启动模式启动Activity时，首先会根据taskAffinity去寻找当前是否存在一个对应名字的任务栈

  • 如果不存在，则会创建一个新的Task，并创建新的Activity实例入栈到新创建的Task中去
  • 如果存在，则得到该任务栈，查找该任务栈中是否存在该Activity实例 
            如果存在该实例，则将它上面的Activity实例都出栈，然后回调启动的Activity实例的onNewIntent方法 
            如果不存在该实例，则新建Activity，并入栈

此外，我们可以将两个不同App中的Activity设置为相同的taskAffinity，这样虽然在不同的应用中，但是Activity会被分配到同一个Task中去。

我们再创建另外一个应用，指定它的taskAffinity和之前的一样，都是com.lyf.test.singleTask

  1. <activity
        android:name=".OtherSingleTaskActivity"
        android:launchMode="singleTask"
        android:taskAffinity="com.lyf.test.singleTask" />

注意：新应用的activity也应设置为singleTask模式。否则效果是不一样的。

先启动一个应用，让他跳转到该Activity后，再按home键让该应用在后台运行，然后启动另一个应用再进入栈内单例Activity，看日志

  1. 2020-04-29 16:28:55.725 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40496 hashCode: 223658940
    2020-04-29 16:28:55.726 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:28:55.760 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40496 hashCode: 223658940
    2020-04-29 16:28:55.766 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40496 hashCode: 223658940
  2.  
  3. 2020-04-29 16:29:02.961 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40496 hashCode: 223658940
    2020-04-29 16:29:03.025 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleTaskActivity taskId: 40497 hashCode: 87000641
    2020-04-29 16:29:03.025 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleTask
    2020-04-29 16:29:03.036 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleTaskActivity taskId: 40497 hashCode: 87000641
    2020-04-29 16:29:03.040 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleTaskActivity taskId: 40497 hashCode: 87000641
    2020-04-29 16:29:03.596 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40496 hashCode: 223658940
    2020-04-29 16:29:03.597 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40496 hashCode: 223658940
  1. 2020-04-29 16:29:27.895 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onCreate()方法*****
    2020-04-29 16:29:27.896 14457-14457/com.lyf.singletaskdemo I/LaunchMode: onCreate: MainActivity taskId: 40499 hashCode: 194327709
    2020-04-29 16:29:27.896 14457-14457/com.lyf.singletaskdemo I/LaunchMode: taskAffinity: com.lyf.singletaskdemo
    2020-04-29 16:29:27.904 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onStart()方法*****
    2020-04-29 16:29:27.908 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onResume()方法*****
  2.  
  3. 2020-04-29 16:29:30.703 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onCreate()方法*****
    2020-04-29 16:29:30.704 14457-14457/com.lyf.singletaskdemo I/LaunchMode: onCreate: SingleTaskActivity taskId: 40497 hashCode: 34523045
    2020-04-29 16:29:30.704 14457-14457/com.lyf.singletaskdemo I/LaunchMode: taskAffinity: com.lyf.test.singleTask
    2020-04-29 16:29:30.710 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onStart()方法*****
    2020-04-29 16:29:30.715 14457-14457/com.lyf.singletaskdemo I/LaunchMode: *****onResume()方法*****

我们看到，指定了相同的taskAffinity的SingleTaskActivity和OtherActivityActivity被启动到了同一个task中，taskId都为40497。

  1. TaskRecord{70a40f7 #40497 A=com.lyf.test.singleTask U=0 StackId=1 sz=2}
        Run #4: ActivityRecord{e30ad3f u0 com.lyf.singletaskdemo/.SingleTaskActivity t40497}
    TaskRecord{c17f593 #40499 A=com.lyf.singletaskdemo U=0 StackId=1 sz=1}
        Run #3: ActivityRecord{c7f6489 u0 com.lyf.singletaskdemo/.MainActivity t40499}
    TaskRecord{70a40f7 #40497 A=com.lyf.test.singleTask U=0 StackId=1 sz=2}
        Run #2: ActivityRecord{d7c5801 u0 com.lyf.launchmodektdemo/.SingleTaskActivity t40497}
    TaskRecord{703dc9 #40496 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=1}
        Run #1: ActivityRecord{5f830e4 u0 com.lyf.launchmodektdemo/.MainActivity t40496}

 四、singleInstance——全局单例模式

这种模式下的Activity会单独占用一个Task栈，具有全局唯一性，即整个系统中就这么一个实例，由于栈内复用的特性，后续的请求均不会创建新的Activity实例，除非这个特殊的任务栈被销毁了。以singleInstance模式启动的Activity在整个系统中是单例的，如果在启动这样的Activity时，已经存在了一个实例，那么会把它所在的任务调度到前台，重用这个实例。

 配置形式：

  1. <activity
  2.             android:name=".SingleInstanceActivity"
  3.             android:launchMode="singleInstance">
  4.             <intent-filter>
  5.                 <action android:name="com.lyf.test.singleinstancedemo" />
  6.  
  7.                 <category android:name="android.intent.category.DEFAULT" />
  8.             </intent-filter>
  9.         </activity>

使用案例：

  1.  
  1. package com.lyf.launchmodektdemo
  2.  
  3. import android.os.Bundle
    import kotlinx.android.synthetic.main.activity_single_instance.*
  4.  
  5. class SingleInstanceActivity : BaseActivity() {
  6.  
  7.     override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_single_instance)
  8.  
  9.         btn_self.setOnClickListener {
                toActivity<SingleInstanceActivity>()
            }
  10.  
  11.         btn_instance.setOnClickListener {
                toActivity<OtherInstanceActivity>()
    //            toActivity<MainActivity>()
            }
        }
    }

现在我们先不指定任何taskAffinity属性，对它做类似singleTask的操作，即从入口MainActivity进入SingleInstanceActivity，然后跳到OtherInstanceActivity，再跳回到SingleInstanceActivity，然后再启动一次SingleInstanceActivity。看看整个过程的日志。

  1. 2020-04-29 16:33:31.542 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40501 hashCode: 252960824
    2020-04-29 16:33:31.542 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:33:31.560 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40501 hashCode: 252960824
    2020-04-29 16:33:31.564 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40501 hashCode: 252960824
  2.  
  3. 2020-04-29 16:33:33.366 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40501 hashCode: 252960824
    2020-04-29 16:33:33.417 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:33.417 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:33:33.427 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:33.431 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:33.989 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40501 hashCode: 252960824
    2020-04-29 16:33:33.990 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40501 hashCode: 252960824
  4.  
  5. 2020-04-29 16:33:36.899 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:36.939 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onCreate: OtherInstanceActivity taskId: 40501 hashCode: 59304459
    2020-04-29 16:33:36.939 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:33:36.945 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: OtherInstanceActivity taskId: 40501 hashCode: 59304459
    2020-04-29 16:33:36.948 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: OtherInstanceActivity taskId: 40501 hashCode: 59304459
    2020-04-29 16:33:37.599 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:37.601 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleInstanceActivity taskId: 40502 hashCode: 196024178
  6.  
  7. 2020-04-29 16:33:39.966 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onPause: OtherInstanceActivity taskId: 40501 hashCode: 59304459
    2020-04-29 16:33:39.991 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:39.991 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:33:39.992 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onRestart: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:39.993 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:39.995 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:40.620 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: OtherInstanceActivity taskId: 40501 hashCode: 59304459
    2020-04-29 16:33:40.622 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onStop: OtherInstanceActivity taskId: 40501 hashCode: 59304459
  8.  
  9. 2020-04-29 16:33:43.046 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:43.046 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleInstanceActivity taskId: 40502 hashCode: 196024178
    2020-04-29 16:33:43.047 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:33:43.049 14220-14220/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40502 hashCode: 196024178

当我们从MainActiviyty进入到SingleInstanceActivity，再进入到OtherInstanceActivity后，此时栈中有3个Activity实例，SingleInstanceActivity单独在一个Task中，而从OtherInstanceActivity跳到SingleInstanceActivity时，并没有创建一个新的SingleInstanceActivity，而是复用了该实例，并且回调了onNewIntent方法。并且原来的OtherInstanceActivity没有出栈，具体见下面的信息，使用命令adb shell dumpsys activity activities可进行查看

  1. TaskRecord{c2d2bf5 #40502 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=1}
        Run #3: ActivityRecord{a002f8d u0 com.lyf.launchmodektdemo/.SingleInstanceActivity t40502}
    TaskRecord{9de7ffb #40501 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=2}
        Run #2: ActivityRecord{c4a3bae u0 com.lyf.launchmodektdemo/.OtherInstanceActivity t40501}
        Run #1: ActivityRecord{28990d4 u0 com.lyf.launchmodektdemo/.MainActivity t40501}

可以看到当前栈中只有三个Activity。

我们看到使用singleInstance启动模式启动一个Activity，它创建了一个新的task。

这时候，如果我们指定SingleInstanceActivity 的taskAffinity值。

  1. <activity
  2.             android:name=".SingleInstanceActivity"
  3.             android:launchMode="singleInstance"
  4.             android:taskAffinity="com.lyf.test.singleInstance">
  5.             <intent-filter>
  6.                 <action android:name="com.lyf.test.singleinstancedemo" />
  7.  
  8.                 <category android:name="android.intent.category.DEFAULT" />
  9.             </intent-filter>
  10.         </activity>

执行上述同样的操作：

  1. 2020-04-29 16:36:52.237 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40506 hashCode: 184844997
    2020-04-29 16:36:52.238 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:36:52.257 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40506 hashCode: 184844997
    2020-04-29 16:36:52.261 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40506 hashCode: 184844997
  2.  
  3. 2020-04-29 16:36:54.081 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40506 hashCode: 184844997
    2020-04-29 16:36:54.146 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:54.147 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
    2020-04-29 16:36:54.160 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:54.165 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:54.707 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40506 hashCode: 184844997
    2020-04-29 16:36:54.708 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40506 hashCode: 184844997
  4.  
  5. 2020-04-29 16:36:56.430 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:56.480 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onCreate: OtherInstanceActivity taskId: 40506 hashCode: 114298043
    2020-04-29 16:36:56.481 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:36:56.488 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStart: OtherInstanceActivity taskId: 40506 hashCode: 114298043
    2020-04-29 16:36:56.492 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onResume: OtherInstanceActivity taskId: 40506 hashCode: 114298043
    2020-04-29 16:36:57.137 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:57.140 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleInstanceActivity taskId: 40507 hashCode: 150301101
  6.  
  7. 2020-04-29 16:36:59.056 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onPause: OtherInstanceActivity taskId: 40506 hashCode: 114298043
    2020-04-29 16:36:59.080 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:59.081 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
    2020-04-29 16:36:59.081 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onRestart: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:59.082 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:59.083 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:36:59.706 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: OtherInstanceActivity taskId: 40506 hashCode: 114298043
    2020-04-29 16:36:59.709 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onStop: OtherInstanceActivity taskId: 40506 hashCode: 114298043
  8.  
  9. 2020-04-29 16:37:01.231 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:37:01.232 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleInstanceActivity taskId: 40507 hashCode: 150301101
    2020-04-29 16:37:01.234 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
    2020-04-29 16:37:01.238 15405-15405/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40507 hashCode: 150301101
  1. TaskRecord{ec31552 #40507 A=com.lyf.test.singleinstancedemo U=0 StackId=1 sz=1}
        Run #3: ActivityRecord{68ce1ba u0 com.lyf.launchmodektdemo/.SingleInstanceActivity t40507}
    TaskRecord{3a472d9 #40506 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=2}
        Run #2: ActivityRecord{b6d1c71 u0 com.lyf.launchmodektdemo/.OtherInstanceActivity t40506}
        Run #1: ActivityRecord{fd90bd5 u0 com.lyf.launchmodektdemo/.MainActivity t40506}

除了SingleInstanceActivity的taskAffinity变化之后，其他的结果与不指定taskAffinity是一样的。singleInstance的优先级大于taskAffinity，所以同时指定它们的时候也会按照singleInstance的设置得到对应的结果。

使用下面的方式分别在两个应用中启动它

  1. Intent singleInstanceIntent = new Intent();
  2. singleInstanceIntent.setAction("com.lyf.test.singleinstancedemo");
  3. startActivity(singleInstanceIntent);

操作和上一个（使用两个app操作）一样，日志如下：

第一个应用启动，并跳转到singleInstance模式的Activity

  1. 2020-04-29 16:39:39.628 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:39:39.629 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
    2020-04-29 16:39:39.651 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:39:39.655 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40512 hashCode: 240024050
  2.  
  3. 2020-04-29 16:39:41.507 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:39:41.556 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleInstanceActivity taskId: 40513 hashCode: 240431118
    2020-04-29 16:39:41.557 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
    2020-04-29 16:39:41.566 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40513 hashCode: 240431118
    2020-04-29 16:39:41.569 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40513 hashCode: 240431118
    2020-04-29 16:39:42.129 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40512 hashCode: 240024050
    2020-04-29 16:39:42.131 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40512 hashCode: 240024050

第二个应用启动，尚未跳转

  1. 2020-04-29 16:40:19.340 16264-16264/com.lyf.singleinstancedemo I/LaunchMode: *****onCreate()方法*****
  2. 2020-04-29 16:40:19.341 16264-16264/com.lyf.singleinstancedemo I/LaunchMode: onCreate: MainActivity taskId: 40514 hashCode: 153400740
  3. 2020-04-29 16:40:19.341 16264-16264/com.lyf.singleinstancedemo I/LaunchMode: taskAffinity: com.lyf.singleinstancedemo
  4. 2020-04-29 16:40:19.355 16264-16264/com.lyf.singleinstancedemo I/LaunchMode: *****onStart()方法*****
  5. 2020-04-29 16:40:19.359 16264-16264/com.lyf.singleinstancedemo I/LaunchMode: *****onResume()方法*****

第二个应用启动，并跳转到singleInstance模式的Activity

  1. 2020-04-29 16:39:39.628 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: MainActivity taskId: 40512 hashCode: 240024050
  2. 2020-04-29 16:39:39.629 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.launchmodektdemo
  3. 2020-04-29 16:39:39.651 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: MainActivity taskId: 40512 hashCode: 240024050
  4. 2020-04-29 16:39:39.655 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: MainActivity taskId: 40512 hashCode: 240024050
  5.  
  6. 2020-04-29 16:39:41.507 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: MainActivity taskId: 40512 hashCode: 240024050
  7. 2020-04-29 16:39:41.556 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onCreate: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  8. 2020-04-29 16:39:41.557 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
  9. 2020-04-29 16:39:41.566 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  10. 2020-04-29 16:39:41.569 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  11. 2020-04-29 16:39:42.129 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: MainActivity taskId: 40512 hashCode: 240024050
  12. 2020-04-29 16:39:42.131 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: MainActivity taskId: 40512 hashCode: 240024050
  13.  
  14. 2020-04-29 16:40:16.810 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onPause: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  15. 2020-04-29 16:40:16.819 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onSaveInstanceState: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  16. 2020-04-29 16:40:16.823 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStop: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  17. 2020-04-29 16:40:31.888 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onNewIntent: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  18. 2020-04-29 16:40:31.889 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: taskAffinity: com.lyf.test.singleinstancedemo
  19. 2020-04-29 16:40:31.892 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onRestart: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  20. 2020-04-29 16:40:31.893 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onStart: SingleInstanceActivity taskId: 40513 hashCode: 240431118
  21. 2020-04-29 16:40:31.897 16149-16149/com.lyf.launchmodektdemo I/LaunchMode: onResume: SingleInstanceActivity taskId: 40513 hashCode: 240431118

我们看到，第一次应用启动SingleInstanceActivity时，由于系统中不存在该实例，所以新建了一个Task，按home键后，使用另一个App进入该Activity，由于系统中已经存在了一个实例，不会再创建新的Task，直接复用该实例，并且回调onNewIntent方法。可以从他们的hashcode中可以看出这是同一个实例。因此我们可以理解为：SingleInstance模式启动的Activity在系统中具有全局唯一性。

  1. TaskRecord{508550a #40513 A=com.lyf.test.singleinstancedemo U=0 StackId=1 sz=1}
        Run #3: ActivityRecord{82b4336 u0 com.lyf.launchmodektdemo/.SingleInstanceActivity t40513}
    TaskRecord{a3d9ff1 #40514 A=com.lyf.singleinstancedemo U=0 StackId=1 sz=1}
        Run #2: ActivityRecord{80e980 u0 com.lyf.singleinstancedemo/.MainActivity t40514}
    TaskRecord{eb83944 #40512 A=com.lyf.launchmodektdemo U=0 StackId=1 sz=1}
        Run #1: ActivityRecord{94299af u0 com.lyf.launchmodektdemo/.MainActivity t40512}

git源码：https://github.com/First-Time/LaunchModeKTDemo.git

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