Android Application的使用及其生命周期

摘要：

1. Application的使用

2. Application的生命周期

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工程代码：LearnContext.zip

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1. Application的使用

多个组件之间数据共享

举例：两个Activity之间数据共享

Application 对同一个应用程序是唯一的，所以可以使用Application进行数据共享

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" alt="" />

定义两个Activity：  MainActivity.java 和 MainActivity2.java， 代码是一样的

TextView tv;
EditText et;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //setContentView(R.layout.activity_main_activity2);
    setContentView(R.layout.activity_main2);

    tv = (TextView) findViewById(R.id.tv);
    et = (EditText) findViewById(R.id.et);

    tv.setText("共享数据：" + getApp().getTextData());

    findViewById(R.id.btnTextData).setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            getApp().setTextData(et.getText().toString());
            tv.setText("共享数据：" + et.getText().toString());
        }
    });
}

public App getApp() {
    return ((App)getApplicationContext());
}

定义一个类App，集成Application

public class App extends Application {

    private String textData = "default";

    public void setTextData(String textData) {
        this.textData = textData;
    }
    public String getTextData() {
        return textData;
    }
}

修改AndroidManifest.xml文件， 使用自定义的Application，两个Activity都是入口：

<application
    android:name="com.carloz.learnapplication.App"
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.carloz.learnapplication.MainActivity2"
        android:label="@string/title_activity_main_activity2" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

结果，在一个Activity修改App的数据，在另一个Activity都能获取到

2. Application的生命周期

给应用程序配置，自定义的Application，然后在Application的生命周期中做一些操作

Application生命周期

public class App extends Application {

    @Override
    public void onCreate() {
        // 程序创建的时候执行
        Log.d(TAG, "onCreate");
        super.onCreate();
    }
    @Override
    public void onTerminate() {
        // 程序终止的时候执行
        Log.d(TAG, "onTerminate");
        super.onTerminate();
    }
    @Override
    public void onLowMemory() {
        // 低内存的时候执行
        Log.d(TAG, "onLowMemory");
        super.onLowMemory();
    }
    @Override
    public void onTrimMemory(int level) {
        // 程序在内存清理的时候执行
        Log.d(TAG, "onTrimMemory");
        super.onTrimMemory(level);
    }
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        Log.d(TAG, "onConfigurationChanged");
        super.onConfigurationChanged(newConfig);
    }

}

打开Activity
08-16 15:16:27.142: D/CARLOZ - Application(28202): onCreate
08-16 15:16:27.172: D/CARLOZ - MainActivity3(28202): onCreate
08-16 15:16:27.232: D/CARLOZ - MainActivity3(28202): onStart
08-16 15:16:27.232: D/CARLOZ - MainActivity3(28202): onResume
HOME键退出应用程序
08-16 15:16:55.372: D/CARLOZ - MainActivity3(28202): onPause
08-16 15:16:55.942: D/CARLOZ - MainActivity3(28202): onStop
08-16 15:16:55.952: D/CARLOZ - Application(28202): onTrimMemory    回收内存
重新打开应用程序
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onRestart
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onStart
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onResume
长按MENU键，打开Recent TASK
08-16 15:17:28.972: D/CARLOZ - MainActivity3(28202): onPause
08-16 15:17:28.992: D/CARLOZ - MainActivity3(28202): onStop
08-16 15:17:29.022: D/CARLOZ - Application(28202): onTrimMemory
彻底关闭应用程序
08-16 15:17:31.542: D/CARLOZ - MainActivity3(28202): onDestroy

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工程代码：LearnContext.zip