03_隐式意图打开activity

想让第一个activity把第二个activity打开的话，在清单文件里面声明一下并且

右键Debug As Android Application居然没有报错

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mimeType  讲HTML的时候就讲过的对应的一个响应头。setContentType("text/html").这个实际上就是一个mime。

通过mime就可以说明当前这个activity可以处理的数据。我当前这个activity接收什么样类型的数据？所以mime就是用来说明我当前应用可以处理的媒体类型都有哪些？可以打开的具体内容是怎么样的？

当然这个东西咱们也可以自定义。自定义的格式是：类型/子类型.

        <activity
            android:name="com.itheima.callnewactivity.SecondActivity">
            <intent-filter >
                <action android:name="com.itheima.second"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:scheme="itheima"/>
            </intent-filter>
            <intent-filter >
                <action android:name="com.itheima.second2"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:scheme="itheima"
                    android:mimeType="itcast/itheima"
                    />
            </intent-filter>

        </activity>

给SecondActivity搞了两个意图过滤器，实际上只需要匹配其中的一个。只要有一个完整的intent-filter被匹配上，我就可以把对应的activity给它打开。

Intent android.content.Intent.setType(String type)

Set an explicit MIME data type. 

This is used to create intents that only specify a type and not data, for example to indicate the type of data to return. 

This method automatically clears any data that was previously set (for example by setData). 

Note: MIME type matching in the Android framework is case-sensitive, unlike formal RFC MIME types. As a result, you should always write your MIME types with lower case letters, or use normalizeMimeType or setTypeAndNormalize to ensure that it is converted to lower case.
Parameters:type The MIME type of the data being handled by this intent.Returns:Returns the same Intent object, for chaining multiple calls into a single statement.See Also:getTypesetTypeAndNormalizesetDataAndTypenormalizeMimeType

首先找FATAL EXCEPTION:main，从这儿开始的。

问题出在哪里？

Intent android.content.Intent.setType(String type)

Set an explicit MIME data type. 

This is used to create intents that only specify a type and not data, for example to indicate the type of data to return. 

This method automatically clears any data that was previously set (for example by setData).

Note: MIME type matching in the Android framework is case-sensitive, unlike formal RFC MIME types. As a result, you should always write your MIME types with lower case letters, or use normalizeMimeType or setTypeAndNormalize to ensure that it is converted to lower case.
Parameters:type The MIME type of the data being handled by this intent.Returns:Returns the same Intent object, for chaining multiple calls into a single statement.See Also:getTypesetTypeAndNormalizesetDataAndTypenormalizeMimeType

This method automatically clears any data that was previously set (for example by setData). 
调用setType()方法会自动清除任何的data数据(通过setData()来设置对应的内容).
所以setType()会自动清除setData()所设置的内容.
办法是先调setType()再调setData().

Intent android.content.Intent.setData(Uri data)

Set the data this intent is operating on. This method automatically clears any type that was previously set by setType or setTypeAndNormalize. 

Note: scheme matching in the Android framework is case-sensitive, unlike the formal RFC. As a result, you should always write your Uri with a lower case scheme, or use Uri.normalizeScheme or setDataAndNormalize to ensure that the scheme is converted to lower case.
Parameters:data The Uri of the data this intent is now targeting.Returns:Returns the same Intent object, for chaining multiple calls into a single statement.See Also:getDatasetDataAndNormalizeandroid.net.Intent.normalize

setData()会清除setType()的数据.这是一个死结。setData()和setType()是互斥的.
所以可以用setDataAndType()把Data和Type一并设置。
程序运行成功了：

通过匹配第二个intent-filter可以把对应的activity给它打开。实际上咱们通过intent-filter方式打开一个activity这就叫一个隐式意图。隐式意图就是说我通过匹配某一个activity的意图过滤器，我把这个意图过滤器里面所有该匹配的内容都匹配上了，那我就可以把对应的activity打开。同样如果你的一个activity希望别人用隐式意图的方式打开，那你就必须设置一个intent-filter。这就是隐式意图。

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你必须搞一个意图过滤器，有了意图过滤器别人才可以用隐式意图的方式打开。还有一点要注意：

 <category android:name="android.intent.category.DEFAULT"/>

需要注意一点的是：category这个DEFAULT虽说不用匹配，但是这个东西必须得有。这个category DEFAULT虽说不需要通过代码的方式去匹配它，但是你想用隐式意图把这个打开，默认的这个category一定要在清单文件里面给它配置上。

---

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.itheima.callnewactivity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.CALL_PHONE"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.itheima.callnewactivity.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.itheima.callnewactivity.SecondActivity">
            <intent-filter >
                <action android:name="com.itheima.second"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:scheme="itheima"/>
            </intent-filter>
            <intent-filter >
                <action android:name="com.itheima.second2"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:scheme="itheima"
                    android:mimeType="itcast/itheima"
                    />
            </intent-filter>

        </activity>
    </application>

</manifest>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="call"
        android:text="打电话" />
    <TextView
        android:id="@+id/tv"
        android:layout_below="@id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#ff0000"
        android:textSize="20sp"
        android:text="第一个activity"/>
        <Button
        android:layout_below="@id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="openSecond"
        android:text="打开第二个activity"/>
        <Button
        android:layout_toRightOf="@id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="openSecond2"
        android:text="打开第二个activity"/>
</RelativeLayout>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="call"
        android:text="打电话" />
    <TextView
        android:layout_below="@id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#00ff00"
        android:textSize="20sp"
        android:text="第二个activity"
        />
</RelativeLayout>

package com.itheima.callnewactivity;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void call(View v){
        Intent intent = new Intent();
        //给意图设置一个动作
        intent.setAction(Intent.ACTION_CALL);
        //给意图设置数据
        intent.setData(Uri.parse("tel:"+110));
        //打开打电话的activity
        startActivity(intent);

    }
   public void openSecond(View v){
       Intent intent = new Intent();
       intent.setAction("com.itheima.second");
       intent.setData(Uri.parse("itheima:"+1223));
       startActivity(intent);
   }
   public void openSecond2(View v){
       Intent intent = new Intent();
       intent.setAction("com.itheima.second2");
       //intent.setData(Uri.parse("itheima:"+1233));
       //intent.setType("itcast/itheima");//
       //intent.setData(Uri.parse("itheima:"+1233));
       intent.setDataAndType(Uri.parse("itheima:"+1223), "itcast/itheima");
       startActivity(intent);
   }
}

package com.itheima.callnewactivity;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;

public class SecondActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
        setContentView(R.layout.activity_second);
    }

    public void call(View v){
        Intent intent = new Intent();
        //给意图设置一个动作
        intent.setAction(Intent.ACTION_CALL);
        //给意图设置数据
        intent.setData(Uri.parse("tel:"+110));
        //打开打电话的activity
        startActivity(intent);

    }

}