BroadcastReceiver使用方式

從行爲上廣播類型有兩種：
無序廣播(Normal broadcasts)：無序且並行執行廣播
有序廣播(Ordered broadcasts)：有序地一個接一個執行廣播

當通過意圖發送廣播時，無論BroadcastReceiver定義在當前應用還是其他應用中，只要BroadcastReceiver對此意圖感興趣(如：匹配Action)，就會得到執行。

有序廣播和無序廣播默認都是運行在UI線程中的，當BroadcastReceiver在10秒內沒有執行完畢，Android會認爲該程序無響應，所以在BroadcastReceiver裏不能做一些比較耗時的操作，否則會彈出ANR(Application No Response)的對話框。如果需要完成一項比較耗時的工作，應該通過Intent發送給Service，由Service來完成，而不是使用子線程的方法來解決，因爲BroadcastReceiver的生命週期很短(在onReceive()執行後BroadcastReceiver的實例就會被銷燬)，子線程可能還沒有結束BroadcastReceiver就先結束了。如果BroadcastReceiver結束了，它的宿主進程還在運行，那麼子線程還會繼續執行。但宿主進程此時很容易在系統需要內在時被優先殺死。因爲它屬於空進程（沒有任何活動組件的進程）。

下面分別講解這兩種廣播


無序廣播：
示例中FirstBroadcastReceiver和SecondBroadcastReceiver在同一個應用中，ThirdBroadcastReceiver在另一個應用中。

他們的執行順序是不可預知的。

應用A中代碼：
定義兩個BroadcastReceiver

public class FirstBroadcastReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		Log.i("CDH", "FirstBroadcastReceiver msg:"+intent.getStringExtra("msg"));
	}
}

public class SecondBroadcastReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		Log.i("CDH", "SecondBroadcastReceiver msg:"+intent.getStringExtra("msg"));
	}
}

AndroidManifest.xml中配置BroadcastReceiver

<receiver android:name=".FirstBroadcastReceiver">
	<intent-filter>
		<action android:name="com.improve.broadcast"/>
	</intent-filter>
</receiver>

<receiver android:name=".SecondBroadcastReceiver">
	<intent-filter>
		<action android:name="com.improve.broadcast"/>
	</intent-filter>
</receiver>

在一個名爲BroadcastReceiverDemo的Activity中定義一個Button，點擊事件如下

new OnClickListener() {
	@Override
	public void onClick(View button) {
		//發送廣播
		Intent intent = new Intent("com.improve.broadcast");
		intent.putExtra("msg", "I am BroadcastReceiverDemo Activity");
		sendBroadcast(intent);
	}
}

應用B中代碼：

public class ThirdBroadcastReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		Log.i("CDH", "ThirdBroadcastReceiver msg:"+intent.getStringExtra("msg"));
	}
}

AndroidManifest.xml中配置BroadcastReceiver

<receiver android:name=".ThirdBroadcastReceiver">
	<intent-filter>
		<action android:name="com.improve.broadcast"/>
	</intent-filter>
</receiver>

運行結果

有序廣播：
通過android:priority="N"設置廣播執行順序(N的取值-1000到1000)，優先級高的廣播先執行。（這裏先執行SecondBroadcastReceiver再執行FirstBroadcastReceiver）
在前一個執行的廣播中設置結果值，傳給下一個廣播。也可以通過BroadcastReceiver.abortBroadcast()終止廣播，後面的廣播接收器不會得到執行。

定義兩個BroadcastReceiver

public class FirstBroadcastReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		Log.i("CDH", "FirstBroadcastReceiver msg:"+intent.getStringExtra("msg"));
		Bundle mBundle = this.getResultExtras(false);//true：前一個廣播沒有結果時創建新的Bundle；false：不創建Bundle
		if (mBundle == null) {
			Log.i("CDH", "沒有獲取到前一個運行的廣播返回的數據");
		} else {
			Log.i("CDH", "前一個運行的廣播返回的數據爲：" + mBundle.getString("msg"));
		}
	}
}

public class SecondBroadcastReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		Log.i("CDH", "SecondBroadcastReceiver msg:"+intent.getStringExtra("msg"));
		Bundle bundle = new Bundle();
		bundle.putString("msg", "SecondBroadcastReceiver");
		setResultExtras(bundle);
	}
}

AndroidManifest.xml中配置BroadcastReceiver

<receiver android:name=".FirstBroadcastReceiver">
	<intent-filter android:priority="1">
		<action android:name="com.improve.broadcast"/>
	</intent-filter>
</receiver>

<receiver android:name=".SecondBroadcastReceiver">
	<intent-filter android:priority="2">
		<action android:name="com.improve.broadcast"/>
	</intent-filter>
</receiver>

在一個名爲BroadcastReceiverDemo的Activity中定義一個Button，點擊事件如下

new OnClickListener() {
	@Override
	public void onClick(View button) {
		//發送廣播
		Intent intent = new Intent("com.improve.broadcast");
		intent.putExtra("msg", "BroadcastReceiverDemo");
		sendOrderedBroadcast(intent, null);
	}
}

運行結果