廣播發送者(調用sendBroadcast方法) - 用於發送廣播;
廣播接收器(BroadcastReceiver) - 用於接收廣播;
意圖內容(Intent)-用於保存廣播相關信息的媒介。
Broadcast是Android中一種廣泛運用的在應用程序之間或應用程序內個組件直接傳輸信息的機制。而BroadcastReceiver是對發送出來的廣播Intent進行過濾接受並響應的一類組件。
BroadcastReceiver廣播接收者用於異步接收廣播Intent,廣播Intent的發送是通過調用Context.sendBroadcast()來實現的。通常一個廣播Intent可以被訂閱了此Intent的多個廣播接收者所接收。
每次廣播Intent發出後,系統就會創建對應的BroadcastReceiver的實例,並自動觸發它的onReceiver()方法,onReceiver()方法執行完後,BroadcastReveiver的實例就會被銷燬。
通常一個BroadcastReceiver對象的生命週期不超過5秒,所以在BroadcastReceiver裏不能做一些比較耗時的操作。如果需要根據Broadcast來完成一項比較耗時的操作,則可以考慮通過Intent啓動一個Service來完成該操作。
實例:BroadcastDemo
運行效果:
代碼清單:
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.rainsong.broadcastdemo"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application android:label="@string/app_name" android:icon="@drawable/ic_launcher">
<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>
<receiver android:name="MyReceiver">
<intent-filter>
<action android:name="com.rainsong.action.NEW_BROADCAST" />
</intent-filter>
</receiver>
</application>
</manifest>
佈局文件:main.xml<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:id="@+id/button1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="發送廣播"
/>
</LinearLayout>
Java源代碼文件:MainActivity.javapackage com.rainsong.broadcastdemo;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity
{
public final String ACTION = "com.rainsong.action.NEW_BROADCAST";
Button btn1;
OnClickListener listener1;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btn1 = (Button)findViewById(R.id.button1);
listener1 = new OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(ACTION);
sendBroadcast(intent);
}
};
btn1.setOnClickListener(listener1);
}
}
Java源代碼文件:MyReceiver.javapackage com.rainsong.broadcastdemo;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
public class MyReceiver extends BroadcastReceiver {
public static int NOTIFICATION_ID = 12345;
@Override
public void onReceive(Context context, Intent intent) {
NotificationManager nm =
(NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
Notification notification = new Notification(android.R.drawable.stat_notify_chat,
"MyReceiver onReceive", System.currentTimeMillis());
Intent intent1 = new Intent(context, MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent1, 0);
notification.setLatestEventInfo(context, "MyReceiver onReceive", null, pendingIntent);
nm.notify(NOTIFICATION_ID, notification);
}
}
代碼邏輯:
單擊“發送廣播”按鈕,我們的程序開始發送廣播Intent,這個廣播Intent被MyReceiver所截獲,然後就開始執行MyReceiver裏的onReceive方法,在onReceive裏邊將一個Notification顯示在狀態欄中。