Android菜鸟的成长笔记（26）——普通广播与有序广播

BroadcastReceiver是Android系统的四大组件之一，BroadcastReceiver是一个全局的系统级监听器，它拥有自己的独立进程。

我们来写一个最简单的广播接收过程

先在manifest中定义一个广播接受者

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.broadcasttest.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="com.example.broadcasttest.MyBroadCast">
            <intent-filter >
                <action android:name="com.meritit.action.MY_BROADCAST"/>
            </intent-filter>
        </receiver>
    </application>

public class MyBroadCast extends BroadcastReceiver{

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(context, "接收到的值为:" + intent.getStringExtra("msg"), Toast.LENGTH_SHORT).show();
	}

}

package com.example.broadcasttest;

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 {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		Button button = (Button) findViewById(R.id.button1);
		button.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				Intent intent = new Intent();
				intent.setAction("com.meritit.action.MY_BROADCAST");
				intent.putExtra("msg", "阳光小强");
				sendBroadcast(intent);
			}
		});
	}
}

上面的例子是一个普通的广播接受者，下面我们来修改一下代码看看有序的广播接受者

        <receiver 
            android:name="com.example.broadcasttest.MyBroadCast">
            <intent-filter android:priority="20">
                <action android:name="com.meritit.action.MY_BROADCAST"/>
            </intent-filter>
        </receiver>
        <receiver 
            android:name="com.example.broadcasttest.MyBroadCast2">
            <intent-filter android:priority="0" >
                <action android:name="com.meritit.action.MY_BROADCAST"/>
            </intent-filter>
        </receiver>

Intent intent = new Intent();
intent.setAction("com.meritit.action.MY_BROADCAST");
intent.putExtra("msg", "阳光小强");
sendOrderedBroadcast(intent, null);

public class MyBroadCast extends BroadcastReceiver{

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(context, "接收到的值为:" + intent.getStringExtra("msg"), Toast.LENGTH_SHORT).show();
		Bundle bundle = new Bundle();
		bundle.putString("msg2", "有序的广播");
		setResultExtras(bundle);
		
		//如果不想继续传播
		//abortBroadcast();
	}

}

public class MyBroadCast2 extends BroadcastReceiver{

	private static final String TAG = "broadcast";

	@Override
	public void onReceive(Context context, Intent intent) {
		Bundle bundle = getResultExtras(true);
		String msg = intent.getStringExtra("msg");
		String msg2 = bundle.getString("msg2");
		Log.i(TAG, msg);
		Log.i(TAG, msg2);
	}

}

除了接收用户发送的广播之外，BroadcastReceiver还有一个重要作用，就是接收系统广播。

详细请看：http://developer.android.com/reference/android/content/Intent.html

下面列出Android常见的广播。

• ACTION_TIME_TICK            
• ACTION_TIME_CHANGED       系统时间被改变
• ACTION_TIMEZONE_CHANGED     系统时区被改变
• ACTION_BOOT_COMPLETED        系统启动完成
• ACTION_PACKAGE_ADDED         系统添加包
• ACTION_PACKAGE_CHANGED       系统的包改变
• ACTION_PACKAGE_REMOVED        系统的包被删除
• ACTION_PACKAGE_RESTARTED      系统的包被重启
• ACTION_PACKAGE_DATA_CLEARED      系统的包数据被清空
• ACTION_UID_REMOVED
• ACTION_BATTERY_CHANGED  电池电量改变
• ACTION_POWER_CONNECTED          系统连接电池
• ACTION_POWER_DISCONNECTED       系统与电源断开
• ACTION_SHUTDOWN                系统被关闭

        <receiver 
            android:name="com.example.broadcasttest.MyBroadCast3">
            <intent-filter >
                <action android:name="android.intent.action.ACTION_BATTERY_LOW"/>
            </intent-filter>
        </receiver>

public class MyBroadCast3 extends BroadcastReceiver{

	@Override
	public void onReceive(Context context, Intent intent) {
		Bundle bundle = intent.getExtras();
		int current = bundle.getInt("level");
		int total = bundle.getInt("scale");
		if(current * 1.0 / total < 0.15){
			Toast.makeText(context, "电池电量过低，请尽快充电", Toast.LENGTH_LONG).show();
		}
	}

}

Android菜鸟的成长笔记（26）——普通广播与有序广播,,5-wow.com