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>广播接收者
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();
}
}向广播接收者发送广播
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);
}
});
}
}运行结果：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>两个广播接收者设置了优先级，上面的优先级比下面的高
Intent intent = new Intent();
intent.setAction("com.meritit.action.MY_BROADCAST");
intent.putExtra("msg", "阳光小强");
sendOrderedBroadcast(intent, null);发送有序广播，注意是sendOrderedBroadcast
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();
}
}优先级高的MyBroadCast先接收到，有序广播接收者可以添加新数据给下个等级的接受者。这种形式就有点像拦截器。
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);
}
}
最后输出结果：
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_TICKACTION_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_REMOVEDACTION_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();
}
}
}