Broadcast Reveiver作用

Broadcast Reveiver作用以及为何要引入（用来接收系统以及自定义消息的）

在系统内通知和判定执行状态

1，系统执行状态，开机了，TF卡插拔，准备关机，电量低了，

2，自定义执行状态，发消息提示更新界面

点击后会打log：顺序是testbroadcast2，testbroadcast

activity代码-----

package com.paoyx;
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 BroadcastActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //设置按钮
        Button button = new Button(this);
        button.setText("send message");
        setContentView(button);
        button.setOnClickListener(new OnClickListener() {
			//按钮点击事件
			public void onClick(View v) {
				//设置intent传递数值 
				Intent intent = new Intent();
				intent.setAction("com.paoyx.broadcast");
				sendBroadcast(intent);
			}
		});
    }
}

2个receiver代码---

package com.paoyx;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyReceiver extends BroadcastReceiver {
	public void onReceive(Context context, Intent intent) {
		// TODO Auto-generated method stub
		if (intent.getAction().equals("com.paoyx.broadcast")) {
			Log.i("log","testbroadcast");
		}
	}
}

package com.paoyx;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyReceiver2 extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		// TODO Auto-generated method stub
		if (intent.getAction().equals("com.paoyx.broadcast")) {
			Log.i("log","testbroadcast2");
		}
	}
}

menifest注册监听代码---

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.paoyx"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-sdk android:minSdkVersion="8" />
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".BroadcastActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        //注册receiver，并设置优先级别，数值大的优先，所以先启动MyReceiver2
        <receiver android:name=".MyReceiver">
            <intent-filter android:priority="1">
                <action android:name="com.paoyx.broadcast"/>
            </intent-filter>
        </receiver>
         <receiver android:name=".MyReceiver2">
            <intent-filter android:priority="2">
                <action android:name="com.paoyx.broadcast"/>
            </intent-filter>
        </receiver>
    </application>
</manifest>