系统开始重启会发送开机重启广播，电量低的时候会发送电量低的广播，广播注册有2种:系统说明文件xml注册和Java代码注册，前者是静态注册(全局注册)后者是动态注册（依赖于当时组建，组件销毁就收不到广播了）。

package com.sxt.day07_04;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;

public class MainActivity extends Activity {
    MyReceiver2 mReceiver;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        registerReceiver();
        setListener();
    }

    private void setListener() {
        sendBroadcast1ClickListener();
        sendBroadcast2ClickListener();
    }

    private void sendBroadcast2ClickListener() {
        findViewById(R.id.btnSendBroadcast_2).setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                Intent intent=new Intent("com.sxt.day07_04.MyReceiver2");//
                intent.putExtra("key", "hello android!");
                sendBroadcast(intent);
            }
        });
    }

    private void sendBroadcast1ClickListener() {
        findViewById(R.id.btnSendBroadcast_1).setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                Intent intent=new Intent("com.sxt.day07_04.MyReceiver1");
                intent.putExtra("key", "hello java!");
                sendBroadcast(intent);
            }
        });
    }

    //java类注册的广播接收者
    private void registerReceiver() {
        mReceiver=new MyReceiver2();
        IntentFilter filter=new IntentFilter();//意图过滤器
        filter.addAction("com.sxt.day07_04.MyReceiver2");//广播的字符串
        registerReceiver(mReceiver, filter);
    }

    class MyReceiver2 extends BroadcastReceiver{
        @Override
        //收到广播执行的方法
        public void onReceive(Context context, Intent intent) {
            Log.i("main","MyReceiver2.onReceive():"+intent.getStringExtra("key"));
        }
    }
    
    @Override
    protected void onDestroy() {
        super.onDestroy();
        //Activity退出的时候取消广播的注册，释放资源.
        unregisterReceiver(mReceiver);
    }
}

package com.sxt.day07_04;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class MyReceiver1 extends BroadcastReceiver {

    @Override
    //收到广播后执行的方法
    public void onReceive(Context context, Intent intent) {
        Log.i("main","MyReceiver1.onReceive():"+intent.getStringExtra("key"));
    }

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sxt.day07_04"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.sxt.day07_04.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>
        注册全局广播接收者
        <receiver android:name="com.sxt.day07_04.MyReceiver1">   广播接收者类
            <intent-filter>
                <action android:name="com.sxt.day07_04.MyReceiver1"/>   广播的字符串是这个就可以接收广播
            </intent-filter>
        </receiver>
    </application>

</manifest>