Android四大组件BroadcastReceiver
每个应用程序都可以对自己感兴趣的广播进行注册，这样程序可以接收到自己感兴趣的广播，这些广播可能来自系统或其他应用程序。
1、注册广播的两种方式：
动态注册：在代码中注册
//例如注册监听网络变化的广播
intentFilter = new IntentFilter();
intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
networkChangeReceiver = new NetworkChangeReceiver();
registerReceiver(networkChangeReceiver,intentFilter);
//在下面的本地广播中也有动态注册方法
静态注册:
在AndroidManifest.xml中注册
类似<activity>标签，android:name指定注册的广播接收器是哪一个，<intent-filter>中的<action>标签指定要接收的广播类型
<application> <receiver android:name=".BootCompleteReceiver"> <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED"/> </intent-filter> </receiver> </application>
2、广播的两种类型
<1>标准广播，一种完全异步执行的广播，广播发出后，广播接收器几乎会在同一时间接收到，无先后顺序。
<2>有序广播
一种同步执行的广播，在广播发出后，同一时刻只会有一个广播接收器接收到该广播，此时广播接收器是有先后顺序的，并且可以在<intent-filter android:priority = "">中指定优先级。并且优先级高的广播接收器还可以阻断其他广播接收器。
<receiver android:name=".AnotherBroadcastReceiver"> <intent-filter android:priority="100"> <action android:name="sunny.example.broadcastreceivermy.MY_BROADCAST"/> </intent-filter> </receiver>
package sunny.example.broadcastreceiverorderedbroadcast;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class AnotherBroadcastReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context,Intent intent){
Toast.makeText(context, "received in AnotherBroadcastReceiver", Toast.LENGTH_SHORT).show();
abortBroadcast();//阻断比其优先级低的广播
}
}
3、发送自定义广播
<1>发送标准广播
//MainActivity.java
package sunny.example.broadcastreceivermy;
import android.support.v7.app.ActionBarActivity;
import android.widget.Button;
import android.os.Bundle;
import android.view.View.OnClickListener;
import android.view.View;
import android.content.Intent;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button sendBroadcast = (Button)findViewById(R.id.sendBroadcast);
sendBroadcast.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v){
Intent intent = new Intent("sunny.example.broadcastreceivermy.MY_BROADCAST");
sendBroadcast(intent);
//sendOrderedBroadcast(intent,null);
}
});
}
}
//自定义广播接收器
package sunny.example.broadcastreceivermy;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class MyBroadcastReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context,Intent intent){
Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show();
//abortBroadcast();
}
}
//AndroidManifest.xml <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="sunny.example.broadcastreceivermy" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="17" /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <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=".MyBroadcastReceiver"> <intent-filter> <action android:name="sunny.example.broadcastreceivermy.MY_BROADCAST"/> </intent-filter> </receiver> </application> </manifest>
<2>发送有序广播
如上发送标准广播中的//sendOrderedBroadcast(intent,null);，不同工程中的两个广播接收器可以在其Manifest文件中设置优先级，使两个接收器接收广播有先后次序
3、使用本地广播
以上发送与接收广播都属于系统全局广播，任何应用程序都可以接收，有安全问题。Android中的本地广播机制可以使广播只在程序内部传递。本地广播只能动态注册。
package sunny.example.broadcastreceiverlocal;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.app.ActionBarActivity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.Button;
import android.widget.Toast;
import android.view.View.OnClickListener;
import android.content.Intent;
import android.view.View;
public class MainActivity extends ActionBarActivity {
private IntentFilter intentFilter;
private LocalReceiver localReceiver;
private LocalBroadcastManager localBroadcastManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//获取实例，以便下面调用LocalBroadcastManager的sendBroadcast()方法发送本地广播
localBroadcastManager = LocalBroadcastManager.getInstance(this);
Button localBroadcast = (Button)findViewById(R.id.localBroadcast);
localBroadcast.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v){
Intent intent = new Intent("sunny.example.broadcastreceiverlocal.LOCAL_BROADCAST");
localBroadcastManager.sendBroadcast(intent);//发送本地广播
}
});
//动态注册本地广播，本地广播是无法通过静态注册的方式接收的，静态广播是为了让程序在未启动的情况下也能收到广播，
//而发送本地广播时，程序肯定启动了
intentFilter = new IntentFilter();
intentFilter.addAction("sunny.example.broadcastreceiverlocal.LOCAL_BROADCAST");
localReceiver = new LocalReceiver();
localBroadcastManager.registerReceiver(localReceiver, intentFilter);//注册本地广播接收器
//以上全在onCreate方法里完成
}
@Override
public void onDestroy(){
super.onDestroy();
localBroadcastManager.unregisterReceiver(localReceiver);//取消注册
}
class LocalReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context,Intent intent){
Toast.makeText(context, "received local broadcast", Toast.LENGTH_LONG).show();
}
}
}