@Allen-miss 2017-05-18T11:47:38.000000Z 字数 4713 阅读 709

全局大喇叭——详解广播机制

Broadcast

标准广播

是一种完全一部执行的广播，在广播发出之后，所有的广播接收器几乎都会在同一时刻接收到这条广播消息，因此她们之间没有任何的先后顺序可言。这种广播的效率会比较高，但同时也就意味着它是无法被拦截的。流程图如上：

无序广播

则是一种同步执行的广播，在广播发出之后，同一时刻只有一个广播接收器内容接收到这条广播消息，当这个广播接收器中的逻辑执行完毕后，广播才会继续传递。所以此时的广播接收器是有先后顺序的，优先级高的广播接收器就可以先收到广播，并且前面的广播接收器还可以拦截正在传递的广播，这样后面的广播接收器就无法收到广播消息了。流程图如上
动态注册

  public class MainActivity extends AppCompatActivity {
    private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }
    class NetworkChangeReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            if(networkInfo!=null&&networkInfo.isAvailable()){
                Toast.makeText(context,"网络可用",Toast.LENGTH_LONG).show();
            }else{
                Toast.makeText(context,"网络不可用",Toast.LENGTH_LONG).show();
            }
        }
    }
    //在onDestroy中注销广播
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
}

AndroidMainifest.xml加入权限
<uses-permission android:name="android.permission.access_network_state" />

静态注册
动态注册的广播接收器可以自由的控制注册与注销，在灵活性方面有很大的优势，但是它也存在着一个缺点，即必须要在程序启动之后才能接受到广播，因为注册逻辑是写在onCreate()中，所以在未启动的情况下接受广播就可以使用我们的 静态注册方式

public class BootCompleteReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"Boot Complete",Toast.LENGTH_LONG).show();
    }
}

AndroidMainifest.xml加入权限

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>

不要在onReceive中添加过多的逻辑或者进行任何耗时的操作，在广播接收器中不允许开线程，当onReceive()运行了较长的时间而没有结束时，程序就会报错。因此广播接受者跟多的扮演的是一种打开程序其他组件的角色，比如创建一条状态通知栏，或者启动一个服务等。

发送自定义广播
1.发送标准广播

//自定义一个广播
public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"receiver in MyBroadcastReceiver",Toast.LENGTH_SHORT).show();
    }
}

//在清单文件注册action
<receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="com.example.seele.broadcasttest.MY_BROADCAST"/>
            </intent-filter>
        </receiver>

//在activity发送广播
 TextView SendBroadCast = (TextView) findViewById(R.id.send_broadcast);
        SendBroadCast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.example.seele.broadcasttest.MY_BROADCAST");
                sendBroadcast(intent);
            }
        });

2.发送有序广播

 SendBroadCast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.example.seele.broadcasttest.MY_BROADCAST");
//                sendBroadcast(intent);
                //发送有序广播第一个参数是Intent，第二个参数是与权限相关的字符串，这里传入的是null
                sendOrderedBroadcast(intent,null);
            }
        });

设置广播的优先级

<receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <!--设置广播的优先级android:priority="100"-->
            <intent-filter android:priority="100">
                <action android:name="com.example.seele.broadcasttest.MY_BROADCAST"/>
            </intent-filter>
        </receiver>

拦截广播

public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"receiver in MyBroadcastReceiver",Toast.LENGTH_SHORT).show();
        //拦截广播
        abortBroadcast();
    }
}

abortBroadcast();就是拦截广播的方法，拦截后别的广播就无法接收；

使用本地广播

public class MainActivity extends AppCompatActivity {
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
    localBroadcastManager = LocalBroadcastManager.getInstance(this);
    TextView SendBroadCast = (TextView) findViewById(R.id.send_broadcast);
    SendBroadCast.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent("com.example.broadcast,LOCAL_BROADCAST");
            //发送本地广播
            localBroadcastManager.sendBroadcast(intent);
        }
    });
    intentFilter = new IntentFilter();
    intentFilter.addAction("com.example.broadcast,LOCAL_BROADCAST");
    localReceiver = new LocalReceiver();
    //注册本地广播监听
    registerReceiver(localReceiver,intentFilter);
}
class LocalReceiver extends BroadcastReceiver{
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"receiver local broadcast",Toast.LENGTH_SHORT).show();
    }
}

代码大部分一样，不一样的就是LocalBroadcastManager本地广播管理器

广播实践
源码下载

全局大喇叭——详解广播机制

内容目录