BroadcastReceiver

Broadcasting is a message mechanism. There are senders and receivers of messages. Broadcasting can realize inter-component communication and inter-process communication.

 

broadcast transmission

Global Broadcast Classification

1. Send a normal broadcast

Intent intent=new Intent("123");

sendBroadcast (intent);

 

2. Send an ordered broadcast:

Ordered broadcast is: broadcast receivers receive broadcasts in sequence according to their own priorities

priority:

<receiver android:name="ddd">

    <intent-filter android:priority="100"/>

</receiver>

The priority range is: Integer.MIN～Integer.MAX, the priority range of the IntentFIlter of the system registered Receiver is -1000～1000. When the priority is the same, code-registered receivers take precedence over statically-registered receivers, and broadcast receivers installed first are higher than those installed later.

setResult: The function passes the result to the next receiver, and the getResult function obtains the result returned by the last BroadcastReceiver,

abort: The function to let the system discard the broadcast and use the broadcast to no longer transmit to other BroadcastReceivers.

Intent intent=new Intent("123");

sendOrderedBroadcast (intent, null); 

 

3. Send sticky broadcast (deprecated in android 5.0/api 21, no longer recommended)

Sticky broadcast: This broadcast will exist until someone Context.removeStickyBroadcast removes it. The application that sends this broadcast must apply for the BROADCAST_STICKY permission.

Intent intent=new Intent("123");

sendStickyBroadcast(intent);

 

permission to broadcast

(Try not to send it to a third party, and restrict others from receiving it) The sender defines the authority, and the receiver applies for the authority.

sender

<permission android:name = "com.android.permission.RECV_XXX"/> 

sendBroadcast(intent,"com.android.permission.RECV_XXX");

接收者

<uses-permission android:name="com.android.permission.RECV_XXX"></uses-permission> 

 

（尽量不接第三方，限制别人发给我）接收者定义权限，发出者申请权限

接收者

<permission android:name = "com.android.permission.SEND_XXX"/> 

<receiver android:name=".XXXReceiver"   

          android:permission="com.android.permission.SEND_XXX">   

</receiver>  

发出者

<uses-permission android:name="com.android.permission.SEND_XXX"></uses-permission> 

sendBroadcaset(intent)

 

广播的标志位

intent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);

从3.1开始广播默认带这个默认带这个标志位。是说，此广播不发给没有运行的应用

intent.addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES);

此广播发给没有运行的广播。

 

应用内广播

Intent intent = new Intent();

LocalBroadcastManager.getInstance(this).sendBroadcast(intent);

 

增强广播的安全性：

1.不发给第三方，发送广播时，指定特定广播接收器所在的包名，这样指定包中的接收器才会收到，具体是通过intent.setPackage(packageName)指定在。

2.不接受第三方，<receiver android:name="ddd" android:exported="false">将exported属性人为设置成false默认是true，不接收第三方匹配的广播。

3.让广播带上权限认证permission。

4.使用应用内广播机制,即安全又高效。

 

广播的接收

BroadcastReceiver

//定义
public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        String name = intent.getStringExtra("name");
    }
}

// 注册
// 静态注册
<receiver
android:exported=["true" | "false"]
android:permission="string" >
</receiver>

<receiver android:name=".MyBroadcastReceiver" >
    <intent-filter>
        <action android:name="BROADCAST_ACTION" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED" />
    </intent-filter>
</receiver>

// 动态注册
mBroadcastReceiver = new MyBroadcastReceiver();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BROADCAST_ACTION);
registerReceiver(mBroadcastReceiver, intentFilter);

// 解注册
unregisterReceiver(mBroadcastReceiver);