Android四大组件之BroadcastReceiver（广播

1.广播接收者是什么：就是用来接收Android系统和自定义的广播的一个Android组建，是四大组件之一，按注册方式分为动态广播和静态广播，按接收的顺序分为有序广播和无序广播。
注意不要在onReceiver不能进行过多的逻辑和任何的耗时操作，在广播接收者中是不允许开启线程的，当onReceiver运行过长时间而没有结束，程序机会报错。所以广播接收者一般用来打开其他的组件。

2.动态注册广播：和隐式启动activity非常的类似

public class BroadcastReceiverDynamicActivity extends AppCompatActivity {

    private IntentFilter filter;
    private NetworkChangeReceiver networkChangeReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_broadcast_receiver_dynamic);
        filter = new IntentFilter();
        filter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver, filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }

    class NetworkChangeReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo info=connectivityManager.getActiveNetworkInfo();
            if (info!=null&&info.isAvailable()){
                Toast.makeText(BroadcastReceiverDynamicActivity.this,"网络连上了",Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(BroadcastReceiverDynamicActivity.this,"网络断开了",Toast.LENGTH_SHORT).show();
            }

        }
    }
}

3.静态注册广播：直接在AndroidManifest.xml文件中注册并添加对应的action,以及权限。

public class BootBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"开机了",Toast.LENGTH_SHORT).show();
    }
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.firstlinecode">

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

    <application
        ...
        <receiver
            android:name=".fourComponents.broadcastReceiver.BootBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>
    </application>

</manifest>

4.自定义广播：定义一个广播接收者，action自定义，然后在activity中sendBroadcast。

 Button button= (Button) findViewById(R.id.triggerBroadcastReceiver);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent("com.firstlinecode.fourComponents.broadcastReceiver.MyBroadcastReceiver");
                sendBroadcast(intent);
            }
        });

public class MyBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"接收到了自定义的广播",Toast.LENGTH_SHORT).show();
    }
}

<receiver
            android:name=".fourComponents.broadcastReceiver.MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="com.firstlinecode.fourComponents.broadcastReceiver.MyBroadcastReceiver" />
            </intent-filter>
        </receiver>

发送有序广播

 Intent intent=new Intent("com.firstlinecode.fourComponents.broadcastReceiver.MyBroadcastReceiver");
//                sendBroadcast(intent);
                sendOrderedBroadcast(intent,null);

设置广播接收者优先级

<intent-filter android:priority="100">
                <action android:name="com.firstlinecode.fourComponents.broadcastReceiver.MyBroadcastReceiver" />
            </intent-filter>

高优先级的广播接收者可以截断有序广播

public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"接收到了自定义的广播",Toast.LENGTH_SHORT).show();
        abortBroadcast();
    }

5.本地广播：就是使用了localBroadcastManager来动态注册和发送的广播。

public class BroadcastReceiverLocalActivity extends AppCompatActivity {

    private LocalBroadcastManager localBroadcastManager;
    private LocalReceiver localReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_broadcast_receiver_local);
        localBroadcastManager = LocalBroadcastManager.getInstance(this);
        Button button= (Button) findViewById(R.id.localReceiver);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent("com.firstlinecode.fourComponents.broadcastReceiver.LocalBroadcastReceiver");
                localBroadcastManager.sendBroadcast(intent);
            }
        });
        IntentFilter filter=new IntentFilter();
        filter.addAction("com.firstlinecode.fourComponents.broadcastReceiver.LocalBroadcastReceiver");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver,filter);


    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);
    }

    class LocalReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"接收到了本地广播",Toast.LENGTH_SHORT).show();
        }
    }