Android 自定义广播

发送和接收定向广播

实现点击发送按钮，收到广播弹出Toast提示

1.新建一个广播MyBroadcastReceiver(直接用新建广播即可，自己创建java类的话不要忘记在manifest文件中进行注册)

public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d("test", "收到消息");
        Toast.makeText(context, "自定义广播接收器已经接收到消息", Toast.LENGTH_SHORT).show();
    }
}

自己创建的话，不要忘记注册

 <receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
</receiver>

2.主活动实现点击事件

Android对广播的要求越来越严，现在构造了intent后必须调用setComponet()方法，并且现在建立intent时不需要添加action参数，在manifest中注册时，也可以不指定action

public class MainActivity extends AppCompatActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d("test", "已发送");
                Intent intent = new Intent();
                //调用setComponent()方法
                intent.setComponent(new ComponentName(getPackageName(), "com.ccc.day09_mybroadcastreceiver.MyBroadcastReceiver"));
                sendBroadcast(intent);
            }
        });
    }
}

效果：

动态注册发送和接收不定向广播

1.新建一个项目程序，创建广播接收器

public class AnotherBroadCastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "收到不定向广播消息", Toast.LENGTH_LONG).show();
    }
}

主活动动态注册广播

public class MainActivity extends AppCompatActivity {
    //设置为静态可以解决重复注册的问题
    static AnotherBroadCastReceiver anotherBroadCastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("MyBroadcast");
        if (anotherBroadCastReceiver == null) {
            anotherBroadCastReceiver = new AnotherBroadCastReceiver();
            registerReceiver(anotherBroadCastReceiver, intentFilter); //动态注册
        }
    }
}

再去修改上面那个项目的主活动，让其发送不定向广播

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("MyBroadcast"); //发送不定向广播
                sendBroadcast(intent);
            }
        });
    }
}

将上面两个项目程序安装在同一个模拟器上，然后依次启动项目2，项目1，项目1点击发送，项目2可以接收
关闭项目2.会发现无法接收项目1发送的广播了,由此可见，动态注册的广播接收器只能在活动启动时接收广播

发送有序广播

发送有序广播用sendOrderedBroadcast()方法，两个参数，第一个是intent,第二个是和权限相关的字符串，填写null就行了
1
2
Intent intent = new Intent("MyBroadcast");
sendOrderedBroadcast(intent,null);

设置优先级大小动态用intentFilter.setPriority(1000); 静态使用android:priority="1000"，优先级高的可以先收到广播

//动态
IntentFilter intentFilter = new IntentFilter();
            intentFilter.addAction("MyBroadcast");
            // setPriority()设置权限大小
            intentFilter.setPriority(1000);
            anotherBroadCastReceiver = new AnotherBroadCastReceiver();
            registerReceiver(anotherBroadCastReceiver, intentFilter);

<!--静态-->
        <receiver
            android:name=".util.BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter android:priority="1000">  <!--在这里设置-->
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>

如果在onReceive()方法中调用了abortBroadcast()方法，那么广播有序广播传递到这里时会被截断，不再往下传

本地广播

前面我们发送和接收的广播都属于系统全局广播，容易引起安全性问题，因此Android引入了一套本地广播机制，使用这个机制发出的广播只能够在应用程序的内部进行传递，并且广播接收器也只能接收本应用程序发出的广播，这样来保证安全性

引入依赖库

1	implementation 'androidx.localbroadcastmanager:localbroadcastmanager:1.0.0'

主活动修改

 public class MainActivity extends AppCompatActivity {
     private IntentFilter intentFilter;
     private LocalReceiver localReceiver;
     private LocalBroadcastManager localBroadcastManger;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

//        获取实例
        localBroadcastManger = localBroadcastManger.getInstance(this);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("LocalBroadcast");
                // 发送广播
                localBroadcastManger.sendBroadcast(intent);
            }
        });
        
//        注册广播
        intentFilter = new IntentFilter();
        intentFilter.addAction("LocalBroadcast");
        localReceiver = new LocalReceiver();
        localBroadcastManger.registerReceiver(localReceiver, intentFilter);
    }

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

     private class LocalReceiver extends BroadcastReceiver {
         @Override
         public void onReceive(Context context, Intent intent) {
             Toast.makeText(context, "已接收到本地广播！",Toast.LENGTH_LONG).show();
         }
     }
 }