3 Broadcast

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3 Broadcast

动态注册监听网络变化

  • 例子

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    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
            intentFilter = new IntentFilter();
            intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
            netWorkChangeReceiver = new NetWorkChangeReceiver();
    //        registerReceiver
            registerReceiver(netWorkChangeReceiver, intentFilter);
        }

        @Override
        protected void onDestroy() {
            super.onDestroy();
    //        unregisterReceiver
            unregisterReceiver(netWorkChangeReceiver);
        }
    //   广播接收器
        class NetWorkChangeReceiver extends BroadcastReceiver{
            @Override
            public void onReceive(Context context, Intent intent) {
    //          ConnectivityManager
                ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(context.CONNECTIVITY_SERVICE);
                NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
                if(networkInfo != null && networkInfo.isAvailable()){
                    Toast.makeText(context, "Network Available", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(context, "Network unavailable", Toast.LENGTH_SHORT).show();
                }
            }
        }
    }

  • 加入权限声明

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

    发送自定义广播

    发送标准广播

  • 自定义广播接收器

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    public class MyBroadcastReceiver extends BroadcastReceiver {

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

  • AndroidManifest.xml修改广播接收器

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    <receiver android:name=".MyBroadcastReceiver"
                android:enabled="true"
                android:exported="true">
                <intent-filter>
                    <action android:name="com.example.broadcasttest.MY_BROADCAST"/>
                </intent-filter>
            </receiver>

  • MainActivity

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    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            Button button = findViewById(R.id.button);
            button.setOnClickListener(v -> {
                Intent intent = new Intent("com.example.broadcasttest.MY_BROADCAST");
                intent.setPackage("com.example.broadcasttest"); // 一定要设置Package，否则无法启动BroadcastReceiver
                sendBroadcast(intent);
            });
        }

    发送有序广播

  • 将MainActivity修改：

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    Intent intent = new Intent("com.example.broadcasttest.MY_ORDDER_BROADCAST0");
                intent.setPackage("com.example.broadcasttest"); // 一定要设置Package，否则无法启动BroadcastReceiver
    //            sendBroadcast(intent);
                sendOrderedBroadcast(intent, null);

  • 新建Receiver

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    public class MyReceiver0 extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "receiver in MyReceiver0", Toast.LENGTH_SHORT).show();
        }
    }

  • 在Manifest.xml部署，优先级20

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    <receiver android:name=".MyReceiver0">
                <intent-filter android:priority="20">
                    <action android:name="com.example.broadcasttest.MY_ORDDER_BROADCAST0"/>
                </intent-filter>
            </receiver>

  • 在onReceive()添加 abortBroadcast();取消广播，下一个接收器不会触发

  • 传递数据给下一个接收器
    上一个接收器：

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    Bundle bundle = new Bundle();
            bundle.putString("first", "this is a message");
            setResultExtras(bundle);

    获取上一个接收器存入的数据

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    Bundle bundle = getResultExtras(true);
            String first = bundle.getString("first");
            Toast.makeText(context, "receiver in MyReceiver1\n"+first, Toast.LENGTH_SHORT).show();