如何在 Android 中使用 BroadcastReceiver onReceive 更新 UI？

Question

我想根据 Java 中的 Android 应用程序中的 WiFi 状态更新 UI。 我无法更新 UI 以显示新字符串。 请帮我。

这是我的代码

public class MainActivity extends AppCompatActivity {
    IntentFilter intentFilter = new IntentFilter();

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

        intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(new NetworkConnectionReceiver(), intentFilter);

        TextView displayStatus = findViewById(R.id.displayStateTextView);
    }
}

class NetworkConnectionReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        Log.i("MyReceiver", Boolean.toString(wifiManager.isWifiEnabled()));
    }
}

Answer 1

您可以使用interface来完成

interface WifiStateListener{
  void onStateChanged(Boolean enabled);
}

然后添加一个构造函数将WifiStateListener传递给BroadcastReceiver

class NetworkConnectionReceiver extends BroadcastReceiver {
    private WifiStateListener mWifiStateListener;
    
    public NetworkConnectionReceiver(WifiStateListener wifistateListener){
        mWifiStateListener = wifistateListener;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        if(mWifiStateListener != null){
            mWifiStateListener.onStateChanged(wifiManager.isWifiEnabled());
        }
        Log.i("MyReceiver", Boolean.toString(wifiManager.isWifiEnabled()));
    }
}

而在Activity中，注册receiver的时候可以通过interface

registerReceiver(new NetworkConnectionReceiver(enabled -> {
    //do based on wifi state change
}), intentFilter);

其他选项是使用 EventBus、Observables 等

Answer 2

使用此代码：

public class MainActivity extends AppCompatActivity {
...

    BroadcastReceiver br = new BroadcastReceiver(){
        @Override
        public void onReceive( Context context, Intent intent ){
           //update UI here directly
           View view = findViewById( R.id.example );
        }
    };

    @Override
    protected void onResume(){
        super.onResume();
        // Check state here
        ...
        IntentFilter filter = new IntentFilter();
        filter.addAction( ConnectivityManager.CONNECTIVITY_ACTION );
        registerReceiver( br, filter);
    }

    @Override
    protected void onPause(){
        super.onPause();
        unregisterReceiver( br );
    }

...
}

Answer 3

您可以使用 LocalBroadCastManager。

首先在 onResume 中使用 LocalBroadCastManager 广播的活动寄存器中写入 broadCastReceiver 取消注册在 onPause 中使用 LocalBroadCastManager 广播的广播，然后写入互联网连接广播并调用您在活动中注册的 LocalBroadCastManager

    private BroadcastReceiver broadCastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
           if(intent.getAction() == "local_broadcast_update_UI"){
              updateUI()
           }
        }
    };

  @Override
  protected void onResume(){
     super.onResume();
     LocalBroadcastManager.getInstance(this).registerReceiver( broadCastReceiver, new 
     IntentFilter("local_broadcast_update_UI"));   
  }

  @Override
  protected void onPause(){
     super.onPause();
  LocalBroadcastManager.getInstance(this).unregisterReceiver("local_broadcast_update_UI");
  }

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {
        final ConnectivityManager connMgr = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);

        final android.net.NetworkInfo wifi = connMgr
                .getNetworkInfo(ConnectivityManager.TYPE_WIFI);

        final android.net.NetworkInfo mobile = connMgr
                .getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

        if (wifi.isAvailable() || mobile.isAvailable()) {
           LocalBroadcastManager.getInstance(context).sendBroadcast(new 
           Intent("local_broadcast_update_UI"));
        }
    }
}