如何解决这个错误（这个类应该提供一个默认的构造函数）？

错误：错误：这个类应该提供一个默认的构造函数（公共构造不带任何参数）如何解决这个错误（这个类应该提供一个默认的构造函数）？

我创建WiFi直接广播接收器。它从签名的apk生成时间获得错误。我附上我的代码。此类可用于接收相同的路由器设备列表。并获得离线连接。

public class WiFiDirectBroadcastReceiver extends BroadcastReceiver { 
     private WifiP2pManager manager; 
     private WifiP2pManager.Channel channel; 
     private MainActivity activity; 
     String TAG = "WiFiDirectBroadcastReceiver"; 
     /** 
    //  * @param manager WifiP2pManager system service 
    //  * @param channel Wifi p2p channel 
    //  * @param activity activity associated with the receiver 
     */ 


     public WiFiDirectBroadcastReceiver(WifiP2pManager manager, WifiP2pManager.Channel channel,MainActivity activity) { 
      super(); 
      this.manager = manager; 
      this.channel = channel; 
      this.activity = activity; 
     } 

     /* 
     * (non-Javadoc)s 
     * @see android.content.BroadcastReceiver#onReceive(android.content.Context, 
     * android.content.Intent) 
     */ 

     @Override 
     public void onReceive(Context context, Intent intent){ 
      String action = intent.getAction(); 
      Log.d(TAG, "P2P action - " + action); 
      if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) { 
       // UI update to indicate wifi p2p status. 
       int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1); 
       if(state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) { 
        // Wifi Direct mode is enabled 
        activity.setIsWifiP2pEnabled(true); 
       }else{ 
        activity.setIsWifiP2pEnabled(false); 
        activity.resetData(); 
       } 
       Log.d(TAG, "P2P state changed - " + state); 
      } else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)){ 
       // request available peers from the wifi p2p manager. This is an 
       // asynchronous call and the calling activity is notified with a 
       // callback on PeerListListener.onPeersAvailable() 
       if(manager != null) { 
        manager.requestPeers(channel, (WifiP2pManager.PeerListListener) activity.getFragmentManager().findFragmentById(R.id.frag_list)); 
       } 
       Log.d(TAG, "P2P peers changed"); 

      } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)){ 
       if(manager == null) { 
        return; 
       } 
       NetworkInfo networkInfo = (NetworkInfo) intent.getParcelableExtra(WifiP2pManager.EXTRA_NETWORK_INFO); 
       if(networkInfo.isConnected()) { 
        // we are connected with the other device, request connection 
        manager.requestConnectionInfo(channel,activity); 

       }else{ 
        // It's a disconnect 
        activity.resetData(); 
       } 
      } else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)){ 
       DeviceListFragment fragment = (DeviceListFragment) activity.getFragmentManager().findFragmentById(R.id.frag_list); 
       if(fragment != null) { 
        fragment.updateThisDevice((WifiP2pDevice) intent.getParcelableExtra(WifiP2pManager.EXTRA_WIFI_P2P_DEVICE)); 
       } 
      } 
     } 
    }

来源

2017-07-01 Vishnu Rajan

你有没有为'BroadcastReceiver'类定义的构造函数？ –

@DarshanMehta我没有使用这些类 –

是的，你做了。你扩展它。它有一个默认的构造函数吗？显然不是。 – EJP

-3

添加一个没有参数的公共构造函数。构造函数有参数。添加另一个没有参数的构造函数只是一个空构造函数。

public WiFiDirectBroadcastReceiver(){ 

    }

来源

2017-07-01 07:53:55

这正是他已经拥有的。 – EJP

类BroadcastReceiver没有默认的构造函数，但你的WiFiDirectBroadcastReceiver类在默认构造方法WiFiDirectBroadcastReceiver()隐式调用它：

public WiFiDirectBroadcastReceiver() { 
    // implicit super() call here, calls BroadcastReceiver(), which doesn't exist 
}

您需要可以致电BroadcastReceiver现有构造的一个通过super(...)，使用任何适当的参数，或提供默认的参数。

来源

2017-07-01 08:00:23 EJP

如何解决这个错误（这个类应该提供一个默认的构造函数）？

回答

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