無法從同一活動中更改片段內的TextView的文本

Question

我正在嘗試更改TextView以在Fragment中提供藍牙連接的狀態，但是在msgReceived.setText(string)時似乎什么也沒發生。 我將如何去做呢？ 這是我的Fragment Java文件：

package dleedesign.dubcommunicationstestapp;

import android.app.Fragment;
import android.bluetooth.BluetoothAdapter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

public class SecondFragment extends Fragment implements View.OnClickListener {

View myView;

public final String TAG = "Main";
private Bluetooth bt;
public Button sendCommand;
public TextView msgReceived;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    myView = inflater.inflate(R.layout.second_layout, container, false);

    sendCommand = (Button) inflater.inflate(R.layout.second_layout, container, false).findViewById(R.id.sendCommand);
    msgReceived = (TextView) inflater.inflate(R.layout.second_layout, container, false).findViewById(R.id.msgReceived);
    msgReceived.setText("Ready to connect");

    bt = new Bluetooth(new MainActivity(), mHandler);
    connectService();

    return myView;
}

@Override
public void onClick(View v)
{
    connectService();
}

public void connectService()
{
    try {
        msgReceived.setText("Connecting...");
        BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
        if(btAdapter.isEnabled())
        {
            bt.start();
            bt.connectDevice("HC-06");
            Log.d(TAG, "Btservice started- listening");
            msgReceived.setText("Connected!");
        }
        else
        {
            Log.w(TAG, "Btservice started - bluetooth is not enabled");
            msgReceived.setText("Bluetooth not enabled");
        }
    } catch (Exception e) {
        Log.e(TAG, "Unable to start bluetooth", e);
        msgReceived.setText("Unable to connect: " + e);
    }
}

private final Handler mHandler = new Handler()
{
    @Override
    public void handleMessage(Message msg)
    {
        switch (msg.what)
        {
            case Bluetooth.MESSAGE_STATE_CHANGE:
                Log.d(TAG, "MESSAGE_STATE_CHANGE: " + msg.arg1);
                break;
            case Bluetooth.MESSAGE_WRITE:
                Log.d(TAG, "MESSAGE_WRITE");
                break;
            case Bluetooth.MESSAGE_READ:
                Log.d(TAG, "MESSAGE_READ");
                break;
            case Bluetooth.MESSAGE_DEVICE_NAME:
                Log.d(TAG, "MESSAGE_DEVICE_NAME " + msg);
                break;
            case Bluetooth.MESSAGE_TOAST:
                Log.d(TAG, "MESSAGE_TOAST " + msg);
                break;
        }
    }
};

}

編輯：這是當我選擇SecondFragment時吐出的LogCat消息：

dleedesign.dubcommunicationstestapp D/BluetoothService: Bounded device 40:EF:4C:C2:A9:32
dleedesign.dubcommunicationstestapp D/BluetoothService: Bounded device 98:D3:31:70:80:C5
dleedesign.dubcommunicationstestapp D/BluetoothService: start
dleedesign.dubcommunicationstestapp D/BluetoothService: setState() 0 -> 1
dleedesign.dubcommunicationstestapp W/BluetoothAdapter: getBluetoothService() called with no BluetoothManagerCallback
dleedesign.dubcommunicationstestapp D/BluetoothService: Socket Type: nullBEGIN mAcceptThreadThread[Thread-20627,5,main]
dleedesign.dubcommunicationstestapp D/BluetoothService: connect to: 98:D3:31:70:80:C5
dleedesign.dubcommunicationstestapp D/BluetoothService: setState() 1 -> 2
dleedesign.dubcommunicationstestapp D/Main: Btservice started- listening
dleedesign.dubcommunicationstestapp I/BluetoothService: BEGIN mConnectThread SocketType:null
dleedesign.dubcommunicationstestapp W/BluetoothAdapter: getBluetoothService() called with no BluetoothManagerCallback
dleedesign.dubcommunicationstestapp D/Main: MESSAGE_STATE_CHANGE: 1
dleedesign.dubcommunicationstestapp D/Main: MESSAGE_STATE_CHANGE: 2
dleedesign.dubcommunicationstestapp E/BluetoothService: Unable to connect socket 
                                                                                       java.io.IOException: read failed, socket might closed or timeout, read ret: -1
                                                                                           at android.bluetooth.BluetoothSocket.readAll(BluetoothSocket.java:517)
                                                                                           at android.bluetooth.BluetoothSocket.readInt(BluetoothSocket.java:528)
                                                                                           at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:320)
                                                                                           at dleedesign.dubcommunicationstestapp.Bluetooth$ConnectThread.run(Bluetooth.java:408)
dleedesign.dubcommunicationstestapp D/BluetoothService: start
dleedesign.dubcommunicationstestapp D/BluetoothService: setState() 2 -> 1
dleedesign.dubcommunicationstestapp D/Main: MESSAGE_TOAST { when=-15ms what=5 target=dleedesign.dubcommunicationstestapp.SecondFragment$1 }
dleedesign.dubcommunicationstestapp D/Main: MESSAGE_STATE_CHANGE: 1

Answer 1

發生的事情是，您每次嘗試執行findViewById時都使用給定的布局findViewById視圖，然后將其強制轉換為TextView。 這是在另一個視圖上調用findViewById ，然后返回。 您應該像在第一行中那樣首先為布局充氣

myview = inflater.inflate....

接着，

msgReceived = (TextView) myView.findViewById(R.id.msgReceived);

（與您嘗試使用的任何其他TextView，Button等相同）

Answer 2

嘗試

msgReceived = (TextView) myView.findViewById(R.id.msgReceived);