java - 两次启动另一个 Activity 时，线程不更新 textview

Question

我有一个通过蓝牙与 Arduino 连接的应用程序。该应用程序正常，但是当我开始另一个 Activity 时，我的 textview 没有更新。 我有一个读取蓝牙数据的 Thread，还有一个刷新 textview 的计时器。

如果您第一次启动 Activity 并且我返回主 Activity textview 刷新正常，但是如果我在返回主 Activity 时再次启动 Activity textview 则不会'刷新。

帮助!!!

创建时:

bluetoothIn = new Handler() {
    public void handleMessage(android.os.Message msg) {
        if (msg.what == handlerState) {
            String readMessage = (String) msg.obj;
            MetrosRecorridos += ((Calibracion / Imanes / 1000) * readMessage.length()) * Sentido;
        }
    }
};

在连接蓝牙的按钮中:

mConnectedThread = new ConnectedThread(mmSocket);
mConnectedThread.start();

线程:

private class ConnectedThread extends Thread {
    private final InputStream mmInStream;
    private final OutputStream mmOutStream;

    //creation of the connect thread
    public ConnectedThread(BluetoothSocket socket) {
        InputStream tmpIn = null;
        OutputStream tmpOut = null;
        try {
            //Create I/O streams for connection
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) { }

        mmInStream = tmpIn;
        mmOutStream = tmpOut;
    }

    public void run() {
        byte[] buffer = new byte[256];
        int bytes;

        // Keep looping to listen for received messages
        while (true) {
            try {
                bytes = mmInStream.read(buffer);            //read bytes from input buffer
                String readMessage = new String(buffer, 0, bytes);
                // Send the obtained bytes to the UI Activity via handler
                bluetoothIn.obtainMessage(handlerState, bytes, -1, readMessage).sendToTarget();
            } catch (IOException e) {
                txtConectado = "Sonda: Desconectado";
                //Toast.makeText(getBaseContext(), "Fallo de conexión", Toast.LENGTH_LONG).show();
                break;
            }
        }
    }
    //write method
    public void write(String input) {
        byte[] msgBuffer = input.getBytes();           //converts entered String into bytes
        try {
            mmOutStream.write(msgBuffer);                //write bytes over BT connection via outstream
        } catch (IOException e) {
            //if you cannot write, close the application
            Toast.makeText(getBaseContext(), "Connection Failure", Toast.LENGTH_LONG).show();
            finish();

        }
    }
}

刷新textview的Timer:

public void startTimer(){
    t = new Timer();
    task = new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    TextView t;
                    t=(TextView)findViewById(R.id.txtA);
                    t.setText(""+MetrosRecorridos);
                }
            });
        }
    };
    t.scheduleAtFixedRate(task, 0, 10);
}

以及我调用另一个 Activity 时的代码:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.opc_ajustes) {
        bluetoothIn.removeCallbacksAndMessages(null);
        Intent i = new Intent(getApplicationContext(), AjustesActivity.class);
        i.putExtra("distancia", Math.floor(MetrosRecorridos / 10));
        startActivityForResult(i, 3);
        return true;
    }
}

谢谢!!!

Answer 1

我无法清楚地理解问题。但我认为线程在暂停 Activity 时停止。在那种情况下，您应该为此目的创建一个单例计时器或将计时器用于应用程序类。在 onResume 方法中的 Activity 中，启动另一个线程来刷新 Textview。希望对您有所帮助

Global Timer in android