Android Studio: Textansicht in Bluetooth Chat-Beispiel

Question

Ich verwende Bluetooth Chat-Beispiel, um Sensordaten von meinem Arduino auf meinem Android-Gerät zu empfangen. Ich versuche, die eingehende Nachricht an eine TextView anzuzeigen. Hier ist mein Code für die Bluetooth Chat Fragment Klasse

package com.example.android.bluetoothchat; 

import android.app.ActionBar; 
import android.app.Activity; 
import android.bluetooth.BluetoothAdapter; 
import android.bluetooth.BluetoothDevice; 
import android.content.Intent; 
import android.os.Bundle; 
import android.os.Handler; 
import android.os.Message; 
import android.support.annotation.Nullable; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.view.KeyEvent; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuInflater; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.view.inputmethod.EditorInfo; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ListView; 
import android.widget.TextView; 
import android.widget.Toast; 

import com.example.android.common.logger.Log; 

/** 
* This fragment controls Bluetooth to communicate with other devices. 
*/ 
public class BluetoothChatFragment extends Fragment { 


private static final String TAG = "BluetoothChatFragment"; 

// Intent request codes 
private static final int REQUEST_CONNECT_DEVICE_SECURE = 1; 
private static final int REQUEST_CONNECT_DEVICE_INSECURE = 2; 
private static final int REQUEST_ENABLE_BT = 3; 

// Layout Views 
private ListView mConversationView; 
private EditText mOutEditText; 
private Button mSendButton; 
private TextView display; 

/** 
* Name of the connected device 
*/ 
private String mConnectedDeviceName = null; 

/** 
* Array adapter for the conversation thread 
*/ 
private ArrayAdapter<String> mConversationArrayAdapter; 

/** 
* String buffer for outgoing messages 
*/ 
private StringBuffer mOutStringBuffer; 

/** 
* Local Bluetooth adapter 
*/ 
private BluetoothAdapter mBluetoothAdapter = null; 

/** 
* Member object for the chat services 
*/ 
private BluetoothChatService mChatService = null; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setHasOptionsMenu(true); 
    // Get local Bluetooth adapter 
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); 

    // If the adapter is null, then Bluetooth is not supported 
    if (mBluetoothAdapter == null) { 
     FragmentActivity activity = getActivity(); 
     Toast.makeText(activity, "Bluetooth is not available", Toast.LENGTH_LONG).show(); 
     activity.finish(); 
    } 
} 


@Override 
public void onStart() { 
    super.onStart(); 
    // If BT is not on, request that it be enabled. 
    // setupChat() will then be called during onActivityResult 
    if (!mBluetoothAdapter.isEnabled()) { 
     Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
     startActivityForResult(enableIntent, REQUEST_ENABLE_BT); 
     // Otherwise, setup the chat session 
    } else if (mChatService == null) { 
     setupChat(); 
    } 
} 

@Override 
public void onDestroy() { 
    super.onDestroy(); 
    if (mChatService != null) { 
     mChatService.stop(); 
    } 
} 

@Override 
public void onResume() { 
    super.onResume(); 

    // Performing this check in onResume() covers the case in which BT was 
    // not enabled during onStart(), so we were paused to enable it... 
    // onResume() will be called when ACTION_REQUEST_ENABLE activity returns. 
    if (mChatService != null) { 
     // Only if the state is STATE_NONE, do we know that we haven't started already 
     if (mChatService.getState() == BluetoothChatService.STATE_NONE) { 
      // Start the Bluetooth chat services 
      mChatService.start(); 
     } 
    } 
} 

@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, 
         @Nullable Bundle savedInstanceState) { 
    return inflater.inflate(R.layout.fragment_bluetooth_chat, container, false); 
} 

@Override 
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { 
    mConversationView = (ListView) view.findViewById(R.id.in); 
    mOutEditText = (EditText) view.findViewById(R.id.edit_text_out); 
    mSendButton = (Button) view.findViewById(R.id.button_send); 
    display = (TextView) view.findViewById(R.id.kotak); 
} 

/** 
* Set up the UI and background operations for chat. 
*/ 
private void setupChat() { 
    Log.d(TAG, "setupChat()"); 

    // Initialize the array adapter for the conversation thread 
    mConversationArrayAdapter = new ArrayAdapter<String>(getActivity(), R.layout.message); 

    mConversationView.setAdapter(mConversationArrayAdapter); 

    // Initialize the compose field with a listener for the return key 
    mOutEditText.setOnEditorActionListener(mWriteListener); 

    // Initialize the send button with a listener that for click events 
    mSendButton.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 
      // Send a message using content of the edit text widget 
      View view = getView(); 
      if (null != view) { 
       TextView textView = (TextView) view.findViewById(R.id.edit_text_out); 
       String message = textView.getText().toString(); 
       sendMessage(message); 
      } 
     } 
    }); 

    // Initialize the BluetoothChatService to perform bluetooth connections 
    mChatService = new BluetoothChatService(getActivity(), mHandler); 

    // Initialize the buffer for outgoing messages 
    mOutStringBuffer = new StringBuffer(""); 
} 

/** 
* Makes this device discoverable for 300 seconds (5 minutes). 
*/ 
private void ensureDiscoverable() { 
    if (mBluetoothAdapter.getScanMode() != 
      BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) { 
     Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); 
     discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300); 
     startActivity(discoverableIntent); 
    } 
} 

/** 
* Sends a message. 
* 
* @param message A string of text to send. 
*/ 
private void sendMessage(String message) { 
    // Check that we're actually connected before trying anything 
    if (mChatService.getState() != BluetoothChatService.STATE_CONNECTED) { 
     Toast.makeText(getActivity(), R.string.not_connected, Toast.LENGTH_SHORT).show(); 
     return; 
    } 

    // Check that there's actually something to send 
    if (message.length() > 0) { 
     // Get the message bytes and tell the BluetoothChatService to write 
     byte[] send = message.getBytes(); 
     mChatService.write(send); 

     // Reset out string buffer to zero and clear the edit text field 
     mOutStringBuffer.setLength(0); 
     mOutEditText.setText(mOutStringBuffer); 
    } 
} 

/** 
* The action listener for the EditText widget, to listen for the return key 
*/ 
private TextView.OnEditorActionListener mWriteListener 
     = new TextView.OnEditorActionListener() { 
    public boolean onEditorAction(TextView view, int actionId, KeyEvent event) { 
     // If the action is a key-up event on the return key, send the message 
     if (actionId == EditorInfo.IME_NULL && event.getAction() == KeyEvent.ACTION_UP) { 
      String message = view.getText().toString(); 
      sendMessage(message); 
     } 
     return true; 
    } 
}; 

/** 
* Updates the status on the action bar. 
* 
* @param resId a string resource ID 
*/ 
private void setStatus(int resId) { 
    FragmentActivity activity = getActivity(); 
    if (null == activity) { 
     return; 
    } 
    final ActionBar actionBar = activity.getActionBar(); 
    if (null == actionBar) { 
     return; 
    } 
    actionBar.setSubtitle(resId); 
} 

/** 
* Updates the status on the action bar. 
* 
* @param subTitle status 
*/ 
private void setStatus(CharSequence subTitle) { 
    FragmentActivity activity = getActivity(); 
    if (null == activity) { 
     return; 
    } 
    final ActionBar actionBar = activity.getActionBar(); 
    if (null == actionBar) { 
     return; 
    } 
    actionBar.setSubtitle(subTitle); 
} 

/** 
* The Handler that gets information back from the BluetoothChatService 
*/ 
private final Handler mHandler = new Handler() { 
    @Override 
    public void handleMessage(Message msg) { 
     FragmentActivity activity = getActivity(); 

     switch (msg.what) { 
      case Constants.MESSAGE_STATE_CHANGE: 
       switch (msg.arg1) { 
        case BluetoothChatService.STATE_CONNECTED: 
         setStatus(getString(R.string.title_connected_to, mConnectedDeviceName)); 
         mConversationArrayAdapter.clear(); 
         break; 
        case BluetoothChatService.STATE_CONNECTING: 
         setStatus(R.string.title_connecting); 
         break; 
        case BluetoothChatService.STATE_LISTEN: 
        case BluetoothChatService.STATE_NONE: 
         setStatus(R.string.title_not_connected); 
         break; 
       } 
       break; 
      case Constants.MESSAGE_WRITE: 
       byte[] writeBuf = (byte[]) msg.obj; 
       // construct a string from the buffer 
       String writeMessage = new String(writeBuf); 
       mConversationArrayAdapter.add("Me: " + writeMessage); 
       break; 
      case Constants.MESSAGE_READ: 
       byte[] readBuf = (byte[]) msg.obj; 
       // construct a string from the valid bytes in the buffer 
       String readMessage = new String(readBuf, 0, msg.arg1); 


       mConversationArrayAdapter.add(mConnectedDeviceName + ": " + readMessage); 
        display.setText(readMessage); 
       break; 

      case Constants.MESSAGE_DEVICE_NAME: 
       // save the connected device's name 
       mConnectedDeviceName = msg.getData().getString(Constants.DEVICE_NAME); 
       if (null != activity) { 
        Toast.makeText(activity, "Connected to " 
          + mConnectedDeviceName, Toast.LENGTH_SHORT).show(); 
       } 
       break; 
      case Constants.MESSAGE_TOAST: 
       if (null != activity) { 
        Toast.makeText(activity, msg.getData().getString(Constants.TOAST), 
          Toast.LENGTH_SHORT).show(); 
       } 
       break; 
     } 
    } 
}; 

public void onActivityResult(int requestCode, int resultCode, Intent data) { 
    switch (requestCode) { 
     case REQUEST_CONNECT_DEVICE_SECURE: 
      // When DeviceListActivity returns with a device to connect 
      if (resultCode == Activity.RESULT_OK) { 
       connectDevice(data, true); 
      } 
      break; 
     case REQUEST_CONNECT_DEVICE_INSECURE: 
      // When DeviceListActivity returns with a device to connect 
      if (resultCode == Activity.RESULT_OK) { 
       connectDevice(data, false); 
      } 
      break; 
     case REQUEST_ENABLE_BT: 
      // When the request to enable Bluetooth returns 
      if (resultCode == Activity.RESULT_OK) { 
       // Bluetooth is now enabled, so set up a chat session 
       setupChat(); 
      } else { 
       // User did not enable Bluetooth or an error occurred 
       Log.d(TAG, "BT not enabled"); 
       Toast.makeText(getActivity(), R.string.bt_not_enabled_leaving, 
         Toast.LENGTH_SHORT).show(); 
       getActivity().finish(); 
      } 
    } 
} 

/** 
* Establish connection with other device 
* 
* @param data An {@link Intent} with {@link DeviceListActivity#EXTRA_DEVICE_ADDRESS} extra. 
* @param secure Socket Security type - Secure (true) , Insecure (false) 
*/ 
private void connectDevice(Intent data, boolean secure) { 
    // Get the device MAC address 
    String address = data.getExtras() 
      .getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS); 
    // Get the BluetoothDevice object 
    BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address); 
    // Attempt to connect to the device 
    mChatService.connect(device, secure); 
} 

@Override 
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { 
    inflater.inflate(R.menu.bluetooth_chat, menu); 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     case R.id.secure_connect_scan: { 
      // Launch the DeviceListActivity to see devices and do scan 
      Intent serverIntent = new Intent(getActivity(), DeviceListActivity.class); 
      startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE_SECURE); 
      return true; 
     } 
     case R.id.insecure_connect_scan: { 
      // Launch the DeviceListActivity to see devices and do scan 
      Intent serverIntent = new Intent(getActivity(), DeviceListActivity.class); 
      startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE_INSECURE); 
      return true; 
     } 
     case R.id.discoverable: { 
      // Ensure this device is discoverable by others 
      ensureDiscoverable(); 
      return true; 
     } 
    } 
    return false; 
}} 

Problem ist, wenn ich die Anwendung in meinem Android gestartet, stürzte die App nach bluetooth Empfangen von Daten. Der Report Bug, den ich von der Anwendung bekomme, ist

java.lang.NullPointerException: 
Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
at 
com.example.android.bluetoothchat.BluetoothChatFragment$3.handleMessage(BluetoothChatFragment.java:315) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5442) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.Zygotelnit$MethodAndArgsCaller.run(Zygotelnit.java:738) 
at com.android.internal.os.Zygotelnit.main(Zygotelnit.java:628) 

Kann jemand mir für dieses Problem helfen? Vielen Dank

Answer 1

entfernen diese von Ihrem TextView textView = (TextView) view.findViewById(R.id.edit_text_out); von Ihrem mSendButton.setOnClickListener und intilize es in Ihre onViewCreated wie unten Code

@Override 
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { 
    mConversationView = (ListView) view.findViewById(R.id.in); 
    mOutEditText = (EditText) view.findViewById(R.id.edit_text_out); 
    mSendButton = (Button) view.findViewById(R.id.button_send); 
    display = (TextView) view.findViewById(R.id.kotak); 
    TextView textView = (TextView) view.findViewById(R.id.edit_text_out); 
}