我正在使用幻灯片片段开发应用。一切正常，应用程序启动没有问题。 View.onClickListener中出现问题。这是我的单个片段部分的代码：
public static class ReceiveSectionFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.receive, container, false);
rootView.findViewById(R.id.bt_server_start)
.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), Receive.class);
startActivity(intent);
}
});
return rootView;
}
}
滑动到目标布局 - R.layout.receive效果很好。所以这里没问题。在R.id.bt_server_start按钮上单击下面的课程：
package com.receive.bluereceive;
import java.io.DataInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.UUID;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.CountDownTimer;
import android.os.Vibrator;
import android.util.Log;
import android.widget.Button;
import android.widget.TextView;
public class Receive extends Activity {
/**
* Default Serial-Port UUID
*/
private String myUUID = "00001101-0000-1000-8000-00805F9B34FB";
/**
* Default Bluetooth adapter on the device.
*/
private final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
/**
* Magic number used in the Bluetooth enabling request.
*/
public final int REQUEST_ENABLE_BT = 2;
/**
* The Server thread.
*/
private AcceptThread DeviceServer;
private NotificationCenter mNotificationCenter;
public final static String EXTRA_MESSAGE = "com.receive.intent.MESSAGE";
public final int BT_ENABLE_TIME = 35;
public final int BT_TIME_BTTIME = 1000 * BT_ENABLE_TIME;
public CountDownTimer BTCountDown;
public CountDownTimer MoveHistoryCountDown;
@Override
protected void onStart() {
super.onStart();
mNotificationCenter = new NotificationCenter();
/*
* Code responsible for calling method NotificationCenter() to print the incoming text to TextView field
*/
registerReceiver(mNotificationCenter, new IntentFilter(EXTRA_MESSAGE));
/*
* Start server on device
*/
ServerThread();
((Button) findViewById(R.id.bt_server_start)).setEnabled(false);
((Button) findViewById(R.id.bt_server_stop)).setEnabled(true);
}
public void ServerThread() {
DeviceServer = new AcceptThread();
DeviceServer.start();
}
private class AcceptThread extends Thread {
/*
* That TAG will appear in the log in Eclipse
*/
private final String ACC_TAG = AcceptThread.class.getName();
/*
* Bluetooth server socket
*/
private final BluetoothServerSocket mServerSocket;
public AcceptThread() {
/*
* Use a temporary object that is later assigned to mServerSocket, because mServerSocket is final
*/
BluetoothServerSocket tmp = null;
try {
/*
* MY_UUID is the app's UUID string, also used by the client code
*/
tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(ACC_TAG, UUID.fromString(myUUID));
} catch (IOException e) { }
mServerSocket = tmp;
}
public void run() {
BluetoothSocket socket = null;
/*
* Keep listening until exception occurs or a socket is returned
*/
while (true) {
try {
Log.i(ACC_TAG,"Listening for a connection nearby...");
socket = mServerSocket.accept();
Log.i(ACC_TAG, "Connected to " + socket.getRemoteDevice().getName());
} catch (IOException e) {
break;
}
/*
* If connection was accepted then proceed with code below
* If Bluetooth socket does not equal null proceed with string reading as know script knows that device is connected
* And if it is first ServerThread start,
*/
if (socket != null) {
try {
String message;
DataInputStream incoming = new DataInputStream(socket.getInputStream());
message = incoming.readUTF();
Intent actual = new Intent(EXTRA_MESSAGE);
actual.putExtra("Message", String.format("%s",message));
getBaseContext().sendBroadcast(actual);
} catch (IOException e) {
Log.e(ACC_TAG, "Error obtaining InputStream from socket");
e.printStackTrace();
}
try {
mServerSocket.close();
} catch (IOException e) { }
break;
}
}
}
/*
* Will cancel the listening socket, and cause the thread to finish
*/
public void cancel() {
try {
mServerSocket.close();
} catch (IOException e) { }
}
}
private Vibrator getVibrator() {
return (Vibrator) getSystemService(VIBRATOR_SERVICE);
}
/*
* NOTIFICATION CLASS, PRINTS THE RECEIVED MESSAGE
*/
public class NotificationCenter extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals(EXTRA_MESSAGE)) {
int counter = 0;
ArrayList<String> historiaAL = new ArrayList<String>();
historiaAL.add(intent.getExtras().getString("Message"));
TextView actual = (TextView)findViewById(R.id.received_string);
actual.setText(historiaAL.get(counter));
TextView history = (TextView)findViewById(R.id.history_string);
String[] historiaA = historiaAL.toArray(new String[historiaAL.size()]);
for(int i = 0; i < historiaAL.size(); i++)
{
history.append(historiaA[i]);
history.append(" \n ");
}
getVibrator().vibrate(500);
MoveHistoryCountDown = new HistoryMove(5000,5);
MoveHistoryCountDown.start();
counter++;
}
}
}
public class HistoryMove extends CountDownTimer {
public HistoryMove (long startTime, long interval) {
super(startTime, interval);
}
@Override
public void onFinish() {
TextView recent = (TextView)findViewById(R.id.received_string);
recent.setText(" ");
}
@Override
public void onTick(long millisUntilFinished) {
}
}
}
所有内容都包含在Manifest.xml中。我从LogCat得到的是：
12-18 00:36:14.136: E/AndroidRuntime(29672): FATAL EXCEPTION: main
12-18 00:36:14.136: E/AndroidRuntime(29672): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.receive.bluereceive/com.receive.bluereceive.Receive}: java.lang.NullPointerException
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread.access$600(ActivityThread.java:153)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.os.Handler.dispatchMessage(Handler.java:99)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.os.Looper.loop(Looper.java:137)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread.main(ActivityThread.java:5227)
12-18 00:36:14.136: E/AndroidRuntime(29672): at java.lang.reflect.Method.invokeNative(Native Method)
12-18 00:36:14.136: E/AndroidRuntime(29672): at java.lang.reflect.Method.invoke(Method.java:511)
12-18 00:36:14.136: E/AndroidRuntime(29672): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
12-18 00:36:14.136: E/AndroidRuntime(29672): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
12-18 00:36:14.136: E/AndroidRuntime(29672): at dalvik.system.NativeStart.main(Native Method)
12-18 00:36:14.136: E/AndroidRuntime(29672): Caused by: java.lang.NullPointerException
12-18 00:36:14.136: E/AndroidRuntime(29672): at com.receive.bluereceive.Receive.onStart(Receive.java:68)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1164)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.Activity.performStart(Activity.java:5114)
12-18 00:36:14.136: E/AndroidRuntime(29672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2271)
12-18 00:36:14.136: E/AndroidRuntime(29672): ... 11 more
可能这是一个新手的错误，但仍然是一个小时，我仍然无法解决这个问题。
请不要降级声誉，我真的不能让它工作，即使它看起来似乎微不足道。
编辑：完整的主要代码 - http://pastebin.com/e4dyW8Th
答案 0 :(得分：2)
我没有在您的活动中的任何地方看到setContentView，这意味着findViewById会返回null。
在您的活动中添加onCreate方法，并致电setContentView设置您的布局。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_activity);
}