使用ArrayList時Service onStart中的NullPointer異常

Question

當我嘗試在Service onStart中使用ArrayList時收到以下異常。

有人可以幫忙嗎？

謝謝格雷厄姆

問題似乎在這里

    @Override
public void onStart(Intent intent, int startid) {
Log.d(TAG, "onStart");
data = intent.getExtras();
ORIG = data.getString("originator");


Toast.makeText(this, "My Service Started with passed in value " + ORIG, Toast.LENGTH_LONG).show();
if(items.contains(ORIG)){
Log.d(TAG, "Element already exists exiting "); 
} else {
Log.d(TAG, "Adding Element");
    items.add(ORIG);

}

這是LOGCAT中提出的例外情況

    E/AndroidRuntime( 7496): FATAL EXCEPTION: main
E/AndroidRuntime( 7496): java.lang.RuntimeException: Unable to start service com    .example.MyService@4052eed0 with Intent { cmp=com.example/.MyService (has extras) }: java.lang.NullPointerException
E/AndroidRuntime( 7496):        at android.app.ActivityThread.handleServiceArgs(    ActivityThread.java:2056)
E/AndroidRuntime( 7496):        at android.app.ActivityThread.access$2800(Activi    tyThread.java:117)
E/AndroidRuntime( 7496):        at android.app.ActivityThread$H.handleMessage(Ac    tivityThread.java:998)
E/AndroidRuntime( 7496):        at android.os.Handler.dispatchMessage(Handler.ja    va:99)
E/AndroidRuntime( 7496):        at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime( 7496):        at android.app.ActivityThread.main(ActivityThrea    d.java:3691)
E/AndroidRuntime( 7496):        at java.lang.reflect.Method.invokeNative(Native    Method)
E/AndroidRuntime( 7496):        at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime( 7496):        at com.android.internal.os.ZygoteInit$MethodAndA    rgsCaller.run(ZygoteInit.java:847)
E/AndroidRuntime( 7496):        at com.android.internal.os.ZygoteInit.main(Zygot    eInit.java:605)
E/AndroidRuntime( 7496):        at dalvik.system.NativeStart.main(Native Method)

E/AndroidRuntime( 7496): Caused by: java.lang.NullPointerException
E/AndroidRuntime( 7496):        at com.example.MyService.onStart(MyService.java:54)
E/AndroidRuntime( 7496):        at android.app.Service.onStartCommand(Service.ja    va:428)
E/AndroidRuntime( 7496):        at android.app.ActivityThread.handleServiceArgs(    ActivityThread.java:2043)
E/AndroidRuntime( 7496):        ... 10 more
W/ActivityManager( 2696):   Force finishing activity com.example/.ServicesDemo
E/        ( 2696): Dumpstate > /data/log/dumpstate_app_error
I/dumpstate( 7586): begin
W/ActivityManager( 2696): Activity pause timeout for HistoryRecord{408759b0 com.    example/.ServicesDemo}

活動致電我的服務

package com.example;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class ServicesDemo extends Activity implements OnClickListener {
  private static final String TAG = "ServicesDemo";
  Button buttonStart, buttonStop;
  EditText Input;
  String x = "";  //test pass to my service

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    buttonStart = (Button) findViewById(R.id.buttonStart);
    buttonStop = (Button) findViewById(R.id.buttonStop);
    Input = (EditText) findViewById(R.id.INPUT);
    buttonStart.setOnClickListener(this);
    buttonStop.setOnClickListener(this);

  }

  public void onClick(View src) {
    switch (src.getId()) {
    case R.id.buttonStart:
      Log.d(TAG, "onClick: starting srvice");
      Intent dataIntent = new Intent(ServicesDemo.this, MyService.class);
      x = Input.getText().toString(); 
      dataIntent.putExtra("originator", x);
      startService(dataIntent);

      break;

    case R.id.buttonStop:

      Log.d(TAG, "onClick: stopping srvice");
      //implicit starting 
      stopService(new Intent(this, MyService.class));
      break;
    }
  }


public static String getTag() {
return TAG;
}
}

我嘗試使用問題的服務在onStart中

package com.example;


import java.util.ArrayList;

import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.widget.Toast;

public class MyService extends Service {

ArrayList<String> items;

public String ORIG = "";
private static final String TAG = "MyService";
public Bundle data = new Bundle();


@Override
public IBinder onBind(Intent intent) {
return null;
}


public static String getTag() {
return TAG;
}


@Override
public void onCreate() {
Toast.makeText(this, "My Service Created", Toast.LENGTH_LONG).show();
Log.d(TAG, "onCreate");


}

@Override
public void onDestroy() {
Toast.makeText(this, "My Service Stopped", Toast.LENGTH_LONG).show();
Log.d(TAG, "onDestroy");

}

@Override
public void onStart(Intent intent, int startid) {
Log.d(TAG, "onStart");
data = intent.getExtras();
ORIG = data.getString("originator");
Toast.makeText(this, "My Service Started with passed in value " + ORIG, Toast.LENGTH_LONG).show();
if(items.contains(ORIG)){
Log.d(TAG, "Element already exists exiting "); 
} else {
Log.d(TAG, "Adding Element");
    items.add(ORIG);

}


Thread initBkgdThread = new Thread(new Runnable() {
public void run() {
//print_result();
}
});
initBkgdThread.start();

}

public void print_result(String orig){
Log.d(TAG, "HELLO WORLD:" + orig);


}

}

Answer 1

看起來數組列表ArrayList <String>項未初始化，因此您在服務MyService的onCreate（）方法中獲得了NullPointerException。

Answer 2

我看不到您初始化ArrayList。 首先初始化數組，然后使用它。 其次，請記住活動的生命周期。