致命的例外：線程10

Question

嗨我要調用一個服務來填充數組，但是我得到異常致命例外時，數組填充print_result中的值。如果聲明items.add（orig）被調用，我有這個問題。

異常

W/dalvikvm(11235): threadid=9: thread exiting with uncaught exception (group=0x4 
001e578) 
E/AndroidRuntime(11235): FATAL EXCEPTION: Thread-10 
E/AndroidRuntime(11235): java.lang.NullPointerException 
E/AndroidRuntime(11235):  at com.example.MyService.print_result(MyService. 
java:62) 
E/AndroidRuntime(11235):  at com.example.MyService$1.run(MyService.java:54 
) 
E/AndroidRuntime(11235):  at java.lang.Thread.run(Thread.java:1019) 
W/ActivityManager(2696): Force finishing activity com.example/.ServicesDemo 
I/OrientationDebug(2696): [pwm] in updateOrientationListenerLp() 
V/OrientationDebug(2696): in updateOrientationListenerLp(), Screen status=true, 
current orientation=1, SensorEnabled=true 
I/OrientationDebug(2696): [pwm] needSensorRunningLp(), return true #4 
I/Launcher(2852): onResume(). mIsNewIntent : false screenOff: false 
E/  (2696): Dumpstate > /data/log/dumpstate_app_error 
I/dumpstate(11275): begin 
D/KeyguardViewMediator(2696): handleTimeout 
W/PowerManagerService(2696): Timer 0x3->0x3|0x3 

代碼：

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 = null; 

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(); 

} 

@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"); 
Log.d(TAG, "onCreate"); 
Thread initBkgdThread = new Thread(new Runnable() { 
public void run() { 
print_result(ORIG); 
} 
}); 
initBkgdThread.start(); 
} 

public void print_result(String orig){ 
Log.d(TAG, "HELLO WORLD:" + orig); 
items.add(orig); 
if (items != null) { 
items.add(orig); 
String toadd = orig.toString(); 

if(items.contains(toadd)){ 
Log.d(TAG, "Element already exists exiting "); 
} else { 
Log.d(TAG, "Adding Element"); 
    items.add(toadd); 

} 

} 
else { 
Log.d(TAG, "IS NULL"); 
} 
} 

} 

Answer 1

你必須首先初始化數組

items = new ArrayList<String>(); 

Answer 2

你永遠不會初始化數組列表items。將此添加到您的onCreate()方法中：

items = new ArrayList<String>(); 

Answer 3

您需要初始化項目。另外你（邊注），一次檢查，如果項目是之前添加orig兩次空，而一旦經過：該工作

items.add(orig); 
if (items != null) { 
    items.add(orig); 
    String toadd = orig.toString(); 

     if(items.contains(toadd)){ 
      Log.d(TAG, "Element already exists exiting "); 
     } 
}