Android的 - Java的NullPointerException異常

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我試圖做一個簡單的應用程序，但我被困在這個討厭的錯誤，我無法找出原因...Android的 - Java的NullPointerException異常

01-06 18:05:04.734: E/AndroidRuntime(1102): FATAL EXCEPTION: main 
01-06 18:05:04.734: E/AndroidRuntime(1102): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.coindroid/com.example.coindroid.EUActivity}: java.lang.NullPointerException 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.os.Handler.dispatchMessage(Handler.java:99) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.os.Looper.loop(Looper.java:137) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at java.lang.reflect.Method.invokeNative(Native Method) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at java.lang.reflect.Method.invoke(Method.java:511) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at dalvik.system.NativeStart.main(Native Method) 
01-06 18:05:04.734: E/AndroidRuntime(1102): Caused by: java.lang.NullPointerException 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at com.example.coindroid.EUActivity.onCreate(EUActivity.java:30) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.Activity.performCreate(Activity.java:5104) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
01-06 18:05:04.734: E/AndroidRuntime(1102):  ... 11 more

是這樣，它似乎我的問題是在第30行，這是這樣的：list.setAdapter（new EUAdapter（this））; 有什麼不對？我的活動僅僅是這樣的：

package com.example.coindroid; 

    import java.util.ArrayList; 
import android.app.Activity; 
import android.content.Context; 
import android.content.res.Resources; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ImageView; 
import android.widget.ListView; 
import android.widget.TextView; 

    public class EUActivity extends Activity {  

ListView list; 

     @Override protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);   
setContentView(R.layout.activity_eu);  
list = (ListView) findViewById(R.layout.activity_eu); 

        list.setAdapter(new EUAdapter(this));   
} 

     } 

      class SingleRow { String title; String description;  int image; SingleRow(String title, String description, int image) {  this.title = title;   this.description = description;   this.image = image;  } } class EUAdapter extends BaseAdapter{ 

     ArrayList<SingleRow> list; Context context; EUAdapter(Context c) {  context = c;  list = new ArrayList<SingleRow>();  Resources res = c.getResources();  String[] titles = res.getStringArray(R.array.titles);  String[] descriptions = res.getStringArray(R.array.description);  int[] images = {R.drawable.queenvictoria1841jpg}; 
        for(int i=0;i<1;i++)  {   list.add(new SingleRow(titles[i], descriptions[i], images[i]));   } 
       } 
       @Override public int getCount() { 
        return list.size();  } 

     @Override public Object getItem(int i) { 
        return list.get(i);  } 

     @Override public long getItemId(int i) { 
        return i; } 

     @Override public View getView(int i, View view, ViewGroup viewGroup) { 


        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);  View row 
    = inflater.inflate(R.layout.single_row, viewGroup, false); 
        TextView title = (TextView)row.findViewById(R.id.name);   TextView description = (TextView)row.findViewById(R.id.year);  ImageView image = (ImageView)row.findViewById(R.id.imageView1); 
        SingleRow temp = list.get(i); 
        title.setText(temp.title);  description.setText(temp.description);  image.setImageResource(temp.image); 
        return row;  } 
      }

提前謝謝你們！

來源

2015-01-06 user3655773

歡迎使用堆棧溢出。要發佈代碼示例，請使用編輯器菜單中的「{}」按鈕，而不是用於創建引號的''''，它們都會創建灰色背景，但只有'{}'會保留行分隔符，並且會添加正確的格式。格式化的問題有更高的回答機會（如果他們發現作者沒有足夠的努力來創建它們，有些人傾向於跳過問題） – Pshemo

我想如果你想得到某人的幫助，你將不得不修復格式 –

什麼是行no：30 in EUActivity.java ??? – Lal

list = (ListView) findViewById(R.layout.activity_eu);

你list爲空。你找不到任何與R.layout ID。在activity_eu佈局中使用與您的列表視圖相對應的R.id ID。

來源

2015-01-06 18:27:09 laalto

您需要在您的適配器的getview方法，而不是返回行的觀點

查看視圖=吹氣.---

來源

2015-01-06 18:30:05 Simar

由於@laalto提到

更換

list = (ListView) findViewById(R.layout.activity_eu);

與

list = (ListView) findViewById(R.id.activity_eu);

因爲您正在通過編號與findViewByID()查找ID從R.java

來源

2015-01-06 18:33:33 Lal

Android的 - Java的NullPointerException異常

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