Question

HY！

我总是在我的代码中获得NullPointerEx。列表大小为7，因此不能为空。 customlistime存在。我不知道我在哪里得到例外。在我的其他程序中，这段代码有效。

请帮忙

调用

Log.e("SP",String.valueOf(list.size())); //List size is 7
ca = new CustomAdapter(this, R.layout.customlistitem, list); //global var
lv.setAdapter(ca); //Error Occurs here

CustomAdaptor：

public class CustomAdapter extends ArrayAdapter<SPEntry>{

    private ArrayList<SPEntry> entries;

    public CustomAdapter(Context context, int textViewResourceId,ArrayList<SPEntry> objects) {
        super(context, textViewResourceId, objects);
        this.entries = objects;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = new ViewHolder();
        LayoutInflater li = (LayoutInflater)CustomAdapter.this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = li.inflate(R.layout.customlistitem,null);
            holder.date = (TextView) convertView.findViewById(R.id.item_date);
            holder.lesson = (TextView) convertView.findViewById(R.id.item_lesson);
            holder.teacher = (TextView) convertView.findViewById(R.id.item_teacher);
            holder.image = (ImageView) convertView.findViewById(R.id.item_picture);
            convertView.setTag(holder);
        }
        else{
              holder = (ViewHolder) convertView.getTag();
        }
        holder.date.setText(entries.get(position).date);
        holder.teacher.setText(entries.get(position).teacher);
        holder.lesson.setText(entries.get(position).lesson);
        Bitmap bt = Bitmap.createScaledBitmap(entries.get(position).picture, 48, 48, false);
        holder.image.setImageBitmap(bt);
        return convertView;         
    } 

}

Viewholder：

public class ViewHolder {

    public ImageView image;
    public TextView date;
    public TextView lesson;
    public TextView teacher;



    ViewHolder()
    {
    }
}

错误码：

10-17 20:49:39.481: ERROR/AndroidRuntime(2767): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.korn.supplierplan/com.korn.supplierplan.view.LVEntries}: java.lang.NullPointerException
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.os.Looper.loop(Looper.java:123)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at android.app.ActivityThread.main(ActivityThread.java:4363)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at java.lang.reflect.Method.invokeNative(Native Method)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at java.lang.reflect.Method.invoke(Method.java:521)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at dalvik.system.NativeStart.main(Native Method)
10-17 20:49:39.481: ERROR/AndroidRuntime(2767): Caused by: java.lang.NullPointerException
10-17 20:49:39.481: ERROR/AndroidRuntime(2767):     at com.korn.supplierplan.view.LVEntries.onCreate(LVEntries.java:30)

调试器中来自ca的图片：

http://img7.imagebanana.com/img/alen3q0g/Unbenannts.png

Answer 1

确保您的ListView变量（lv）已初始化。

Answer 2

这不是CustomAdapter问题。这是您的ListView对象lv问题，很明显它没有初始化或没有从布局中膨胀。

在您的布局XML文件中添加ListView并在将CustomAdapter设置为ListView

之前添加此内容

ListView lv = (ListView)findViewById(R.id.lv_sp);

ca = new CustomAdapter(this, R.layout.customlistitem, list); 
lv.setAdapter(ca);

编辑：更新代码，尝试清理项目并再次运行！

ListView的CustomAdapter中的NullPointerException

2 个答案: