Java Android中未知的NullPointerException

今天我得到了一个未知的NullPointerException，我无法复制它。 Logcat显示由于我的代码，它没有发生。 由于ListView中的某些内容而发生异常，我的问题是，它没有指向发生异常的代码。 我不熟悉安卓系统 下面是日志：

02-07 18:32:46.796: D/AndroidRuntime(20239): Shutting down VM
02-07 18:32:46.796: W/dalvikvm(20239): threadid=1: thread exiting with uncaught exception (group=0x412ec2a0)
02-07 18:32:46.806: E/AndroidRuntime(20239): FATAL EXCEPTION: main
02-07 18:32:46.806: E/AndroidRuntime(20239): java.lang.NullPointerException
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.AbsListView.obtainView(AbsListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.ListView.makeAndAddView(ListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.ListView.fillDown(ListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.ListView.fillSpecific(ListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.ListView.layoutChildren(ListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.AbsListView.onLayout(AbsListView.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:690)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.onLayout(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.LinearLayout.onLayout(LinearLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.widget.FrameLayout.onLayout(FrameLayout.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.View.layout(View.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewGroup.layout(ViewGroup.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.Choreographer.doCallbacks(Choreographer.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.Choreographer.doFrame(Choreographer.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.os.Handler.handleCallback(Handler.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.os.Handler.dispatchMessage(Handler.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.os.Looper.loop(Looper.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at android.app.ActivityThread.main(ActivityThread.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at java.lang.reflect.Method.invoke(Method.java:511)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
02-07 18:32:46.806: E/AndroidRuntime(20239):    at dalvik.system.NativeStart.main(Native Method)

任何帮助都将不胜感激

好的，这是我的适配器代码

private class FileAdapter extends BaseAdapter {
    private final Context mContext;
    private final Bitmap mFolderBitmap, mFileBitmap;

    FileAdapter(Context context) {
        mContext = context;
        addHeader();
        mFolderBitmap = BitmapFactory.decodeResource(getResources(),
                R.drawable.ic_folder);
        mFileBitmap = BitmapFactory.decodeResource(getResources(),
                R.drawable.ic_file);
    }

    public void addHeader() {
        // add empty view with height of ActionBar
        View view = new View(mContext);
        view.setLayoutParams(new AbsListView.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                MainActivity.ACTIONBAR_HEIGHT));
        getListView().addHeaderView(view);
    }

    @Override
    public int getCount() {
        return mFileList.size();
    }

    @Override
    public Object getItem(int position) {
        return mFileList.get(position);
    }

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

    @Override
    public void notifyDataSetChanged() {
        super.notifyDataSetChanged();
        multiChoiceListener.refresh();
    }

    public void setChecked(View view) {
        if (view != null) {
            view.setBackgroundColor(getResources().getColor(R.color.BLUE));
        }
    }

    public void setUnchecked(View view) {
        if (view != null) {
            view.setBackgroundColor(getResources().getColor(R.color.WHITE));
        }
    }

    public void setChecked(int pos) {
        View view = getChildAt(getListView(), pos);
        setChecked(view);

    }

    public void setUnchecked(int pos) {
        View view = getChildAt(getListView(), pos);
        setUnchecked(view);

    }

    private View getChildAt(AbsListView listView, Integer position) {
        return listView.getChildAt(position + 1
                - listView.getFirstVisiblePosition());
    }

    @Override
    public View getView(final int position, View convertView,
            ViewGroup parent) {
        final ViewHolder vh;

        if (convertView == null) {
            vh = new ViewHolder();
            convertView = LayoutInflater.from(mContext).inflate(
                    R.layout.file_fragment_list_item, parent, false);
            vh.iv = (ImageView) convertView.findViewById(R.id.fileIconView);
            vh.tv = (TextView) convertView.findViewById(R.id.fileTextView);

            convertView.setTag(vh);

        } else {
            vh = (ViewHolder) convertView.getTag();
        }

        vh.iv.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                multiChoiceListener.selectionChanged(position);
            }
        });

        if (multiChoiceListener.isChecked(position)) {
            setChecked(convertView);
        } else {
            setUnchecked(convertView);
        }

        final File file = mFileList.get(position);
        if (file == null)
            return null;

        if (file.isDirectory()) {
            vh.iv.setImageBitmap(mFolderBitmap);
        } else {
            vh.iv.setImageBitmap(mFileBitmap);
        }
        // Set text
        vh.tv.setText(file.getName());

        return convertView;
    }

    private class ViewHolder {
        ImageView iv;
        TextView tv;
    }

}

---

您可能在

适配器的
getView（）
函数中返回了
null
视图。让它返回正确的视图
而不使用任何代码我们如何跟踪原因？？？最有可能的原因是适配器的getView（…）方法失败。@RanjitPati没有代码您就无法找出编码问题的原因是什么？你是干什么的？一个noob？|=^]@MohammadS Ya可能是，但比您更好，您试图通过一些不清楚和不确定的答案，仅通过logcat来建议空指针。可能您正在从适配器实现的getView方法返回空视图。