android - 在 Android 中单击按钮时出现 NullPointerException

Question

我有带有图像的 GridView ，我选择了多个图像并在主 Activity 中的按钮单击事件中删除了选定的图像。但是没有选择任何图像按下按钮得到空指针异常并且应用程序崩溃了。如何解决这个问题。这是我的按钮代码。提前致谢。

imgDeleteImagesFromGallery = (ImageView) findViewById(R.id.imgDeleteImage);
imgDeleteImagesFromGallery.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v)
    {
        ArrayList<String> selectedItems = gridAdapter.getCheckedItems();
        if(selectedItems.size() > 0)
        {
            Toast.makeText(AddPost.this, "Total photos selected: "+selectedItems.size(), Toast.LENGTH_SHORT).show();
            Log.e(AddPost.class.getSimpleName(), "Selected Items: " + selectedItems.toString());

            Iterator it = picsName.iterator();
            while (it.hasNext())
            {
                strFilePath = it.next().toString();
                Log.e("strFilePath ", " strFilePath = " + strFilePath);
                File file = new File(strFilePath);
                if (file.exists())
                {
                    boolean result = file.delete();
                    Log.e("File deleted ", " From classnkk_images = " + result);
                }
            }

            gridAdapter.notifyDataSetChanged();
            int countImg = gridAdapter.getCount();
            textTotalImages.setText(Integer.toString(countImg));
        }

    }
});





class GridView_Adapter extends BaseAdapter {

        private LayoutInflater mInflater;
        SparseBooleanArray mSparseBooleanArray;
        public GridView_Adapter() {
            mInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            mSparseBooleanArray = new SparseBooleanArray();
        }

        public ArrayList<String> getCheckedItems() {
            ArrayList<String> mTempArry = new ArrayList<String>();

            for(int i=0;i<insertImageAudioList.size();i++) {
                if(mSparseBooleanArray.get(i)) {
                    mTempArry.add(insertImageAudioList.get(i));
                }}
            return mTempArry;
        }

        public int getCount() {
            return insertImageAudioList.size();
        }

        public Object getItem(int position) {
            return position;
        }

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

        @Override
        public View getView(final int position, View convertView, ViewGroup parent)
        {
            final ViewHolder holder;
            if (convertView == null)
            {
                holder = new ViewHolder();
                convertView = mInflater.inflate(R.layout.add_post_grid_item_layout, parent , false);
                holder.image = (ImageView) convertView.findViewById(R.id.image);
                holder.checkbox = (CheckBox) convertView.findViewById(R.id.itemCheckBox);
                convertView.setTag(holder);
            }
            else
            {
                holder = (ViewHolder) convertView.getTag();
            }

            String strImagePosition = insertImageAudioList.get(position);
            if (strImagePosition.endsWith(mp3_Pattern))
            {
                Log.e("In if condition  ","strImagePosition = "+strImagePosition);
                holder.image.setImageResource(R.drawable.resize_audio_control);

            }
            if (strImagePosition.endsWith(png_Pattern) || strImagePosition.endsWith(jpg_pattern) || strImagePosition.endsWith(bmp_pattern) || strImagePosition.endsWith(gif_pattern) || strImagePosition.endsWith(jpeg_pattern))
            {
                //Log.e("strImagePosition "," = "+strImagePosition);
                String strBaseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
                String filepath = strBaseDir + "/classnkk_images/" + strImagePosition;
                File file = new File(filepath);

                    fileName.add(file.getAbsolutePath());
                    Bitmap myBitmap = BitmapFactory.decodeFile(filepath);
                    holder.image.setImageBitmap(myBitmap);
            }


            holder.checkbox.setTag(position);


            holder.checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
                {
                    mSparseBooleanArray.put((Integer) buttonView.getTag(), isChecked);
                    int pos = (Integer) buttonView.getTag();
                    if (!buttonView.isChecked())
                    {
                        picsName.remove((String) insertImageAudioList.get(pos));
                    }
                    else if (buttonView.isChecked())
                    {
                        if (!picsName.contains((String) insertImageAudioList.get(pos)))
                        {
                            picsName.add((String) insertImageAudioList.get(pos));
                        }
                    }
                    notifyDataSetChanged();

                }
            });


            return convertView;
        }

        class ViewHolder
        {
            ImageView image;
            CheckBox checkbox;
            int id;
        }
    }

这行错误

ArrayList<String> selectedItems = gridAdapter.getCheckedItems();

Answer 1

您的gridAdapter 为空

将这一行作为第一行放在你的 onClick 方法中

GridView_Adapter gridAdapter = new GridView_Adapter();