无法通过意图从手机图库加载图片并将其设置在gridview上

Question

我是Android新手，想要通过意图从手机图库加载图片，并希望在gridView上显示列表项。

但是当我在选择后加载图库时，图像未显示。

活动

private static final int CODE = 0; 
public GridView gridView; 
public Uri selectedImageUri; 
ImageAdapter imageAdapter;

... 

    gridView = (GridView) findViewById(R.id.gridview);
    gridView.setAdapter(new ImageAdapter(this));
    imageAdapter = new ImageAdapter(this);
    gridView.setAdapter(imageAdapter);
    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int 
    position, long id) {

            Toast.makeText(MainActivity.this, "" + position + "",
                    Toast.LENGTH_LONG).show();
        }
    });
    Button loadImageButton = (Button) findViewById(R.id.load_image_button);
    loadImageButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent();
            intent.setType("image/*");
            intent.setAction(Intent.ACTION_GET_CONTENT);
            startActivityForResult(Intent.createChooser(intent, "Select 
            Picture"), CODE);
        }
    });
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent 
    intent) {
    super.onActivityResult(requestCode, resultCode, intent);

    if (requestCode == CODE && resultCode == RESULT_OK && intent != null) {
        selectedImageUri = intent.getData();

        String[] filePathColumn = { MediaStore.Images.Media.DATA };

        Cursor cursor = getContentResolver().query(selectedImageUri,
                filePathColumn, null, null, null);
        cursor.moveToFirst();
        columnIndex = cursor.getColumnIndex(filePathColumn[0]);
        String picturePath = cursor.getString(columnIndex);
        objImageAdapter.addToList(picturePath);
        cursor.close();
        imageView = (ImageView)findViewById(R.id.image_view);
        imageView.setImageBitmap(BitmapFactory.decodeFile(picturePath));

适配器类

public class ImageAdapter extends BaseAdapter {

    public ImageView imageView;
    private Context vContext;
    ArrayList<String> arrayList = new ArrayList<String>();

    public ImageAdapter(Context context) {
        this.vContext = context;
    }

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

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

    public void addToList(String stringPath) {
        this.arrayList.add(stringPath);
        this.notifyDataSetChanged();
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null) {
            imageView = new ImageView(vContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(2, 2, 2, 2);
        } else {
            imageView = (ImageView) convertView;
        }

        String path = arrayList.get(position);
        Bitmap bitmap = BitmapFactory.decodeFile(path);
        imageView.setImageBitmap(bitmap);
        return imageView;