Click and hold to select multiple image. Don't just click on image. Also you can receive those image using this. 
int PICK_IMAGE_MULTIPLE = 1;
String imageEncoded;
List<String> imagesEncodedList;
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    try {
        // When an Image is picked
        if (requestCode == 1 && resultCode == RESULT_OK
                && null != data) {
            // Get the Image from data
            String[] filePathColumn = { MediaStore.Images.Media.DATA };
            imagesEncodedList = new ArrayList<String>();
            if(data.getData()!=null){
                Uri mImageUri=data.getData();
                // Get the cursor
                Cursor cursor = getContentResolver().query(mImageUri,
                        filePathColumn, null, null, null);
                // Move to first row
                cursor.moveToFirst();
                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                imageEncoded  = cursor.getString(columnIndex);
                cursor.close();
            }else {
                if (data.getClipData() != null) {
                    ClipData mClipData = data.getClipData();
                    ArrayList<Uri> mArrayUri = new ArrayList<Uri>();
                    for (int i = 0; i < mClipData.getItemCount(); i++) {
                        ClipData.Item item = mClipData.getItemAt(i);
                        Uri uri = item.getUri();
                        mArrayUri.add(uri);
                        // Get the cursor
                        Cursor cursor = getContentResolver().query(uri, filePathColumn, null, null, null);
                        // Move to first row
                        cursor.moveToFirst();
                        int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                        imageEncoded  = cursor.getString(columnIndex);
                        imagesEncodedList.add(imageEncoded);
                        cursor.close();
                    }
                    Log.v("LOG_TAG", "Selected Images" + mArrayUri.size());
                }
            }
        } else {
            Toast.makeText(this, "You haven't picked Image",
                    Toast.LENGTH_LONG).show();
        }
    } catch (Exception e) {
        Toast.makeText(this, "Something went wrong", Toast.LENGTH_LONG)
                .show();
    }
    super.onActivityResult(requestCode, resultCode, data);
}