Switching to another activity takes longer in android

On pressing the camera button (addImage) I move the screen to another action. In this case, it takes a long time to open a new activity. Can anyone tell me what the problem is and how to solve it?

public class Gallery_Activity extends Activity {

AsyncTaskLoadFiles myAsyncTaskLoadFiles;
private ProgressDialog pDialog;
public class AsyncTaskLoadFiles extends AsyncTask<Void, String, Void> {

    File targetDirector;
    ImageAdapter myTaskAdapter;
    ImageView   imageDetail;

    public AsyncTaskLoadFiles(ImageAdapter adapter) {
        myTaskAdapter = adapter;
    }

    @Override
    protected void onPreExecute() {

        pDialog = new ProgressDialog(Gallery_Activity.this);
        pDialog.setIndeterminateDrawable(getResources().getDrawable(R.anim.progress));
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();

        String ExternalStorageDirectoryPath = Environment.getExternalStorageDirectory().getAbsolutePath();

        String targetPath = ExternalStorageDirectoryPath + "/Partypad/";
        targetDirector = new File(targetPath);
        myTaskAdapter.clear();
        super.onPreExecute();
    }

    @Override
    protected Void doInBackground(Void... params) {

        File[] files = targetDirector.listFiles();
        Arrays.sort(files);
        for (File file : files) {
            publishProgress(file.getAbsolutePath());
            if (isCancelled()) break;
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(String... values) {
        myTaskAdapter.add(values[0]);
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(Void result) {
        myTaskAdapter.notifyDataSetChanged();
        super.onPostExecute(result);

        if (pDialog.isShowing())
            pDialog.dismiss();
    }

}

public class ImageAdapter extends BaseAdapter {

    private Context mContext;
    ArrayList<String> itemList = new ArrayList<String>();
    byte[] _image;
    int _id;


    public ImageAdapter(Context c) {
        mContext = c;
    }

    void add(String path) {
        itemList.add(path);
    }

    void clear() {
        itemList.clear();
    }

    void remove(int index){
        itemList.remove(index);
    }

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

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return itemList.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }

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

        ImageView imageView;
        if (convertView == null) { // if it not recycled, initialize some
                                    // attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(220, 220));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);

            convertView = imageView;

            holder = new ViewHolder();
            holder.image = imageView;
            holder.position = position;
            convertView.setTag(holder);
        } else {
            //imageView = (ImageView) convertView;
            holder = (ViewHolder) convertView.getTag();
            ((ImageView)convertView).setImageBitmap(null);
        }

        //Bitmap bm = decodeSampledBitmapFromUri(itemList.get(position), 220, 220);
        // Using an AsyncTask to load the slow images in a background thread
        new AsyncTask<ViewHolder, Void, Bitmap>() {
            private ViewHolder v;

            @Override
            protected Bitmap doInBackground(ViewHolder... params) {
                v = params[0];
                Bitmap bm = decodeSampledBitmapFromUri(itemList.get(position), 220, 220);
                return bm;
            }

            @Override
            protected void onPostExecute(Bitmap result) {
                super.onPostExecute(result);
                v.image.setImageBitmap(result);

            }
        }.execute(holder);
        return convertView;
    }

    public Bitmap decodeSampledBitmapFromUri(String path, int reqWidth,
            int reqHeight) {

        Bitmap bm = null;
        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth,
                reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        bm = BitmapFactory.decodeFile(path, options);

        return bm;
    }

    public int calculateInSampleSize(

    BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            if (width > height) {
                inSampleSize = Math.round((float) height
                        / (float) reqHeight);
            } else {
                inSampleSize = Math.round((float) width / (float) reqWidth);
            }
        }

        return inSampleSize;
    }

    class ViewHolder {
        ImageView image;
        int position;
    }

}

ImageAdapter myImageAdapter;

 Button addImage;
 GridView gridview;
 ImageView bigimg;
 ImageView img;
 Button share,reload,back;
 Bitmap bmp;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.gallery_view);

     gridview = (GridView) findViewById(R.id.gridview);
     myImageAdapter = new ImageAdapter(this);
     gridview.setAdapter(myImageAdapter);

    addImage = (Button) findViewById(R.id.btnAdd);

    addImage.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent add = new Intent(Gallery_Activity.this,Camera_Activity.class);
            startActivity(add);
        }
    });

    back = (Button) findViewById(R.id.back);

    back.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent add = new Intent(Gallery_Activity.this,Gallery_Activity.class);
            startActivity(add);
            //gridview.setVisibility(View.VISIBLE);
        }
    });


        share = (Button) findViewById(R.id.share);
        reload = (Button) findViewById(R.id.reload);

        share.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {


              img.setImageBitmap(bmp);


                    Uri bmpUri = getLocalBitmapUri(img);
                    if (bmpUri != null) {
                        // Construct a ShareIntent with link to image
                        Intent shareIntent = new Intent();
                        shareIntent.setAction(Intent.ACTION_SEND);
                        shareIntent.putExtra(Intent.EXTRA_STREAM, bmpUri);
                        shareIntent.putExtra(Intent.EXTRA_TEXT, "Shared via PartyPad");
                        shareIntent.putExtra(Intent.EXTRA_TEXT, "Shared via PartyPad   https://play.google.com/store/apps/details?id=com.appsinbox.partypad&hl=en");
                        shareIntent.setType("image/*");
                        // Launch sharing dialog for image
                        startActivity(Intent.createChooser(shareIntent, "Share Party Image"));    
                    } else {
                        // ...sharing failed, handle error
                    }

        }
        });

    myAsyncTaskLoadFiles = new AsyncTaskLoadFiles(myImageAdapter);
    myAsyncTaskLoadFiles.execute();

    gridview.setOnItemClickListener(myOnItemClickListener);

    Button buttonReload = (Button)findViewById(R.id.reload);
    buttonReload.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View arg0) {

            //Cancel the previous running task, if exist.
            myAsyncTaskLoadFiles.cancel(true);

            //new another ImageAdapter, to prevent the adapter have
            //mixed files
            myImageAdapter = new ImageAdapter(Gallery_Activity.this);
            gridview.setAdapter(myImageAdapter);
            myAsyncTaskLoadFiles = new AsyncTaskLoadFiles(myImageAdapter);
            myAsyncTaskLoadFiles.execute();
        }});

}



        public Uri getLocalBitmapUri(ImageView imageView) {
            // Extract Bitmap from ImageView drawable
            Drawable drawable = imageView.getDrawable();
            Bitmap bmp = null;
            if (drawable instanceof BitmapDrawable){
               bmp = ((BitmapDrawable) imageView.getDrawable()).getBitmap();
            } else {
               return null;
            }
            // Store image to default external storage directory
            Uri bmpUri = null;
            try {
                File file =  new File(Environment.getExternalStoragePublicDirectory(  
                    Environment.DIRECTORY_DOWNLOADS), "share_image_" + System.currentTimeMillis() + ".png");
                file.getParentFile().mkdirs();
                FileOutputStream out = new FileOutputStream(file);
                bmp.compress(Bitmap.CompressFormat.PNG, 90, out);
                out.close();
                bmpUri = Uri.fromFile(file);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return bmpUri;
        }

OnItemClickListener myOnItemClickListener = new OnItemClickListener() {

    @Override
    public void onItemClick(AdapterView<?> parent, View view, final int position,
            long id) {
        String prompt = "remove " + (String) parent.getItemAtPosition(position);
        String prompt1 = (String) parent.getItemAtPosition(position);
        System.out.println("PATH TEST "+prompt1);
        //Toast.makeText(getApplicationContext(), prompt, Toast.LENGTH_SHORT).show();

           bmp = BitmapFactory.decodeFile(prompt1);
           img = (ImageView) findViewById(R.id.big);
           gridview.setVisibility(View.GONE);
           img.setVisibility(View.VISIBLE);
           img.setImageBitmap(bmp);
           share.setVisibility(view.VISIBLE);
           back.setVisibility(view.VISIBLE);
           addImage.setVisibility(view.GONE);

    }
};



}