assetsから呼び出した画像をgridviewで表示して、サムネイルをタップした際に画面全体に表示させるには

assetsから呼び出した画像をgridviewで表示して、サムネイルをタップした際に画面全体に表示させたいのですが、やり方がわかりません。
画像を表示させることはできました。
どのように記載すれば全体表示できるのでしょうか。

MainActivity

public class MainActivity extends AppCompatActivity {
private AssetManager assetManager;
private ImageView imageViewbyCode;
private LinearLayout myLayoutP;
private final static String TAG = "MainActivity";
private GridView gridView = null;
ArrayList<String> listPath;
ArrayList<Bitmap> bitmapList;
GridViewAdpter gridViewAdapter;

    @Override
    protected void onCreate (Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    Toolbar toolbar = findViewById(R.id.toolbar);

    toolbar.setLogo(R.mipmap.ic_launcher);

    setSupportActionBar(toolbar);

    CollapsingToolbarLayout toolbarLayout = findViewById(R.id.toolbarLayout);

    toolbarLayout.setTitle(getString(R.string.toolbar_title));

    toolbarLayout.setExpandedTitleColor(Color.WHITE);

    toolbarLayout.setCollapsedTitleTextColor(Color.LTGRAY);

    gridView = (GridView) findViewById(R.id.gridviewframes);

    assetManager = getAssets();
    bitmapList = new ArrayList<Bitmap>();



    try {
        listAllImages();
    } catch (Exception e) {

    }
    try {
        gridViewAdapter = new GridViewAdpter(MainActivity.this, bitmapList);
        gridView.setAdapter(gridViewAdapter);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public void listAllImages(){
    Bitmap bitmap = null;
    try{
        String[] imgPath = assetManager.list("photos");
        for(int i = 0; i< imgPath.length; i++){
            InputStream is = assetManager.open("photos/"+imgPath[i]);
            Log.d(TAG, imgPath[i]);
            bitmap = BitmapFactory.decodeStream(is);
            bitmapList.add(bitmap);
        }
    }catch (IOException e){
        Log.e(TAG, e.getMessage());
    }
}

}

GridViewAdapter

public class GridViewAdapter extends BaseAdapter {
Context mContext;

ArrayList<Bitmap> mImageArray;

GridViewAdapter(Context context, ArrayList<Bitmap> imgArray) {
    this.mContext = context;
    mImageArray = imgArray;
}

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

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

@Override
public long getItemId(int position) {
    return 0;
}

@Override
public boolean isEnabled(int i) {
    return true;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    View gridView;

    gridView = new View(mContext);

    gridView = inflater.inflate(R.layout.gridview, null);

    ImageView stickerImage = (ImageView) gridView.findViewById(R.id.sticker_item);

    stickerImage.setImageBitmap(mImageArray.get(position));

    stickerImage.setScaleType(ImageView.ScaleType.FIT_XY);
    stickerImage.setLayoutParams(new ViewGroup.LayoutParams(300, 300));
    return  gridView;
}

}