Question

There are two things I want to achieve with the Gallery view:

1) when a user makes a selection within the Gallery view I do not want the images to move (i.e. I do not want the selected image to move to the center)

2) when a user makes a selection within the Gallery view I want the selected image to be highlighted orange on ACTION_DOWN, and the highlight removed on ACTION_UP – just like on Buttons.

How is that done ?

Answer 1

Solved it myself …

the following features are included in this sample code

1. apparently-endless horizontal
   scrolling
2. selection detection without using
   the GODAWFUL
   Gallery.setOnItemSelectedListener().
3. highlighting the selection
   (although this needs more work –
   namely storing the selection because
   the Gallery will lose the
   highlighting after it’s scrolled
   off-screen)

---

public class ActivityMine extends Activity implements OnTouchListener
{
    //UI references
    private Gallery mGallery;

    //member variables
    private float fX, fY;
    private ImageBuffer mImageBuffer;//just an array of images


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

        //get references to UI components
        mGallery = (Gallery) findViewById(R.id.filter_gallery);

        //make widgets touch sensitive
        mGallery.setOnTouchListener(this);

        //connect Gallery with adapter
        mGallery.setAdapter(new GalleryAdapter(this, mImageBuffer));

        //auto-select first image (position 1073741820)
        final int iTemp = (int)( Integer.MAX_VALUE / 2 ) - ( ( Integer.MAX_VALUE / 2 ) % mImageBuffer.getCount() );
        mGallery.setSelection(iTemp);
    }


    @Override
    protected void onDestroy()
    {
        super.onDestroy();
    }


    public boolean onTouch(View v, MotionEvent event)
    {
        final int actionPerformed = event.getAction();
        final int widgetID = v.getId();

        if (actionPerformed == MotionEvent.ACTION_DOWN)
        {
            if (widgetID == R.id.filter_gallery)
            {
                fX=event.getRawX();
                fY=event.getRawY();
            }
        }

        if (actionPerformed == MotionEvent.ACTION_UP)
        {
            switch (widgetID)
            {
                case R.id.filter_gallery:
                {
                    final float posX = event.getRawX();
                    final float posY = event.getRawY();

                    final float MAXPRESSRANGE = 10.0f;

                    //detect if user performed a simple press
                    if ((posX < fX+MAXPRESSRANGE) && (posX > fX-MAXPRESSRANGE))
                    {
                        if ((posY < fY+MAXPRESSRANGE) && (posY > fY-MAXPRESSRANGE))
                        {
                            //valid press detected!

                            //convert gallery coordinates to a position
                            final int iPosition = mGallery.pointToPosition((int)event.getX(), (int)event.getY());

                            if (iPosition != AdapterView.INVALID_POSITION)
                            {
                                //this is necessary to obtain the index of the view currently visible and pressed
                                final int iVisibleViewIndex = iPosition - mGallery.getFirstVisiblePosition();

                                //get a reference to the child and modify the border
                                View child = mGallery.getChildAt(iVisibleViewIndex);
                                if (child != null)
                                {
                                    RelativeLayout borderImg = (RelativeLayout)child;
                                    borderImg.setBackgroundColor(0xFFFFFFFF);
                                }
                            }

                            // consume event
                            return true;
                        }
                    }
                }//end of: case R.id.filter_gallery
            }//end of: switch()
        }

        return false;//do not consume event otherwise the UI widget touched won't receive the event
    }


    public class GalleryAdapter extends BaseAdapter
    {
        //member variables
        private Context mContext;
        private ImageBuffer mImageBuffer;


        public GalleryAdapter(Context context, ImageBuffer imageBuffer)
        {
            mContext = context;
            mImageBuffer = imageBuffer;
        }

        //get count of images in the gallery
        public int getCount()
        {
            return Integer.MAX_VALUE;
        }

        public Object getItem(int position)
        {
            if (position >= mImageBuffer.getCount())
            { 
                position = position % mImageBuffer.getCount(); 
            }
            return position;
        }

        public long getItemId(int position)
        {
            if (position >= mImageBuffer.getCount())
            { 
                position = position % mImageBuffer.getCount(); 
            }
            return position;
        }

        //returns the individual images to the widget as it requires them
        public View getView(int position, View convertView, ViewGroup parent)
        {
            final ImageView imgView = new ImageView(mContext);

            if (position >= mImageBuffer.getCount())
            { 
                position = position % mImageBuffer.getCount(); 
            }

            imgView.setImageBitmap(mImageBuffer.getBitmapFromBuffer(position));

            //put black borders around the image
            final RelativeLayout borderImg = new RelativeLayout(mContext);
            borderImg.setPadding(5, 5, 5, 5);
            borderImg.setBackgroundColor(0xff000000);
            borderImg.addView(imgView);
            return borderImg;
        }
    }
}



import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;

public class ImageBuffer
{
    //member variables
    private Activity mActivity;
    private Map<String,Integer> mIndexMap;
    private List<Bitmap> mBitmapList;
    private int mImageCount;


    public ImageBuffer(Activity activity)
    {
        mActivity = activity;
        mIndexMap = new HashMap<String,Integer>();
        mBitmapList = new ArrayList<Bitmap>();
        mImageCount=0;
    }


    public int getCount()
    {
        return mImageCount;
    }


    public int putAssetBitmapInBuffer(String assetfilename, String overrideFilename)
    {
        int iValueToReturn = -1;

        try
        {
            Bitmap bitmap = getBitmapFromAsset(assetfilename);
            if (bitmap != null)
            {
                final int iIndex = mBitmapList.size();
                if (overrideFilename == null)
                {
                    mIndexMap.put(assetfilename, iIndex);
                }
                else
                {
                    mIndexMap.put(overrideFilename, iIndex);
                }
                mBitmapList.add(bitmap);
                iValueToReturn = iIndex;
                mImageCount++;
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

        return iValueToReturn;
    }


    /**
     * put an image from filesystem folder into buffer
     * @param filename name of file, i.e. "image.png"
     * @param strSubFolder subfolder, i.e. "/products"
     * @param bGetFromSDCARD when true the image is read from SDCARD, otherwise main memory
     * @return on success: index of image in buffer. on error: -1
     */
    public int putLocalFSbitmapInBuffer(String filename, String strSubFolder, boolean bGetFromSDCARD)
    {
        int iValueToReturn = -1;

        Bitmap bitmap = getBitmapFromLocalFS(filename, strSubFolder, bGetFromSDCARD);
        if (bitmap != null)
        {
            final int iIndex = mBitmapList.size();
            mIndexMap.put(filename, iIndex);
            mBitmapList.add(bitmap);
            iValueToReturn = iIndex;
            mImageCount++;
        }

        return iValueToReturn;
    }


    public Bitmap getBitmapFromBuffer(String assetfilename)
    {
        Bitmap bitmap = null;

        if (mIndexMap.containsKey(assetfilename))
        {
            final int iIndex = mIndexMap.get(assetfilename);
            bitmap = mBitmapList.get(iIndex);
        }

        return bitmap;
    }


    public Bitmap getBitmapFromBuffer(int position)
    {
        Bitmap bitmap = null;

        if (position < mBitmapList.size() && position > -1)
        {
            bitmap = mBitmapList.get(position);
        }

        return bitmap;
    }


    /**
     * get bitmap from assets folder in project
     * @param assetfilename name of asset, i.e. "image.png"
     * @return Bitmap
     * @exception IOException when file is not found
     */
    private Bitmap getBitmapFromAsset(String assetfilename) throws IOException
    {
        AssetManager assetManager = mActivity.getAssets();

        InputStream istr = assetManager.open(assetfilename);
        Bitmap bitmap = BitmapFactory.decodeStream(istr);
        istr.close();

        return bitmap;
    }


    /**
     * get bitmap from file system
     * @param filename name of image, i.e. "image.png"
     * @param strSubFolder subfolder, i.e. "/products"
     * @param bGetFromSDCARD when true the image is read from SDCARD, otherwise main memory
     * @return Bitmap
     */
    private Bitmap getBitmapFromLocalFS(String filename, String strSubFolder, boolean bGetFromSDCARD)
    {
        File file;

        if (bGetFromSDCARD == true)
        {
            //store in SDCARD
            file = new File(Environment.getExternalStorageDirectory()+strSubFolder, filename);
        }
        else
        {
            //store in main memory
            file = new File(mActivity.getFilesDir().getAbsolutePath()+strSubFolder, filename);
        }


        Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());

        return bitmap;
    }

}