Zoom Image on Double Tap in android

The code below shows how we can zoom image on double tap in anroid, it's custom view class which will help us to make zoom image effect in anroid

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.view.GestureDetector.OnGestureListener;
import android.widget.FrameLayout.LayoutParams;

/**
 * Custom class to zoom image in android
 *
 * @author Yash@iotasol.com
 */
public class ZoomImageView extends View implements OnGestureListener {

    private static final int SCALING_FACTOR = 50;
    private final int LANDSCAPE = 1;
    private GestureDetector gestureDetector;
    private Drawable image = null;
    private int scalefactor = 0;
    private int orientation;
    private int zoomCtr = 0;
    private long lastTouchTime = 0;
    private int winX, winY, imageX, imageY, scrollX = 0, scrollY = 0, left,
    top, bottom, right;

    public ZoomImageView(Context context, int orientation) {
        super(context);
        setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
                LayoutParams.FILL_PARENT));
        this.orientation = orientation;
        gestureDetector = new GestureDetector(this);
    }

   
    public void setImage(Drawable bitmap, Activity activity) {
        image = bitmap;
        imageSetting(activity);
    }

    public void setImage(Bitmap bitmap, Activity activity) {
        image = new BitmapDrawable(bitmap).getCurrent();
        imageSetting(activity);
    }

    /**
     * Works in both landscape and potrait mode.
     */
    private void imageSetting(Activity activity) {
        scrollX = scrollY = 0;
        scalefactor = 0;
        imageX = winX = activity.getWindow().getWindowManager()
                .getDefaultDisplay().getWidth();
        imageY = winY = activity.getWindow().getWindowManager()
                .getDefaultDisplay().getHeight();
        if (orientation == LANDSCAPE) {
            imageX = 3 * imageY / 4;
        }
        calculatePos();
    }

    public void calculatePos() {
        int tempx, tempy;
        tempx = imageX + imageX * scalefactor / 100;
        tempy = imageY + imageY * scalefactor / 100;
        left = (winX - tempx) / 2;
        top = (winY - tempy) / 2;
        right = (winX + tempx) / 2;
        bottom = (winY + tempy) / 2;
        invalidate();
    }

   
    /**
     * Redraws the bitmap when zoomed or scrolled.
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (image == null)
            return;

        image.setBounds(left + scrollX, top + scrollY, right + scrollX, bottom
                + scrollY);
        image.draw(canvas);
    }

    public void zoomIn() {
        scalefactor += SCALING_FACTOR;
        calculatePos();
    }

    public void zoomOut() {
        if (scalefactor == 0)
            return;
        scrollX = scrollY = 0;
        scalefactor -= SCALING_FACTOR;
        calculatePos();
    }

    public void scroll(int x, int y) {
        scrollX += x / 5;
        scrollY += y / 5;
        if (scrollX + left > 0) {
            scrollX = 0 - left;
        } else if (scrollX + right < winX) {
            scrollX = winX - right;
        }
        if (scrollY + top > 0) {
            scrollY = 0 - top;
        } else if (scrollY + bottom < winY) {
            scrollY = winY - bottom;
        }
        invalidate();
    }

    @Override
    public boolean onTouchEvent(MotionEvent me) {
        boolean onTouchEvent = gestureDetector.onTouchEvent(me);
        return onTouchEvent;
    }

    @Override
    public boolean onDown(MotionEvent arg0) {
        long thisTime = arg0.getEventTime();
        if (thisTime - lastTouchTime < 250) {
            lastTouchTime = -1;
            onDoubleTap();
            return true;
        }
        lastTouchTime = thisTime;
        return true;
    }
   
    @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
                float distanceY) {
            if (zoomCtr == 0)
                return false;
            scroll((int) (e2.getX() - e1.getX()), (int) (e2.getY() - e1.getY()));
            return true;
        }
   
        private void onDoubleTap() {
            if (zoomCtr == 0) {
                zoomCtr++;
                zoomIn();
                return;
            }
            zoomCtr--;
            zoomOut();
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        // TODO Auto-generated method stub
        return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {
    }

   

    @Override
    public void onShowPress(MotionEvent e) {

    }

    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        // TODO Auto-generated method stub
        return true;
    }
}


Below is the test class which is used as example to run the ZoomImageView

import android.app.Activity;
import android.os.Bundle;

public class TestTapActivity extends Activity {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ZoomImageView imageView = new ZoomImageView(this, getWindow()
                .getWindowManager().getDefaultDisplay().getOrientation());
        imageView.setImage(this.getResources().getDrawable(R.drawable.sample1),
                this);

        this.setContentView(imageView);
    }
}

I hope this post will be helpful. 

Please share your comments and and you can also contact me @ info@iotasol.com or visit our site www.iotasol.com , www.iotadomains.com.