tt-rss-android/org.fox.ttrss/src/main/java/it/sephiroth/android/library/imagezoom/ImageViewTouch.java

package it.sephiroth.android.library.imagezoom;

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.ScaleGestureDetector.OnScaleGestureListener;
import android.view.ViewConfiguration;

public class ImageViewTouch extends ImageViewTouchBase {

	private static final float SCROLL_DELTA_THRESHOLD = 1.0f;
	static final float MIN_ZOOM = 0.9f;
	protected ScaleGestureDetector mScaleDetector;
	protected GestureDetector mGestureDetector;
	protected int mTouchSlop;
	protected float mCurrentScaleFactor;
	protected float mScaleFactor;
	protected int mDoubleTapDirection;
	protected OnGestureListener mGestureListener;
	protected OnScaleGestureListener mScaleListener;
	protected boolean mDoubleTapToZoomEnabled = true;
	protected boolean mScaleEnabled = true;
	protected boolean mScrollEnabled = true;

    private OnImageViewTouchDoubleTapListener doubleTapListener;

    public interface OnScaleChangedListener {
		public void onScaleChanged(float scale);
	}
    
    protected OnScaleChangedListener mScaleChangedListener;
    
	public ImageViewTouch( Context context, AttributeSet attrs ) {
		super( context, attrs );
	}
	
	@Override
	protected void init() {
		super.init();
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
		mGestureListener = getGestureListener();
		mScaleListener = getScaleListener();

		mScaleDetector = new ScaleGestureDetector( getContext(), mScaleListener );
		mGestureDetector = new GestureDetector( getContext(), mGestureListener, null, true );

		mCurrentScaleFactor = 1f;
		mDoubleTapDirection = 1;
	}

    public void setDoubleTapListener( OnImageViewTouchDoubleTapListener doubleTapListener ){
        this.doubleTapListener = doubleTapListener;
    }

	public void setDoubleTapToZoomEnabled( boolean value ) {
		mDoubleTapToZoomEnabled = value;
	}

	public void setScaleEnabled( boolean value ) {
		mScaleEnabled = value;
	}

	public void setScrollEnabled( boolean value ) {
		mScrollEnabled = value;
	}

	public boolean getDoubleTapEnabled() {
		return mDoubleTapToZoomEnabled;
	}

	protected OnGestureListener getGestureListener() {
		return new GestureListener();
	}

	protected OnScaleGestureListener getScaleListener() {
		return new ScaleListener();
	}

	@Override
	protected void onBitmapChanged( Drawable drawable ) {
		super.onBitmapChanged( drawable );

		float v[] = new float[9];
		mSuppMatrix.getValues( v );
		mCurrentScaleFactor = v[Matrix.MSCALE_X];
	}

	@Override
	protected void _setImageDrawable( final Drawable drawable, final boolean reset, final Matrix initial_matrix, final float maxZoom ) {
		super._setImageDrawable( drawable, reset, initial_matrix, maxZoom );
		mScaleFactor = getMaxZoom() / 3;
	}

	@Override
	public boolean onTouchEvent( MotionEvent event ) {
		mScaleDetector.onTouchEvent( event );
		if ( !mScaleDetector.isInProgress() ) mGestureDetector.onTouchEvent( event );
		int action = event.getAction();
		switch ( action & MotionEvent.ACTION_MASK ) {
			case MotionEvent.ACTION_UP:
				if ( getScale() < 1f ) {
					zoomTo( 1f, 50 );
				}
				break;
		}
		return true;
	}

	@Override
	protected void onZoom( float scale ) {
		super.onZoom( scale );
		if ( !mScaleDetector.isInProgress() ) mCurrentScaleFactor = scale;
		
		if (mScaleChangedListener != null) {
			mScaleChangedListener.onScaleChanged(mCurrentScaleFactor);
		}
	}

	protected float onDoubleTapPost( float scale, float maxZoom ) {
		if ( mDoubleTapDirection == 1 ) {
			if (mCurrentScaleFactor - 1.0f < 0.01) { //( scale + ( mScaleFactor * 2 ) ) <= maxZoom

				float scaleFactor = mScaleFactor;

				RectF bitmapRect = getBitmapRect();
				
				float w = bitmapRect.right - bitmapRect.left;
				float h = bitmapRect.bottom - bitmapRect.top;
				
				if (w < getWidth()) {
					scaleFactor = (float)getWidth() / w - scale;
				} else if (h < getHeight()) {
					scaleFactor = (float)getHeight() / h - scale;
				}
				
				return scale + scaleFactor;
			} else {
				mDoubleTapDirection = -1;
				return maxZoom;
			}
		} else {
			mDoubleTapDirection = 1;
			return 1f;
		}
	}
	
	/**
	 * Determines whether this ImageViewTouch can be scrolled.
	 * @param direction
	 * 				- positive direction value means scroll from right to left, 
	 * 				negative value means scroll from left to right
	 * 
	 * @return true if there is some more place to scroll, false - otherwise.
	 */
	public boolean canScroll(int direction) {
		RectF bitmapRect = getBitmapRect();
		updateRect(bitmapRect, mScrollRect);
		Rect imageViewRect = new Rect();
		getGlobalVisibleRect(imageViewRect);
		
		if (bitmapRect.right >= imageViewRect.right) {
			if (direction < 0) {
				return Math.abs(bitmapRect.right - imageViewRect.right) > SCROLL_DELTA_THRESHOLD;
			}
		}
		
		double bitmapScrollRectDelta = Math.abs(bitmapRect.left - mScrollRect.left);
		return bitmapScrollRectDelta > SCROLL_DELTA_THRESHOLD;
	}
	
	public class GestureListener extends GestureDetector.SimpleOnGestureListener {

		@Override
		public boolean onDoubleTap( MotionEvent e ) {
			Log.i( LOG_TAG, "onDoubleTap. double tap enabled? " + mDoubleTapToZoomEnabled);
			if (mDoubleTapToZoomEnabled) {
				float scale = getScale();
				float targetScale = scale;
				targetScale = onDoubleTapPost( scale, getMaxZoom() );
				targetScale = Math.min( getMaxZoom(), Math.max( targetScale, MIN_ZOOM ) );
				mCurrentScaleFactor = targetScale;
				zoomTo( targetScale, e.getX(), e.getY(), 200 );
				invalidate();
            }

            if( null != doubleTapListener ){
                doubleTapListener.onDoubleTap();
            }

			return super.onDoubleTap( e );
		}

		@Override
		public void onLongPress( MotionEvent e ) {
			if ( isLongClickable() ) {
				if ( !mScaleDetector.isInProgress() ) {
					setPressed( true );
					performLongClick();
				}
			}
		}

		@Override
		public boolean onScroll( MotionEvent e1, MotionEvent e2, float distanceX, float distanceY ) {
			if ( !mScrollEnabled ) return false;

			if ( e1 == null || e2 == null ) return false;
			if ( e1.getPointerCount() > 1 || e2.getPointerCount() > 1 ) return false;
			if ( mScaleDetector.isInProgress() ) return false;
			if ( getScale() == 1f ) return false;
			scrollBy( -distanceX, -distanceY );
			invalidate();
			return super.onScroll( e1, e2, distanceX, distanceY );
		}

		@Override
		public boolean onFling( MotionEvent e1, MotionEvent e2, float velocityX, float velocityY ) {
			if ( !mScrollEnabled ) return false;

			if ( e1.getPointerCount() > 1 || e2.getPointerCount() > 1 ) return false;
			if ( mScaleDetector.isInProgress() ) return false;

			float diffX = e2.getX() - e1.getX();
			float diffY = e2.getY() - e1.getY();

			if ( Math.abs( velocityX ) > 800 || Math.abs( velocityY ) > 800 ) {
				scrollBy( diffX / 2, diffY / 2, 300 );
				invalidate();
			}
			return super.onFling( e1, e2, velocityX, velocityY );
		}
	}

	public class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {

		@SuppressWarnings("unused")
		@Override
		public boolean onScale( ScaleGestureDetector detector ) {
			float span = detector.getCurrentSpan() - detector.getPreviousSpan();
			float targetScale = mCurrentScaleFactor * detector.getScaleFactor();
			if ( mScaleEnabled ) {
				targetScale = Math.min( getMaxZoom(), Math.max( targetScale, MIN_ZOOM ) );
				zoomTo( targetScale, detector.getFocusX(), detector.getFocusY() );
				mCurrentScaleFactor = Math.min( getMaxZoom(), Math.max( targetScale, MIN_ZOOM ) );
				mDoubleTapDirection = 1;
				invalidate();
				return true;
			}
			return false;
		}
	}

    public interface OnImageViewTouchDoubleTapListener {
        void onDoubleTap();
    }
    
    public void setOnScaleChangedListener(OnScaleChangedListener listener) {
    	mScaleChangedListener = listener;
    }
}