Java 类android.view.ScaleGestureDetector.SimpleOnScaleGestureListener 实例源码

public HotSpotNodeView( Context context ) {
    super( context );
    this.setClickable( true );
    this.setFocusable( false );
    this.setWillNotDraw( false );  // Layouts have onDraw() disabled by default.

    rectPaint = new Paint( Paint.ANTI_ALIAS_FLAG );
    rectPaint.setColor( otherColor );
    rectPaint.setStyle( Paint.Style.STROKE );
    rectPaint.setStrokeWidth( 1 );
    rectPaint.setStrokeCap( Paint.Cap.ROUND );
    rectPaint.setStrokeJoin( Paint.Join.ROUND );
    rectPaint.setStrokeMiter( 1 );
    rectPaint.setPathEffect( new DashPathEffect( new float[] {1f, 2f}, 0 ) );

    gestureDetector = new GestureDetector( context, new SimpleOnGestureListener() {
        @Override
        public boolean onSingleTapUp( MotionEvent e ) {
            if ( hotspotNode != null ) {
                for ( ZoneHolder zoneHolder : zoneHolders ) {
                    float paddedX = e.getX() + HotSpotNodeView.this.getPaddingLeft();
                    float paddedY = e.getY() + HotSpotNodeView.this.getPaddingTop();

                    if ( zoneHolder.currentZoneRect.contains( paddedX, paddedY ) ) {

                        if ( zoneHolder.imageRef != null ) {
                            zoneHolder.revealed = !zoneHolder.revealed;
                            HotSpotNodeView.this.invalidate();
                            // Keep looping through layers? Sure.
                        }
                        else if ( zoneHolder.linkTarget != -1 ) {
                            HotSpotNodeView.this.getNavCtrl().setReaderNode( zoneHolder.linkTarget );
                            break;
                        }
                    }
                }
            }

            return true;
        }

        @Override
        public boolean onScroll( MotionEvent e1, MotionEvent e2, float distanceX, float distanceY ) {

            handleScroll( distanceX, distanceY );  // Delta since last scroll, NOT since initial drag.
            return true;
        }

        @Override
        public boolean onDown( MotionEvent e ) {
            return true;  // Necessary for all other gesture methods to work.
        }
    });

    scaleDetector = new ScaleGestureDetector( context, new SimpleOnScaleGestureListener() {
        public boolean onScale( ScaleGestureDetector detector ) {
            float newScale = scale;
            newScale *= detector.getScaleFactor();
            newScale = Math.max( minScale, Math.min( newScale, 2.0f ) );
            handleScale( newScale );

            return true;
        }
    });


    this.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch( View v, MotionEvent e ) {
            if ( gestureDetector.onTouchEvent( e ) ) {
                return true;
            }
            else if ( scaleDetector.onTouchEvent( e ) ) {
                return true;
            }
            // Check MotionEvent.ACTION_UP here if interested in end-of-scroll.

            return false;
        }
    });
}