如何將最小值和最大值放大到佈局

Question

我有以下允許我無限放大和縮小的方式，但是我試圖設置一個min和max縮放值，以便佈局不會太大或太小。我試圖使用，但我只是不明白在代碼中放置它的位置。

private static final float MIN_ZOOM = 1.0f; 
private static final float MAX_ZOOM = //set Maximum zooming level 
float scale = Math.max(MIN_ZOOM, Math.min(scale, MAX_ZOOM)); 

public class ZoomableView extends RelativeLayout { 

    // States. 
    private static final byte NONE = 0; 
    private static final byte DRAG = 1; 
    private static final byte ZOOM = 2; 

    private byte mode = NONE; 

    // Matrices used to move and zoom image. 
    private Matrix matrix = new Matrix(); 
    private Matrix matrixInverse = new Matrix(); 
    private Matrix savedMatrix = new Matrix(); 

    // Parameters for zooming. 
    private PointF start = new PointF(); 
    private PointF mid = new PointF(); 
    private float oldDist = 1f; 
    private float[] lastEvent = null; 
    private long lastDownTime = 0l; 

    private float[] mDispatchTouchEventWorkingArray = new float[2]; 
    private float[] mOnTouchEventWorkingArray = new float[2]; 


    @Override 
    public boolean dispatchTouchEvent(MotionEvent ev) { 
     mDispatchTouchEventWorkingArray[0] = ev.getX(); 
     mDispatchTouchEventWorkingArray[1] = ev.getY(); 
     mDispatchTouchEventWorkingArray = screenPointsToScaledPoints(mDispatchTouchEventWorkingArray); 
     ev.setLocation(mDispatchTouchEventWorkingArray[0], mDispatchTouchEventWorkingArray[1]); 
     return super.dispatchTouchEvent(ev); 
    } 

    public ZoomableView(Context context) { 
     super(context); 
     init(context); 
    } 

    public ZoomableView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     init(context); 
    } 

    public ZoomableView(Context context, AttributeSet attrs, int defStyleAttr) { 
     super(context, attrs, defStyleAttr); 
     init(context); 
    } 


    private void init(Context context) { 

    } 


    /** 
    * Determine the space between the first two fingers 
    */ 
    private float spacing(MotionEvent event) { 
     float x = event.getX(0) - event.getX(1); 
     float y = event.getY(0) - event.getY(1); 
     return (float) Math.sqrt(x * x + y * y); 
    } 

    /** 
    * Calculate the mid point of the first two fingers 
    */ 
    private void midPoint(PointF point, MotionEvent event) { 
     float x = event.getX(0) + event.getX(1); 
     float y = event.getY(0) + event.getY(1); 
     point.set(x/2, y/2); 
    } 

    private float[] scaledPointsToScreenPoints(float[] a) { 
     matrix.mapPoints(a); 
     return a; 
    } 

    private float[] screenPointsToScaledPoints(float[] a) { 
     matrixInverse.mapPoints(a); 
     return a; 
    } 


    @Override 
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) { 
     int childCount = getChildCount(); 
     for (int i = 0; i < childCount; i++) { 
      View child = getChildAt(i); 
      if (child.getVisibility() != GONE) { 
       child.layout(left, top, left + child.getMeasuredWidth(), top + child.getMeasuredHeight()); 
      } 
     } 
    } 

    @Override 
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
     super.onMeasure(widthMeasureSpec, heightMeasureSpec); 

     int childCount = getChildCount(); 
     for (int i = 0; i < childCount; i++) { 
      View child = getChildAt(i); 
      if (child.getVisibility() != GONE) { 
       measureChild(child, widthMeasureSpec, heightMeasureSpec); 
      } 
     } 
    } 

    @Override 
    protected void dispatchDraw(Canvas canvas) { 
     float[] values = new float[9]; 
     matrix.getValues(values); 
     canvas.save(); 
     canvas.translate(values[Matrix.MTRANS_X], values[Matrix.MTRANS_Y]); 
     canvas.scale(values[Matrix.MSCALE_X], values[Matrix.MSCALE_Y]); 
     super.dispatchDraw(canvas); 
     canvas.restore(); 
    } 

    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
     // handle touch events here 
     mOnTouchEventWorkingArray[0] = event.getX(); 
     mOnTouchEventWorkingArray[1] = event.getY(); 

     mOnTouchEventWorkingArray = scaledPointsToScreenPoints(mOnTouchEventWorkingArray); 

     event.setLocation(mOnTouchEventWorkingArray[0], mOnTouchEventWorkingArray[1]); 

     switch (event.getAction() & MotionEvent.ACTION_MASK) { 
      case MotionEvent.ACTION_DOWN: 
       savedMatrix.set(matrix); 
       mode = DRAG; 
       lastEvent = null; 
       long downTime = event.getDownTime(); 
       if (downTime - lastDownTime < 300l) { 
        float density = getResources().getDisplayMetrics().density; 
        if (Math.max(Math.abs(start.x - event.getX()), Math.abs(start.y - event.getY())) < 40.f * density) { 
         savedMatrix.set(matrix); 
         mid.set(event.getX(), event.getY()); 
         mode = ZOOM; 
         lastEvent = new float[4]; 
         lastEvent[0] = lastEvent[1] = event.getX(); 
         lastEvent[2] = lastEvent[3] = event.getY(); 
        } 
        lastDownTime = 0l; 
       } else { 
        lastDownTime = downTime; 
       } 
       start.set(event.getX(), event.getY()); 
       break; 
      case MotionEvent.ACTION_POINTER_DOWN: 
       oldDist = spacing(event); 
       if (oldDist > 10f) { 
        savedMatrix.set(matrix); 
        midPoint(mid, event); 
        mode = ZOOM; 
       } 
       lastEvent = new float[4]; 
       lastEvent[0] = event.getX(0); 
       lastEvent[1] = event.getX(1); 
       lastEvent[2] = event.getY(0); 
       lastEvent[3] = event.getY(1); 
       break; 
      case MotionEvent.ACTION_UP: 
      case MotionEvent.ACTION_POINTER_UP: 
       mode = NONE; 
       lastEvent = null; 
       break; 
      case MotionEvent.ACTION_MOVE: 
       final float density = getResources().getDisplayMetrics().density; 
       if (mode == DRAG) { 
        matrix.set(savedMatrix); 
        float dx = event.getX() - start.x; 
        float dy = event.getY() - start.y; 
        matrix.postTranslate(dx, dy); 
        matrix.invert(matrixInverse); 
        if (Math.max(Math.abs(start.x - event.getX()), Math.abs(start.y - event.getY())) > 20.f * density) { 
         lastDownTime = 0l; 
        } 
       } else if (mode == ZOOM) { 
        if (event.getPointerCount() > 1) { 
         float newDist = spacing(event); 
         if (newDist > 10f * density) { 
          matrix.set(savedMatrix); 
          float scale = (newDist/oldDist); 
          matrix.postScale(scale, scale, mid.x, mid.y); 
          matrix.invert(matrixInverse); 
         } 
        } else { 
         matrix.set(savedMatrix); 
         float scale = event.getY()/start.y; 
         matrix.postScale(scale, scale, mid.x, mid.y); 
         matrix.invert(matrixInverse); 
        } 
       } 
       break; 
     } 

     invalidate(); 
     return true; 
    } 


} 

Answer 1

你需要做一個類擴展的RelativeLayout，那裏你可以通過覆蓋getMaxZoomLevel()和getMinZoomLevel()，這樣的設置：

public class ZoomableView extends RelativeLayout { 

@Override 
public int getMaxZoomLevel() { 
    return 22; 
} 

@Override 
public int getMinZoomLevel() { 
    return 12; 
} 

}