如何在Android中计算缩放画布的坐标



我正在使用Android项目。我很难理解如何使用ScaleDetector和Canvas。

我有一个名为printTable的矩形列表。我在onDraw()方法中绘制了屏幕上的每个矩形。然后我有第二个列表,名为listPointer,包含矩形和矩形的id。我正在TouchEvent上查看在屏幕上绘制的矩形列表。如果矩形包含X,Y我打印有关单击矩形的id的信息。

问题是当我移动画布或缩放画布时,如何计算我的X,Y?

public class Painter extends View {
    //
    private static final int INVALID_POINTER_ID = -1;
    private float mPosX;
    private float mPosY;
    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;
    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;
    //
    Paint paint = new Paint();
    List<Table> printTable = new ArrayList<Table>(); // lista wyświetlanych stolików
    //
    List<Pointer> listPointer = new ArrayList<Pointer>();
    //
    public Painter(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }
    public Painter(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }
    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();
            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));
            invalidate();
            return true;
        }
    }
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // Let the ScaleGestureDetector inspect all events.
        mScaleDetector.onTouchEvent(ev);
        final int action = ev.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();
            mLastTouchX = x;
            mLastTouchY = y;
            mActivePointerId = ev.getPointerId(0);
            for(int i = 0; i<listPointer.size(); i++)
            {
                if(listPointer.get(i).getRectangle().contains((int)(Math.round(x)), (int)(Math.round(y))))
                {
                    if(listPointer.get(i).getIsItTable())
                    {
                        Log.e("Exc", "Stolik "+listPointer.get(i).getId());
                    }
                    else
                    {
                        Log.e("Exc", "Button "+listPointer.get(i).getId());
                    }
                }
            }
            break;
        }
        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);
            // Only move if the ScaleGestureDetector isn't processing a gesture.
            if (!mScaleDetector.isInProgress()) {
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;
                mPosX += dx;
                mPosY += dy;
                invalidate();
            }
            mLastTouchX = x;
            mLastTouchY = y;
            break;
        }
        case MotionEvent.ACTION_UP: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }
        case MotionEvent.ACTION_CANCEL: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }
        case MotionEvent.ACTION_POINTER_UP: {
            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
                    >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
            final int pointerId = ev.getPointerId(pointerIndex);
            if (pointerId == mActivePointerId) {
                // This was our active pointer going up. Choose a new
                // active pointer and adjust accordingly.
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                mLastTouchX = ev.getX(newPointerIndex);
                mLastTouchY = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
            }
            break;
        }
        }
        return true;
    }
    //
    public Painter(Context context) {
        this(context, null, 0);
        paint.setColor(Color.BLACK);
        List<Table> printTable = Bridge.getTables(getContext()); 
    }
    @SuppressLint("DrawAllocation")
    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
            Rect rect = null;
            RectF rectF = null;
            // czyszczenie tablicy
            listPointer.clear();
            for(int j = 0; j<printTable.size(); j++)
            {
                Table item = printTable.get(j);
                // Obsługa rozciągania
                canvas.save();
                Log.d("DEBUG", "X: "+mPosX+" Y: "+mPosY);
                canvas.translate(mPosX, mPosY);
                canvas.scale(mScaleFactor, mScaleFactor);
                // dodaje do tablicy stołów
                paint.setColor(getResources().getColor(R.color.green));
                rect = new Rect(item.getX1(), item.getY1(), item.getX2(), item.getY2());
                rectF = new RectF(rect);
                canvas.drawRoundRect(rectF, 0,0, paint);
                listPointer.add(new Pointer(rect, true, j));
                canvas.restore();
            }
    }

获取视图的矩阵。它应该包含所有的缩放和平移。然后将作为向量的x,y坐标乘以用于缩放视图的矩阵。这应该将预缩放/预平移坐标转换为缩放坐标。如果需要较少的乘法运算,您也可以将后缩放坐标乘以该矩阵的倒数,以获得预缩放坐标。

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