在 canvas 上跟踪触摸输入

Question

我有一个由 canvas drawrect 制成的 5x5 方块的游戏板：

protected void onDraw(Canvas canvas) {
    for (int rowNo = 0; rowNo < nSquares; rowNo++) {
        paint.setColor(((rowNo & 1) == 0) ? colorA : colorB);
        for (int colNo = 0; colNo < nSquares; colNo++) {
            int left = colNo * squareWidth;
            int top = rowNo * squareWidth;

            Rect areaRect = new Rect(left, top, left + squareWidth, top + squareWidth);
            canvas.drawRect(areaRect, paint);


            paint.setColor((paint.getColor() == colorA) ? colorB : colorA);

            paint.setTextSize((float)(squareWidth*0.8));

            RectF bounds = new RectF(areaRect);
            String letter = "A";
            bounds.right = paint.measureText(letter, 0, letter.length());
            bounds.bottom = paint.descent() - paint.ascent();

            bounds.left += (areaRect.width() - bounds.right) / 2.0f;
            bounds.top += (areaRect.height() - bounds.bottom) / 2.0f;

            canvas.drawText(letter, bounds.left, bounds.top - paint.ascent(), paint);
        }
    }

我想跟踪触摸输入以获取用户正在触摸的方块.. 我的尝试是

public boolean onTouchEvent(MotionEvent event){ 

    int action = MotionEventCompat.getActionMasked(event);

    int x = (int)event.getX();
    int y = (int)event.getY();
    Log.i(DEBUG_TAG, "Position: (" + x + ", " + y + ")");

    int squareTouched = gameBoard.getSquare(x,y);
}

getSquare 在哪里

public int getSquare(int x, int y) {
    int row = 0;
    int col = 0;
    for(int rowNo = 1; rowNo <= nSquares; rowNo++) {
        Log.i("Row", "Width: " + squareWidth + " rowNo: " + rowNo + " rowNo*squareW: " + rowNo*squareWidth + " y: " + y);
        if(rowNo*squareWidth > y)
        {
            row = rowNo;
            break;
        }
    }

    for (int colNo = 1; colNo <= nSquares; colNo++) {
        if(colNo*squareWidth > x)
        {
            col = colNo;
            break;
        }
    }
    Log.i(DEBUG_TAG, "Row: " + row + " Col: " + col);
    return (row-1)*nSquares + col;
}

问题是onTouchEvent getX 和getY 指的是屏幕0,0，但是当我绘制正方形时0,0,0,0 指的是视图原点？我对吗？如何获得相对于游戏板视图的输入位置？获取屏幕中的视图位置并将其 add/subtract 定位到 tochEvent x 和 y 位置是否是一种解决方案？

Answer 1

我假设 onDraw() 和 getSquare() 属于 GameBoardView 并且 onTouchEvent() 属于其直接父级。如果是这样，那么 onTouchEvent() 应该是这样的

    public boolean onTouchEvent(MotionEvent event){
          int action = MotionEventCompat.getActionMasked(event);
          int x = (int)event.getX() - gameBoard.getX();
          int y = (int)event.getY() - gameBoard.getY();
          Log.i(DEBUG_TAG, "Position: (" + x + ", " + y + ")");

          int squareTouched = gameBoard.getSquare(x, y);
    }

在视图中，onDraw() 和 onTouchEvent() 中的 x 和 y 都相对于视图本身（滚动视图时除外）。由于在您的情况下 onTouchEvent() 属于父项而 onDraw() 属于子项，因此我使用 View.getX() 和 getY() 来转换坐标。 View.getX() returns 视图相对于其父视图的 x 位置加上 translationX。

Answer 2

我无法将 gameBoard().getX/Y() 设置为 return 正确的值。我的猜测是操作栏被排除在外？

我现在用getLocationOnScreen

    @Override
public boolean onTouchEvent(MotionEvent event){ 

    int action = MotionEventCompat.getActionMasked(event);
    int boardLocation[] = new int[2];
    gameBoard.getLocationOnScreen(boardLocation);

    int touchX = (int)event.getX();
    int touchY = (int)event.getY();

    int x = touchX - boardLocation[0];
    int y = touchY - boardLocation[1];

    int squareTouched = gameBoard.getSquare(x,y);
}

这解决了我的问题..

在 canvas 上跟踪触摸输入

Track touch input on canvas

android

canvas

touch