canvas.drawLine不可见

Question

我正在尝试使用drawLine（）绘制数独网格的线条但是每条线条逐渐变得更暗淡，直到它们在屏幕的一半处不可见。 screenshot of emulator

canvas.drawLine(0, (i + 1) * tileHeight,getWidth(), (i + 1) * tileHeight, gridPaint ); //horizontal lines

我知道他们在那里是因为在旋转屏幕的短暂时间内，线条会按预期显示，但随后它们会再次消失。

我已经尝试了各种方法来解决这个问题，但我仍然不知道是什么造成了这个

private static final String TAG = "Soduku";
private final Game game; //game logic
private float tileWidth;
private float tileHeight;
private int selX; //x index of selection
private int selY; //y index of selection
private Rect selRect = new Rect();

private Paint gridPaint = new Paint();

public PuzzleView(Context context) {
    super(context);
    this.game = (Game)context;
    setFocusable(true);
    setFocusableInTouchMode(true);

    gridPaint.setColor(getResources().getColor(R.color.black));

}

@Override
protected void onSizeChanged(int w, int h, int oldW, int oldH) {
    tileWidth = w / 9f;
    tileHeight = h / 9f;
    getRect(selX, selY, selRect);
    Log.d(TAG, "onSizeChaned: width " + tileWidth + ", height " + tileHeight);
    super.onSizeChanged(w, h, oldW, oldH);
}

private void getRect(int x, int y, Rect rect) {
    rect.set((int) (x * tileWidth), (int) (y * tileHeight), (int) (x * Math.pow((double) tileWidth, 2)),
            (int) (y * Math.pow((double) tileHeight, 2)));
}


@Override
protected void onDraw(Canvas canvas) {
    invalidate();
    Log.d("onDraw", "tileHeight - " + ((Float) tileHeight).toString());
    for(int i = 0; i < 9; i++) {
        canvas.drawLine(0, (i + 1) * tileHeight,getWidth(), (i + 1) * tileHeight, gridPaint ); //horizontal lines
        canvas.drawLine((i + 1) * tileWidth, 0, (i + 1) * tileWidth, getHeight(), gridPaint); //vertical lines
    }


}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    Log.d(TAG, "onKeyDown: keyCode " + keyCode + ", keyEvent " + event);
    switch(keyCode) {
        case KeyEvent.KEYCODE_DPAD_UP:
            select(selX, selY - 1);
            break;
        case KeyEvent.KEYCODE_DPAD_DOWN:
            select(selX, selY + 1);
            break;
        case KeyEvent.KEYCODE_DPAD_LEFT:
            select(selX - 1, selY);
            break;
        case KeyEvent.KEYCODE_DPAD_RIGHT:
            select(selX + 1, selY);
            break;
        case KeyEvent.KEYCODE_0:
        case KeyEvent.KEYCODE_SPACE: setSelectedTile(0); break;
        case KeyEvent.KEYCODE_1: setSelectedTile(1); break;
        case KeyEvent.KEYCODE_2: setSelectedTile(2); break;
        case KeyEvent.KEYCODE_3: setSelectedTile(3); break;
        case KeyEvent.KEYCODE_4: setSelectedTile(4); break;
        case KeyEvent.KEYCODE_5: setSelectedTile(5); break;
        case KeyEvent.KEYCODE_6: setSelectedTile(6); break;
        case KeyEvent.KEYCODE_7: setSelectedTile(7); break;
        case KeyEvent.KEYCODE_8: setSelectedTile(8); break;
        case KeyEvent.KEYCODE_9: setSelectedTile(9); break;
        case KeyEvent.KEYCODE_ENTER:
        case KeyEvent.KEYCODE_DPAD_CENTER:
            game.showKeypadOrError(selX, selY);
            break;
        default:
            return super.onKeyDown(keyCode, event);
    }
    return true;
}

//locate the selected square
private void select(int x, int y) {
    invalidate(selRect);
    selX = Math.min(Math.max(x,0), 8);
    selY = Math.min(Math.max(y,0), 8);
    getRect(selX, selY, selRect);
    invalidate(selRect);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    if(event.getAction() != MotionEvent.ACTION_DOWN) {
        return super.onTouchEvent(event);
    }
    select((int)(event.getX() / tileWidth), (int)(event.getY() / tileHeight));
    game.showKeypadOrError(selX, selY);
    Log.d(TAG, "onTouchEvent: x" + selX + ", y" + selY);
    return true;
}

public void setSelectedTile(int tile) {
    if(game.setTileIfValid(selX, selY, tile)) {
        invalidate();
    } else {
        //number not valid for selected tile
        Log.d(TAG, "setSelectedTile: invalid - " + tile);
        startAnimation(AnimationUtils.loadAnimation(game, R.anim.shake));
    }
}