java - 如何绘制不同颜色的多条线并撤消，重做android中的路径？

Question

我想在 View 上用不同的颜色绘制多条线，然后撤消，重做android中的路径。

我使用位图绘制选项，每条路径都有独特的颜色，但撤消、重做不起作用。

这是我的位图绘制代码:

public MyView(Context context, Object object) {
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);
    
    mPath = new Path();
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setColor(0xFFFFFF00);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(3);

    mBitmap = Bitmap.createBitmap(320, 480, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

protected void onSizeChanged(int w, int h, int oldw, int oldh) 
{
    super.onSizeChanged(w, h, oldw, oldh);
}

protected void onDraw(Canvas canvas) 
{
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    for (Path p : paths)
    {
        canvas.drawPath(p, mPaint);
    }
    canvas.drawPath(mPath, mPaint);
}

public boolean onTouchEvent(MotionEvent event)
{
    float x = event.getX();
    float y = event.getY();
    int action = event.getAction();
    int action1=event.getAction();
    switch (event.getAction())
    {
    case MotionEvent.ACTION_DOWN:
        undonePaths.clear();
        mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
        startPoint = new PointF(event.getX(), event.getY());
        endPoint = new PointF();
        invalidate();
        //   isDrawing = true;
        break;
    case MotionEvent.ACTION_MOVE:
        float dx = Math.abs(x - mX);
        System.out.println("action move");
        float dy = Math.abs(y - mY);
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE)
        {
            //  currentDrawingPath.path.quadTo(mX,mY,(x + mX)/2, (y + mY)/2);
        }
        mX = x;
        mY = y;
        endPoint.x = event.getX();
        endPoint.y = event.getY();
        isDrawing = true;
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        mPath.lineTo(mX, mY);
        paths.add(mPath);
        mPath = new Path();
        //  mCanvas.drawPath(mPath, ppaint);
        endPoint.x = event.getX();
        endPoint.y = event.getY();
        isDrawing = false;
        invalidate();
        break;
    default:
        break;
    }       
}

不使用位图时，如果我为路径选择蓝色，则我会遇到颜色问题，这意味着所有先前的路径都将更改为蓝色；

这是我的代码

protected void onDraw(Canvas canvas) 
{
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    for (Path p : paths)
    {
        canvas.drawPath(p, mPaint);
    }
    canvas.drawPath(mPath, mPaint);
}

谁能帮我在android中用不同颜色的独特路径绘制多条路径？

Answer 1

当您处理 MotionEvent.ACTION_UP 时:您需要保存用于绘制路径的颜色，如下所示:

case MotionEvent.ACTION_UP:
    paths.add(mPath);
    colorsMap.put(mPath,selectedColor); // store the color of mPath
    ...

在绘制路径之前，您需要设置绘制颜色:

protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    for (Path p : paths)
    {
        mPaint.setColor(colorsMap.get(p));
        canvas.drawPath(p, mPaint);
    }
    mPaint.setColor(selectedColor);
    canvas.drawPath(mPath, mPaint);
}

colorsMap 是一个简单的实例变量:

private Map<Path, Integer> colorsMap = new HashMap<Path, Integer>();    

要实现撤消/重做功能，您只需从路径中删除最后一个元素(并将其存储在 undoneList 中，以便在重做时可以恢复它)。见Android Canvas Redo and Undo Operation