Question

我正在创建一个基本的绘图应用程序。以下函数用于绘制线。

public void touchEventLine(MotionEvent event){

        Log.e("Canvas","Line Specific Event");
        float x = event.getX();
        float y = event.getY();


        switch (event.getAction()){

            case MotionEvent.ACTION_DOWN:

                Log.e("Canvas","Line Specific Event: Action Down");
                startX=x;
                startY=y;
                mPath.moveTo(startX,startY);
                Log.e("Canvas","Line Specific Event: Moved to X:"+startX+"  Y:"+startY);
                mX=x;
                mY=y;
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:

                Log.e("Canvas","Line Specific Event: Action Move");
                endX=x;
                endY=y;
                drawLine(endX,endY);
                Log.e("Canvas","Line Specific Event: Drawing From X:"+startX+"  Y:"+startY+"   to X:"+endX+"  Y:"+endY);
                paths.add(mPath);
                colorsMap.put(mPath,selectedColor);
                mPath = new Path();
                isDrawing++;
                invalidate();
                if(isDrawing>1) {
                    paths.remove(paths.size() - 2);
                    isDrawing--;
                }
                break;
            case MotionEvent.ACTION_UP:



                Log.e("Canvas","Line Specific Event: Action Up");
                endX=x;
                endY=y;

                drawLine(endX,endY);
                paths.add(mPath);
                colorsMap.put(mPath,selectedColor);
                mPath = new Path();
                paths.remove(paths.size() - 2);
                invalidate();
                isDrawing=0;
                break;



        }

    }

和 drawLine（）函数是

private void drawLine(float x2,float y2){

        mPath.lineTo(x2,y2);
        invalidate();
        Log.e("Canvas","Line Drawn");

    }

我的 onDraw（）功能

protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(mBitmap, 0, 0, canvasPaint);
        canvas.drawPath(mPath,drawPaint);

        for (Path p : paths) {

            int curColor= colorsMap.get(p);
            drawPaint.setColor(curColor);
            canvas.drawPath(p, drawPaint);
        }

        Log.e("Canvas","OnDraw() Called");


    }

我的问题是该线是从屏幕的左上角绘制的。我相信它是（0,0）。我使用相同的逻辑绘制圆形和矩形，两者都工作正常。我的逻辑是否有任何错误。？我怎样才能解决这个问题..？提前致谢

Answer 1

这很容易。你应该打电话

path.moveTo(firstPoint_X, firstPoint_y);

在图纸的第一步。

（在您调用mPath = new Path（）;）的每一行之后

如果你不打电话

path.moveTo

在创建Path类的新实例后的

方法，默认情况下它从屏幕的位置（0,0）开始绘制

Android Canvas绘图线

1 个答案: