如何拖动和画线？答案

【问题标题】：How to drag and draw a line?如何拖动和画线？
【发布时间】：2023-03-22 14:41:01
【问题描述】：

我是 android 编程新手，我创建了一个应用程序来绘制一个矩形和一个圆形。现在我想画椭圆和线条。我知道drawLine取起点x，起点y，终点x和终点y。

这是我在 mycustomView.java 中尝试过的，但我只能将线从左上角拖到右下角，从右下角拖到左上角？如何让它适用于所有方向？

 protected void onDraw(Canvas canvas) {
    this.canvas = canvas;

    canvas.drawColor(Color.WHITE);

    for (int i = 0; i < numberShapes; i++) {
        paint.setColor(Color.parseColor("#" + Integer.toHexString(Integer.parseInt(shapes[i].getColor())).substring(2))); //avoids alpha
        paint.setStrokeWidth(shapes[i].getBorder());
         //some code here....

                    else if(shapes[i].getShapeType().equals("Ellipse")){
            RectF rect= new RectF(shapes[i].getX(),shapes[i].getY(),shapes[i].getX() + shapes[i].getWidth(),shapes[i].getY() + shapes[i].getHeight());
            canvas.drawOval(rect,paint);

        }
        else if(shapes[i].getShapeType().equals("StraightLine")){
           canvas.drawLine(shapes[i].getX(),shapes[i].getY(),shapes[i].getX() + shapes[i].getWidth(),shapes[i].getY() + shapes[i].getWidth(),paint);
        }
    }

}
}

这是我的 viewShapes.java 和我的动作事件

public boolean onTouch(View v, MotionEvent ev) {
            //Circle is the default shape if can't find the key
            String selectedShapeDrawing = getActivity().getSharedPreferences("settings", Context.MODE_PRIVATE).getString("selectedShapeDrawing", "Circle");
            int x = (int) ev.getX(); int y = (int) ev.getY();
            int dX, dY;

            int action = MotionEventCompat.getActionMasked(ev);
            switch (action){
                case MotionEvent.ACTION_DOWN:
                    mLastTouchX = x; mLastTouchY = y;
                    break;
                case MotionEvent.ACTION_MOVE:


                        break;
                case MotionEvent.ACTION_UP:
                    if ((selectedShapeDrawing.equals("Rectangle")) || selectedShapeDrawing.equals("Circle") || selectedShapeDrawing.equals("Ellipse")) {
                        //some code here...                        }
                   if(selectedShapeDrawing.equals("StraightLine")){
                        if((x>mLastTouchX) && (y>mLastTouchY)) {

                            storeShape(selectedShapeDrawing, mLastTouchX, mLastTouchY, x, y);
                        }

                        else if((x<mLastTouchX) && (y<mLastTouchY)) {

                            storeShape(selectedShapeDrawing, x, y, mLastTouchX, mLastTouchY);
                        }
                        else if((x>mLastTouchX) && (y<mLastTouchY)) {

                            storeShape(selectedShapeDrawing,mLastTouchX, y,x,mLastTouchY);
                        }

                        else if((x<mLastTouchX) && (y>mLastTouchY)) {

                            storeShape(selectedShapeDrawing, x,mLastTouchY,mLastTouchX, y);
                        }

任何帮助将不胜感激！

编辑：这是我的商店形状

 private void storeShape(String shape, int x, int y, int deltaX, int deltaY) 
{
    int selectedColor = getActivity().getSharedPreferences("settings", Context.MODE_PRIVATE).getInt("selectColor", 0);

    ContentValues contentValues = new ContentValues();
    contentValues.put(SchemeShapes.Shape.SHAPE_TYPE, shape);
    contentValues.put(SchemeShapes.Shape.SHAPE_X, x);
    contentValues.put(SchemeShapes.Shape.SHAPE_Y, y);

    contentValues.put(SchemeShapes.Shape.SHAPE_RADIUS, Math.max(deltaX, deltaY));



    contentValues.put(SchemeShapes.Shape.SHAPE_WIDTH, deltaX);
    contentValues.put(SchemeShapes.Shape.SHAPE_HEIGHT, deltaY);
    contentValues.put(SchemeShapes.Shape.SHAPE_BORDER_THICKNESS, 10);
    contentValues.put(SchemeShapes.Shape.SHAPE_COLOR, selectedColor);

    resolver.insert(SchemeShapes.Shape.CONTENT_URI, contentValues);
}

【问题讨论】：

参考：stackoverflow.com/questions/3616676/…
什么是storeshape？？
它存储所选形状的半径、高度...等

标签： android motionevent

【解决方案1】：

好吧，我在我的 canvas.drawLine 中把它复杂化了一点，我应该这样做：

else if(shapes[i].getShapeType().equals("StraightLine")){
    canvas.drawLine(shapes[i].getX(), shapes[i].getY(), shapes[i].getWidth(), shapes[i].getHeight(), paint);
}

在我的 Action_Up 中我应该这样做：

if ((selectedShapeDrawing.equals("StraightLine"))) {
    storeShape(selectedShapeDrawing,mLastTouchX,mLastTouchY,x,y); 
}

【讨论】：

【解决方案2】：

您可以尝试以下方法：

public boolean onTouch(View v, MotionEvent event) {
        switch(event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startX = event.getRawX();
                startY = event.getRawY();
                break;

            case MotionEvent.ACTION_UP:
                Paint paint = new Paint(); 
                paint.setStrokeWidth(10f);
                paint.setColor(getResources().getColor(R.color.text_red));
                canvas.drawLine(startX, startY, event.getRawX(), event.getRawY(), paint);
                break;
        }
    }

【讨论】：