how draw curves lines [closed]

问题:

Please, someone could help me draw this line in red color between point A(720,1140) the middle oof circle and point B (375,490)

 Bitmap bitmap = Bitmap.createBitmap((int) getWindowManager()
            .getDefaultDisplay().getWidth(), (int) getWindowManager()
            .getDefaultDisplay().getHeight(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    drawingImageView.setImageBitmap(bitmap);
    DisplayMetrics metrics = this.getResources().getDisplayMetrics();
    int x = metrics.widthPixels;
    int y = metrics.heightPixels;
    Paint paint1 = new Paint () ;
    paint1.setStrokeWidth(10);
    int margin = 100;
    int margin1 = 300;
    int top = 0 + margin;
    int bottom = canvas.getHeight() - margin;
    int left = 0 + margin1;
    int right = canvas.getWidth() - margin1;
    int centerX = x / 2;
    int centerY = y / 2;
    canvas.drawCircle(x / 2, y / 2, 50, paint1);
    canvas.drawLine(centerX, top, centerX, bottom,paint1);
    canvas.drawLine(left, centerY, right, centerY,paint1);

回答1:

Here is what I did:

• Found the point in between the 2 given points
• Calculated the angle 90 degrees between the 2 points
• Calculated the point X pixels from the middle point using the calculated degree from before.
• Used "path.cubicTo" with these 3 points (Takes both negative and positive values to determine which way the line should curve).

Here is my code!

public PaintApplication drawCurve(int x1, int y1, int x2, int y2, int curveRadius, int padding, int color, int lineWidth) {

        Paint paint  = new Paint();
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(lineWidth);
        paint.setColor(ContextCompat.getColor(context, color));

        final Path path = new Path();
        int midX            = x1 + ((x2 - x1) / 2);
        int midY            = y1 + ((y2 - y1) / 2);
        float xDiff         = midX - x1;
        float yDiff         = midY - y1;
        double angle        = (Math.atan2(yDiff, xDiff) * (180 / Math.PI)) - 90;
        double angleRadians = Math.toRadians(angle);
        float pointX        = (float) (midX + curveRadius * Math.cos(angleRadians));
        float pointY        = (float) (midY + curveRadius * Math.sin(angleRadians));

        path.moveTo(x1, y1);
        path.cubicTo(x1,y1,pointX, pointY, x2, y2);
        canvas.drawPath(path, paint);

        return this;
    }

I created a Paint application based on this coding idea.

For screenshot refer here

Hope this helps !!