DrawArc上的图像，定位问题(DrawArc on image, positioning issue)

 我有一个可测量的标尺，我试图在它上面画一条线。 （固定位置，不是固定值） 
 
 不幸的是，我没有任何绘画经验。 （我认为它很难理解） 
 
 目前看起来像这样： https : //i.stack.imgur.com/5tkXEl.png 
 
 正如你所看到的，它没有定位正确，我很害怕在其他设备上看它。 
 
 代码（Class extends View）： 
 
private void init(Context context) {
    bounds = new Rect();
    gaugeBackground = ContextCompat.getDrawable(context, R.drawable.gauge);
    arcPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    arcPaint.setColor(Color.RED);
    arcPaint.setStyle(Paint.Style.STROKE);
    arcPaint.setStrokeWidth(7f);
}

protected void onDraw(Canvas canvas) {
    canvas.getClipBounds(bounds);
    gaugeBackground.setBounds(bounds);
    gaugeBackground.draw(canvas);

    float padding = 5;
    float size = getWidth() < getHeight() ? getWidth() : getHeight();
    float width = size - (2 * padding);
    float height = size - (2 * padding);
    float radius = (width < height ? width /2 : height /2);

    float rectLeft = (width /2) - radius + padding;
    float rectTop = (getHeight() /2) - radius + padding;
    float rectRight = (getWidth() /2) - radius + padding + width;
    float rectBottom = (getHeight() /2) - radius + padding + height;

    RectF mRect = new RectF(rectLeft, rectTop, rectRight, rectBottom);
    canvas.drawArc(mRect, 119f, 300f, false, arcPaint);
}
 
 有人能提供有用的信息吗？ 我希望我终于得到整个RectF /绘图的东西.. 

I have a drawable of a gauge and I try to draw a line on it. (Fixed position, not fixed value)
 
Unfortunately I don't have any experience with drawing. (And I think its hard to understand)
 
At the moment it looks like this: https://i.stack.imgur.com/5tkXEl.png
 
As you can see, its not positioned right and I'm quite afraid of looking at it on other devices.
 
Code (Class extends View):
 
private void init(Context context) {
    bounds = new Rect();
    gaugeBackground = ContextCompat.getDrawable(context, R.drawable.gauge);
    arcPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    arcPaint.setColor(Color.RED);
    arcPaint.setStyle(Paint.Style.STROKE);
    arcPaint.setStrokeWidth(7f);
}

protected void onDraw(Canvas canvas) {
    canvas.getClipBounds(bounds);
    gaugeBackground.setBounds(bounds);
    gaugeBackground.draw(canvas);

    float padding = 5;
    float size = getWidth() < getHeight() ? getWidth() : getHeight();
    float width = size - (2 * padding);
    float height = size - (2 * padding);
    float radius = (width < height ? width /2 : height /2);

    float rectLeft = (width /2) - radius + padding;
    float rectTop = (getHeight() /2) - radius + padding;
    float rectRight = (getWidth() /2) - radius + padding + width;
    float rectBottom = (getHeight() /2) - radius + padding + height;

    RectF mRect = new RectF(rectLeft, rectTop, rectRight, rectBottom);
    canvas.drawArc(mRect, 119f, 300f, false, arcPaint);
}
 
Can someone provide helpful information? I hope I finally get the whole RectF/Drawing stuff..

原文：https://stackoverflow.com/questions/41675246