问在android中绘制半椭圆形形状
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Stack Overflow用户

提问于 2020-04-28 16:44:03

回答 1查看 179关注 0票数 1

我正试着在安卓系统中用drawArc在两个textView之间画一道弧线。我的要求是实现一个弧形，如图所示

哪一个是正确的弧形。但是当我尝试的时候，我没有得到一个完美的弧形，我得到了一个半椭圆形的弧形

。

下面是我的代码片段：

public class ArcView extends View {

    final RectF oval = new RectF();
    Path myPath = new Path();
    Paint paint;
    float left, top, right, bottom;

    public FlightStatusArcView(Context context) {
        super(context);
    }
    public FlightStatusArcView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs);
    }
    public FlightStatusArcView(Context context, AttributeSet attrs, int defStyleAttr)     {
        super(context, attrs, defStyleAttr);
        init(attrs);
    }

    private void init(AttributeSet set) {
        if (set == null)
            return;
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }

    public void setArcProperties(float l, float t, float r, float b) {
        left = l;
        top = t;
        right = r;
        bottom = b;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        oval.set(left, top, right, bottom);
        paint.setColor(Color.WHITE);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(5f);

        canvas.drawArc(oval, 180f, 180f, false, paint);
        drawArrow(canvas);
    }



    private void drawArrow(Canvas canvas) {

        canvas.save();

        Paint p = new Paint();
        p.setColor(Color.WHITE);
        p.setStyle(Paint.Style.FILL);
        p.setStrokeWidth(4f);

        float startX = oval.left + 20;
        float startY = oval.top + (oval.centerY() - oval.top)/ 2;

        Path path = new Path();
        path.moveTo(startX, startY-20);
        path.lineTo(startX + 20, startY + 20);
        path.lineTo(startX + 30, startY -17);
        path.close();
        canvas.drawPath(path, p);
        canvas.restore();
    }


}

请帮助如何使用画布apis实现完美的弧形。

java

android

canvas

回答 1

Stack Overflow用户

回答已采纳

发布于 2020-04-28 17:49:07

您可以将Path与quadTo或cubicTo一起使用来绘制这样的曲线。这将允许您绘制二次或三次bezier曲线。例如，具有两个相同控制点(x2, y2)的三次贝塞尔曲线构造如下：

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    paint.setColor(Color.BLACK);
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeWidth(5f);

    Path p = new Path();

    float x1 = 100;
    float y1 = 256;

    float x2 = 400;
    float y2 = 32;

    float x3 = 700;
    float y3 = 256;

    p.moveTo(x1, y1);

    p.cubicTo(x2, y2, x2, y2, x3, y3);
    canvas.drawPath(p, paint);
    drawArrow(canvas);
}