onDraw 三角形按钮

Question

在我创建的扩展 Button 的 class 中，我覆盖了 onDraw 函数以在指向中心的按钮右侧创建一个三角形：

相反，这是我得到的：

这是我写的：

Paint paint = new Paint();

@Override
public void onDraw(Canvas canvas)
{
    Paint paint = new Paint();

    paint.setColor(android.graphics.Color.BLACK);
    canvas.drawPaint(paint);

    paint.setStrokeWidth(4);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);

    Point center = new Point(getWidth()/2, getHeight()/2);    
    Point a=new Point(getWidth(), 0);;
    Point b=new Point(getWidth(), getHeight());;

    paint.setColor(Color.RED);    

    Path path= new Path();
    path.setFillType(Path.FillType.EVEN_ODD);
    path.lineTo(b.x, b.y);
    path.lineTo(center.x, center.y);
    path.lineTo(a.x, a.y);
    path.close();
    canvas.drawPath(path, paint);
}

Answer 1

您忘记移动到它的初始点。

类似

path.moveTo(point1_draw.x,point1_draw.y);

在你第一次 lineTo()

之前

因为 lineTo() 需要 "last point" 来开始分段。

void lineTo(float x, float y) // Add a line from the last point to the specified point (x,y).

因此，最后，您的鳕鱼将如下所示：

    Path path= new Path();
    path.setFillType(Path.FillType.EVEN_ODD);
    path.moveTo(a.x, a.y);           // Move to a
    path.lineTo(center.x, center.y); // Segment from a to center
    path.lineTo(b.x, b.y);           // Segment from center to b
    path.close();                    // Segment from b to a
    canvas.drawPath(path, paint);

onDraw 三角形按钮

onDraw triangle on Button

android

android-canvas