如何改变Android Canvas.drawTextOnPath（）的输出

Question

我是Android的新手，我编写了以下示例代码。

public class Circle extends View {
    Paint paint = new Paint();
    Path path = new Path();
    private static final String s = "Hello world example";

    public Circle(Context context) {
      super(context);
      paint.setColor(Color.BLACK);
      paint.setStyle(Style.STROKE);
      paint.setStrokeWidth(2);
      paint.setAntiAlias(true);
      paint.setTextSize(30);
    }

    public void onDraw(Canvas c) {    
      path.addCircle(getWidth()/2, getHeight()/2, 180, Direction.CW);
      c.drawTextOnPath(s, path, 0, 10, paint);
      setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    } 

  }

Canvas.drawTextOnPath()显示从右侧开始的文本（我的意思是正X轴）。我想以时钟方式显示顶部的文本。我想改变文本的起始位置。我对Android Canvas.translate()和Canvas.scale()感到困惑。或者我应该使用Canvas.rotate()？我已粘贴下面的输出，以便清楚地理解我的问题。

我想以这种形式显示输出。

Answer 1

可以使用arc代替圆圈：

Path path = new Path(); RectF rect = new RectF(width/2 - radius, height/2 - radius, width/2 + radius, height/2 + radius); path.addArc(rect 270, 270); canvas.drawTextOnPath(msg., path, 0, 0, paint);

可以使用Matrix翻译，旋转和缩放路径。 例如，上面的代码将从第一象限开始绘制文本，即从（y，0）开始。要从（-y，0）顺时针方向开始绘图，

 Path path = new Path();
 RectF rect = new RectF(width/2 - radius, height/2 - radius, width/2 + radius, height/2 + radius);
 Matrix matrix = new Matrix();
 matrix.setScale(-1, -1, width/2, height/2);
 path.addArc(rect, 270, 270);
 path.transform(matrix);
 canvas.drawTextOnPath(msg, path, 0, 0, paint);

Answer 2

在应用和Canvas方法之前，我在代码中添加了Canvas.rotate(float degrees, float px, float py)，最终修复了我的Canvas问题。以下是代码。

public class Circle extends View {
    Paint paint = new Paint();
    Path path = new Path();
    private static final String s = "Hello world example";

    public Circle(Context context) {
      super(context);
      paint.setColor(Color.BLACK);
      paint.setStyle(Style.STROKE);
      paint.setStrokeWidth(2);
      paint.setAntiAlias(true);
      paint.setTextSize(30);
    }

    public void onDraw(Canvas c) {   
      c.rotate(-90, getWidth()/2, getHeight()/2);
      path.addCircle(getWidth()/2, getHeight()/2, 180, Direction.CW);
      c.drawTextOnPath(s, path, 0, 10, paint);
      setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    } 
}

之前我尝试Canvas.rotate(float degrees)但没有奏效。但是，Canvas.rotate(float degrees, float px, float py)工作了！