java如何改变Android画布的输出。drawTextOnPath（）

Question

我是Android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()显示的是从右侧开始的文本（我指的是正X轴）。我想按时钟顺序从顶部显示文本。我想更改文本的起始位置。我对安卓Canvas.translate()和Canvas.scale()感到困惑。或者我应该使用Canvas.rotate()？为了清楚地理解我的问题，我粘贴了下面的输出

我想以这种形式显示输出

Answer 1

可以使用圆弧代替圆：

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);

使用矩阵可以平移、旋转和缩放路径。 例如，上面的代码将从第一个象限开始绘制文本，即从（y，0）开始。要以顺时针方向从（-y，0）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

通过在应用和Canvas方法之前在代码中添加Canvas.rotate(float degrees, float px, float py)，我终于解决了我的Canvas问题。下面是代码

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);
    } 
}

我以前试过Canvas.rotate(float degrees)，但没有成功。然而，Canvas.rotate(float degrees, float px, float py)成功了