Question

我正在尝试使用canvas绘制椭圆。但它永远不会被绘制。这是我的自定义view.i的代码也使用了setwillnotdraw（false）仍然没有在屏幕上绘制

public class Myview extends View{
Paint paint;
RectF rect;
    public Myview(Context context ) {
        super(context);
        init();
        setWillNotDraw(false);
    }

        public Myview(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
        setWillNotDraw(false);
    }

    public Myview(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
        setWillNotDraw(false);
    }

private void init() {
        rect = new RectF(0.1f, 0.1f, getWidth(), getHeight());
        paint =new Paint();
        paint.setShader(new LinearGradient(0.40f, 0.0f, 100.60f, 100.0f, 
                                           Color.parseColor("#ffffff"),
                                           Color.parseColor("#Ffffff"),
                                           Shader.TileMode.CLAMP));
    }

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    setMeasuredDimension(200, 200);
}



@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawOval(rect, paint);
    }



}

任何建议??

Answer 1

在init（）中调用时：rect = new RectF（0.1f，0.1f，getWidth（），getHeight（））;

getWidth（）＆amp; getHeight（）返回0

Answer 2

问题是getWidth（）和getHeight（）是O.根据您的要求更改。

您可以使用以下作为参考。

public class MainActivity extends Activity
{    

MyView mv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mv= new MyView(this);
setContentView(mv);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(20);
mPaint.setShader(new LinearGradient(0.40f, 0.0f, 100.60f, 100.0f, 
      Color.RED,
      Color.RED,
      Shader.TileMode.CLAMP));

}

private Paint       mPaint;

public class MyView extends View{
  Paint paint;
  RectF rect;
   public MyView(Context context) {
          super(context);
          rect = new RectF(20, 20, 100,100);
          //canvas.drawOval(new RectF(50, 50, 20, 40), p)
   }
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

      setMeasuredDimension(200, 200);

  }



  @Override
      protected void onDraw(Canvas canvas) {
          super.onDraw(canvas);
          canvas.drawOval(rect, mPaint);

      }
  }
}

根据您的要求更改坐标和颜色。上面绘制了一个圆圈，但是您可以更改坐标以绘制像canvas.drawOval那样的椭圆形（新的RectF（50,50,20,40），mPaint）;

enter image description here

自定义视图Canvas onDraw（）不会绘制任何内容

2 个答案: