自定义视图Canvas onDraw()不会绘制任何内容 [英] Custom view Canvas onDraw() doesnt draw anything

问题描述

我正在尝试使用画布绘制一个椭圆形，但是它从未被绘制过. 这是我的自定义视图代码.我还用过setWillNotDraw(false)仍然没有任何东西画在屏幕上.

I am trying to draw a oval using canvas, but it never gets drawn. Here is my code for the custom view. I have also used setWillNotDraw(false) still nothing gets drawn on the screen.

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(0.1 f, 0.1 f, getWidth(), getHeight());
        paint = new Paint();
        paint.setShader(new LinearGradient(0.40 f, 0.0 f, 100.60 f, 100.0 f,
            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);
    }
}

有什么建议吗?

推荐答案

问题是getWidth()和getHeight()是O.将其更改为您的要求.

The problem is getWidth() and getHeight() is O. Change that to your requirement.

您可以使用以下内容作为参考.

You can use the below as a reference.

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);

      }
  }
}

根据需要更改坐标和颜色.上面绘制了一个圆，但是您可以更改坐标以绘制椭圆，例如canvas.drawOval(new RectF(50，50，20，40)，mPaint);

Change the co-ordinates and color to your requirements. The above draws a circle but you can change the co-ordinates to draw oval something like canvas.drawOval(new RectF(50, 50, 20, 40), mPaint);

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