android - 如何暂停 Canvas 以特定角度旋转 2 秒？

Question

我做了一个旋钮，但我想在特定角度停止旋钮 2 秒。我想在 260f 和 -20f 停止它。

谁能建议怎么做？

这是来自博客的代码。我根据自己的要求做了很多改动。

public class RotatoryKnobView extends ImageView  {

  private float angle = -20f;
  private float theta_old=0f;

  private RotaryKnobListener listener;

  public interface RotaryKnobListener {
    public void onKnobChanged(float arg);
  }

  public void setKnobListener(RotaryKnobListener l )
  {
    listener = l;
  }

  public RotatoryKnobView(Context context) {
    super(context);
    initialize();
  }

  public RotatoryKnobView(Context context, AttributeSet attrs)
  {
    super(context, attrs);
    initialize();
  }

  public RotatoryKnobView(Context context, AttributeSet attrs, int defStyle)
  {
    super(context, attrs, defStyle);
    initialize();
  }

  private float getTheta(float x, float y)
  {
    float sx = x - (getWidth() / 2.0f);
    float sy = y - (getHeight() / 2.0f);

    float length = (float)Math.sqrt( sx*sx + sy*sy);
    float nx = sx / length;
    float ny = sy / length;
    float theta = (float)Math.atan2( ny, nx );

    final float rad2deg = (float)(180.0/Math.PI);
    float thetaDeg = theta*rad2deg;

    return (thetaDeg < 0) ? thetaDeg + 360.0f : thetaDeg;
  }

  public void initialize()
  {
    this.setImageResource(R.drawable.rotoron);
    setOnTouchListener(new OnTouchListener()
      {
 @Override
 public boolean onTouch(View v, MotionEvent event) {
   float x = event.getX(0);
   float y = event.getY(0);
   float theta = getTheta(x,y);

   switch(event.getAction() & MotionEvent.ACTION_MASK)
     {
     case MotionEvent.ACTION_POINTER_DOWN:
       theta_old = theta;
       break;
     case MotionEvent.ACTION_MOVE:
       invalidate();
       float delta_theta = theta - theta_old;
       theta_old = theta;
       int direction = (delta_theta > 0) ? 1 : -1;
       angle += 5*direction;
       notifyListener(angle+20);
       break;
     }
   return true;
 }
      });
  }

  private void notifyListener(float arg)
  {
    if (null!=listener)
      listener.onKnobChanged(arg);
  }

  protected void onDraw(Canvas c)
  {if(angle==257f){
      try {
            synchronized (c) {

                c.wait(5000);
                angle=260f;
            }

        } catch (InterruptedException e) {
        }
  }
  else if(angle==-16f)
  {
      try {
            synchronized (c) {
                c.wait(5000);
                angle=-20f;
            }

        } catch (InterruptedException e) {

        }
  }
  else
      if(angle>260f)
          {

          angle=-20f;
         }
      else if(angle<-20f)
          {

          angle=260f;
         }
      else{
          c.rotate(angle,getWidth()/2,getHeight()/2);   

      }
    super.onDraw(c);
  }
} 

Answer 1

你可以设置一个固定的角​​度，2秒后使用postDelayed清除。

    public class RotatoryKnobView extends ImageView {

    private float angle = -20f;
    private float theta_old=0f;

    private RotaryKnobListener listener;

    private Float fixedAngle;
    private float settleAngle;

    private Runnable unsetFixedAngle = new Runnable() {
        @Override
        public void run() {
            angle = settleAngle;
            fixedAngle = null;
            invalidate();
        }
    };

    public interface RotaryKnobListener {
        public void onKnobChanged(float arg);
    }

    public void setKnobListener(RotaryKnobListener l )
    {
        listener = l;
    }

    public RotatoryKnobView(Context context) {
        super(context);
        initialize();
    }

    public RotatoryKnobView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        initialize();
    }

    public RotatoryKnobView(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        initialize();
    }

    private float getTheta(float x, float y)
    {
        float sx = x - (getWidth() / 2.0f);
        float sy = y - (getHeight() / 2.0f);

        float length = (float)Math.sqrt( sx*sx + sy*sy);
        float nx = sx / length;
        float ny = sy / length;
        float theta = (float)Math.atan2( ny, nx );

        final float rad2deg = (float)(180.0/Math.PI);
        float thetaDeg = theta*rad2deg;

        return (thetaDeg < 0) ? thetaDeg + 360.0f : thetaDeg;
    }

    public void initialize()
    {
        this.setImageResource(R.drawable.rotoron);
        setOnTouchListener(new OnTouchListener()
        {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                float x = event.getX(0);
                float y = event.getY(0);
                float theta = getTheta(x,y);

                switch(event.getAction() & MotionEvent.ACTION_MASK)
                {
                    case MotionEvent.ACTION_POINTER_DOWN:
                        theta_old = theta;
                        break;
                    case MotionEvent.ACTION_MOVE:
                        invalidate();
                        float delta_theta = theta - theta_old;
                        theta_old = theta;
                        int direction = (delta_theta > 0) ? 1 : -1;
                        angle += 5*direction;
                        notifyListener(angle+20);
                        break;
                }
                return true;
            }
        });
    }

    private void notifyListener(float arg)
    {
        if (null!=listener)
            listener.onKnobChanged(arg);
    }

    void setFixedAngle(float angle, float settleAngle) {
        fixedAngle = angle;
        this.settleAngle = settleAngle;
        postDelayed(unsetFixedAngle, 2000);
    }

    protected void onDraw(Canvas c)
    {
        if(fixedAngle==null) {
            if (angle > 270) {
                setFixedAngle(270, -15);
            } else if (angle < -20f) {
                setFixedAngle(-20, 260);
            }
        }
        Log.d("angle", "angle: " + angle + " fixed angle: " + fixedAngle);
        c.rotate(fixedAngle == null ? angle : fixedAngle,getWidth()/2,getHeight()/2);

        super.onDraw(c);
    }
}

`