在类中绘制一条延伸“活动”的行 [英] Drawing a line in a class which extends "Activity'

问题描述

我有一个ImageView在我的Activity中加载一张图片，并希望在其上绘制一些线条。好像我无法将我绘制的线条叠加到ImageView上。如果我创建一个扩展'View'的新类（myPainter），从活动中挂钩myPainter.onDraw（）然后在onCreate（）中调用setContentView（mp），我得到的就是绘制的线条。我的ImageView已从onCreate（）中删除。如何让ImageView和线条以相同的布局显示？我也为ImageView覆盖了onTouch（），所以我可以从中获取xy点击位置。

I have an ImageView loading a picture in my Activity and want to draw some lines on it. It seems like I'm not able to overlay the lines I draw onto the ImageView. If I create a new class (myPainter) which extends 'View', hook myPainter.onDraw() and then setContentView(mp) in onCreate() from the activity, all I get are the drawn lines. My ImageView is gone from onCreate(). How do I get the ImageView and lines to show up in the same layout? I'm also Override'ing onTouch() for the ImageView so I can get the xy click locations from it.

    public class myPainter extends View
    {
    public myPainter (Context context)
       {
        super (context);
       }

     @Override
       protected void onDraw(Canvas canvas) 
     {
      super.onDraw (canvas);
      Paint p = new Paint();
          p.setColor(Color.RED);

         canvas.drawLine (E_XMIN, E_YMIN, E_XMAX, E_YMAX, p);
     }
    }


     @Override
     public void onCreate (Bundle savedInstanceState)
     {
      super.onCreate (savedInstanceState);
      setContentView (R.layout.main);
      ImageView iv = (ImageView) findViewById(R.id.ImageView01);
      iv.setOnTouchListener (this);

// this draws my lines, but I loose the pic above ^^^
      myPainter mp = new myPainter(this);        
      setContentView(mp);
     }

---

更新：

我想我已经把自己画成了一个角落。我现在如何在onTouchEvent（）方法中向此代码添加frameAnimation？就像用户触摸屏幕的地方一样。如果我将代码添加到myPainter（）类，Android rocketAnimation示例会导致异常：

I think I've literally painted myself into a corner. How would I add a frameAnimation to this code now in the onTouchEvent() method? Like where the user touches the screen. The Android rocketAnimation example causes an exception if I add code to the myPainter() class:

  @Override
  public boolean onTouchEvent (MotionEvent event)
  {

        //Log.d (TAG, "touchevent in myPainter");
        switch (event.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                    Log.d (TAG, "down x:" + event.getX() + " y:" + event.getY());

                    int wClick = getClick (event.getX(), event.getY());


                    AnimationDrawable touchAni;
                    ImageView iv = (ImageView) findViewById (R.drawable.triangle);
                    iv.setBackgroundResource (R.drawable.nova);
                    touchAni = (AnimationDrawable) iv.getBackground ();
                   touchAni.start ();

                   return true;
        }

       return super.onTouchEvent (event);
  }

推荐答案

我试图实施建议以上，但无法获得我的目标功能。也许我没有完全解决我的问题，或者只是一般性的误解。我最终在myPainter main方法中添加了一个setBackgroundResource（）来获取屏幕上的图像。我想我已经按需要工作并发布下面的代码，以防它帮助其他人。感谢您提供帮助！

I tried to implement the suggestions above, but could not get the functionality I was aiming for. Perhaps I've not framed my question completely, or just a general misunderstanding. I ended up adding a setBackgroundResource() in the myPainter main method to get the image on the screen. I think I've got it working as needed and posting the code below in case it helps someone else. Thanks for offering your help!

    class myPainter extends View implements myConst
    {
        private final static String TAG = "** myPainter **";

        public myPainter (Context context)
       {
           super (context);       
           Log.d (TAG, "new myPainter");
           setBackgroundResource (R.drawable.triangle);
       }

        @Override
       protected void onDraw(Canvas canvas) 
        {
            super.onDraw (canvas);     
            Log.d (TAG, "new myPainter");

            Paint p = new Paint ();
           p.setColor (Color.RED);
          canvas.drawLine (E_XMIN, E_YMIN, E_XMAX, E_YMIN, p);
        }


       /** 
         * called to determine what part of the triangle was clicked
         * @param x
         * @param y
         * @return click id from myConst
         */
        private int getClick (float x,  float y)
        {
            int id = 0;
                // insert logic to test x,y locations and return
                // region ID of what was clicked
                ...

            return (id);
        }

      @Override
      public boolean onTouchEvent (MotionEvent event)
      {
            Log.d (TAG, "touchevent in myPainter");
switch (event.getAction())
            {
                case MotionEvent.ACTION_DOWN:
                        Log.d (TAG, "down x:" + event.getX() + " y:" + event.getY());

                        int wClick = getClick (event.getX(), event.getY());
                break;
            }

           return false;
      }

    }

然后我的主应用程序类有这对于onCreate（）：

And then my main application class has this for onCreate():

/** Called when the activity is first created. */
@Override
public void onCreate (Bundle savedInstanceState)
{
    super.onCreate (savedInstanceState);
    setContentView (R.layout.main);

    myPainter mp = new myPainter(getApplicationContext());
    mp.invalidate ();
    setContentView(mp);

    //ImageView iv = (ImageView) findViewById(R.id.ImageView01);
    //iv.setOnTouchListener (this);

}

这篇关于在类中绘制一条延伸“活动”的行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！