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我正在开发一个绘图应用程序并进行扩展View，并希望实现 OnTouchListener。代码如下：

public class DoodleView extends View implements OnTouchListener  //ERROR1
{
   private Bitmap bitmap; // drawing area for display or saving
   private Canvas bitmapCanvas; // used to draw on bitmap
   private Paint paintScreen; // use to draw bitmap onto screen
   private Paint paintLine; // used to draw lines onto bitmap

   private Path    mPath;
   private Paint   mPaint, circlePaint, outercirclePaint;  
   private ArrayList<Path> paths = new ArrayList<Path>();
   private ArrayList<Path> undonePaths = new ArrayList<Path>();
   private float xleft,xright,xtop,xbottom;
   private float mX, mY;

   // DoodleView constructor initializes the DoodleView
   public DoodleView(Context context) 
   {
      super(context); // pass context to View's constructor
      this.context_new=context;
      this.setOnTouchListener(this); //ERROR2

      paintScreen = new Paint(); // used to display bitmap onto screen

      // set the initial display settings for the painted line
      paintLine = new Paint();
      paintLine.setAntiAlias(true); // smooth edges of drawn line
      paintLine.setColor(Color.BLACK); // default color is black
      paintLine.setStyle(Paint.Style.STROKE); // solid line
      paintLine.setStrokeWidth(5); // set the default line width
      paintLine.setStrokeCap(Paint.Cap.ROUND); // rounded line ends

      mPath = new Path();
      paths.add(mPath);

   } // end DoodleView constructor

OnSizeChanged：

   @Override
   public void onSizeChanged(int w, int h, int oldW, int oldH)
   {
      super.onSizeChanged(w, h, oldW, oldH);
      DoodlzViewWidth = w;     
      DoodlzViewHeight = h;

      bitmap = Bitmap.createBitmap(getWidth(), DoodlzViewHeight, Bitmap.Config.ARGB_8888);

      bitmapCanvas = new Canvas(bitmap);
      bitmap.eraseColor(Color.WHITE); // erase the BitMap with white 
   }

绘制：

   @Override
   protected void onDraw(Canvas canvas)
   {
       canvas.drawBitmap(bitmap, 0, 0, paintScreen); // draw the background screen
       // for each path currently being drawn
       for (Path p : paths){canvas.drawPath(p, paintLine);}
       Toast.makeText(getContext(), "ondraw", Toast.LENGTH_SHORT).show();              
   }

触摸事件：

   @Override
   public boolean onTouchEvent(View arg0, MotionEvent event) //ERROR3
   {

          float x = event.getX();
          float y = event.getY();

          switch (event.getAction())
          {
              case MotionEvent.ACTION_DOWN:
                  touchStarted(x, y);
                  invalidate();
                  break;
              case MotionEvent.ACTION_MOVE:
                  touchMoved(x, y);
                  invalidate();
                  break;
              case MotionEvent.ACTION_UP:
                  touchEnded();
                  invalidate();
                  break;
          }
          return true;
    }

但是，我真的很挠头，不知道为什么

  1. ERROR1：实现 OnTouchListener 报告红色下划线表示 OnTouchListener cannot be resolved to a type，并建议导入android.view.View。但是我尝试点击导入它仍然不愿意被导入，我看到导入列​​表已经在那里了

  2. ERROR2: The method setOnTouchListener(View.OnTouchListener) in the type View is not applicable for the arguments (DoodleView), 应该是因为 ERROR1

  3. ERROR3: The method onTouchEvent(View, MotionEvent) of type DoodleView must override or implement a supertype method，应该也是因为ERROR1。

有谁知道发生了什么？我被卡在这里一动不动！非常感谢！

4

1 回答 1

3

这似乎是一个简单的导入问题。尝试添加

import android.view.View

如果您的班级中尚未出现并更改班级声明，如下所示：

public class DoodleView extends View implements View.OnTouchListener {
....
于 2013-02-19T12:32:34.457 回答