安卓觸摸不顯示在畫布上

我剛開始使用觸摸事件。所以我搜索一個例子，發現這個http://www.vogella.com/articles/AndroidTouch/article.html ..教程是偉大的，但有一點是，當我運行的代碼。我將手指向各個方向移動，而不是在cavas中顯示..我的意思是它沒有繪製任何東西。安卓觸摸不顯示在畫布上

這裏是我的代碼：

public class SingleTouchEventView extends View { 
    private Paint paint = new Paint(); 
    private Path path = new Path(); 
    public SingleTouchEventView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     paint.setAntiAlias(true); 
     paint.setStrokeWidth(6f); 
     paint.setColor(Color.BLACK); 
     paint.setStyle(Paint.Style.STROKE); 
     paint.setStrokeJoin(Paint.Join.ROUND); 

    } 


    @Override 
    protected void onDraw(Canvas canvas) { 
     canvas.drawPath(path,paint); 

    } 

    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
     float eventX = event.getX(); 
     float eventY = event.getY(); 

     switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: 
       path.moveTo(eventX, eventY); 
       return true; 
      case MotionEvent.ACTION_MOVE: 
       path.lineTo(eventX, eventY); 
       break; 
      case MotionEvent.ACTION_UP: 
       // nothing to do 
       break; 
      default: 
       return false; 
     } 

     // Schedules a repaint. 
     invalidate(); 
     return true; 
    } 
}

和我的主要activty

public class SingleTouchActivity extends Activity { 
    /** 
    * Called when the activity is first created. 
    */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(new SingleTouchEventView(this,null)); 
    } 
}

我失去的是什麼？由於

來源

2013-01-24 thenewbie

這是一個總猜測，但不要在'ACTION_DOWN'上調用'return' – seaplain

Ahm does not work .. :( – thenewbie

代碼是否碰到了你的構造函數？在日誌中添加我唯一的原因是因爲你的構造函數被設置爲從'xml'中調用，你所做的調用看起來有效，但是一個簡單的檢查不會傷害 – seaplain

嘗試這樣

@Override 
public boolean onTouchEvent(MotionEvent ev) { 
    // Let the ScaleGestureDetector inspect all events. 
    mScaleDetector.onTouchEvent(ev); 

    final int action = ev.getAction(); 
    switch (action & MotionEvent.ACTION_MASK) { 
     case MotionEvent.ACTION_DOWN: { 
      final float x = ev.getX(); 
      final float y = ev.getY(); 
      mLastTouchX = x; 
      mLastTouchY = y; 
      mActivePointerId = ev.getPointerId(0); 
      break; 
     } 

     case MotionEvent.ACTION_MOVE: { 
      final int pointerIndex = ev.findPointerIndex(mActivePointerId); 
      final float x = ev.getX(pointerIndex); 
      final float y = ev.getY(pointerIndex); 

      // Only move if the ScaleGestureDetector isn't processing a gesture. 
      if (!mScaleDetector.isInProgress()) { 
       final float dx = x - mLastTouchX; 
       final float dy = y - mLastTouchY; 

       mPosX += dx; 
       mPosY += dy; 

       invalidate(); 
      } 

      mLastTouchX = x; 
      mLastTouchY = y; 

      break; 
     } 

     case MotionEvent.ACTION_UP: { 
      mActivePointerId = INVALID_POINTER_ID; 
      break; 
     } 

     case MotionEvent.ACTION_CANCEL: { 
      mActivePointerId = INVALID_POINTER_ID; 
      break; 
     } 

     case MotionEvent.ACTION_POINTER_UP: { 
      final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
        >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; 
      final int pointerId = ev.getPointerId(pointerIndex); 
      if (pointerId == mActivePointerId) { 
       // This was our active pointer going up. Choose a new 
       // active pointer and adjust accordingly. 
       final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 
       mLastTouchX = ev.getX(newPointerIndex); 
       mLastTouchY = ev.getY(newPointerIndex); 
       mActivePointerId = ev.getPointerId(newPointerIndex); 
      } 
      break; 
     } 
    }  
    return true; 
}

欲瞭解更多信息，請檢查該link

來源

2013-01-24 06:00:51 Janmejoy

試試如下：

private void touch_up() 
{ 
    path.lineTo(m_X, m_Y); 
    // commit the path to our offscreen 
    canvas.drawPath(m_path, m_paint); 
    // kill this so we don't double draw 
    path.reset(); 
} 
private void touch_start(float p_x, float p_y) 
{ 
    path.reset(); 
    path.moveTo(p_x, p_y); 
    m_X = p_x; 
    m_Y = p_y; 
} 
private void touch_move(float p_x, float p_y) 
{ 
    float m_dx = Math.abs(p_x - m_X); 
    float m_dy = Math.abs(p_y - m_Y); 
    if (m_dx >= TOUCH_TOLERANCE || m_dy >= TOUCH_TOLERANCE) 
    { 
     m_path.quadTo(m_X, m_Y, (p_x + m_X)/2, (p_y + m_Y)/2); 
     m_X = p_x; 
     m_Y = p_y;   
     m_pathDrawn = true; 
    }  
}

對於onTouchEvent：

@Override 
public boolean onTouchEvent(MotionEvent p_event) 
{ 
    float m_x = p_event.getX(); 
    float m_y = p_event.getY();  
    switch (p_event.getAction()) 
    { 
     case MotionEvent.ACTION_DOWN: 
      touch_start(m_x, m_y); 
      invalidate();     
      break; 
     case MotionEvent.ACTION_MOVE: 
      touch_move(m_x, m_y); 
      invalidate(); 
      break; 
     case MotionEvent.ACTION_UP: 
      touch_up(); 
      invalidate();     
      break; 
    } 
    return true; 
}

我希望它能幫助你。

來源

2013-01-24 06:01:21 GrIsHu

安卓觸摸不顯示在畫布上

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