如何在Android中将图像拖出一半界限

Question

我正在制作应用程序，其中我想在屏幕上拖动图像。现在所有的东西都可以正常工作，但是如果用户从左向右滑动，则图像会进一步向右移动。我不想这样做。

我想要的是图像不应该出去一半的边界宽度。我的意思是图像视图应该只在视图/边界的一边。我希望它在每个坐标的边界都有一半，我的意思是左，右，上和下。它不应该消失。为此，我正在使用触摸监听器。现在，我能够做旋转，缩放和拖动（尽管它走出去的束缚）

所以现在我想它不应该走出去的束缚，这里是我使用的代码：

@Override 
public boolean onTouch(View v, MotionEvent event) { 

    // ImageView view = (ImageView) v; 


    //view.setScaleType(ImageView.ScaleType.MATRIX); 
    float scale; 

    // Dump touch event to log 
    dumpEvent(event); 

    // Handle touch events here... 


    ImageView imageView = (ImageView) v; 

    switch (event.getAction() & MotionEvent.ACTION_MASK) { 

     case MotionEvent.ACTION_DOWN: 
      savedMatrix.set(matrix); 
      start.set(event.getX(), event.getY()); 
      mode = DRAG; 
      lastEvent = null; 
      break; 

     case MotionEvent.ACTION_POINTER_DOWN: 
      oldDistance = spacing(event); 
      if (oldDistance > 10f) { 
       savedMatrix.set(matrix); 
       midPoint(mid, event); 
       mode = ZOOM; 
           lastEvent = new float[4]; 
      lastEvent[0] = event.getX(0); 
      lastEvent[1] = event.getX(1); 
      lastEvent[2] = event.getY(0); 
      lastEvent[3] = event.getY(1); 
      d = rotation(event); 

      } 
      break; 

     case MotionEvent.ACTION_UP: 
     case MotionEvent.ACTION_POINTER_UP: 
      mode = NONE; 
      lastEvent = null; 
      break; 

     case MotionEvent.ACTION_MOVE: 
      if (mode == DRAG) { 
       float newX = event.getX() - start.x; 
       float newY = event.getY() - start.y; 
       if (newX <= 0-(imageView.getDrawable() 
         .getIntrinsicWidth())){ 

        Log.v("Bounds", "0-drawable width"); 
        break; 

       }else if (newX >= screenWidth-(imageView.getDrawable() 
         .getIntrinsicWidth())){ 

        Log.v("Bounds", "screen wdith-drawable width"); 
        break; 

       }else if(newY <= 0-(imageView.getDrawable() 
         .getIntrinsicHeight())){ 

        Log.v("Bounds", "Y 0-drawable width"); 
        break; 


       }else if(newY >= (screenHeight-imageView.getDrawable() 
         .getIntrinsicHeight())) { 

        Log.v("Bounds", "y Screen-drawable width"); 
        break; 


       } 



       matrix.set(savedMatrix); 
       matrix.postTranslate(newX, newY); 




      } else if (mode == ZOOM && event.getPointerCount() == 2) { 
       float newDistance = spacing(event); 
       if (newDistance > 10f) { 
        matrix.set(savedMatrix); 
        scale = newDistance/oldDistance; 
        float[] values = new float[9]; 
        matrix.getValues(values); 
        float currentScale = values[Matrix.MSCALE_X]; 
        if (scale * currentScale > MAX_ZOOM) 
         scale = MAX_ZOOM/currentScale; 
        else if (scale * currentScale < MIN_ZOOM) 
         scale = MIN_ZOOM/currentScale; 
        matrix.postScale(scale, scale, mid.x, mid.y); 
       } 
       if (lastEvent != null) { 
        newRot = rotation(event); 
        float r = newRot - d; 
        /* changes must be 

        float[] values = new float[9]; 
        matrix.getValues(values); 
        float tx = values[2]; 
        float ty = values[5]; 
        float sx = values[0]; 
        float xc = (view.getWidth()/2) * sx; 
        float yc = (view.getHeight()/2) * sx; 
        matrix.postRotate(r, tx + xc, ty + yc); 
        */ 
        float[] values = new float[9]; 
        matrix.getValues(values); 
        float tx = values[2]; 
        float ty = values[5]; 
        float sx = values[0]; 
        float xc = (imageView.getWidth()/2) * sx; 
        float yc = (imageView.getHeight()/2) * sx; 
        matrix.postRotate(r, tx + xc, ty + yc); 
        //I commented 
        matrix.postRotate(r, imageView.getMeasuredWidth()/2, 
          imageView.getMeasuredHeight()/2); 
       } 

      } 


      break; 
    } 

      imageView.setImageMatrix(matrix); 
      return true; 
    } 

Eidt

，这是我的XML

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:id="@+id/rl_capture"> 


<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:id="@+id/fl_camera"> 

    <ImageView 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:contentDescription="content_desc_overlay" 
     android:src="@drawable/ic_launcher" 
     android:id="@+id/img_view" 

     /> 


    <ImageView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/iv_overlay" 
     android:src="@drawable/groom01" 
     android:scaleType="matrix" 

     /> 

</FrameLayout> 


    <Button 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="New Button" 
     android:id="@+id/btn_screenshot" 
     android:layout_gravity="right|top" 
     /> 

</RelativeLayout> 

Answer 1

嗯。这有点令人困惑。是否有某些特殊原因使用intrinsicWidth/intrinsicHeight？这些通常不会产生我认为他们会产生的收益（see here）。我假设您的imageView设置为LayoutParams，并且您的重力不会设置，因此图像的原点位于左上角。这是我会做的（未经测试 - 请告诉我是否有问题）：

case MotionEvent.ACTION_MOVE: 
     if (mode == DRAG) { 
      float newX = event.getX() - start.x; 
      float newY = event.getY() - start.y; 

      if (newX < -imageView.getWidth()/2)){ 

       Log.v("Bounds", "0-drawable width"); 
       newX = -imageView.getWidth()/2; 

      }else if (newX > screenWidth-(imageView.getWidth()/2)){ 

       Log.v("Bounds", "screen wdith-drawable width"); 
       newX = screenWidth-(imageView.getWidth()/2); 
      } 


      // not else-if: consider the corners! 
      if(newY < -imageView.getHeight()/2){ 

       Log.v("Bounds", "Y 0-drawable width"); 
       newY = -imageView.getHeight()/2; 


      }else if(newY > (screenHeight-imageView.getHeight()/2)) { 

       Log.v("Bounds", "y Screen-drawable width"); 
       newY = screenHeight-imageView.getHeight()/2; 

      } 

等等。