DragSurface.java :  » Widget » mobile-anarchy-widgets » com » MobileAnarchy » Android » Widgets » DragAndDrop » Android Open Source

package com.MobileAnarchy.Android.Widgets.DragAndDrop;

import android.content.Context;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.widget.FrameLayout;

public class DragSurface extends FrameLayout {

  private float draggedViewHalfHeight;
  private float draggedViewHalfWidth;
  private int framesCount;
  
  private Boolean isDragging;
  private DraggableItem draggedItem;
  
  public DragSurface(Context context, AttributeSet attrs) {
    super(context, attrs);
    isDragging = false;
  }

  // =========================================
  // Touch Events Listener
  // =========================================

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    if (isDragging && event.getAction() == MotionEvent.ACTION_UP) {
      // Dragging ended
      removeAllViews();
      isDragging = false;
      
      DragAndDropManager.getInstance().stoppedDragging();
    }

    if (isDragging && event.getAction() == MotionEvent.ACTION_MOVE) {
      // Move the dragged view to it's new position
      repositionView(event.getX(), event.getY());
      
      // Mark this event as handled (so that other UI elements will not intercept it)
      return true;
    }
    
    return false;
  }

  public void startDragging(DraggableItem draggableItem) {
    this.draggedItem = draggableItem;
    this.draggedItem.getDraggedView().setVisibility(INVISIBLE);
    isDragging = true;
    addView(this.draggedItem.getDraggedView());
    //repositionView(x, y);
    framesCount = 0;
  }

  private void repositionView(float x, float y) {
    draggedViewHalfHeight = draggedItem.getDraggedView().getHeight() / 2f;
    draggedViewHalfWidth = draggedItem.getDraggedView().getWidth() / 2f;
    
    // If the dragged view was not drawn yet, skip this phase 
    if (draggedViewHalfHeight == 0 || draggedViewHalfWidth == 0)
      return;
    
    framesCount++;
    
    //Log.d(TAG, "Original = (x=" + x + ", y=" + y + ")");
    //Log.d(TAG, "Size (W=" + draggedViewHalfWidth + ", H=" + draggedViewHalfHeight + ")");

    x = x - draggedViewHalfWidth;
    y = y - draggedViewHalfHeight;
    
    x = Math.max(x, 0);
    x = Math.min(x, getWidth() - draggedViewHalfWidth * 2);

    y = Math.max(y, 0);
    y = Math.min(y, getHeight() - draggedViewHalfHeight * 2);

    //Log.d(TAG, "Moving view to (x=" + x + ", y=" + y + ")");
    FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, 
        LayoutParams.WRAP_CONTENT, Gravity.TOP + Gravity.LEFT);
    
    lp.setMargins((int)x, (int)y, 0, 0);
    draggedItem.getDraggedView().setLayoutParams(lp);

    // hte first couple of dragged frame's positions are not calculated correctly,
    // so we have a threshold before making the dragged view visible again
    if (framesCount < 2)
      return;

    draggedItem.getDraggedView().setVisibility(VISIBLE);
  }
  
}