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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.launcher3;
     18 
     19 import android.graphics.Rect;
     20 
     21 import com.android.launcher3.accessibility.DragViewStateAnnouncer;
     22 import com.android.launcher3.dragndrop.DragView;
     23 
     24 /**
     25  * Interface defining an object that can receive a drag.
     26  *
     27  */
     28 public interface DropTarget {
     29 
     30     class DragObject {
     31         public int x = -1;
     32         public int y = -1;
     33 
     34         /** X offset from the upper-left corner of the cell to where we touched.  */
     35         public int xOffset = -1;
     36 
     37         /** Y offset from the upper-left corner of the cell to where we touched.  */
     38         public int yOffset = -1;
     39 
     40         /** This indicates whether a drag is in final stages, either drop or cancel. It
     41          * differentiates onDragExit, since this is called when the drag is ending, above
     42          * the current drag target, or when the drag moves off the current drag object.
     43          */
     44         public boolean dragComplete = false;
     45 
     46         /** The view that moves around while you drag.  */
     47         public DragView dragView = null;
     48 
     49         /** The data associated with the object, after item is dropped. */
     50         public ItemInfo dragInfo = null;
     51 
     52         /** The data associated with the object  being dragged */
     53         public ItemInfo originalDragInfo = null;
     54 
     55         /** Where the drag originated */
     56         public DragSource dragSource = null;
     57 
     58         /** The object is part of an accessible drag operation */
     59         public boolean accessibleDrag;
     60 
     61         /** Post drag animation runnable */
     62         public Runnable postAnimationRunnable = null;
     63 
     64         /** Indicates that the drag operation was cancelled */
     65         public boolean cancelled = false;
     66 
     67         /** Defers removing the DragView from the DragLayer until after the drop animation. */
     68         public boolean deferDragViewCleanupPostAnimation = true;
     69 
     70         public DragViewStateAnnouncer stateAnnouncer;
     71 
     72         public DragObject() {
     73         }
     74 
     75         /**
     76          * This is used to compute the visual center of the dragView. This point is then
     77          * used to visualize drop locations and determine where to drop an item. The idea is that
     78          * the visual center represents the user's interpretation of where the item is, and hence
     79          * is the appropriate point to use when determining drop location.
     80          */
     81         public final float[] getVisualCenter(float[] recycle) {
     82             final float res[] = (recycle == null) ? new float[2] : recycle;
     83 
     84             // These represent the visual top and left of drag view if a dragRect was provided.
     85             // If a dragRect was not provided, then they correspond to the actual view left and
     86             // top, as the dragRect is in that case taken to be the entire dragView.
     87             // R.dimen.dragViewOffsetY.
     88             int left = x - xOffset;
     89             int top = y - yOffset;
     90 
     91             // In order to find the visual center, we shift by half the dragRect
     92             res[0] = left + dragView.getDragRegion().width() / 2;
     93             res[1] = top + dragView.getDragRegion().height() / 2;
     94 
     95             return res;
     96         }
     97     }
     98 
     99     /**
    100      * Used to temporarily disable certain drop targets
    101      *
    102      * @return boolean specifying whether this drop target is currently enabled
    103      */
    104     boolean isDropEnabled();
    105 
    106     /**
    107      * Handle an object being dropped on the DropTarget
    108      */
    109     void onDrop(DragObject dragObject);
    110 
    111     void onDragEnter(DragObject dragObject);
    112 
    113     void onDragOver(DragObject dragObject);
    114 
    115     void onDragExit(DragObject dragObject);
    116 
    117     /**
    118      * Check if a drop action can occur at, or near, the requested location.
    119      * This will be called just before onDrop.
    120      * @return True if the drop will be accepted, false otherwise.
    121      */
    122     boolean acceptDrop(DragObject dragObject);
    123 
    124     void prepareAccessibilityDrop();
    125 
    126     // These methods are implemented in Views
    127     void getHitRectRelativeToDragLayer(Rect outRect);
    128 }
    129