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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.PointF;
     20 import android.graphics.Rect;
     21 
     22 import com.android.launcher3.accessibility.DragViewStateAnnouncer;
     23 
     24 /**
     25  * Interface defining an object that can receive a drag.
     26  *
     27  */
     28 public interface DropTarget {
     29 
     30     public static final String TAG = "DropTarget";
     31 
     32     public static class DragObject {
     33         public int x = -1;
     34         public int y = -1;
     35 
     36         /** X offset from the upper-left corner of the cell to where we touched.  */
     37         public int xOffset = -1;
     38 
     39         /** Y offset from the upper-left corner of the cell to where we touched.  */
     40         public int yOffset = -1;
     41 
     42         /** This indicates whether a drag is in final stages, either drop or cancel. It
     43          * differentiates onDragExit, since this is called when the drag is ending, above
     44          * the current drag target, or when the drag moves off the current drag object.
     45          */
     46         public boolean dragComplete = false;
     47 
     48         /** The view that moves around while you drag.  */
     49         public DragView dragView = null;
     50 
     51         /** The data associated with the object being dragged */
     52         public Object dragInfo = null;
     53 
     54         /** Where the drag originated */
     55         public DragSource dragSource = null;
     56 
     57         /** The object is part of an accessible drag operation */
     58         public boolean accessibleDrag;
     59 
     60         /** Post drag animation runnable */
     61         public Runnable postAnimationRunnable = null;
     62 
     63         /** Indicates that the drag operation was cancelled */
     64         public boolean cancelled = false;
     65 
     66         /** Defers removing the DragView from the DragLayer until after the drop animation. */
     67         public boolean deferDragViewCleanupPostAnimation = true;
     68 
     69         public DragViewStateAnnouncer stateAnnouncer;
     70 
     71         public DragObject() {
     72         }
     73 
     74         /**
     75          * This is used to compute the visual center of the dragView. This point is then
     76          * used to visualize drop locations and determine where to drop an item. The idea is that
     77          * the visual center represents the user's interpretation of where the item is, and hence
     78          * is the appropriate point to use when determining drop location.
     79          */
     80         public final float[] getVisualCenter(float[] recycle) {
     81             final float res[] = (recycle == null) ? new float[2] : recycle;
     82 
     83             // These represent the visual top and left of drag view if a dragRect was provided.
     84             // If a dragRect was not provided, then they correspond to the actual view left and
     85             // top, as the dragRect is in that case taken to be the entire dragView.
     86             // R.dimen.dragViewOffsetY.
     87             int left = x - xOffset;
     88             int top = y - yOffset;
     89 
     90             // In order to find the visual center, we shift by half the dragRect
     91             res[0] = left + dragView.getDragRegion().width() / 2;
     92             res[1] = top + dragView.getDragRegion().height() / 2;
     93 
     94             return res;
     95         }
     96     }
     97 
     98     /**
     99      * Used to temporarily disable certain drop targets
    100      *
    101      * @return boolean specifying whether this drop target is currently enabled
    102      */
    103     boolean isDropEnabled();
    104 
    105     /**
    106      * Handle an object being dropped on the DropTarget
    107      *
    108      * @param source DragSource where the drag started
    109      * @param x X coordinate of the drop location
    110      * @param y Y coordinate of the drop location
    111      * @param xOffset Horizontal offset with the object being dragged where the original
    112      *          touch happened
    113      * @param yOffset Vertical offset with the object being dragged where the original
    114      *          touch happened
    115      * @param dragView The DragView that's being dragged around on screen.
    116      * @param dragInfo Data associated with the object being dragged
    117      *
    118      */
    119     void onDrop(DragObject dragObject);
    120 
    121     void onDragEnter(DragObject dragObject);
    122 
    123     void onDragOver(DragObject dragObject);
    124 
    125     void onDragExit(DragObject dragObject);
    126 
    127     /**
    128      * Handle an object being dropped as a result of flinging to delete and will be called in place
    129      * of onDrop().  (This is only called on objects that are set as the DragController's
    130      * fling-to-delete target.
    131      */
    132     void onFlingToDelete(DragObject dragObject, PointF vec);
    133 
    134     /**
    135      * Check if a drop action can occur at, or near, the requested location.
    136      * This will be called just before onDrop.
    137      *
    138      * @param source DragSource where the drag started
    139      * @param x X coordinate of the drop location
    140      * @param y Y coordinate of the drop location
    141      * @param xOffset Horizontal offset with the object being dragged where the
    142      *            original touch happened
    143      * @param yOffset Vertical offset with the object being dragged where the
    144      *            original touch happened
    145      * @param dragView The DragView that's being dragged around on screen.
    146      * @param dragInfo Data associated with the object being dragged
    147      * @return True if the drop will be accepted, false otherwise.
    148      */
    149     boolean acceptDrop(DragObject dragObject);
    150 
    151     void prepareAccessibilityDrop();
    152 
    153     // These methods are implemented in Views
    154     void getHitRectRelativeToDragLayer(Rect outRect);
    155     void getLocationInDragLayer(int[] loc);
    156     int getLeft();
    157     int getTop();
    158 }
    159