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      1 /*
      2  * Copyright 2016, 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.example.android.dragsource;
     18 
     19 import android.content.ClipData;
     20 import android.net.Uri;
     21 import android.view.DragEvent;
     22 import android.view.View;
     23 import android.widget.ImageView;
     24 
     25 /**
     26  * OnDragListener for ImageViews.
     27  * Sets colors of the target when DragEvents fire. When a drop is received, the {@link Uri} backing
     28  * the first {@link android.content.ClipData.Item} in the {@link DragEvent} is set as the image
     29  * resource of the ImageView.
     30  */
     31 public class ImageDragListener implements View.OnDragListener {
     32 
     33     private static final int COLOR_INACTIVE = 0xFF888888;
     34 
     35     private static final int COLOR_ACTIVE = 0xFFCCCCCC;
     36 
     37     private static final int COLOR_HOVER = 0xFFEEEEEE;
     38 
     39     @Override
     40     public boolean onDrag(View view, DragEvent event) {
     41         // Change the color of the target for all events.
     42         // For the drop action, set the view to the dropped image.
     43         switch (event.getAction()) {
     44             case DragEvent.ACTION_DRAG_STARTED:
     45                 setTargetColor(view, COLOR_ACTIVE);
     46                 return true;
     47 
     48             case DragEvent.ACTION_DRAG_ENTERED:
     49                 setTargetColor(view, COLOR_HOVER);
     50                 return true;
     51 
     52             case DragEvent.ACTION_DRAG_LOCATION:
     53                 processLocation(event.getX(), event.getY());
     54                 return true;
     55 
     56             case DragEvent.ACTION_DRAG_EXITED:
     57                 setTargetColor(view, COLOR_ACTIVE);
     58                 return true;
     59 
     60             case DragEvent.ACTION_DROP:
     61                 return processDrop(view, event);
     62 
     63             case DragEvent.ACTION_DRAG_ENDED:
     64                 setTargetColor(view, COLOR_INACTIVE);
     65                 return true;
     66 
     67             default:
     68                 break;
     69         }
     70 
     71         return false;
     72     }
     73 
     74     private void setTargetColor(View view, int color) {
     75         view.setBackgroundColor(color);
     76     }
     77 
     78     private boolean processDrop(View view, DragEvent event) {
     79         ClipData clipData = event.getClipData();
     80         if (clipData == null || clipData.getItemCount() == 0) {
     81             return false;
     82         }
     83         ClipData.Item item = clipData.getItemAt(0);
     84         if (item == null) {
     85             return false;
     86         }
     87         Uri uri = item.getUri();
     88         if (uri == null) {
     89             return false;
     90         }
     91         return setImageUri(view, event, uri);
     92     }
     93 
     94     protected void processLocation(float x, float y) {
     95     }
     96 
     97     protected boolean setImageUri(View view, DragEvent event, Uri uri) {
     98         if (!(view instanceof ImageView)) {
     99             return false;
    100         }
    101         ((ImageView) view).setImageURI(uri);
    102         return true;
    103     }
    104 }
    105