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      1 /*
      2  * Copyright (C) 2014 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 android.view;
     18 
     19 import android.graphics.Outline;
     20 import android.graphics.drawable.Drawable;
     21 
     22 /**
     23  * Interface by which a View builds its {@link Outline}, used for shadow casting and clipping.
     24  */
     25 public abstract class ViewOutlineProvider {
     26     /**
     27      * Default outline provider for Views, which queries the Outline from the View's background,
     28      * or generates a 0 alpha, rectangular Outline the size of the View if a background
     29      * isn't present.
     30      *
     31      * @see Drawable#getOutline(Outline)
     32      */
     33     public static final ViewOutlineProvider BACKGROUND = new ViewOutlineProvider() {
     34         @Override
     35         public void getOutline(View view, Outline outline) {
     36             Drawable background = view.getBackground();
     37             if (background != null) {
     38                 background.getOutline(outline);
     39             } else {
     40                 outline.setRect(0, 0, view.getWidth(), view.getHeight());
     41                 outline.setAlpha(0.0f);
     42             }
     43         }
     44     };
     45 
     46     /**
     47      * Maintains the outline of the View to match its rectangular bounds,
     48      * at <code>1.0f</code> alpha.
     49      *
     50      * This can be used to enable Views that are opaque but lacking a background cast a shadow.
     51      */
     52     public static final ViewOutlineProvider BOUNDS = new ViewOutlineProvider() {
     53         @Override
     54         public void getOutline(View view, Outline outline) {
     55             outline.setRect(0, 0, view.getWidth(), view.getHeight());
     56         }
     57     };
     58 
     59     /**
     60      * Maintains the outline of the View to match its rectangular padded bounds,
     61      * at <code>1.0f</code> alpha.
     62      *
     63      * This can be used to enable Views that are opaque but lacking a background cast a shadow.
     64      */
     65     public static final ViewOutlineProvider PADDED_BOUNDS = new ViewOutlineProvider() {
     66         @Override
     67         public void getOutline(View view, Outline outline) {
     68             outline.setRect(view.getPaddingLeft(),
     69                     view.getPaddingTop(),
     70                     view.getWidth() - view.getPaddingRight(),
     71                     view.getHeight() - view.getPaddingBottom());
     72         }
     73     };
     74 
     75     /**
     76      * Called to get the provider to populate the Outline.
     77      *
     78      * This method will be called by a View when its owned Drawables are invalidated, when the
     79      * View's size changes, or if {@link View#invalidateOutline()} is called
     80      * explicitly.
     81      *
     82      * The input outline is empty and has an alpha of <code>1.0f</code>.
     83      *
     84      * @param view The view building the outline.
     85      * @param outline The empty outline to be populated.
     86      */
     87     public abstract void getOutline(View view, Outline outline);
     88 }
     89