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 package android.content.res;
17 
18 import android.content.pm.ActivityInfo.Config;
19 
20 /**
21  * A cache class that can provide new instances of a particular resource which may change
22  * depending on the current {@link Resources.Theme} or {@link Configuration}.
23  * <p>
24  * A constant state should be able to return a bitmask of changing configurations, which
25  * identifies the type of configuration changes that may invalidate this resource. These
26  * configuration changes can be obtained from {@link android.util.TypedValue}. Entities such as
27  * {@link android.animation.Animator} also provide a changing configuration method to include
28  * their dependencies (e.g. An AnimatorSet's changing configuration is the union of the
29  * changing configurations of each Animator in the set)
30  * @hide
31  */
32 abstract public class ConstantState<T> {
33 
34     /**
35      * Return a bit mask of configuration changes that will impact
36      * this resource (and thus require completely reloading it).
37      */
getChangingConfigurations()38     abstract public @Config int getChangingConfigurations();
39 
40     /**
41      * Create a new instance without supplying resources the caller
42      * is running in.
43      */
newInstance()44     public abstract T newInstance();
45 
46     /**
47      * Create a new instance from its constant state.  This
48      * must be implemented for resources that change based on the target
49      * density of their caller (that is depending on whether it is
50      * in compatibility mode).
51      */
newInstance(Resources res)52     public T newInstance(Resources res) {
53         return newInstance();
54     }
55 
56     /**
57      * Create a new instance from its constant state.  This must be
58      * implemented for resources that can have a theme applied.
59      */
newInstance(Resources res, Resources.Theme theme)60     public T newInstance(Resources res, Resources.Theme theme) {
61         return newInstance(res);
62     }
63 }
64