1 /*
2  * Copyright (C) 2019 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 com.android.launcher3.util;
17 
18 import android.content.Intent;
19 import android.os.Bundle;
20 import android.os.IBinder;
21 
22 import androidx.annotation.Nullable;
23 
24 import com.android.launcher3.BaseActivity;
25 
26 import java.lang.ref.WeakReference;
27 
28 /**
29  * Helper class to statically track activity creation
30  * @param <T> The activity type to track
31  */
32 public final class ActivityTracker<T extends BaseActivity> {
33 
34     private WeakReference<T> mCurrentActivity = new WeakReference<>(null);
35 
36     private static final String EXTRA_SCHEDULER_CALLBACK = "launcher.scheduler_callback";
37 
38     @Nullable
getCreatedActivity()39     public <R extends T> R getCreatedActivity() {
40         return (R) mCurrentActivity.get();
41     }
42 
onActivityDestroyed(T activity)43     public void onActivityDestroyed(T activity) {
44         if (mCurrentActivity.get() == activity) {
45             mCurrentActivity.clear();
46         }
47     }
48 
49     /**
50      * Call {@link SchedulerCallback#init(BaseActivity, boolean)} when the activity is ready.
51      * If the activity is already created, this is called immediately, otherwise we add the
52      * callback as an extra on the intent, and will call init() when we get handleIntent().
53      * @param callback The callback to call init() on when the activity is ready.
54      * @param intent The intent that will be used to initialize the activity, if the activity
55      *               doesn't already exist. We add the callback as an extra on this intent.
56      */
runCallbackWhenActivityExists(SchedulerCallback<T> callback, Intent intent)57     public void runCallbackWhenActivityExists(SchedulerCallback<T> callback, Intent intent) {
58         T activity = mCurrentActivity.get();
59         if (activity != null) {
60             callback.init(activity, activity.isStarted());
61         } else {
62             callback.addToIntent(intent);
63         }
64     }
65 
handleCreate(T activity)66     public boolean handleCreate(T activity) {
67         mCurrentActivity = new WeakReference<>(activity);
68         return handleIntent(activity, activity.getIntent(), false);
69     }
70 
handleNewIntent(T activity, Intent intent)71     public boolean handleNewIntent(T activity, Intent intent) {
72         return handleIntent(activity, intent, activity.isStarted());
73     }
74 
handleIntent(T activity, Intent intent, boolean alreadyOnHome)75     private boolean handleIntent(T activity, Intent intent, boolean alreadyOnHome) {
76         if (intent != null && intent.getExtras() != null) {
77             IBinder stateBinder = intent.getExtras().getBinder(EXTRA_SCHEDULER_CALLBACK);
78             if (stateBinder instanceof ObjectWrapper) {
79                 SchedulerCallback<T> handler =
80                         ((ObjectWrapper<SchedulerCallback>) stateBinder).get();
81                 if (!handler.init(activity, alreadyOnHome)) {
82                     intent.getExtras().remove(EXTRA_SCHEDULER_CALLBACK);
83                 }
84                 return true;
85             }
86         }
87         return false;
88     }
89 
90     public interface SchedulerCallback<T extends BaseActivity> {
91 
92         /**
93          * Called when the activity is ready.
94          * @param alreadyOnHome Whether the activity is already started.
95          * @return Whether to continue receiving callbacks (i.e. if the activity is recreated).
96          */
init(T activity, boolean alreadyOnHome)97         boolean init(T activity, boolean alreadyOnHome);
98 
99         /**
100          * Adds this callback as an extra on the intent, so we can retrieve it in handleIntent() and
101          * call {@link #init}. The intent should be used to start the activity after calling this
102          * method in order for us to get handleIntent().
103          */
addToIntent(Intent intent)104         default Intent addToIntent(Intent intent) {
105             Bundle extras = new Bundle();
106             extras.putBinder(EXTRA_SCHEDULER_CALLBACK, ObjectWrapper.wrap(this));
107             intent.putExtras(extras);
108             return intent;
109         }
110     }
111 }
112