Unifying activity tracker callback

> Using a common class for both Launcher and RecentsActivity
> Removing static refenrece to LauncherModel and using a common pattern for
  tracking activities

Bug: 141376165
Bug: 137568159
Change-Id: Ic1897abe6913ec78e25725118eedf5b468d5ec70

src/com/android/launcher3/util/ActivityTracker.java

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.launcher3.util;
+
+import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.IBinder;
+
+import androidx.annotation.Nullable;
+
+import com.android.launcher3.BaseActivity;
+
+import java.lang.ref.WeakReference;
+
+/**
+ * Helper class to statically track activity creation
+ */
+public final class ActivityTracker<T extends BaseActivity> implements Runnable {
+
+    private WeakReference<T> mCurrentActivity = new WeakReference<>(null);
+    private WeakReference<SchedulerCallback<T>> mPendingCallback = new WeakReference<>(null);
+
+    private static final String EXTRA_SCHEDULER_CALLBACK = "launcher.scheduler_callback";
+
+    @Nullable
+    public <R extends T> R getCreatedActivity() {
+        return (R) mCurrentActivity.get();
+    }
+
+    public void onActivityDestroyed(T activity) {
+        if (mCurrentActivity.get() == activity) {
+            mCurrentActivity.clear();
+        }
+    }
+
+    public void schedule(SchedulerCallback<? extends T> callback) {
+        synchronized (this) {
+            mPendingCallback = new WeakReference<>((SchedulerCallback<T>) callback);
+        }
+        MAIN_EXECUTOR.execute(this);
+    }
+
+    @Override
+    public void run() {
+        T activity = mCurrentActivity.get();
+        if (activity != null) {
+            initIfPending(activity, activity.isStarted());
+        }
+    }
+
+    public boolean initIfPending(T activity, boolean alreadyOnHome) {
+        SchedulerCallback<T> pendingCallback = mPendingCallback.get();
+        if (pendingCallback != null) {
+            if (!pendingCallback.init(activity, alreadyOnHome)) {
+                clearReference(pendingCallback);
+            }
+            return true;
+        }
+        return false;
+    }
+
+    public boolean clearReference(SchedulerCallback<? extends T> handler) {
+        synchronized (this) {
+            if (mPendingCallback.get() == handler) {
+                mPendingCallback.clear();
+                return true;
+            }
+            return false;
+        }
+    }
+
+    public boolean hasPending() {
+        return mPendingCallback.get() != null;
+    }
+
+    public boolean handleCreate(T activity) {
+        mCurrentActivity = new WeakReference<>(activity);
+        return handleIntent(activity, activity.getIntent(), false, false);
+    }
+
+    public boolean handleNewIntent(T activity, Intent intent) {
+        return handleIntent(activity, intent, activity.isStarted(), true);
+    }
+
+    private boolean handleIntent(
+            T activity, Intent intent, boolean alreadyOnHome, boolean explicitIntent) {
+        boolean result = false;
+        if (intent != null && intent.getExtras() != null) {
+            IBinder stateBinder = intent.getExtras().getBinder(EXTRA_SCHEDULER_CALLBACK);
+            if (stateBinder instanceof ObjectWrapper) {
+                SchedulerCallback<T> handler =
+                        ((ObjectWrapper<SchedulerCallback>) stateBinder).get();
+                if (!handler.init(activity, alreadyOnHome)) {
+                    intent.getExtras().remove(EXTRA_SCHEDULER_CALLBACK);
+                }
+                result = true;
+            }
+        }
+        if (!result && !explicitIntent) {
+            result = initIfPending(activity, alreadyOnHome);
+        }
+        return result;
+    }
+
+    public interface SchedulerCallback<T extends BaseActivity> {
+
+        boolean init(T activity, boolean alreadyOnHome);
+
+        default Intent addToIntent(Intent intent) {
+            Bundle extras = new Bundle();
+            extras.putBinder(EXTRA_SCHEDULER_CALLBACK, ObjectWrapper.wrap(this));
+            intent.putExtras(extras);
+            return intent;
+        }
+    }
+}