Add lifecycle observers for future mixin structures.

- Converted VisibilityLoggerMixin into a LifecyclerObservable so we
  don't have to call logger.onResume/onPause manually in most fragments.
- Observable will be useful when we provide logics across all
  fragment/activity, eg log lifecycle event latencies.
- Also added new tests for lifecycle component.

Bug: 30681529
Test: RunSettingsRoboTests

Change-Id: Ida39300aeb42f71b2e0bbfaebd0c51dc468cb5e8

src/com/android/settings/core/InstrumentedActivity.java

@@ -16,27 +16,18 @@
 
 package com.android.settings.core;
 
-import android.app.Activity;
-
 import com.android.settings.core.instrumentation.Instrumentable;
 import com.android.settings.core.instrumentation.VisibilityLoggerMixin;
+import com.android.settings.core.lifecycle.ObservableActivity;
 
 /**
  * Instrumented activity that logs visibility state.
  */
-public abstract class InstrumentedActivity extends Activity implements Instrumentable {
+public abstract class InstrumentedActivity extends ObservableActivity implements Instrumentable {
 
-    private final VisibilityLoggerMixin mVisibilityLoggerMixin = new VisibilityLoggerMixin(this);
-
-    @Override
-    public void onResume() {
-        super.onResume();
-        mVisibilityLoggerMixin.onResume(this);
+    public InstrumentedActivity() {
+        // Mixin that logs visibility change for activity.
+        getLifecycle().addObserver(new VisibilityLoggerMixin(getMetricsCategory()));
     }
 
-    @Override
-    public void onPause() {
-        super.onPause();
-        mVisibilityLoggerMixin.onPause(this);
-    }
 }

src/com/android/settings/core/InstrumentedFragment.java

@@ -17,31 +17,23 @@
 package com.android.settings.core;
 
 import android.os.Bundle;
-import android.support.v14.preference.PreferenceFragment;
 
-import com.android.settings.core.instrumentation.VisibilityLoggerMixin;
 import com.android.settings.core.instrumentation.Instrumentable;
+import com.android.settings.core.instrumentation.VisibilityLoggerMixin;
+import com.android.settings.core.lifecycle.ObservablePreferenceFragment;
 
 /**
  * Instrumented fragment that logs visibility state.
  */
-public abstract class InstrumentedFragment extends PreferenceFragment implements Instrumentable {
+public abstract class InstrumentedFragment extends ObservablePreferenceFragment
+        implements Instrumentable {
 
-    private final VisibilityLoggerMixin mVisibilityLoggerMixin = new VisibilityLoggerMixin(this);
+    public InstrumentedFragment() {
+        // Mixin that logs visibility change for activity.
+        getLifecycle().addObserver(new VisibilityLoggerMixin(getMetricsCategory()));
+    }
 
     @Override
     public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
     }
-
-    @Override
-    public void onResume() {
-        super.onResume();
-        mVisibilityLoggerMixin.onResume(getActivity());
-    }
-
-    @Override
-    public void onPause() {
-        super.onPause();
-        mVisibilityLoggerMixin.onPause(getActivity());
-    }
 }

src/com/android/settings/core/instrumentation/VisibilityLoggerMixin.java

@@ -16,30 +16,34 @@
 
 package com.android.settings.core.instrumentation;
 
-import android.content.Context;
+import com.android.settings.core.lifecycle.LifecycleObserver;
+import com.android.settings.core.lifecycle.events.OnPause;
+import com.android.settings.core.lifecycle.events.OnResume;
 
 /**
  * Logs visibility change of a fragment.
  */
-public class VisibilityLoggerMixin {
+public class VisibilityLoggerMixin implements LifecycleObserver, OnResume, OnPause {
 
-    private final Instrumentable mInstrumentable;
+    private final int mMetricsCategory;
     private final LogWriter mLogWriter;
 
-    public VisibilityLoggerMixin(Instrumentable instrumentable) {
-        this(instrumentable, MetricsFactory.get().getLogger());
+    public VisibilityLoggerMixin(int metricsCategory) {
+        this(metricsCategory, MetricsFactory.get().getLogger());
     }
 
-    public VisibilityLoggerMixin(Instrumentable instrumentable, LogWriter logWriter) {
-        mInstrumentable = instrumentable;
+    public VisibilityLoggerMixin(int metricsCategory, LogWriter logWriter) {
+        mMetricsCategory = metricsCategory;
         mLogWriter = logWriter;
     }
 
-    public void onResume(Context context) {
-        mLogWriter.visible(context, mInstrumentable.getMetricsCategory());
+    @Override
+    public void onResume() {
+        mLogWriter.visible(null /* context */, mMetricsCategory);
     }
 
-    public void onPause(Context context) {
-        mLogWriter.hidden(context, mInstrumentable.getMetricsCategory());
+    @Override
+    public void onPause() {
+        mLogWriter.hidden(null /* context */, mMetricsCategory);
     }
 }

src/com/android/settings/core/lifecycle/Lifecycle.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle;
+
+import android.annotation.UiThread;
+
+import com.android.settings.core.lifecycle.events.OnDestroy;
+import com.android.settings.core.lifecycle.events.OnPause;
+import com.android.settings.core.lifecycle.events.OnResume;
+import com.android.settings.core.lifecycle.events.OnStart;
+import com.android.settings.core.lifecycle.events.OnStop;
+import com.android.settings.utils.ThreadUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Dispatcher for lifecycle events.
+ */
+public class Lifecycle {
+
+    protected final List<LifecycleObserver> mObservers = new ArrayList<>();
+
+    /**
+     * Registers a new observer of lifecycle events.
+     */
+    @UiThread
+    public <T extends LifecycleObserver> T addObserver(T observer) {
+        ThreadUtils.ensureMainThread();
+        mObservers.add(observer);
+        return observer;
+    }
+
+    public void onStart() {
+        for (LifecycleObserver observer : mObservers) {
+            if (observer instanceof OnStart) {
+                ((OnStart) observer).onStart();
+            }
+        }
+    }
+
+    public void onResume() {
+        for (LifecycleObserver observer : mObservers) {
+            if (observer instanceof OnResume) {
+                ((OnResume) observer).onResume();
+            }
+        }
+    }
+
+    public void onPause() {
+        for (LifecycleObserver observer : mObservers) {
+            if (observer instanceof OnPause) {
+                ((OnPause) observer).onPause();
+            }
+        }
+    }
+
+    public void onStop() {
+        for (LifecycleObserver observer : mObservers) {
+            if (observer instanceof OnStop) {
+                ((OnStop) observer).onStop();
+            }
+        }
+    }
+
+    public void onDestroy() {
+        for (LifecycleObserver observer : mObservers) {
+            if (observer instanceof OnDestroy) {
+                ((OnDestroy) observer).onDestroy();
+            }
+        }
+    }
+}

src/com/android/settings/core/lifecycle/LifecycleObserver.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle;
+
+/**
+ * Observer of lifecycle events.
+ */
+public interface LifecycleObserver {
+}

src/com/android/settings/core/lifecycle/ObservableActivity.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle;
+
+import android.app.Activity;
+
+/**
+ * {@link Activity} that has hooks to observe activity lifecycle events.
+ */
+public class ObservableActivity extends Activity {
+
+    private final Lifecycle mLifecycle = new Lifecycle();
+
+    protected Lifecycle getLifecycle() {
+        return mLifecycle;
+    }
+
+    @Override
+    protected void onStart() {
+        mLifecycle.onStart();
+        super.onStart();
+    }
+
+    @Override
+    protected void onResume() {
+        mLifecycle.onResume();
+        super.onResume();
+    }
+
+    @Override
+    protected void onPause() {
+        mLifecycle.onPause();
+        super.onPause();
+    }
+
+    @Override
+    protected void onStop() {
+        mLifecycle.onStop();
+        super.onStop();
+    }
+
+    @Override
+    protected void onDestroy() {
+        mLifecycle.onDestroy();
+        super.onDestroy();
+    }
+}

src/com/android/settings/core/lifecycle/ObservablePreferenceFragment.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle;
+
+
+import android.annotation.CallSuper;
+import android.support.v14.preference.PreferenceFragment;
+
+/**
+ * {@link PreferenceFragment} that has hooks to observe fragment lifecycle events.
+ */
+public abstract class ObservablePreferenceFragment extends PreferenceFragment {
+
+    private final Lifecycle mLifecycle = new Lifecycle();
+
+    protected Lifecycle getLifecycle() {
+        return mLifecycle;
+    }
+
+    @CallSuper
+    @Override
+    public void onStart() {
+        mLifecycle.onStart();
+        super.onStart();
+    }
+
+    @CallSuper
+    @Override
+    public void onResume() {
+        mLifecycle.onResume();
+        super.onResume();
+    }
+
+    @CallSuper
+    @Override
+    public void onPause() {
+        mLifecycle.onPause();
+        super.onPause();
+    }
+
+}

src/com/android/settings/core/lifecycle/events/OnDestroy.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle.events;
+
+public interface OnDestroy {
+    void onDestroy();
+}

src/com/android/settings/core/lifecycle/events/OnPause.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle.events;
+
+public interface OnPause {
+    void onPause();
+}

src/com/android/settings/core/lifecycle/events/OnResume.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle.events;
+
+public interface OnResume {
+    void onResume();
+}

src/com/android/settings/core/lifecycle/events/OnStart.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle.events;
+
+public interface OnStart {
+
+    void onStart();
+}

src/com/android/settings/core/lifecycle/events/OnStop.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2016 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.settings.core.lifecycle.events;
+
+public interface OnStop {
+
+    void onStop();
+}