Add DynamicAvailabilityPreferenceController

This is a PreferenceController that correctly handles the case of
isAvailable() changing dynamically, while the Settings page containing
the preference in question is open.

Bug: 32692748
Test: m RunSettingsRoboTests

Change-Id: I95e22bbc7bdc17bacd2bf6b82fa5b535494d5bce

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

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2017 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;
+
+import android.content.Context;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.core.lifecycle.Lifecycle;
+import com.android.settings.core.lifecycle.LifecycleObserver;
+import com.android.settings.core.lifecycle.events.OnResume;
+
+public abstract class DynamicAvailabilityPreferenceController extends PreferenceController
+        implements LifecycleObserver, OnResume {
+
+    private Preference mPreference;
+    private PreferenceScreen mScreen;
+
+    public DynamicAvailabilityPreferenceController(Context context, Lifecycle lifecycle) {
+        super(context);
+        if (lifecycle != null) {
+            lifecycle.addObserver(this);
+        }
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        mScreen = screen;
+        mPreference = screen.findPreference(getPreferenceKey());
+        super.displayPreference(screen);
+    }
+
+    @Override
+    public void onResume() {
+        if (!isAvailable()) {
+            removePreference(mScreen, getPreferenceKey());
+            return;
+        }
+
+        updateState(mPreference);
+        if (mScreen.findPreference(getPreferenceKey()) == null) {
+            mScreen.addPreference(mPreference);
+        }
+    }
+}

tests/robotests/src/com/android/settings/core/DynamicAvailabilityPreferenceControllerTest.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2017 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;
+
+import android.content.Context;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.SettingsRobolectricTestRunner;
+import com.android.settings.TestConfig;
+import com.android.settings.core.lifecycle.Lifecycle;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+/**
+ * Tests for {@link DynamicAvailabilityPreferenceController}.
+ */
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public final class DynamicAvailabilityPreferenceControllerTest {
+
+    private final String PREFERENCE_KEY = "preference_key";
+
+    private @Mock Context mContext;
+    private @Mock Preference mPreference;
+    private @Mock PreferenceScreen mScreen;
+    private @Mock Lifecycle mLifecycle;
+
+    private boolean mIsAvailable;
+    private Preference mUpdatedPreference = null;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        when(mPreference.getKey()).thenReturn(PREFERENCE_KEY);
+        when(mScreen.findPreference(PREFERENCE_KEY)).thenReturn(mPreference);
+        when(mScreen.getPreferenceCount()).thenReturn(1);
+        when(mScreen.getPreference(0)).thenReturn(mPreference);
+    }
+
+    @Test
+    public void testAvailableToUnavailable() {
+        mIsAvailable = true;
+
+        final DynamicAvailabilityPreferenceController controller
+                = new DynamicAvailabilityPreferenceControllerTestable(mLifecycle);
+        verify(mLifecycle).addObserver(controller);
+
+        controller.displayPreference(mScreen);
+        verify(mScreen, never()).removePreference(mPreference);
+        verify(mScreen, never()).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isNull();
+
+        controller.onResume();
+        verify(mScreen, never()).removePreference(mPreference);
+        verify(mScreen, never()).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isEqualTo(mPreference);
+
+        mUpdatedPreference = null;
+        mIsAvailable = false;
+        controller.onResume();
+        verify(mScreen).removePreference(mPreference);
+        verify(mScreen, never()).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isNull();
+    }
+
+    @Test
+    public void testUnavailableToAvailable() {
+        mIsAvailable = false;
+
+        final DynamicAvailabilityPreferenceController controller
+                = new DynamicAvailabilityPreferenceControllerTestable(mLifecycle);
+        verify(mLifecycle).addObserver(controller);
+
+        controller.displayPreference(mScreen);
+        verify(mScreen).removePreference(mPreference);
+        verify(mScreen, never()).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isNull();
+
+        reset(mScreen);
+        controller.onResume();
+        verify(mScreen, never()).removePreference(mPreference);
+        verify(mScreen, never()).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isNull();
+
+        mIsAvailable = true;
+        controller.onResume();
+        verify(mScreen, never()).removePreference(mPreference);
+        verify(mScreen).addPreference(mPreference);
+        assertThat(mUpdatedPreference).isEqualTo(mPreference);
+    }
+
+
+    private class DynamicAvailabilityPreferenceControllerTestable
+            extends DynamicAvailabilityPreferenceController {
+        public DynamicAvailabilityPreferenceControllerTestable(Lifecycle lifecycle) {
+            super(DynamicAvailabilityPreferenceControllerTest.this.mContext, lifecycle);
+        }
+
+        @Override
+        public boolean isAvailable() {
+            return mIsAvailable;
+        }
+
+        @Override
+        public void updateState(Preference preference) {
+            mUpdatedPreference = preference;
+        }
+
+        @Override
+        public String getPreferenceKey() {
+            return PREFERENCE_KEY;
+        }
+    }
+}