RTL: Navigate to previous tab when back.

When go back from RTL language, user should be navigated to the
previous setting tab.

Bug: 31145366
Test: make RunSettingsRoboTests

Change-Id: I2f2ec727f9737ea0e52dac9950c8af34559e3d9a

src/com/android/settings/widget/RtlCompatibleViewPager.java

@@ -17,10 +17,12 @@
 package com.android.settings.widget;
 
 import android.content.Context;
+import android.os.Parcelable;
 import android.support.v4.view.ViewPager;
 import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.view.View;
+import android.os.Parcel;
 
 import java.util.Locale;
 
@@ -54,6 +56,23 @@ public final class RtlCompatibleViewPager extends ViewPager {
         super.setCurrentItem(getRtlAwareIndex(item));
     }
 
+    @Override
+    public Parcelable onSaveInstanceState() {
+        Parcelable parcelable = super.onSaveInstanceState();
+
+        RtlSavedState rtlSavedState = new RtlSavedState(parcelable);
+        rtlSavedState.position = getCurrentItem();
+        return rtlSavedState;
+    }
+
+    @Override
+    public void onRestoreInstanceState(Parcelable state) {
+        RtlSavedState rtlSavedState = (RtlSavedState) state;
+        super.onRestoreInstanceState(rtlSavedState.getSuperState());
+
+        setCurrentItem(rtlSavedState.position);
+    }
+
     /**
      * Get a "RTL friendly" index. If the locale is LTR, the index is returned as is.
      * Otherwise it's transformed so view pager can render views using the new index for RTL. For
@@ -70,4 +89,38 @@ public final class RtlCompatibleViewPager extends ViewPager {
         }
         return index;
     }
+
+    static class RtlSavedState extends BaseSavedState {
+        int position;
+
+        public RtlSavedState(Parcelable superState) {
+            super(superState);
+        }
+
+        private RtlSavedState(Parcel in) {
+            super(in);
+            position = in.readInt();
+        }
+
+        @Override
+        public void writeToParcel(Parcel out, int flags) {
+            super.writeToParcel(out, flags);
+            out.writeInt(position);
+        }
+
+        public static final Parcelable.Creator<RtlSavedState> CREATOR
+                = new Parcelable.Creator<RtlSavedState>() {
+            @Override
+            public RtlSavedState createFromParcel(Parcel in) {
+                return new RtlSavedState(in);
+            }
+
+            @Override
+            public RtlSavedState[] newArray(int size) {
+                return new RtlSavedState[size];
+            }
+        };
+
+    }
+
 }

tests/robotests/src/com/android/settings/shadow/ShadowTextUtils.java

@@ -0,0 +1,47 @@
+/*
+ * 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.shadow;
+
+import android.icu.util.ULocale;
+import android.os.SystemProperties;
+import android.provider.Settings;
+import android.text.TextUtils;
+import android.view.View;
+import org.robolectric.annotation.Implementation;
+import org.robolectric.annotation.Implements;
+
+import java.util.Locale;
+
+/**
+ * Important: The current robolectric doesn't support API 24, so I copy the code
+ * from API 24 here to make it compatible. Once robolectric is upgraded to 24,
+ * We can delete this shadow class.
+ **/
+@Implements(TextUtils.class)
+public class ShadowTextUtils {
+
+    @Implementation
+    public static int getLayoutDirectionFromLocale(Locale locale) {
+        return ((locale != null && !locale.equals(Locale.ROOT)
+                && ULocale.forLocale(locale).isRightToLeft())
+                // If forcing into RTL layout mode, return RTL as default
+                || SystemProperties.getBoolean(Settings.Global.DEVELOPMENT_FORCE_RTL, false))
+                ? View.LAYOUT_DIRECTION_RTL
+                : View.LAYOUT_DIRECTION_LTR;
+    }
+
+}

tests/robotests/src/com/android/settings/widget/RtlCompatibleViewPagerTest.java

@@ -0,0 +1,139 @@
+/*
+ * 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.widget;
+
+import android.annotation.Nullable;
+import android.app.Activity;
+import android.os.Bundle;
+import android.os.Parcelable;
+import android.text.TextUtils;
+import android.view.View;
+import android.view.ViewGroup;
+import com.android.settings.TestConfig;
+import com.android.settings.shadow.ShadowTextUtils;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Locale;
+
+import android.support.v4.view.PagerAdapter;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+import org.robolectric.Robolectric;
+
+@RunWith(RobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class RtlCompatibleViewPagerTest {
+    private ViewPagerTestActivity mTestActivity;
+    private RtlCompatibleViewPager mTestViewPager;
+    private Locale mLocaleEn;
+    private Locale mLocaleHe;
+
+    @Before
+    public void setUp() {
+        mTestActivity = Robolectric.setupActivity(ViewPagerTestActivity.class);
+        mTestViewPager = mTestActivity.getViewPager();
+        mLocaleEn = new Locale("en");
+        mLocaleHe = new Locale("he");
+    }
+
+    @Test
+    @Config(shadows = {ShadowTextUtils.class})
+    public void testRtlCompatible() {
+        testRtlCompatibleInner(0);
+        testRtlCompatibleInner(1);
+    }
+
+    private void testRtlCompatibleInner(int currentItem) {
+        // Set up the environment
+        Locale.setDefault(mLocaleEn);
+        assertEquals(View.LAYOUT_DIRECTION_LTR,
+                TextUtils.getLayoutDirectionFromLocale(Locale.getDefault()));
+        mTestViewPager.setCurrentItem(currentItem);
+        assertEquals(currentItem, mTestViewPager.getCurrentItem());
+
+        // Simulate to change the language to RTL
+        Parcelable savedInstance = mTestViewPager.onSaveInstanceState();
+        Locale.setDefault(mLocaleHe);
+        assertEquals(View.LAYOUT_DIRECTION_RTL,
+                TextUtils.getLayoutDirectionFromLocale(Locale.getDefault()));
+        mTestViewPager.onRestoreInstanceState(savedInstance);
+
+        assertEquals(currentItem, mTestViewPager.getCurrentItem());
+    }
+
+
+    /**
+     * Test activity that contains RTL viewpager
+     */
+    private static class ViewPagerTestActivity extends Activity {
+        private RtlCompatibleViewPager mViewPager;
+
+        @Override
+        protected void onCreate(@Nullable Bundle savedInstanceState) {
+            super.onCreate(savedInstanceState);
+
+            mViewPager = new RtlCompatibleViewPager(ViewPagerTestActivity.this);
+            mViewPager.setAdapter(new ViewPagerAdapter());
+
+            setContentView(mViewPager);
+        }
+
+        public RtlCompatibleViewPager getViewPager() {
+            return mViewPager;
+        }
+    }
+
+    /**
+     * Test viewpager adapter, uses 2 view to test it
+     */
+    private static final class ViewPagerAdapter extends PagerAdapter {
+
+        private static final int ITEM_COUNT = 2;
+
+        public ViewPagerAdapter() {
+        }
+
+        @Override
+        public int getCount() {
+            return ITEM_COUNT;
+        }
+
+        @Override
+        public boolean isViewFromObject(View view, Object object) {
+            return view == object;
+        }
+
+        @Override
+        public void destroyItem(ViewGroup collection, int position, Object view) {
+            collection.removeView((View) view);
+        }
+
+        @Override
+        public Object instantiateItem(ViewGroup container, int position) {
+            return null;
+        }
+
+        @Override
+        public CharSequence getPageTitle(int position) {
+            return null;
+        }
+    }
+}