Add compatibility utility class for LocaleSpan

This is a groundwork for enabling LocaleSpan support.
LocaleSpan is available in API Level 17 and later. We need some
abstraction layer as usual.

BUG: 16029304
Change-Id: Iead1afdc540216edb1b17f91a40d9edb2e790168

java/src/com/android/inputmethod/compat/LocaleSpanCompatUtils.java

+/*
+ * Copyright (C) 2014 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.inputmethod.compat;
+
+import com.android.inputmethod.annotations.UsedForTesting;
+import com.android.inputmethod.compat.CompatUtils;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.util.Locale;
+
+@UsedForTesting
+public final class LocaleSpanCompatUtils {
+    // Note that LocaleSpan(Locale locale) has been introduced in API level 17
+    // (Build.VERSION_CODE.JELLY_BEAN_MR1).
+    private static Class<?> getLocalSpanClass() {
+        try {
+            return Class.forName("android.text.style.LocaleSpan");
+        } catch (ClassNotFoundException e) {
+            return null;
+        }
+    }
+    private static final Constructor<?> LOCALE_SPAN_CONSTRUCTOR;
+    private static final Method LOCALE_SPAN_GET_LOCALE;
+    static {
+        final Class<?> localeSpanClass = getLocalSpanClass();
+        LOCALE_SPAN_CONSTRUCTOR = CompatUtils.getConstructor(localeSpanClass, Locale.class);
+        LOCALE_SPAN_GET_LOCALE = CompatUtils.getMethod(localeSpanClass, "getLocale");
+    }
+
+    @UsedForTesting
+    public static boolean isLocaleSpanAvailable() {
+        return (LOCALE_SPAN_CONSTRUCTOR != null && LOCALE_SPAN_GET_LOCALE != null);
+    }
+
+    @UsedForTesting
+    public static Object newLocaleSpan(final Locale locale) {
+        return CompatUtils.newInstance(LOCALE_SPAN_CONSTRUCTOR, locale);
+    }
+
+    @UsedForTesting
+    public static Locale getLocaleFromLocaleSpan(final Object localeSpan) {
+        return (Locale) CompatUtils.invoke(localeSpan, null, LOCALE_SPAN_GET_LOCALE);
+    }
+}

tests/src/com/android/inputmethod/compat/LocaleSpanCompatUtilsTests.java

+/*
+ * Copyright (C) 2014 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.inputmethod.compat;
+
+import android.os.Build;
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+
+import java.util.Locale;
+
+@SmallTest
+public class LocaleSpanCompatUtilsTests extends AndroidTestCase {
+    public void testInstantiatable() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
+            // LocaleSpan isn't yet available.
+            return;
+        }
+        assertTrue(LocaleSpanCompatUtils.isLocaleSpanAvailable());
+        final Object japaneseLocaleSpan = LocaleSpanCompatUtils.newLocaleSpan(Locale.JAPANESE);
+        assertNotNull(japaneseLocaleSpan);
+        assertEquals(Locale.JAPANESE,
+                LocaleSpanCompatUtils.getLocaleFromLocaleSpan(japaneseLocaleSpan));
+    }
+}