Use shouldOfferSwitchingToNextInputMethod when available

With this CL, LatinIME starts using
InputMethodManager#shouldOfferSwitchingToNextInputMethod when
available and API level is higher than 19 (KitKat).

Note that relevant settings of LatinIME will be ignored if
InputMethodManager#shouldOfferSwitchingToNextInputMethod is
considered to be available at the moment. We will revisit
here to reorganize the user visible settings before the
new global IME switching mechanism becomes publicly
available.

BUG: 12965588
Change-Id: I0188fa56cba8e983c61cef3ae3400a0e3821f718

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

@@ -28,6 +28,12 @@ public final class InputMethodManagerCompatWrapper {
     private static final Method METHOD_switchToNextInputMethod = CompatUtils.getMethod(
             InputMethodManager.class, "switchToNextInputMethod", IBinder.class, Boolean.TYPE);
 
+    // Note that InputMethodManager.shouldOfferSwitchingToNextInputMethod() has been introduced
+    // in API level 19 (Build.VERSION_CODES.KITKAT).
+    private static final Method METHOD_shouldOfferSwitchingToNextInputMethod =
+            CompatUtils.getMethod(InputMethodManager.class,
+                    "shouldOfferSwitchingToNextInputMethod", IBinder.class);
+
     public final InputMethodManager mImm;
 
     public InputMethodManagerCompatWrapper(final Context context) {
@@ -38,4 +44,9 @@ public final class InputMethodManagerCompatWrapper {
         return (Boolean)CompatUtils.invoke(mImm, false /* defaultValue */,
                 METHOD_switchToNextInputMethod, token, onlyCurrentIme);
     }
+
+    public boolean shouldOfferSwitchingToNextInputMethod(final IBinder token) {
+        return (Boolean)CompatUtils.invoke(mImm, false /* defaultValue */,
+                METHOD_shouldOfferSwitchingToNextInputMethod, token);
+    }
 }

java/src/com/android/inputmethod/keyboard/KeyboardSwitcher.java

@@ -123,7 +123,7 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
         builder.setOptions(
                 mSubtypeSwitcher.isShortcutImeEnabled(),
                 settingsValues.mShowsVoiceInputKey,
-                settingsValues.isLanguageSwitchKeyEnabled());
+                mLatinIME.shouldSwitchToOtherInputMethods());
         mKeyboardLayoutSet = builder.build();
         mCurrentSettingsValues = settingsValues;
         try {

java/src/com/android/inputmethod/latin/LatinIME.java

@@ -1229,7 +1229,7 @@ public class LatinIME extends InputMethodService implements KeyboardActionListen
     // TODO: Revise the language switch key behavior to make it much smarter and more reasonable.
     public void switchToNextSubtype() {
         final IBinder token = getWindow().getWindow().getAttributes().token;
-        if (mSettings.getCurrent().mIncludesOtherImesInLanguageSwitchList) {
+        if (shouldSwitchToOtherInputMethods()) {
             mRichImm.switchToNextInputMethod(token, false /* onlyCurrentIme */);
             return;
         }
@@ -1799,4 +1799,28 @@ public class LatinIME extends InputMethodService implements KeyboardActionListen
         p.println(settingsValues.dump());
         // TODO: Dump all settings values
     }
+
+    public boolean shouldSwitchToOtherInputMethods() {
+        // TODO: Revisit here to reorganize the settings. Probably we can/should use different
+        // strategy once the implementation of
+        // {@link InputMethodManager#shouldOfferSwitchingToNextInputMethod} is defined well.
+        final boolean fallbackValue = mSettings.getCurrent().mIncludesOtherImesInLanguageSwitchList;
+        final IBinder token = getWindow().getWindow().getAttributes().token;
+        if (token == null) {
+            return fallbackValue;
+        }
+        return mRichImm.shouldOfferSwitchingToNextInputMethod(token, fallbackValue);
+    }
+
+    public boolean shouldShowLanguageSwitchKey() {
+        // TODO: Revisit here to reorganize the settings. Probably we can/should use different
+        // strategy once the implementation of
+        // {@link InputMethodManager#shouldOfferSwitchingToNextInputMethod} is defined well.
+        final boolean fallbackValue = mSettings.getCurrent().isLanguageSwitchKeyEnabled();
+        final IBinder token = getWindow().getWindow().getAttributes().token;
+        if (token == null) {
+            return fallbackValue;
+        }
+        return mRichImm.shouldOfferSwitchingToNextInputMethod(token, fallbackValue);
+    }
 }

java/src/com/android/inputmethod/latin/RichInputMethodManager.java

@@ -20,6 +20,7 @@ import static com.android.inputmethod.latin.Constants.Subtype.KEYBOARD_MODE;
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.os.Build;
 import android.os.IBinder;
 import android.preference.PreferenceManager;
 import android.util.Log;
@@ -406,4 +407,15 @@ public final class RichInputMethodManager {
         mSubtypeListCacheWithoutImplicitlySelectedSubtypes.clear();
         mInputMethodInfoCache.clear();
     }
+
+    public boolean shouldOfferSwitchingToNextInputMethod(final IBinder binder,
+            boolean defaultValue) {
+        // Use the default value instead on Jelly Bean MR2 and previous where
+        // {@link InputMethodManager#shouldOfferSwitchingToNextInputMethod} isn't yet available
+        // and on KitKat where the API is still just a stub to return true always.
+        if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.KITKAT) {
+            return defaultValue;
+        }
+        return mImmWrapper.shouldOfferSwitchingToNextInputMethod(binder);
+    }
 }