Client-side reimplementation of IMM#setCurrentInputMethodSubtype()

This is a preparation to mark
InputMethodManager#setCurrentInputMethodSubtype() deprecated.

InputMethodManager#setCurrentInputMethodSubtype(), which was
introduced in Android 4.0 ICS [1], was probably mistakenly exposed as
a public API, because it has required WRITE_SECURE_SETTINGS that
typical applications cannot have.

Keeping maintaining InputMethodManager#setCurrentInputMethodSubtype()
is not that simple because now we are about to enable per-profile IME
mode, where this method needs to have a more clear spec about what
"Current" means.

An ideal solution is just removing this method, because if the caller
already has WRITE_SECURE_SETTINGS permission, they can just directly
update Settings.Secure.SELECTED_INPUT_METHOD_SUBTYPE to achieve the
same goal.  However, given that this has been a public API, it would
probably make sense to provide a fallback implementation like I did
for null IME token in InputMethodManager#setInputMethod() [2].

Either way, InputMethodManager#setCurrentInputMethodSubtype() will be
marked as deprecated in a subsequent CL.

 [1]: I55daa19ba924999def544bf841f00bf54852f3e1
      b66d287e3003a0934d5714fbf15e554b3c814906
 [2]: I42dd0325b01c527009bf85566ca8ba0766b2294e
      0c1ebffdb3a459dbae549d462b97cdcdc5602816

Bug: 123249820
Test: manually done with a test app that has WRITE_SECURE_SETTINGS
Change-Id: I76da83c57cffc6b73defccfd4a1b5734c958a97e

1 files changed, 40 insertions, 2 deletions

diff --git a/core/java/android/view/inputmethod/InputMethodManager.java b/core/java/android/view/inputmethod/InputMethodManager.java
index 14a5e3bd1417..15088d2070d2 100644
--- a/core/java/android/view/inputmethod/InputMethodManager.java
+++ b/core/java/android/view/inputmethod/InputMethodManager.java
@@ -27,6 +27,7 @@ import android.annotation.SystemService;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
 import android.app.ActivityThread;
+import android.content.ComponentName;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.pm.PackageManager;
@@ -2492,11 +2493,48 @@ public final class InputMethodManager {
      */
     @RequiresPermission(WRITE_SECURE_SETTINGS)
     public boolean setCurrentInputMethodSubtype(InputMethodSubtype subtype) {
+        if (Process.myUid() == Process.SYSTEM_UID) {
+            Log.w(TAG, "System process should not call setCurrentInputMethodSubtype() because "
+                    + "almost always it is a bug under multi-user / multi-profile environment. "
+                    + "Consider directly interacting with InputMethodManagerService "
+                    + "via LocalServices.");
+            return false;
+        }
+        if (subtype == null) {
+            // See the JavaDoc. This is how this method has worked.
+            return false;
+        }
+        final Context fallbackContext = ActivityThread.currentApplication();
+        if (fallbackContext == null) {
+            return false;
+        }
+        if (fallbackContext.checkSelfPermission(WRITE_SECURE_SETTINGS)
+                != PackageManager.PERMISSION_GRANTED) {
+            return false;
+        }
+        final ContentResolver contentResolver = fallbackContext.getContentResolver();
+        final String imeId = Settings.Secure.getString(contentResolver,
+                Settings.Secure.DEFAULT_INPUT_METHOD);
+        if (ComponentName.unflattenFromString(imeId) == null) {
+            // Null or invalid IME ID format.
+            return false;
+        }
+        final List<InputMethodSubtype> enabledSubtypes;
         try {
-            return mService.setCurrentInputMethodSubtype(subtype);
+            enabledSubtypes = mService.getEnabledInputMethodSubtypeList(imeId, true);
         } catch (RemoteException e) {
-            throw e.rethrowFromSystemServer();
+            return false;
         }
+        final int numSubtypes = enabledSubtypes.size();
+        for (int i = 0; i < numSubtypes; ++i) {
+            final InputMethodSubtype enabledSubtype = enabledSubtypes.get(i);
+            if (enabledSubtype.equals(subtype)) {
+                Settings.Secure.putInt(contentResolver,
+                        Settings.Secure.SELECTED_INPUT_METHOD_SUBTYPE, enabledSubtype.hashCode());
+                return true;
+            }
+        }
+        return false;
     }
 
     /**