Accessibility settings should update after gesture to enable accessibility.

1. We have added a global gesture to enable accessibility which is long press
   on power follower by a long press with two fingers. If this gesture is
   performed when accessibility settings are on the screen, accessibility and
   the screen-reader are enabled while the UI does not reflect that and the
   user may try to enable the already enabled screen-reader which will show
   two irrelevant warning dialogs - one for enabling the screen-reader and
   one for enabling explore by touch (assuming the screen-reader requests it).
   This change adds a simple content observer for the relevant accessibility
   settings which upon a change calls the functions to refresh the settings UI.

bug:7309127

Change-Id: I45851d7789e24e9e0a5bc5aaac39db9a12b60e0c

src/com/android/settings/AccessibilitySettings.java

@@ -30,6 +30,7 @@ import android.content.SharedPreferences;
 import android.content.pm.ResolveInfo;
 import android.content.pm.ServiceInfo;
 import android.content.res.Configuration;
+import android.database.ContentObserver;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Handler;
@@ -150,6 +151,9 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
         }
     };
 
+    private final SettingsContentObserver mSettingsContentObserver =
+            new SettingsContentObserver(mHandler);
+
     private final RotationPolicy.RotationPolicyListener mRotationPolicyListener =
             new RotationPolicy.RotationPolicyListener() {
                 @Override
@@ -190,6 +194,7 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
         offerInstallAccessibilitySerivceOnce();
 
         mSettingsPackageMonitor.register(getActivity(), getActivity().getMainLooper(), false);
+        mSettingsContentObserver.register();
         RotationPolicy.registerRotationPolicyListener(getActivity(),
                 mRotationPolicyListener);
     }
@@ -199,6 +204,7 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
         mSettingsPackageMonitor.unregister();
         RotationPolicy.unregisterRotationPolicyListener(getActivity(),
                 mRotationPolicyListener);
+        mSettingsContentObserver.unregister();
         super.onPause();
     }
 
@@ -1009,4 +1015,28 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
             mSummaryPreference.setSummary(summary);
         }
     }
+
+    private final class SettingsContentObserver extends ContentObserver {
+
+        public SettingsContentObserver(Handler handler) {
+            super(handler);
+        }
+
+        public void register() {
+            getContentResolver().registerContentObserver(Settings.Secure.getUriFor(
+                    Settings.Secure.ACCESSIBILITY_ENABLED), false, this);
+            getContentResolver().registerContentObserver(Settings.Secure.getUriFor(
+                    Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES), false, this);
+        }
+
+        public void unregister() {
+            getContentResolver().unregisterContentObserver(this);
+        }
+
+        @Override
+        public void onChange(boolean selfChange, Uri uri) {
+            loadInstalledServices();
+            updateServicesPreferences();
+        }
+    }
 }