Add setting for the assist gesture sensitivity control.

The sensitivity control is only visible when the assist gesture itself
is enabled.

Test: make -j RunSettingsRoboTests; manual test on supported/unsupported
      configurations.

Change-Id: I584975794c5cf9d788e93167292d142ae2faf1c5

src/com/android/settings/gestures/AssistGesturePreferenceController.java

@@ -17,29 +17,90 @@
 package com.android.settings.gestures;
 
 import android.content.Context;
+import android.net.Uri;
 import android.provider.Settings;
 import android.support.v7.preference.Preference;
-import android.util.ArrayMap;
+import android.support.v7.preference.PreferenceScreen;
 
+import com.android.settings.applications.assist.AssistSettingObserver;
 import com.android.settings.core.lifecycle.Lifecycle;
+import com.android.settings.core.lifecycle.events.OnPause;
+import com.android.settings.core.lifecycle.events.OnResume;
 import com.android.settings.overlay.FeatureFactory;
-import com.android.settings.search2.InlineSwitchPayload;
-import com.android.settings.search2.ResultPayload;
 
-public class AssistGesturePreferenceController extends GesturePreferenceController {
+import java.util.Arrays;
+import java.util.List;
+
+public class AssistGesturePreferenceController extends GesturePreferenceController
+        implements OnPause, OnResume {
 
     private static final String PREF_KEY_VIDEO = "gesture_assist_video";
     private static final String PREF_KEY_ASSIST_GESTURE = "gesture_assist";
 
+    private final AssistGestureFeatureProvider mFeatureProvider;
+    private final SettingObserver mSettingObserver;
+    private boolean mWasAvailable;
+
+    private PreferenceScreen mScreen;
+    private Preference mPreference;
+
     public AssistGesturePreferenceController(Context context, Lifecycle lifecycle) {
         super(context, lifecycle);
+        mFeatureProvider = FeatureFactory.getFactory(context).getAssistGestureFeatureProvider();
+        mSettingObserver = new SettingObserver();
+        mWasAvailable = isAvailable();
     }
 
     @Override
     public boolean isAvailable() {
-        AssistGestureFeatureProvider provider =
-                FeatureFactory.getFactory(mContext).getAssistGestureFeatureProvider();
-        return provider.isSupported(mContext);
+        return mFeatureProvider.isSupported(mContext);
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        mScreen = screen;
+        mPreference = screen.findPreference(getPreferenceKey());
+        // Call super last or AbstractPreferenceController might remove the preference from the
+        // screen (if !isAvailable()) before we can save a reference to it.
+        super.displayPreference(screen);
+    }
+
+    @Override
+    public void onResume() {
+        mSettingObserver.register(mContext.getContentResolver(), true /* register */);
+        if (mWasAvailable != isAvailable()) {
+            // Only update the preference visibility if the availability has changed -- otherwise
+            // the preference may be incorrectly added to screens with collapsed sections.
+            updatePreference();
+            mWasAvailable = isAvailable();
+        }
+    }
+
+    @Override
+    public void onPause() {
+        mSettingObserver.register(mContext.getContentResolver(), false /* register */);
+    }
+
+    private void updatePreference() {
+        if (mPreference == null) {
+            return;
+        }
+
+        if (isAvailable()) {
+            if (mScreen.findPreference(getPreferenceKey()) == null) {
+                mScreen.addPreference(mPreference);
+            }
+        } else {
+            mScreen.removePreference(mPreference);
+        }
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        final boolean enabled = (boolean) newValue;
+        Settings.Secure.putInt(mContext.getContentResolver(),
+                Settings.Secure.ASSIST_GESTURE_ENABLED, enabled ? 1 : 0);
+        return true;
     }
 
     @Override
@@ -52,18 +113,29 @@ public class AssistGesturePreferenceController extends GesturePreferenceControll
         return PREF_KEY_ASSIST_GESTURE;
     }
 
-    @Override
-    public boolean onPreferenceChange(Preference preference, Object newValue) {
-        final boolean enabled = (boolean) newValue;
-        Settings.Secure.putInt(mContext.getContentResolver(),
-                Settings.Secure.ASSIST_GESTURE_ENABLED, enabled ? 1 : 0);
-        return true;
-    }
-
     @Override
     protected boolean isSwitchPrefEnabled() {
         final int assistGestureEnabled = Settings.Secure.getInt(mContext.getContentResolver(),
                 Settings.Secure.ASSIST_GESTURE_ENABLED, 1);
         return assistGestureEnabled != 0;
     }
+
+    class SettingObserver extends AssistSettingObserver {
+
+        private final Uri ASSIST_GESTURE_ENABLED_URI =
+                Settings.Secure.getUriFor(Settings.Secure.ASSIST_GESTURE_ENABLED);
+
+        @Override
+        protected List<Uri> getSettingUris() {
+            return Arrays.asList(ASSIST_GESTURE_ENABLED_URI);
+        }
+
+        @Override
+        public void onSettingChange() {
+            if (mWasAvailable != isAvailable()) {
+                updatePreference();
+                mWasAvailable = isAvailable();
+            }
+        }
+    }
 }