Refactor SettingsContentObserver and add it to follow typing feature.

Refactor SettingsContentObserver and rename it to
AccessibilitySettingsContentObserver. Besides, we register it to observe
follow typing feature preference value.

The reasons behind refactor:
1. We change callback signature due to the consistency for register it
by preference key, not by Uri.
2. We refactor the default preference key to a seperate method. Since
the default value is related to accessibility, we rename it with
accessibility prefix.
3. We can register different callback for difference collections of
preference keys.

Default preference keys: They existed in the previous constructor.
1. Settings.Secure.ACCESSIBILITY_ENABLED
2. Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES

Bug: 194668976
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
           AccessibilitySettingsTest
           AccessibilitySettingsContentObserverTest
           AccessibilityShortcutPreferenceFragmentTest
           MagnificationFollowTypingPreferenceControllerTest
           ToggleFeaturePreferenceFragmentTest
           ToggleScreenMagnificationPreferenceFragmentTest
Change-Id: Iafd27e044ebe2536ae7ae55c1c80af54f7f0f822

src/com/android/settings/accessibility/ToggleAccessibilityServicePreferenceFragment.java

@@ -35,7 +35,6 @@ import android.content.pm.ResolveInfo;
 import android.content.pm.ServiceInfo;
 import android.net.Uri;
 import android.os.Bundle;
-import android.os.Handler;
 import android.os.SystemClock;
 import android.text.TextUtils;
 import android.util.Log;
@@ -65,15 +64,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
 
     private static final String EMPTY_STRING = "";
 
-    private final SettingsContentObserver mSettingsContentObserver =
-            new SettingsContentObserver(new Handler()) {
-                @Override
-                public void onChange(boolean selfChange, Uri uri) {
-                    updateSwitchBarToggleSwitch();
-                }
-            };
-
-    private Dialog mDialog;
+    private Dialog mWarningDialog;
     private BroadcastReceiver mPackageRemovedReceiver;
     private boolean mDisabledStateLogged = false;
     private long mStartTimeMillsForLogging = 0;
@@ -108,6 +99,13 @@ public class ToggleAccessibilityServicePreferenceFragment extends
         }
     }
 
+    @Override
+    protected void registerKeysToObserverCallback(
+            AccessibilitySettingsContentObserver contentObserver) {
+        super.registerKeysToObserverCallback(contentObserver);
+        contentObserver.registerObserverCallback(key -> updateSwitchBarToggleSwitch());
+    }
+
     @Override
     public void onStart() {
         super.onStart();
@@ -123,7 +121,11 @@ public class ToggleAccessibilityServicePreferenceFragment extends
     public void onResume() {
         super.onResume();
         updateSwitchBarToggleSwitch();
-        mSettingsContentObserver.register(getContentResolver());
+    }
+
+    @Override
+    public void onPause() {
+        super.onPause();
     }
 
     @Override
@@ -172,7 +174,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
                 if (info == null) {
                     return null;
                 }
-                mDialog = AccessibilityServiceWarning
+                mWarningDialog = AccessibilityServiceWarning
                         .createCapabilitiesDialog(getPrefContext(), info,
                                 this::onDialogButtonFromEnableToggleClicked,
                                 this::onDialogButtonFromUninstallClicked);
@@ -183,7 +185,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
                 if (info == null) {
                     return null;
                 }
-                mDialog = AccessibilityServiceWarning
+                mWarningDialog = AccessibilityServiceWarning
                         .createCapabilitiesDialog(getPrefContext(), info,
                                 this::onDialogButtonFromShortcutToggleClicked,
                                 this::onDialogButtonFromUninstallClicked);
@@ -194,7 +196,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
                 if (info == null) {
                     return null;
                 }
-                mDialog = AccessibilityServiceWarning
+                mWarningDialog = AccessibilityServiceWarning
                         .createCapabilitiesDialog(getPrefContext(), info,
                                 this::onDialogButtonFromShortcutClicked,
                                 this::onDialogButtonFromUninstallClicked);
@@ -205,16 +207,16 @@ public class ToggleAccessibilityServicePreferenceFragment extends
                 if (info == null) {
                     return null;
                 }
-                mDialog = AccessibilityServiceWarning
+                mWarningDialog = AccessibilityServiceWarning
                         .createDisableDialog(getPrefContext(), info,
                                 this::onDialogButtonFromDisableToggleClicked);
                 break;
             }
             default: {
-                mDialog = super.onCreateDialog(dialogId);
+                mWarningDialog = super.onCreateDialog(dialogId);
             }
         }
-        return mDialog;
+        return mWarningDialog;
     }
 
     @Override
@@ -402,7 +404,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
     }
 
     private void onDialogButtonFromUninstallClicked() {
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
         final Intent uninstallIntent = createUninstallPackageActivityIntent();
         if (uninstallIntent == null) {
             return;
@@ -436,12 +438,12 @@ public class ToggleAccessibilityServicePreferenceFragment extends
             mIsDialogShown.set(false);
             showPopupDialog(DialogEnums.LAUNCH_ACCESSIBILITY_TUTORIAL);
         }
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
     }
 
     private void onDenyButtonFromEnableToggleClicked() {
         handleConfirmServiceEnabled(/* confirmed= */ false);
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
     }
 
     void onDialogButtonFromShortcutToggleClicked(View view) {
@@ -465,7 +467,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
         mIsDialogShown.set(false);
         showPopupDialog(DialogEnums.LAUNCH_ACCESSIBILITY_TUTORIAL);
 
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
 
         mShortcutPreference.setSummary(getShortcutTypeSummary(getPrefContext()));
     }
@@ -473,7 +475,7 @@ public class ToggleAccessibilityServicePreferenceFragment extends
     private void onDenyButtonFromShortcutToggleClicked() {
         mShortcutPreference.setChecked(false);
 
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
     }
 
     void onDialogButtonFromShortcutClicked(View view) {
@@ -491,11 +493,11 @@ public class ToggleAccessibilityServicePreferenceFragment extends
         mIsDialogShown.set(false);
         showPopupDialog(DialogEnums.EDIT_SHORTCUT);
 
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
     }
 
     private void onDenyButtonFromShortcutClicked() {
-        mDialog.dismiss();
+        mWarningDialog.dismiss();
     }
 
     private boolean onPreferenceClick(boolean isChecked) {