Fix trust agent summary not being updated.

- move the handling for enabling the trust agent preference and its
summary from displayPreference() into updateState(), so that when user
navigates to change screen lock or update trust agent and returns to the
security settings page, the trust agent preference enabled state and
summary will be refreshed correctly.

Change-Id: I60bccfdff755a046a9f5453d39a7ac9d3ce0277c
Fixes: 72420147
Test: make RunSettingsRoboTests

src/com/android/settings/security/trustagent/ManageTrustAgentsPreferenceController.java

@@ -20,7 +20,6 @@ import android.content.Context;
 import android.os.UserHandle;
 import android.support.annotation.VisibleForTesting;
 import android.support.v7.preference.Preference;
-import android.support.v7.preference.PreferenceScreen;
 
 import com.android.internal.widget.LockPatternUtils;
 import com.android.settings.R;
@@ -52,21 +51,18 @@ public class ManageTrustAgentsPreferenceController extends BasePreferenceControl
     }
 
     @Override
-    public void displayPreference(PreferenceScreen screen) {
-        super.displayPreference(screen);
-        final Preference preference = screen.findPreference(getPreferenceKey());
-        if (preference == null) {
-            return;
-        }
+    public void updateState(Preference preference) {
         final int numberOfTrustAgent = getTrustAgentCount();
         if (!mLockPatternUtils.isSecure(MY_USER_ID)) {
             preference.setEnabled(false);
             preference.setSummary(R.string.disabled_because_no_backup_security);
         } else if (numberOfTrustAgent > 0) {
+            preference.setEnabled(true);
             preference.setSummary(mContext.getResources().getQuantityString(
                     R.plurals.manage_trust_agents_summary_on,
                     numberOfTrustAgent, numberOfTrustAgent));
         } else {
+            preference.setEnabled(true);
             preference.setSummary(R.string.manage_trust_agents_summary);
         }
     }

tests/robotests/src/com/android/settings/security/trustagent/ManageTrustAgentsPreferenceControllerTest.java

@@ -16,14 +16,12 @@
 
 package com.android.settings.security.trustagent;
 
-import static com.android.settings.core.BasePreferenceController.AVAILABLE;
 import static com.google.common.truth.Truth.assertThat;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.Mockito.when;
 
 import android.content.Context;
 import android.support.v7.preference.Preference;
-import android.support.v7.preference.PreferenceScreen;
 
 import com.android.internal.widget.LockPatternUtils;
 import com.android.settings.R;
@@ -50,8 +48,6 @@ public class ManageTrustAgentsPreferenceControllerTest {
     private TrustAgentManager mTrustAgentManager;
     @Mock
     private LockPatternUtils mLockPatternUtils;
-    @Mock
-    private PreferenceScreen mScreen;
 
     private FakeFeatureFactory mFeatureFactory;
     private Context mContext;
@@ -70,8 +66,6 @@ public class ManageTrustAgentsPreferenceControllerTest {
         mController = new ManageTrustAgentsPreferenceController(mContext);
         mPreference = new Preference(mContext);
         mPreference.setKey(mController.getPreferenceKey());
-        when(mScreen.findPreference(mController.getPreferenceKey()))
-                .thenReturn(mPreference);
     }
 
     @Test
@@ -86,10 +80,10 @@ public class ManageTrustAgentsPreferenceControllerTest {
     }
 
     @Test
-    public void displayPreference_isNotSecure_shouldDisablePreference() {
+    public void updateState_isNotSecure_shouldDisablePreference() {
         when(mLockPatternUtils.isSecure(anyInt())).thenReturn(false);
 
-        mController.displayPreference(mScreen);
+        mController.updateState(mPreference);
 
         assertThat(mPreference.isEnabled()).isFalse();
         assertThat(mPreference.getSummary())
@@ -97,12 +91,12 @@ public class ManageTrustAgentsPreferenceControllerTest {
     }
 
     @Test
-    public void displayPreference_isSecure_noTrustAgent_shouldShowGenericSummary() {
+    public void updateState_isSecure_noTrustAgent_shouldShowGenericSummary() {
         when(mLockPatternUtils.isSecure(anyInt())).thenReturn(true);
         when(mTrustAgentManager.getActiveTrustAgents(mContext, mLockPatternUtils))
                 .thenReturn(new ArrayList<>());
 
-        mController.displayPreference(mScreen);
+        mController.updateState(mPreference);
 
         assertThat(mPreference.isEnabled()).isTrue();
         assertThat(mPreference.getSummary())
@@ -110,12 +104,12 @@ public class ManageTrustAgentsPreferenceControllerTest {
     }
 
     @Test
-    public void displayPreference_isSecure_hasTrustAgent_shouldShowDetailedSummary() {
+    public void updateState_isSecure_hasTrustAgent_shouldShowDetailedSummary() {
         when(mLockPatternUtils.isSecure(anyInt())).thenReturn(true);
         when(mTrustAgentManager.getActiveTrustAgents(mContext, mLockPatternUtils))
                 .thenReturn(Arrays.asList(new TrustAgentManager.TrustAgentComponentInfo()));
 
-        mController.displayPreference(mScreen);
+        mController.updateState(mPreference);
 
         assertThat(mPreference.isEnabled()).isTrue();
         assertThat(mPreference.getSummary())