Refer to the last Hotspot password when generating the password

- Query the last Hotspot password when security type is SECURITY_TYPE_OPEN and it will be used when the user changes to another security type

- If the last hotspot password is an empty string, then generate random password

Bug: 201789473
Test: manual test
atest -c WifiHotspotRepositoryTest
make RunSettingsRoboTests ROBOTEST_FILTER=WifiTetherPasswordPreferenceControllerTest

Change-Id: Id3a846099238433e7b6c8b934fa26a74df0dcb61

tests/robotests/src/com/android/settings/wifi/tether/WifiTetherPasswordPreferenceControllerTest.java

@@ -35,7 +35,9 @@ import android.net.wifi.WifiManager;
 
 import androidx.preference.PreferenceScreen;
 
+import com.android.settings.testutils.FakeFeatureFactory;
 import com.android.settings.widget.ValidatedEditTextPreference;
+import com.android.settings.wifi.repository.WifiHotspotRepository;
 import com.android.settingslib.core.instrumentation.MetricsFeatureProvider;
 
 import org.junit.Before;
@@ -65,6 +67,8 @@ public class WifiTetherPasswordPreferenceControllerTest {
     private PreferenceScreen mScreen;
     @Mock
     private MetricsFeatureProvider mMetricsFeatureProvider;
+    @Mock
+    private WifiHotspotRepository mWifiHotspotRepository;
 
     private WifiTetherPasswordPreferenceController mController;
     private ValidatedEditTextPreference mPreference;
@@ -73,6 +77,10 @@ public class WifiTetherPasswordPreferenceControllerTest {
     @Before
     public void setUp() {
         MockitoAnnotations.initMocks(this);
+        FakeFeatureFactory featureFactory = FakeFeatureFactory.setupForTest();
+        when(featureFactory.getWifiFeatureProvider().getWifiHotspotRepository())
+                .thenReturn(mWifiHotspotRepository);
+
         mPreference = new ValidatedEditTextPreference(RuntimeEnvironment.application);
         mConfig = new SoftApConfiguration.Builder().setSsid("test_1234")
                 .setPassphrase(INITIAL_PASSWORD, SoftApConfiguration.SECURITY_TYPE_WPA2_PSK)
@@ -91,6 +99,11 @@ public class WifiTetherPasswordPreferenceControllerTest {
                 mMetricsFeatureProvider);
     }
 
+    @Test
+    public void constructor_shouldQueryLastPasswordIfNeeded() {
+        verify(mWifiHotspotRepository).queryLastPasswordIfNeeded();
+    }
+
     @Test
     public void displayPreference_shouldStylePreference() {
         mController.displayPreference(mScreen);