[android] Use LiveEvent to communicate password validation and account deletion

briar-android/src/main/java/org/briarproject/briar/android/activity/BaseActivity.java

@@ -172,6 +172,12 @@ public abstract class BaseActivity extends AppCompatActivity
 				.commit();
 	}
 
+	protected boolean isFragmentAdded(String fragmentTag) {
+		FragmentManager fm = getSupportFragmentManager();
+		Fragment f = fm.findFragmentByTag(fragmentTag);
+		return f != null && f.isAdded();
+	}
+
 	private boolean showScreenFilterWarning() {
 		// If the dialog is already visible, filter the tap
 		ScreenFilterDialogFragment f = findDialogFragment();

briar-android/src/main/java/org/briarproject/briar/android/login/PasswordFragment.java

@@ -35,7 +35,7 @@ import static org.briarproject.briar.android.util.UiUtils.showSoftKeyboard;
 @ParametersNotNullByDefault
 public class PasswordFragment extends BaseFragment implements TextWatcher {
 
-	private final static String TAG = PasswordFragment.class.getName();
+	final static String TAG = PasswordFragment.class.getName();
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -60,7 +60,9 @@ public class PasswordFragment extends BaseFragment implements TextWatcher {
 
 		viewModel = ViewModelProviders.of(requireActivity(), viewModelFactory)
 				.get(StartupViewModel.class);
-		viewModel.getPasswordValidated().observe(this, this::onPasswordValidated);
+		viewModel.getPasswordValidated().observeEvent(this, valid -> {
+			if (!valid) onPasswordInvalid();
+		});
 
 		signInButton = v.findViewById(R.id.btn_sign_in);
 		signInButton.setOnClickListener(view -> onSignInButtonClicked());
@@ -103,19 +105,14 @@ public class PasswordFragment extends BaseFragment implements TextWatcher {
 		viewModel.validatePassword(password.getText().toString());
 	}
 
-	private void onPasswordValidated(@Nullable Boolean valid) {
-		if (valid != null && !valid) {
-			setError(input, getString(R.string.try_again), true);
-			signInButton.setVisibility(VISIBLE);
-			progress.setVisibility(INVISIBLE);
-			password.setText(null);
-
-			// show the keyboard again
-			showSoftKeyboard(password);
+	private void onPasswordInvalid() {
+		setError(input, getString(R.string.try_again), true);
+		signInButton.setVisibility(VISIBLE);
+		progress.setVisibility(INVISIBLE);
+		password.setText(null);
 
-			// reset validation state for configuration changes
-			viewModel.getPasswordValidated().setValue(null);
-		}
+		// show the keyboard again
+		showSoftKeyboard(password);
 	}
 
 	public void onForgottenPasswordClick() {

briar-android/src/main/java/org/briarproject/briar/android/login/StartupActivity.java

@@ -5,8 +5,6 @@ import android.arch.lifecycle.ViewModelProviders;
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
-import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentManager;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
@@ -63,8 +61,8 @@ public class StartupActivity extends BaseActivity implements
 			onAccountDeleted();
 			return;
 		}
-		viewModel.getAccountDeleted().observe(this, deleted -> {
-			if (deleted != null && deleted) onAccountDeleted();
+		viewModel.getAccountDeleted().observeEvent(this, deleted -> {
+			if (deleted) onAccountDeleted();
 		});
 		viewModel.getState().observe(this, this::onStateChanged);
 	}
@@ -85,7 +83,12 @@ public class StartupActivity extends BaseActivity implements
 
 	private void onStateChanged(State state) {
 		if (state == SIGNED_OUT) {
-			showInitialFragment(new PasswordFragment());
+			// Configuration changes such as screen rotation
+			// can cause this to get called again.
+			// Don't replace the fragment in that case to not lose view state.
+			if (!isFragmentAdded(PasswordFragment.TAG)) {
+				showInitialFragment(new PasswordFragment());
+			}
 		} else if (state == SIGNED_IN) {
 			startService(new Intent(this, BriarService.class));
 		} else if (state == STARTING) {
@@ -93,9 +96,7 @@ public class StartupActivity extends BaseActivity implements
 			// This can happen because several LifecycleManager states are
 			// mapped to STARTING, so this can get called several times
 			// as the app's lifecycle advances.
-			FragmentManager fm = getSupportFragmentManager();
-			Fragment f = fm.findFragmentByTag(OpenDatabaseFragment.TAG);
-			if (f == null || !f.isVisible()) {
+			if (!isFragmentAdded(OpenDatabaseFragment.TAG)) {
 				showNextFragment(new OpenDatabaseFragment());
 			}
 		} else if (state == STARTED) {

briar-android/src/main/java/org/briarproject/briar/android/login/StartupViewModel.java

@@ -15,6 +15,8 @@ import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState;
 import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 
 import java.util.concurrent.Executor;
@@ -43,10 +45,10 @@ public class StartupViewModel extends AndroidViewModel
 	@IoExecutor
 	private final Executor ioExecutor;
 
-	private final MutableLiveData<Boolean> passwordValidated =
-			new MutableLiveData<>();
-	private final MutableLiveData<Boolean> accountDeleted =
-			new MutableLiveData<>();
+	private final MutableLiveEvent<Boolean> passwordValidated =
+			new MutableLiveEvent<>();
+	private final MutableLiveEvent<Boolean> accountDeleted =
+			new MutableLiveEvent<>();
 	private final MutableLiveData<State> state = new MutableLiveData<>();
 
 	@Inject
@@ -103,16 +105,16 @@ public class StartupViewModel extends AndroidViewModel
 	void validatePassword(String password) {
 		ioExecutor.execute(() -> {
 			boolean signedIn = accountManager.signIn(password);
-			passwordValidated.postValue(signedIn);
+			passwordValidated.postEvent(signedIn);
 			if (signedIn) state.postValue(SIGNED_IN);
 		});
 	}
 
-	MutableLiveData<Boolean> getPasswordValidated() {
+	LiveEvent<Boolean> getPasswordValidated() {
 		return passwordValidated;
 	}
 
-	LiveData<Boolean> getAccountDeleted() {
+	LiveEvent<Boolean> getAccountDeleted() {
 		return accountDeleted;
 	}
 
@@ -123,7 +125,7 @@ public class StartupViewModel extends AndroidViewModel
 	@UiThread
 	void deleteAccount() {
 		accountManager.deleteAccount();
-		accountDeleted.setValue(true);
+		accountDeleted.setEvent(true);
 	}
 
 }