我想在我的Android应用程序中实现登录活动，我使用了Android Studio的登录活动模板。根据Google的文档（https://developer.android.com/studio/projects/templates#LoginActivity），它应该包括一个可用于我的目的的AsyncTask，但是似乎当前版本的Android Studio不再提供这个功能。
我使用的当前Android Studio版本是3.4（2019年4月10日），我的SDK版本为：
我在之前的项目中使用了asynctask进行HTTP调用，但是它是在同一个Activity内实现的，而不是使用这个模板。 在哪里放置asynctask并调用它最好呢？
谢谢！
模板中的其他类：
LoginRepository.java
minSdkVersion 23
targetSdkVersion 26
我有一个LoginDataSource.java类，其中包含以下代码，我认为这些代码将用于进行身份验证工作。但是，当我在TODO行下方调用我的HTTP方法时，它会给出一个异常，指出无法在主线程中执行异步操作：
/**
* Class that handles authentication w/ login credentials and retrieves user information.
*/
public class LoginDataSource {
public Result<LoggedInUser> login(String username, String password) {
try {
// TODO: handle loggedInUser authentication
LoggedInUser fakeUser =
new LoggedInUser(
java.util.UUID.randomUUID().toString(),
"Jane Doe");
return new Result.Success<>(fakeUser);
} catch (Exception e) {
return new Result.Error(new IOException("Error logging in", e));
}
}
public void logout() {
// TODO: revoke authentication
}
}
我在之前的项目中使用了asynctask进行HTTP调用，但是它是在同一个Activity内实现的，而不是使用这个模板。 在哪里放置asynctask并调用它最好呢？
谢谢！
模板中的其他类：
LoginRepository.java
/**
* Class that requests authentication and user information from the remote data source and
* maintains an in-memory cache of login status and user credentials information.
*/
public class LoginRepository {
private static volatile LoginRepository instance;
private LoginDataSource dataSource;
// If user credentials will be cached in local storage, it is recommended it be encrypted
// @see https://developer.android.com/training/articles/keystore
private LoggedInUser user = null;
// private constructor : singleton access
private LoginRepository(LoginDataSource dataSource) {
this.dataSource = dataSource;
}
public static LoginRepository getInstance(LoginDataSource dataSource) {
if (instance == null) {
instance = new LoginRepository(dataSource);
}
return instance;
}
public boolean isLoggedIn() {
return user != null;
}
public void logout() {
user = null;
dataSource.logout();
}
private void setLoggedInUser(LoggedInUser user) {
this.user = user;
// If user credentials will be cached in local storage, it is recommended it be encrypted
// @see https://developer.android.com/training/articles/keystore
}
public Result<LoggedInUser> login(String username, String password) {
// handle login
Result<LoggedInUser> result = dataSource.login(username, password);
if (result instanceof Result.Success) {
setLoggedInUser(((Result.Success<LoggedInUser>) result).getData());
}
return result;
}
}
LoggedInUserView.java
/**
* Class exposing authenticated user details to the UI.
*/
class LoggedInUserView implements Serializable {
private String displayName;
//... other data fields that may be accessible to the UI
LoggedInUserView(String displayName) {
this.displayName = displayName;
}
String getDisplayName() {
return displayName;
}
}
LoginViewModel.java
public class LoginViewModel extends ViewModel {
private MutableLiveData<LoginFormState> loginFormState = new MutableLiveData<>();
private MutableLiveData<LoginResult> loginResult = new MutableLiveData<>();
private LoginRepository loginRepository;
LoginViewModel(LoginRepository loginRepository) {
this.loginRepository = loginRepository;
}
LiveData<LoginFormState> getLoginFormState() {
return loginFormState;
}
LiveData<LoginResult> getLoginResult() {
return loginResult;
}
public void login(String username, String password) {
// can be launched in a separate asynchronous job
Result<LoggedInUser> result = loginRepository.login(username, password);
if (result instanceof Result.Success) {
LoggedInUser data = ((Result.Success<LoggedInUser>) result).getData();
loginResult.setValue(new LoginResult(new LoggedInUserView(data.getDisplayName())));
} else {
loginResult.setValue(new LoginResult(R.string.login_failed));
}
}
public void loginDataChanged(String username, String password) {
if (!isUserNameValid(username)) {
loginFormState.setValue(new LoginFormState(R.string.invalid_username, null));
} else if (!isPasswordValid(password)) {
loginFormState.setValue(new LoginFormState(null, R.string.invalid_password));
} else {
loginFormState.setValue(new LoginFormState(true));
}
}
// A placeholder username validation check
private boolean isUserNameValid(String username) {
if (username == null) {
return false;
}
if (username.contains("@")) {
return Patterns.EMAIL_ADDRESS.matcher(username).matches();
} else {
return !username.trim().isEmpty();
}
}
// A placeholder password validation check
private boolean isPasswordValid(String password) {
return password != null && password.trim().length() > 5;
}
}
LoginActivity.java
public class LoginActivity extends AppCompatActivity {
private LoginViewModel loginViewModel;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
loginViewModel = ViewModelProviders.of(this, new LoginViewModelFactory())
.get(LoginViewModel.class);
final EditText usernameEditText = findViewById(R.id.username);
final EditText passwordEditText = findViewById(R.id.password);
final Button loginButton = findViewById(R.id.login);
final ProgressBar loadingProgressBar = findViewById(R.id.loading);
loginViewModel.getLoginFormState().observe(this, new Observer<LoginFormState>() {
@Override
public void onChanged(@Nullable LoginFormState loginFormState) {
if (loginFormState == null) {
return;
}
loginButton.setEnabled(loginFormState.isDataValid());
if (loginFormState.getUsernameError() != null) {
usernameEditText.setError(getString(loginFormState.getUsernameError()));
}
if (loginFormState.getPasswordError() != null) {
passwordEditText.setError(getString(loginFormState.getPasswordError()));
}
}
});
loginViewModel.getLoginResult().observe(this, new Observer<LoginResult>() {
@Override
public void onChanged(@Nullable LoginResult loginResult) {
if (loginResult == null) {
return;
}
loadingProgressBar.setVisibility(View.GONE);
if (loginResult.getError() != null) {
showLoginFailed(loginResult.getError());
}
if (loginResult.getSuccess() != null) {
updateUiWithUser(loginResult.getSuccess());
}
setResult(Activity.RESULT_OK);
//Complete and destroy login activity once successful
finish();
}
});
TextWatcher afterTextChangedListener = new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
// ignore
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// ignore
}
@Override
public void afterTextChanged(Editable s) {
loginViewModel.loginDataChanged(usernameEditText.getText().toString(),
passwordEditText.getText().toString());
}
};
usernameEditText.addTextChangedListener(afterTextChangedListener);
passwordEditText.addTextChangedListener(afterTextChangedListener);
passwordEditText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_DONE) {
loginViewModel.login(usernameEditText.getText().toString(),
passwordEditText.getText().toString());
}
return false;
}
});
loginButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
loadingProgressBar.setVisibility(View.VISIBLE);
loginViewModel.login(usernameEditText.getText().toString(),
passwordEditText.getText().toString());
}
});
}
private void updateUiWithUser(LoggedInUserView model) {
String welcome = getString(R.string.welcome) + model.getDisplayName();
// TODO : initiate successful logged in experience
Toast.makeText(getApplicationContext(), welcome, Toast.LENGTH_LONG).show();
}
private void showLoginFailed(@StringRes Integer errorString) {
Toast.makeText(getApplicationContext(), errorString, Toast.LENGTH_SHORT).show();
}
}