好的,所以我有一个LoginActivity。当用户登录时,除非用户退出,否则我不希望活动再次显示。我该怎么做?我对android很新,所以请耐心等待。这只是ADT的一个例子,我计划稍后添加我的数据库功能,但是现在我只是保留它以用于测试目的。
package com.example.imet;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import android.widget.TextView;
/**
* Activity which displays a login screen to the user, offering registration as
* well.
*/
public class MainActivity extends Activity {
/**
* A dummy authentication store containing known user names and passwords.
* TODO: remove after connecting to a real authentication system.
*/
private static final String[] DUMMY_CREDENTIALS = new String[] {
"foo@example.com:hello", "bar@example.com:world" };
/**
* The default email to populate the email field with.
*/
public static final String EXTRA_EMAIL = "com.example.android.authenticatordemo.extra.EMAIL";
/**
* Keep track of the login task to ensure we can cancel it if requested.
*/
private UserLoginTask mAuthTask = null;
// Values for email and password at the time of the login attempt.
private String mEmail;
private String mPassword;
// UI references.
private EditText mEmailView;
private EditText mPasswordView;
private View mLoginFormView;
private View mLoginStatusView;
private TextView mLoginStatusMessageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the login form.
mEmail = getIntent().getStringExtra(EXTRA_EMAIL);
mEmailView = (EditText) findViewById(R.id.email);
mEmailView.setText(mEmail);
mPasswordView = (EditText) findViewById(R.id.password);
mPasswordView
.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView textView, int id,
KeyEvent keyEvent) {
if (id == R.id.login || id == EditorInfo.IME_NULL) {
attemptLogin();
return true;
}
return false;
}
});
mLoginFormView = findViewById(R.id.login_form);
mLoginStatusView = findViewById(R.id.login_status);
mLoginStatusMessageView = (TextView) findViewById(R.id.login_status_message);
findViewById(R.id.sign_in_button).setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View view) {
attemptLogin();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
getMenuInflater().inflate(R.menu.login, menu);
return true;
}
/**
* Attempts to sign in or register the account specified by the login form.
* If there are form errors (invalid email, missing fields, etc.), the
* errors are presented and no actual login attempt is made.
*/
public void attemptLogin() {
if (mAuthTask != null) {
return;
}
// Reset errors.
mEmailView.setError(null);
mPasswordView.setError(null);
// Store values at the time of the login attempt.
mEmail = mEmailView.getText().toString();
mPassword = mPasswordView.getText().toString();
boolean cancel = false;
View focusView = null;
// Check for a valid password.
if (TextUtils.isEmpty(mPassword)) {
mPasswordView.setError(getString(R.string.error_field_required));
focusView = mPasswordView;
cancel = true;
} else if (mPassword.length() < 4) {
mPasswordView.setError(getString(R.string.error_invalid_password));
focusView = mPasswordView;
cancel = true;
}
// Check for a valid email address.
if (TextUtils.isEmpty(mEmail)) {
mEmailView.setError(getString(R.string.error_field_required));
focusView = mEmailView;
cancel = true;
} else if (!mEmail.contains("@")) {
mEmailView.setError(getString(R.string.error_invalid_email));
focusView = mEmailView;
cancel = true;
}
if (cancel) {
// There was an error; don't attempt login and focus the first
// form field with an error.
focusView.requestFocus();
} else {
// Show a progress spinner, and kick off a background task to
// perform the user login attempt.
mLoginStatusMessageView.setText(R.string.login_progress_signing_in);
showProgress(true);
mAuthTask = new UserLoginTask();
mAuthTask.execute((Void) null);
}
}
/**
* Shows the progress UI and hides the login form.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
private void showProgress(final boolean show) {
// On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
// for very easy animations. If available, use these APIs to fade-in
// the progress spinner.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
int shortAnimTime = getResources().getInteger(
android.R.integer.config_shortAnimTime);
mLoginStatusView.setVisibility(View.VISIBLE);
mLoginStatusView.animate().setDuration(shortAnimTime)
.alpha(show ? 1 : 0)
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mLoginStatusView.setVisibility(show ? View.VISIBLE
: View.GONE);
}
});
mLoginFormView.setVisibility(View.VISIBLE);
mLoginFormView.animate().setDuration(shortAnimTime)
.alpha(show ? 0 : 1)
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mLoginFormView.setVisibility(show ? View.GONE
: View.VISIBLE);
}
});
} else {
// The ViewPropertyAnimator APIs are not available, so simply show
// and hide the relevant UI components.
mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
}
}
/**
* Represents an asynchronous login/registration task used to authenticate
* the user.
*/
public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
@Override
protected Boolean doInBackground(Void... params) {
// TODO: attempt authentication against a network service.
try {
// Simulate network access.
Thread.sleep(2000);
} catch (InterruptedException e) {
return false;
}
for (String credential : DUMMY_CREDENTIALS) {
String[] pieces = credential.split(":");
if (pieces[0].equals(mEmail)) {
// Account exists, return true if the password matches.
return pieces[1].equals(mPassword);
}
}
// TODO: register the new account here.
return true;
}
@Override
protected void onPostExecute(final Boolean success) {
mAuthTask = null;
showProgress(false);
if (success) {
finish();
} else {
mPasswordView
.setError(getString(R.string.error_incorrect_password));
mPasswordView.requestFocus();
}
}
@Override
protected void onCancelled() {
mAuthTask = null;
showProgress(false);
}
}
}
答案 0 :(得分:4)
您可以做的最简单的事情是将登录状态保存在SharedPreferences
文件中。这是我的一个应用程序的工作示例。我使用CheckBox
让用户决定应用程序是否应该存储登录状态。您可以修改该部分,以便在用户进行身份验证后自动保存。
/***** SHAREDPREFERENCES INSTANCES AND STRING FOR THE PATH *****/
SharedPreferences prefsNagSetting;
private static final String NAG_PREFS = "socially_you_nag_prefs";
/* THE EDITOR */
Editor editor;
在onCreate()
中,实例化SharedPreference
:
prefsNagSetting = getApplicationContext().getSharedPreferences(NAG_PREFS, Context.MODE_PRIVATE);
// GET THE NAG SETTING
boolean blNagSetting = prefsNagSetting.getBoolean(NAG_SETTING, false);
if (blNagSetting == true) {
/* Create an Intent that will start the Menu-Activity. */
Intent startMainPage = new Intent(SignIn.this, SplashScreen.class);
startMainPage.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(startMainPage);
finish();
} else { // NO NEED FOR THE else BLOCK. JUST AN ILLUSTRATION
// SHOW THE LOGIN SCREEN
}
在我的应用程序中,我有一个CheckBox,用于检查用户是否希望应用程序记住登录信息。修改此逻辑为您自己。
/* TOGGLE THE CHECKBOX FOR THE NAG SETTING */
chkbxNagSetting.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// EDITOR INSTANCE TO SAVE THE NAG SETTING
editor = prefsNagSetting.edit();
// GET THE NAG SETTING CHECKBOX
if (chkbxNagSetting.isChecked()) {
editor.putBoolean(NAG_SETTING, true);
} else {
editor.putBoolean(NAG_SETTING, false);
}
editor.commit();
}
});
答案 1 :(得分:0)
最简单的方法是将用户状态保存在SharedPreferences
中的布尔变量中。然后,每次用户打开应用程序时检查值,并相应地显示登录活动或用户登录后要显示的下一个活动。在继续之前,您可能需要检查以下主题和博客:
Android User Session Management using Shared Preferences
Android check user logged in before, else start login activity
希望这有帮助。