2

好的，所以我有一个 LoginActivity。当用户登录时，我不希望该活动再次出现，除非用户退出。我该怎么做？我对android还很陌生，所以请多多包涵。这只是 ADT 中的一个简单示例，我计划稍后添加我的数据库功能，但现在我只是保持原样用于测试目的。

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);
    }
}

}

4

2 回答 2

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中的一个工作示例。我使用 aCheckBox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在用户验证后自动保存。

/***** SHAREDPREFERENCES INSTANCES AND STRING FOR THE PATH *****/
SharedPreferences prefsNagSetting;
private static final String NAG_PREFS = "socially_you_nag_prefs";

/* THE EDITOR */
Editor editor;

在 中onCreate()，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。为你自己修改这个逻辑。

/* 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();
    }
});
于 2013-06-11T02:29:46.867 回答
0

最简单的方法是将用户的状态保存在一个布尔变量中SharedPreferences。然后，您在每次用户打开应用程序时检查该值，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线程和博客：

使用共享首选项的 Android 用户会话管理

Android检查用户之前登录，否则开始登录活动

检查每个活动的登录

希望这可以帮助。

于 2013-06-11T02:23:06.967 回答