Add a "Remember me" checkbox

I just built this into my app, here's the basic code and some explanation:

Basically the key here is SharedPreferences. You'll setup a SharedPreferences object and store your username and password after the user has entered them. Then, when they run the application again, the preferences will have their data stored and will then repopulate the login fields.

LoginActivity.java

package com.realsimpleapps.LoginTesting;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;

public class LoginActivity extends Activity implements OnClickListener {

    private String username,password;
    private Button ok;
    private EditText editTextUsername,editTextPassword;
    private CheckBox saveLoginCheckBox;
    private SharedPreferences loginPreferences;
    private SharedPreferences.Editor loginPrefsEditor;
    private Boolean saveLogin;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        ok = (Button)findViewById(R.id.buttonLogin);
        ok.setOnClickListener(this);
        editTextUsername = (EditText)findViewById(R.id.editTextUsername);
        editTextPassword = (EditText)findViewById(R.id.editTextPassword);
        saveLoginCheckBox = (CheckBox)findViewById(R.id.saveLoginCheckBox);
        loginPreferences = getSharedPreferences("loginPrefs", MODE_PRIVATE);
        loginPrefsEditor = loginPreferences.edit();

        saveLogin = loginPreferences.getBoolean("saveLogin", false);
        if (saveLogin == true) {
            editTextUsername.setText(loginPreferences.getString("username", ""));
            editTextPassword.setText(loginPreferences.getString("password", ""));
            saveLoginCheckBox.setChecked(true);
        }
    }

    public void onClick(View view) {
        if (view == ok) {
            InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.hideSoftInputFromWindow(editTextUsername.getWindowToken(), 0);

            username = editTextUsername.getText().toString();
            password = editTextPassword.getText().toString();

            if (saveLoginCheckBox.isChecked()) {
                loginPrefsEditor.putBoolean("saveLogin", true);
                loginPrefsEditor.putString("username", username);
                loginPrefsEditor.putString("password", password);
                loginPrefsEditor.commit();
            } else {
                loginPrefsEditor.clear();
                loginPrefsEditor.commit();
            }

            doSomethingElse();
        }
    }

    public void doSomethingElse() {
        startActivity(new Intent(LoginActivity.this, MainActivity.class));
        LoginActivity.this.finish();
    }
}

The method at end, doSomethingElse() is your placeholder to go to the next step for your application. My doSomethingElse() method simply loads another activity.

Here's a basic xml file for the login page:

login.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#000"
    android:padding="10dp" >

    <EditText
        android:id="@+id/editTextUsername"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/imageView1"
        android:hint="Username"
        android:inputType="textNoSuggestions"
        android:imeOptions="actionNext" />

    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/editTextUsername"
        android:hint="Password"
        android:inputType="textPassword"
        android:imeOptions="actionDone" />

    <CheckBox
        android:id="@+id/saveLoginCheckBox"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/editTextPassword"
        android:text="Save Login?"
        android:textColor="#FFF" />

    <Button
        android:id="@+id/buttonLogin"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/saveLoginCheckBox"
        android:layout_marginTop="40dp"
        android:text="Login" />

</RelativeLayout>

IMPORTANT: You'll likely want to encrypt the password before storing it in SharedPreferences. Details for that are beyond the scope of this question, but here is the code I used to do that: http://www.androidsnippets.com/encryptdecrypt-strings. You'll have to come up with some kind of key schema too.

This code has been tested on Android 2.1, SDK 7. Let me know how it works for you.

David