获取全局上下文(getApplicationContext)_创建Shared Preference工具类_实现自动登录

获取全局上下文(getApplicationContext)_创建Shared Preference工具类_实现自动登录

===========================获取全局上下文(getApplicationContext)========================

1.在com.example.autologin.myapplication包中创建Myapplication extends Application

代码:

 public class Myapplication extends Application
 {
     private static Context context;

     @Override
     public void onCreate()
     {
         super.onCreate();

         context = getApplicationContext();
     }

     public static Context getAppContext()
     {
         return context;
     }
 }

2.在AndroidManifest.xml中添加属性, 申明Myapplication:

android:name="com.example.autologin.myapplication.Myapplication"

代码:

 <!-- 申明Myapplication -->
 <application
     android:name="com.example.autologin.myapplication.Myapplication"
     android:allowBackup="true"
     android:icon="@drawable/ic_launcher"
     android:label="@string/app_name"
     android:theme="@style/AppTheme" >

     <!-- ....... -->

 </application>

================================创建Shared Preference工具类==============================

在包com.example.autologin.utils中创建SpUtil.java类:

代码:

 public class SpUtil
 {
     //
     //通过全局上下文创建静态SharedPreferences对象
     //
     private static SharedPreferences sp =
             Myapplication.getAppContext().getSharedPreferences("user",Context.MODE_PRIVATE);

     //静态保存用户账号密码方法
     public static void saveUser(String name, String pwd)
     {
         Editor edit = sp.edit();
         edit.putString("username", name);
         edit.putString("pwd", pwd);

         edit.commit();

     }

     //
     //保存是否有过登录的状态
     //
     public static void isLogin(boolean isLogin)
     {
         Editor edit = sp.edit();
         edit.putBoolean("islogin", isLogin);
         edit.commit();
     }

     //
     //读取是否有过登录的状态
     //
     public static boolean getIsLogin()
     {
         return sp.getBoolean("islogin", false);
     }
 }

=============================实现自动登录============================

创建欢迎页面SplashActivity.java,读取登录状态,若有过登录则直接跳转主页面,没有登录过跳转登录页面

代码:

 Handler handler = new Handler();
 handler.postDelayed(new Runnable()
 {
     @Override
     public void run()
     {
         //
         //如果有过登录
         //直接跳转主页面
         //
         if (SpUtil.getIsLogin())
         {
             Intent intent = new Intent(SplashActivity.this, MainActivity.class);
             startActivity(intent);
             SplashActivity.this.finish();
         } else
         {
             //
             //如果没有登录过登录
             //跳转登录页面
             //
             Intent intent = new Intent(SplashActivity.this, LoginActivity.class);
             startActivity(intent);
             SplashActivity.this.finish();
         }

     }
 }, 3000);

**注意: 将SplashActivity.java设置为启动页面