Android基础--键值对存储(SharedPreferences)

SharedPreferences用于将键值对形式的数据存储到当前应用专属的存储空间中

package com.itheima.sharedpreferences;



import android.os.Bundle;

import android.app.Activity;

import android.content.SharedPreferences;

import android.content.SharedPreferences.Editor;

import android.text.TextUtils;

import android.view.View;

import android.widget.CheckBox;

import android.widget.EditText;

import android.widget.Toast;



public class MainActivity extends Activity {

    private EditText et_username;

    private EditText et_password;

    private CheckBox cb_isAutoLogin;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        et_username = (EditText) findViewById(R.id.et_username);

        et_password = (EditText) findViewById(R.id.et_password);

        cb_isAutoLogin = (CheckBox) findViewById(R.id.isAutoLogin);

        readAccount();

    }

    

  //如果之前用户将信息存储到手机上,需要对用户信息进行回显

      private void readAccount() {

          SharedPreferences sPreferences = getSharedPreferences("userInfo", MODE_PRIVATE);

          String username =sPreferences.getString("username", "");

          String password = sPreferences.getString("password", "");

          et_username.setText(username);

          et_password.setText(password);

      }

 // 登录 ,将用户名和密码保存到内部存储空间

     public void login(View v) {

         String username = et_username.getText().toString();

         String password = et_password.getText().toString();

         if(TextUtils.isEmpty(username)||TextUtils.isEmpty(password)){

             Toast.makeText(this, "用户名或密码不能为空", Toast.LENGTH_SHORT).show();

             return;

         }

         if (cb_isAutoLogin.isChecked()) {

             //文件名不用写扩展名,会自动添加xml扩展名

               /*

                * name Desired preferences file. 

                * If a preferences file by this name does not exist, it will be created 

                * when you retrieve an editor (SharedPreferences.edit()) and then commit changes (Editor.commit()).

                */

             SharedPreferences sPreferences = getSharedPreferences("userInfo", MODE_PRIVATE);

             Editor editor = sPreferences.edit();

             editor.putString("username", username);

             editor.putString("password", password);

             editor.commit();

         }

         Toast.makeText(this, "登录成功", 0).show();

     }

    

}

文件存储结构如下图:

 

布局文件:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >



    <EditText

        android:id="@+id/et_username"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="@string/_username" />



    <EditText

        android:id="@+id/et_password"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="@string/_password" 

        android:inputType="textPassword"/>



    <RelativeLayout

        android:layout_width="match_parent"

        android:layout_height="wrap_content" >



        <CheckBox

            android:id="@+id/isAutoLogin"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_alignParentLeft="true"

            android:text="@string/_autologin" 

            android:layout_centerVertical="true"/>



        <Button

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_alignParentRight="true"

            android:text="@string/_login" 

            android:onClick="login"/>

    </RelativeLayout>



</LinearLayout>