用戶登錄(記住密碼)

用戶登錄頁面，點擊登陸後會出現welcomeyou的頁面，選中記住密碼，再次打開會保存用戶名和密碼。主要是將用戶名和密碼保存在rememberpassword.xml中。
1、運行效果圖：

2、實現過程：
(1)、佈局文件:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/activity_main"
    android:background="@drawable/loginbg"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="bzu.edu.cn.case_login.MainActivity">
    <include layout="@layout/login_top">
    </include>
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/deer"
        android:id="@+id/imageView"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />
</RelativeLayout>

login_top.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/logintop_groungdg"
    android:padding="@dimen/activity_horizontal_margin">
    <EditText
        android:id="@+id/etName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:background="@android:drawable/edit_text"
        android:drawableLeft="@drawable/icon_user"
        android:hint="@string/etName"
        android:drawablePadding="10dp"
        >
        <requestFocus/>
    </EditText>
    <EditText
        android:id="@+id/etPassword"
        android:layout_below="@id/etName"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:background="@android:drawable/edit_text"
        android:drawableLeft="@drawable/icon_pass"
        android:hint="@string/etName"
        android:drawablePadding="10dp">
        <requestFocus/>
    </EditText>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/etPassword"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">
        <CheckBox
            android:layout_width="0dp"
            android:layout_height="48dp"
            android:layout_weight="1"
            android:id="@+id/cblsRemember"
            android:textSize="20sp"
            android:text="記住密碼"/>
        <Button
            android:onClick="login"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_marginLeft="10dp"
            android:background="@drawable/btn_select"
            android:text="@string/btnLogin"
            android:textSize="20sp"/>
    </LinearLayout>
</RelativeLayout>

需要的圖片：

將btn_select.xml，btn_shape.xml，btn_shape_after.xml和logintop_groungdg.xml放到drawable中
logintop_groungdg.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
    <corners android:radius="10dp"></corners>
    <solid android:color="#55FFFFFF"></solid>
</shape>

btn_select.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:drawable="@drawable/btn_shape" android:state_pressed="false"></item>
    <item android:drawable="@drawable/btn_shape_after" android:state_pressed="true"></item>
</selector>

btn_shape.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<solid android:color="#FF72CAE1"></solid>
    <corners android:radius="10dp"></corners>
</shape>

btn_shape_after.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<solid android:color="#87cefa"></solid>
    <corners android:radius="10dp"></corners>
</shape>

activity_welcome.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_welcome"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="bzu.edu.cn.case_login.WelcomeActivity">
   <TextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
       android:text="welcome you"
       android:textSize="45sp"/>
</RelativeLayout>

(2)、
MainActivity.xml

package bzu.edu.cn.case_login;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private EditText etName;
    private EditText etPassword;
    private SharedPreferences sharedPreferences;
    private CheckBox cblsRemember;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        sharedPreferences = getSharedPreferences("rememberpassword", Context.MODE_PRIVATE);
        boolean isRemembered=sharedPreferences.getBoolean("rememberpassword",false);
        if (isRemembered){
            String name=sharedPreferences.getString("name","");
            String password=sharedPreferences.getString("password","");
            etName.setText(name);
            etPassword.setText(password);
            cblsRemember.setChecked(true);
        }
    }
    private void initView() {
        etName = (EditText) findViewById(R.id.etName);
        etPassword = (EditText) findViewById(R.id.etPassword);
        cblsRemember = (CheckBox) findViewById(R.id.cblsRemember);
    }

    public void login(View view) {
        String name = etName.getText().toString();
        String password = etPassword.getText().toString();
        if ("admin".equals(name) && "123456".equals(password)) {
            SharedPreferences.Editor editor = sharedPreferences.edit();
            if (cblsRemember.isChecked()) {
                editor.putBoolean("rememberpassword", true);
                editor.putString("name", name);
                editor.putString("password", password);
            }else{
                editor.clear();
            }
            editor.commit();
            Intent intent=new Intent(this,WelcomeActivity.class);
            startActivity(intent);
            finish();
        }else {
            Toast.makeText(this,"賬號或密碼有誤",Toast.LENGTH_LONG).show();
        }
    }
}

WelcomeActivity.xml

package bzu.edu.cn.case_login;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class WelcomeActivity extends AppCompatActivity {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);
    }
}

3、清單文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="bzu.edu.cn.case_login">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".WelcomeActivity"></activity>
    </application>
</manifest>

保存用戶名和密碼使用了SharedPreferences，它是一種輕型的數據存儲方式，它的本質是基於XML文件存儲key-value鍵值對數據，通常用來存儲一些簡單的配置信息。其存儲位置在/data/data/<包名>/shared_prefs目錄下。SharedPreferences對象本身只能獲取數據而不支持存儲和修改，存儲修改是通過Editor對象實現。