<?xml version="1.0" encoding="utf-8"?>
<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:gravity="center_horizontal"
 android:orientation="vertical"
 tools:context="com.studying.myapplication.MainActivity">

 <!--用户名-->
 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">

  <TextView
   android:layout_width="0dp"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:gravity="center"
   android:text="用户名" />

  <EditText
   android:id="@+id/username"
   android:layout_width="0dp"
   android:layout_height="wrap_content"
   android:layout_weight="4" />
 </LinearLayout>

 <!--密码-->
 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">

  <TextView
   android:layout_width="0dp"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:gravity="center"
   android:text="密码" />

  <EditText
   android:id="@+id/passward"
   android:layout_width="0dp"
   android:layout_height="wrap_content"
   android:layout_weight="4"
   android:inputType="textPassword" />
 </LinearLayout>

 <!--是否记住用户名-->
 <CheckBox
  android:id="@+id/remember"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:checked="false"
  android:text="记住用户名" />

 <!--登录-->
 <Button
  android:id="@+id/login"
  android:layout_width="200dp"
  android:layout_height="35dp"
  android:text="登录"
  android:textSize="12sp" />

</LinearLayout>

public class MainActivity extends Activity implements View.OnClickListener {

 private SharedPreferences mPref;
 private SharedPreferences.Editor mEditor;
 private EditText mUserName;
 private EditText mPassword;
 private CheckBox mIsRemember;
 private Button mLogin;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  init();
 }

 private void init() {
  mUserName = (EditText) findViewById(R.id.username);
  mPassword = (EditText) findViewById(R.id.passward);
  mIsRemember = (CheckBox) findViewById(R.id.remember);
  mLogin = (Button) findViewById(R.id.login);
  mLogin.setOnClickListener(this);

  mPref = getSharedPreferences("user_data", MODE_PRIVATE);
  mEditor = mPref.edit();

  //若之前曾设置过记住用户名，则读取并设置用户名
  if (mPref.getBoolean("is_remember", false)) {
   mUserName.setText(mPref.getString("user_name", ""));
  }
 }

 @Override
 public void onClick(View v) {
  switch (v.getId()) {
   case R.id.login:
    String userName = mUserName.getText().toString().trim();
    String password = mPassword.getText().toString().trim();
    //测试用账号
    if ("admin".equals(userName) && "123456".equals(password)) {
     Toast.makeText(this, "登录成功！", Toast.LENGTH_SHORT).show();
     //若勾选了记住用户名，则保存数据
     if (mIsRemember.isChecked()) {
      mEditor.putString("user_name", userName);
      mEditor.putBoolean("is_remember", true);
      mEditor.commit();
     }
    } else {
     Toast.makeText(this, "用户名或密码错误！", Toast.LENGTH_SHORT).show();
    }
    break;
  }
 }
}