<?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:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="登录界面"android:textSize="30dp"android:background="#DBDBDB"android:layout_gravity="center"></TextView><EditTextandroid:id="@+id/et1"android:layout_width="match_parent"android:layout_height="wrap_content"android:hint="请输入用户名"/><EditTextandroid:id="@+id/et2"android:layout_width="match_parent"android:layout_height="wrap_content"android:password="true"android:hint="请输入密码"/><Buttonandroid:id="@+id/bt1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="登录"android:layout_gravity="center"/></LinearLayout>

package com.example.app3;import android.content.DialogInterface;
import android.content.Intent;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;public class MainActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button bt1 = (Button)findViewById(R.id.bt1);bt1.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent myIntent = new Intent(MainActivity.this,Second.class);startActivity(myIntent);}});}protected  void dialog(){AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);builder.setTitle("提示");builder.setIcon(R.mipmap.ic_launcher);builder.setMessage("退出？");builder.setPositiveButton("確定", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();MainActivity.this.finish();}});builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}});builder.create().show();}@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {if(keyCode==event.KEYCODE_BACK){dialog();}return super.onKeyDown(keyCode, event);}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="歡迎來到您的個人空間"/>
</LinearLayout>

package com.example.app3;import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;/*** Created by Mr.Wu on 2016/9/27.*/
public class Second extends AppCompatActivity {@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.layout);
}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {menu.add(Menu.NONE,1,1,"个人信息保护");menu.add(Menu.NONE,2,2,"设置");menu.add(Menu.NONE,3,3,"问卷调查");menu.add(Menu.NONE,4,4,"关于");menu.add(Menu.NONE,5,5,"帮助");return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {switch (item.getItemId()){case 1:Toast.makeText(Second.this,"你点击了个人信息保护",Toast.LENGTH_SHORT).show();break;case 2:Toast.makeText(Second.this,"你点击了设置",Toast.LENGTH_SHORT).show();break;case 3:Toast.makeText(Second.this,"你点击了问卷调查",Toast.LENGTH_SHORT).show();break;case 4:Toast.makeText(Second.this,"你点击了关于",Toast.LENGTH_SHORT).show();break;case 5:Toast.makeText(Second.this,"你点击了帮助",Toast.LENGTH_SHORT).show();break;}return super.onOptionsItemSelected(item);}