如何在Android应用中使用AlertDialog实现一个对话框

AlertDialog.Builder builder = new AlertDialog.Builder(this);
   builder.setTitle("确认对话框");
   builder.setIcon(R.drawable.icon_72);
   builder.setMessage("这里是对话框内容");
   builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface arg0, int arg1) {
     // TODO Auto-generated method stub
     Toast.makeText(AlertDialog_text.this, "点击了确定按钮", 1).show();
    }
   });
   AlertDialog dialog = builder.create();
   dialog.show(); //显示、

final String[] items = new String[]{"语文","数学","英语","物理","化学"}; //列表项
   Builder alertdialog = new AlertDialog.Builder(this); 
   alertdialog.setTitle("你喜欢的课程").setItems(items, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     Toast.makeText(AlertDialog_lianxi.this, items[which], Toast.LENGTH_SHORT).show();
    }
   });
   alertdialog.create().show();     //创建显示列表

final String[] items_fruit = new String[]{"苹果","香蕉","橘子","西瓜","梨"};
   Builder alerdialog = new AlertDialog.Builder(this);
   //设置列表标题
   alerdialog.setTitle("你喜欢的水果");
   //设置单选列表
   alerdialog.setSingleChoiceItems(items_fruit, 0, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     Toast.makeText(AlertDialog_lianxi.this, items_fruit[which], Toast.LENGTH_SHORT).show();
    }
   });
   //设置取消按钮并且设置响应事件
   alerdialog.setNegativeButton("取消", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     //取消按钮响应事件
    }
   });
   //添加确定按钮 并且设置响应事件
   alerdialog.setPositiveButton("确定", new DialogInterface.OnClickListener() {  
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     //确定按钮响应事件
    }
   });
   alerdialog.create().show();//创建显示列表

final String[] items_fruit1 = new String[]{"苹果","香蕉","橘子","西瓜","梨"}; //设置项
   final boolean[] items_fruit_selected = new boolean[]{true,false,false,false,false}; 
   Builder alerdialog1 = new AlertDialog.Builder(this);
   //设置列表标题
   alerdialog1.setTitle("你喜欢的水果");
   //设置多选列表
   alerdialog1.setMultiChoiceItems(items_fruit1, items_fruit_selected, new DialogInterface.OnMultiChoiceClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which, boolean isChecked) {
     // TODO Auto-generated method stub
     items_fruit_selected[which] = isChecked;
    }
   });
   //设置取消按钮并且设置响应事件
   alerdialog1.setNegativeButton("取消", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     //取消按钮响应事件
    }
   });
   //添加确定按钮 并且设置响应事件,将选择的项显示
   alerdialog1.setPositiveButton("确定", new DialogInterface.OnClickListener() {  
    @Override
    public void onClick(DialogInterface dialog, int which) {
     // TODO Auto-generated method stub
     //确定按钮响应事件
     StringBuilder stringBuilder = new StringBuilder();
     for(int i=0;i<items_fruit_selected.length;i++)
     {
      if(items_fruit_selected[i] == true)
      {
       stringBuilder.append(items_fruit1[i]+"、");
      }
     }
     Toast.makeText(AlertDialog_lianxi.this, stringBuilder.toString(), Toast.LENGTH_SHORT).show();
    }
   });
   alerdialog1.create().show();//创建显示列表

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:gravity="center_horizontal"
 android:orientation="vertical" >
 <EditText 
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:editable="false"
  android:text="自定义对话框"/>
 <TextView 
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="这里是自定义对话框的内容"
  android:textSize="20dp"
  />
 <Button 
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="确定"
  />
</LinearLayout>

layout_dialog

package com.example.demo1;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity {
 private Button btn_openDialog;
 private View view;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  btn_openDialog = (Button) findViewById(R.id.id_submit);
  btn_openDialog.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    view = LayoutInflater.from(MainActivity.this).inflate(R.layout.layout_dialog, null);
    AlertDialog dialog = new AlertDialog.Builder(MainActivity.this)
          .setTitle("主题")
          .setIcon(R.drawable.ic_launcher)
          .setView(view)
          .setPositiveButton("取消", new DialogInterface.OnClickListener() {
          @Override
          public void onClick(DialogInterface dialog, int which) {
           // TODO Auto-generated method stub
          }
         })
          .create();
    dialog.show();
   }
  });
 }
}

MainActivity.class