怎么把dialog的圆角改为直角啊？


问题：如图，四个圆角改为直角。
java代码：package com.bxdm.xwplayer.online.util;import com.example.httptext.R;import android.app.Activity;  
import android.app.AlertDialog;  
import android.app.ProgressDialog;   
import android.os.Bundle;  
import android.view.LayoutInflater;  
import android.view.View;  
  
public class test extends Activity {  
    /** Called when the activity is first created. */  
    ProgressDialog p_dialog;  
  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.dialog);
        LayoutInflater factory = LayoutInflater  
                .from(test.this);  
        final View DialogView = factory.inflate(  
                R.layout.dialog, null);  
        AlertDialog dlg = new AlertDialog.Builder(  
                test.this)
//                .setTitle("")  
//             .setMessage("") 
//                .setView(DialogView)  
                .create();
        dlg.setView(DialogView, 0, 0, 0, 0);
        dlg.show();    
    }  
} 
布局文件：<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="#FFFFFF" >    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="horizontal" >        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="" />        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:layout_marginRight="15dp"
            android:src="@drawable/close" />
    </RelativeLayout>
<TextView 
android:layout_margin="100dip"
    android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>