代码：

import android.app.Activity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
   
    public void click(View view){
        MyDialogFragmnet myDialogFragmnet = new MyDialogFragmnet();
        myDialogFragmnet.show(getFragmentManager(), "dialog");
    }
}

activiy_main布局

<RelativeLayout 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: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=".MainActivity" >

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click"
        android:text="DialogFragment对话框" />
</RelativeLayout>

MyDialogFragment

import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.app.AlertDialog.Builder;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
 * 官方推荐使用DialogFragment
 * 传统的对话框屏幕切换时 会消失 第一：不会保存用户输入的值 第二：还会报异常
 * @author Administrator
 *
 */
public class MyDialogFragmnet extends DialogFragment {

    
//  @Override
//  public Dialog onCreateDialog(Bundle savedInstanceState) {
//      AlertDialog.Builder dialog = new AlertDialog.Builder(getActivity());
//      dialog.setIcon(R.drawable.ic_launcher).setTitle("提示").setMessage("正在下载中...");
//      return super.onCreateDialog(savedInstanceState);
//  }
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.custom_dialog, container, false);
        return view;
    }
}

dialog_activity

<?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:orientation="vertical"
    android:padding="10dp" >
    
    <TextView 
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="UserName:"/>
    
    <EditText 
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/textView"
        android:layout_alignBaseline="@id/textView"
        android:hint="请输入用户名"/>
    
    <Button 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_below="@id/editText"
        android:text="OK"/>
</RelativeLayout>