对话框

再布局中首先加一个按钮执行onclick方法

点击按钮创建对话框

<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:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:text="Button"
        android:onClick="OnClick" />

</RelativeLayout>

package com.example;


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


public class MainActivity extends Activity {


private ProgressDialog s;


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void OnClick(View v){
//建立对话框
s=new ProgressDialog(this,ProgressDialog.THEME_HOLO_LIGHT);
s.setMessage("正在读取数据");
//点击对话框其他区域不退出
s.setCanceledOnTouchOutside(false);
s.show();
}
 @Override
public void onBackPressed() {
s.cancel();
super.onBackPressed();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}


}