MainActivity如下面:

package cc.testprogressdialog;

import android.os.Bundle;

import android.view.Gravity;

import android.view.View;

import android.view.ViewGroup.LayoutParams;

import android.widget.FrameLayout;

import android.widget.LinearLayout;

import android.widget.ProgressBar;

import android.app.Activity;

import android.app.ProgressDialog;

import android.content.Context;

/**

 * Demo描写叙述:

 * 利用代码在屏幕中间位置显示ProgressDialog和ProgressBar

 *

 * 參考资料:

 * 1 http://blog.csdn.net/lfdfhl/article/details/18913435

 * 2 http://blog.csdn.net/lfdfhl/article/details/9299075

 * 3 http://rocye.iteye.com/blog/1258936

 *   Thank you very much

 *

 * 假设在某个线性布局中动态加入一个控件,而且想让该控件在布局中居中.

 * 也可採用createProgressBar()方法中相似的方式

 *

 */

public class MainActivity extends Activity {

	private Context mContext;

	private ProgressBar mProgressBar;

    private ProgressDialog mProgressDialog;

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);

		//显示ProgressBar

		createProgressBar();

		//显示ProgressDialog

		//createProgressDialog();

	}

	private void createProgressBar(){

		mContext=this;

		//整个Activity布局的终于父布局,參见參考资料

		FrameLayout rootFrameLayout=(FrameLayout) findViewById(android.R.id.content);

		FrameLayout.LayoutParams layoutParams=

	    new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

		layoutParams.gravity=Gravity.CENTER;

		mProgressBar=new ProgressBar(mContext);

		mProgressBar.setLayoutParams(layoutParams);

		mProgressBar.setVisibility(View.VISIBLE);

		rootFrameLayout.addView(mProgressBar);

	}

	private void createProgressDialog(){

		mContext=this;

		mProgressDialog=new ProgressDialog(mContext);

		mProgressDialog.setMessage("...请您稍等...");

		mProgressDialog.show();

	}

}

main.xml例如以下:

<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"

   >

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="在屏幕中间位置显示ProgressDialog和ProgressBar"

        android:layout_centerHorizontal="true" />

</RelativeLayout>