android 入门demo 进度条

package com.isoftstone.cry;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;

public class ProgressBarDialog extends Activity 
{
	private Button btn1 ,btn2 ;
	private ProgressBar progressBar ;
	@Override
	protected void onCreate(Bundle savedInstanceState) 
	{
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.progressbar);
		
		btn1 = (Button)findViewById(R.id.progressBarbutton1);
		btn2 = (Button)findViewById(R.id.progressBarbutton2);
		progressBar = (ProgressBar)findViewById(R.id.progressBar1);
		
		btn1.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				progressBar.incrementProgressBy(10);
			}
		});
		
		btn2.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				progressBar.incrementProgressBy(-10);
			}
		});
	}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/progressBarbutton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button1" />

    <Button
        android:id="@+id/progressBarbutton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button2" />


    <ProgressBar
        android:id="@+id/progressBar1"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>