当我们的应用在进行耗时操作时，显示一个进度条呈现给用户，让用户知道当前进度是一个很好的体验，接下来我们就来简单了解下ProgressBar（本文主要针对初学者，大神可以绕开啦），先看效果图：

进度条ProgressBar共有几种样式，如圆形，长条形等等，本例中用的是长条形：

style="@android:style/Widget.ProgressBar.Horizontal"

主程序（MainActivity）代码：

package com.example.progressBar;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	private ProgressBar progressBar;
	private TextView progressText;
	private Button btn;
	private int progress=5;
	private Handler handler;
	
	@SuppressLint("HandlerLeak")
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		progressBar=(ProgressBar) findViewById(R.id.progressBar);
		progressBar.setProgress(5);
		progressText=(TextView) findViewById(R.id.progressText);
		btn=(Button) findViewById(R.id.btn);
		btn.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View arg0) {
				//子线程完成耗时操作
			    new Thread(new Task()).start();
			}
		});
		
		//主线程更新UI
		handler=new Handler(){
			@Override
			public void handleMessage(Message msg) {
				switch (msg.what) {
				case 0:
					progressBar.setProgress(progress);//更新进度
					progressText.setText(""+progress);
					break;
				case 1:
					progressBar.setProgress(0);
					progressText.setText("0");
					Toast.makeText(getApplicationContext(), "进入游戏！！！", Toast.LENGTH_SHORT).show();
					break;
				}
			};
		};
		
	}

	private class Task implements Runnable {
		@Override
		public void run() {
			while (true) {
				dowork();
				Message msg = new Message();
				if (progress < 5&&progress>0) {
					msg.what = 0;
					handler.sendMessage(msg);
				} else if (progress <=0) {
					msg.what = 1;
					handler.sendMessage(msg);
					break;
				}
				
			}
		}
	}
	
	//耗时操作，每执行一次，暂停一秒
	private void dowork() {
		try {
			Thread.sleep(1000);
			--progress;
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="开始"/>

    <ProgressBar
        android:id="@+id/progressBar"
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:layout_centerInParent="true"
        android:max="5" 
        style="@android:style/Widget.ProgressBar.Horizontal"/>
    <TextView 
        android:id="@+id/progressText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_below="@+id/progressBar"
        android:text="5"
        android:textSize="20sp"/>

</RelativeLayout>