Android之利用Handler实现ProgressBar进度条

res/layout/main.xml文件内容如下：<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <ProgressBar        android:id="@+id/pbar"        style="?android:attr/progressBarStyleHorizontal"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:visibility="gone"        />        <Button            android:id="@+id/btnStart"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:text="@string/btnText"            /></LinearLayout>package syit.david;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ProgressBar;public class DemoActivity extends Activity {    public ProgressBar pBar;    public Button btnStart;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                //查找控件        pBar = (ProgressBar)findViewById(R.id.pbar);        btnStart = (Button)findViewById(R.id.btnStart);                //为按钮绑定监听事件        btnStart.setOnClickListener(new ButtonListener());    }        class ButtonListener implements OnClickListener    {        @Override        public void onClick(View v)        {            pBar.setVisibility(View.VISIBLE);            updateBarHandler.post(updateThread);        }    }        //消息异步机制    public Handler updateBarHandler = new  Handler()    {        @Override        public void handleMessage(Message msg)        {            pBar.setProgress(msg.arg1);            updateBarHandler.post(updateThread);        }    };            public Runnable updateThread = new Runnable()    {        int i =0;        @Override        public void run()        {            i+=10;            Message msg = updateBarHandler.obtainMessage();            msg.arg1 = i;            try            {                Thread.sleep(1000);            } catch (Exception e)            {                e.printStackTrace();            }            //将msg加入到消息队列中            updateBarHandler.sendMessage(msg);            if(i==100)            {                updateBarHandler.removeCallbacks(updateThread);                pBar.setVisibility(View.GONE);            }        }    };}