实现异步多线程下载文件

我是基于一名大神的思路写的，如果想看更多内容，下面大神的blog地址
http://blog.youkuaiyun.com/shimiso/article/details/6763664

xml文件

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity">
    <ProgressBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/progressbar1"
        style="?android:attr/progressBarStyleHorizontal"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="textview1"
        android:id="@+id/textview1"/>
    <ProgressBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/progressbar2"
        style="?android:attr/progressBarStyleHorizontal"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="textview1"
        android:id="@+id/textview2"/>



</LinearLayout>

Activity

public class MainActivity extends AppCompatActivity {
    private TextView textView1,textView2;
    private ProgressBar progressBar1,progressBar2;

    //文件存储地址
    private String downLoadingpath= Environment.getExternalStorageDirectory().getAbsolutePath()+ File.separator;


    //下载地址
    private String downloadingFile1="http://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";
    private String downloadingFile2="http://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";

    //声明已经读过的长度变量
    private int hasRead=0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView1= (TextView) findViewById(R.id.textview1);
        textView2= (TextView) findViewById(R.id.textview2);
        progressBar1= (ProgressBar) findViewById(R.id.progressbar1);
        progressBar2= (ProgressBar) findViewById(R.id.progressbar2);

        downLoad(downloadingFile1,downLoadingpath,progressBar1,textView1);
        downLoad(downloadingFile2,downLoadingpath,progressBar2,textView2);
    }
    private void downLoad(String url,String targetPath,ProgressBar pb,TextView textView)
    {
            DownloadThread downloadThread=new DownloadThread(url,targetPath,pb,textView);
        downloadThread.start();
    }

    //自定义Handler类处理线程消息
    public class MyHandler extends Handler{
        private ProgressBar pb;
        private TextView textView;

        public MyHandler(ProgressBar pb, TextView textView) {
            this.pb = pb;
            this.textView = textView;
        }

        @Override
        public void handleMessage(Message msg) {
            this.pb.setProgress(msg.arg1);
            this.textView.setText(msg.arg1+"%");
            super.handleMessage(msg);
        }
    }

    public  class DownloadThread extends Thread{
        String url="";
        private String targetPath="";

        private int hasDownLoad=0;

        private int len=-1;

        private byte buffer[]=new byte[4*1024];

        private int size=0;
        //下载速度
        private int rate=0;

        private MyHandler myHandler=null;
        private Message msg=null;

        private ProgressBar pb=null;
        private TextView textView=null;

        public DownloadThread(String url, String targetPath, ProgressBar pb, TextView textView) {
            this.url = url;
            this.targetPath = targetPath;
            this.pb = pb;
            this.textView = textView;

            myHandler=new MyHandler(this.pb,this.textView);
        }

        @Override
        public void run() {
            String targetFileName=this.targetPath
                    +this.url.substring(this.url.lastIndexOf("/")
                    +1,this.url.length());
            File downloadFile=new File(targetFileName);

            if (!downloadFile.exists())
            {
                try {
                    downloadFile.createNewFile();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            try {
                URL fileUrl=new URL(this.url);

                HttpURLConnection conn= (HttpURLConnection) fileUrl.openConnection();

                //获取文件大小
                size=conn.getContentLength();

                InputStream is=conn.getInputStream();
                OutputStream os=new FileOutputStream(targetFileName);

                while ((len=is.read(buffer))!=-1)
                {
                    os.write(buffer);

                    hasDownLoad+=len;

                    rate=(hasDownLoad*100/size);

                    msg=new Message();
                    msg.arg1=rate;
                    myHandler.sendMessage(msg);

                    Log.e("rate----------",rate+"%");
                }

                } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {

            }
        }
    }
}

这是最基础的写法，基于handler更新UI，使用httpurlconnection下载文件内容，然后进行文件保存操作。

就截取了一部分下载过程。