多线程下载，进度条，以及安装

基于HTTP协议的多线程下载，实现思路如下： 1.通过URL实例获取HTTPConnection； 2.根据HTTPConnection获取文件大小，通过文件大小，设置的线程数，计算每一个现场下载文件的起止Byte数。 3.在每个线程里，通过connection.setRequestProperty设置获取文件的Byte的起止位置。 4.线程中，获取到下载文件后，先在本地创建临时文件，通过seek方法设置文件偏置点，然后将下载文件流write到临时文件。下面我们来看一下代码的实现：MainActivity中没有多少操作：MainActivity：import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import com.honey.two.utils.DialogUtils;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //这里做展示弹框以及功能操作        DialogUtils.showUpdataDialog(this);    }}下面再来看看DialogUtils：import android.annotation.SuppressLint;import android.app.AlertDialog;import android.app.ProgressDialog;import android.content.Context;import android.content.DialogInterface;import android.content.Intent;import android.net.Uri;import android.os.AsyncTask;import android.os.SystemClock;import com.honey.two.net.DownloadThread;import java.io.File;import java.io.IOException;public class DialogUtils {    public static long MAX_SIZE = 0;    public static long PROGRESS = -2;    public static void showUpdataDialog(final Context context){        AlertDialog.Builder builder=new AlertDialog.Builder(context);        builder.setTitle("是否更新")                .setMessage("版本太低，建议更新")                .setNegativeButton("以后再说", null)                .setPositiveButton("立即更新", new DialogInterface.OnClickListener() {                    @Override                    public void onClick(DialogInterface dialogInterface, int i) {                        new DownloadThread("http://169.254.177.227:8080/tm/alipay_wap_main.apk", context.getCacheDir() + "/alipay_wap_main.apk").start();                        showProgress(context);                    }                }).show();    }    @SuppressLint("StaticFieldLeak")    public static void showProgress(final Context context){        final ProgressDialog pd = new ProgressDialog(context);        pd.setTitle("正在更新");        pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);        pd.setMax(100);        pd.show();        new AsyncTask<String, Integer, String>(){            @Override            protected String doInBackground(String... strings) {                while (PROGRESS + 1 < MAX_SIZE){                    SystemClock.sleep(100);                    if(MAX_SIZE>0){                        publishProgress((int)(PROGRESS * 100 / MAX_SIZE));                    }                }                return null;            }            @Override            protected void onPostExecute(String s) {                super.onPostExecute(s);                pd.dismiss();                //安装的思路                File file = new File(context.getCacheDir() +"/alipay_wap_main.apk");                String[] command = {"chmod", "777", file.getPath() };                ProcessBuilder builder = new ProcessBuilder(command);                try {                    builder.start();                } catch (IOException e) {                    e.printStackTrace();                }                Intent intent = new Intent(Intent.ACTION_VIEW);                // 由于没有在Activity环境下启动Activity,设置下面的标签                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);                intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");                context.startActivity(intent);            }            @Override            protected void onProgressUpdate(Integer... values) {                super.onProgressUpdate(values);                pd.setProgress(values[0]);            }        }.execute();    }}这是DownloadTask：public class DownloadTask extends Thread{    String downloadUrl;    String path;    int blockSize;    int startPosition;    public DownloadTask(String downloadUrl, String path, int blockSize, int startPosition) {        this.downloadUrl = downloadUrl;        this.path = path;        this.blockSize = blockSize;        this.startPosition = startPosition;    }    @Override    public void run() {        NetUtils.downloadFile(downloadUrl,path,blockSize,startPosition);    }}这是DownloadThread：import com.honey.two.utils.DialogUtils;public class DownloadThread extends Thread{    private String downloadUrl = "";    private String path;    private int threadNum = 5;    public DownloadThread(String downloadUrl, String path) {        this.downloadUrl = downloadUrl;        this.path = path;    }    @Override    public void run() {        super.run();        int len=NetUtils.getFileLength(downloadUrl);        DialogUtils.MAX_SIZE = len;        //例如  1000kb  3   333        int blockSize = len/threadNum;//        //四舍五入---  让一个数字+0。5在四舍五入 就变成 向上取整//        int blockSize = (int) Math.round(tempSize + 0.5);        //计算出下载块以后   创建线程执行下载操作        for (int i = 0; i < threadNum; i++) {            //计算开始位置            int startPosition = blockSize * i;            //让最后一个线程下载的大小是正好的，  总长度 - 除了最后一个块的大小和            if(i == threadNum - 1){                blockSize = len - blockSize * (threadNum - 1);            }            new DownloadTask(downloadUrl, path, blockSize, startPosition).start();        }    }    public void setThreadNum(int threadNum){        this.threadNum = threadNum;    }}这是NetUtils：import android.util.Log;import com.honey.two.utils.DialogUtils;import java.io.BufferedInputStream;import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;public class NetUtils {    public static void downloadFile(String downloadUrl, String path, int blockSize, int startPosition){        BufferedInputStream bis=null;        RandomAccessFile raf=null;        try {            File file=new File(path);            if (!file.exists()){                file.createNewFile();            }            URL url=new URL(downloadUrl);            Log.i("===download===", "downloadFile: "+downloadUrl);            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();            urlConnection.setReadTimeout(8000);            urlConnection.setConnectTimeout(8000);            if(blockSize>0){                long end = blockSize + startPosition - 1;                urlConnection.setRequestProperty("Range","bytes="+startPosition+"-"+end);                Log.i(Thread.currentThread() + "======", "bytes====" + startPosition + "-" + end);            }            int code=urlConnection.getResponseCode();            if(code<400){                bis=new BufferedInputStream(urlConnection.getInputStream());                raf=new RandomAccessFile(file,"rwd");                raf.seek(startPosition);                int len=0;                byte[] buff=new byte[1024*8];                while ((len=bis.read(buff))!=-1){                    synchronized (NetUtils.class){                        raf.write(buff,0,len);                        if(DialogUtils.PROGRESS<0){                            DialogUtils.PROGRESS=0;                        }                        DialogUtils.PROGRESS+=len;                    }                }            }        } catch (Exception e) {            e.printStackTrace();        }finally {            if(bis!=null){                try {                    bis.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if(raf!=null){                try {                    raf.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }    public static int getFileLength(String downloadUrl){        int len=0;        try {            URL url=new URL(downloadUrl);            HttpURLConnection connection= (HttpURLConnection) url.openConnection();            connection.setReadTimeout(8000);            connection.setConnectTimeout(8000);            len=connection.getContentLength();        } catch (Exception e) {            e.printStackTrace();        }        return len;    }}