服务

import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Environment;
import android.os.IBinder;
import android.support.v7.app.NotificationCompat;
import android.util.Log;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

/**
 * Created by dk on 2016/11/25.
 */

public class DownloadSignatureService extends Service {
    protected static final String fileRootPath = Environment.getExternalStorageDirectory() + File.separator;
    protected static final String fileDownloadPath = "sunrise/download/";
    protected int fileSzie;//文件大小
    protected int fileCache;//文件缓存
    protected String fileName = "";//文件名
    protected String fileNametemp = "";//临时文件
    protected String urlStr = "";//下载url
    protected File downloaddir, downloadfile, downloadfiletemp;
    protected static NotificationManager mNotifyManager;
    protected static NotificationCompat.Builder mBuilder;
    protected static final int notifiID = 0x000;
    protected static final String TAG = "LLL::";

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.e(TAG, "onStartCommand");
        urlStr = (String) intent.getExtras().get("signatureurl");
        Log.e(TAG, "urlStr = " + urlStr);
        /*Signature Download Url*/
        DownloadFile(urlStr);
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.e(TAG, "onDestroy");
        super.onDestroy();
    }

    /**
     * Download Signature
     *
     * @param downloadUrl
     */
    protected void DownloadFile(String downloadUrl) {
        Log.e(TAG, "DownloadFile");
        /*文件名*/
        fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/") + 1);
        /*缓存文件*/
        fileNametemp = "download.tmp";
        /*下载目录*/
        downloaddir = new File(fileRootPath + fileDownloadPath);
        downloadfile = new File(fileRootPath + fileDownloadPath + fileName);
        downloadfiletemp = new File(fileRootPath + fileDownloadPath + fileNametemp);

        if (!downloaddir.exists()) {
            downloaddir.mkdirs();
        }
        /*如何文件存在 这安装文件*/
        if (downloadfile.exists()) {
            installApp(DownloadSignatureService.this, fileRootPath + fileDownloadPath + fileName);
        }
        /*否则下载文件*/
        else {
            mNotifyManager =
                    (NotificationManager) DownloadSignatureService.this.getSystemService(DownloadSignatureService.this.NOTIFICATION_SERVICE);
            mBuilder = new NotificationCompat.Builder(DownloadSignatureService.this);
            mBuilder.setContentTitle("下载 电子签名App")
                    .setContentText("正在下载···")
                    .setProgress(100, 0, false)
                    .setSmallIcon(android.R.drawable.stat_sys_download);
            //downloadfile
            new AsyncTask<String, Integer, String>() {
                @Override
                protected void onPreExecute() {
                    mBuilder.setTicker("下载电子签名").setProgress(100, 0, false);
                    mNotifyManager.notify(notifiID, mBuilder.build());

                    super.onPreExecute();
                }

                @Override
                protected void onProgressUpdate(Integer... values) {
                    Log.e(TAG, "---下载缓存" + values[0] + "---");
                    int pp = ((values[0] + 1) * 100 / fileSzie);
                    mBuilder.setProgress(100, pp, false).setContentText("已下载" + pp + "%");
                    mNotifyManager.notify(notifiID, mBuilder.build());
                    super.onProgressUpdate(values);
                }

                @Override
                protected String doInBackground(String... params) {
                    try {
                        fileName = params[0].substring(params[0].lastIndexOf("/") + 1);
                        Log.e("LLL", "---fileName = " + fileName);
                        //获取文件名
                        URL myURL = new URL(params[0]);
                        URLConnection conn = myURL.openConnection();
                        conn.setDoInput(true);
                        conn.connect();
                        InputStream is = conn.getInputStream();
                        fileSzie = conn.getContentLength();//根据响应获取文件大小
                        if (fileSzie <= 0) {
                            throw new RuntimeException("无法获知文件大小 ");
                        }
                        if (is == null) throw new RuntimeException("stream is null");
                        /*下载目录*/
                        if (!downloaddir.exists()) {
                            downloaddir.mkdirs();
                        }
                        //把数据存入 路径+文件名
                        FileOutputStream fos = new FileOutputStream(downloadfiletemp);
                        byte buf[] = new byte[1024];
                        fileCache = 0;
                        do {
                            //循环读取
                            int numread = is.read(buf);
                            if (numread == -1) {
                                break;
                            }
                            fos.write(buf, 0, numread);
                            fileCache += numread;
                            this.publishProgress(fileCache);

                        } while (true);

                        try {
                            is.close();
                        } catch (Exception ex) {
                            Log.e("tag", "error: " + ex.getMessage());
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    return "下载成功";
                }

                @Override
                protected void onPostExecute(String s) {
                    /*下载成功后*/
                    if (downloadfiletemp.exists()) {
                        downloadfiletemp.renameTo(downloadfile);
                    }
                    Toast.makeText(DownloadSignatureService.this, s, Toast.LENGTH_SHORT).show();
                    /*取消通知*/
                    mBuilder.setContentText(s).setProgress(100, 0, false);
                    mNotifyManager.cancel(notifiID);
                    installApp(DownloadSignatureService.this, fileRootPath + fileDownloadPath + fileName);
                    /*service kill 自杀*/
                    DownloadSignatureService.this.stopSelf();
                    super.onPostExecute(s);
                }
            }.execute(downloadUrl);

        }


    }

    /**
     * install Apk
     *
     * @param context
     * @param filePath
     */
    public void installApp(Context context, String filePath) {
        File _file = new File(filePath);
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setDataAndType(Uri.fromFile(_file), "application/vnd.android.package-archive");
        context.startActivity(intent);
    }
}

启动服务

bundle = new Bundle();
bundle.putString("signatureurl", Instance.SignatureUrl“你下载的地址”);/*电子签名下载地址*/
Intent it = new Intent().setClass(ctx, DownloadSignatureService.class).putExtras(bundle);
startService(it);

权限

<!-- 读写存储卡的权限 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <!-- 访问联网权限 -->
    <uses-permission android:name="android.permission.INTERNET" />

 配置

 <service android:name=".Service.DownloadSignatureService" />

 这个已经已经很简单易懂了，可以参考下，下载完成后自动安装，等等，需要的可以看看，

AsyncTask<String, Integer, String>()下载更新ui