弹框--更新下载--安装

    /**
     * show出对话框
     */
    private void showUpdataDialog() {
        AlertDialog.Builder builder = new Builder(this);
        builder.setTitle("版本升级");
        builder.setMessage(info.getDescription());
        builder.setCancelable(false);
        builder.setPositiveButton("是", new OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                System.out.println("升级");
                // 判断SD卡状态是否可用
                if (Environment.getExternalStorageState().equals(
                        Environment.MEDIA_MOUNTED)) {
                    // 下载是耗时的工作，需要放入到子线程里面去执行
                    DownLoadFileThreadTask download = new DownLoadFileThreadTask(
                            info.getApkurl(), "/sdcard/new.apk");
                    pd.show();
                    new Thread(download).start();
                    mainUI();
                } else {

                }
            }
        });
        builder.setNegativeButton("否", new OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                System.out.println("不升级，进入主界面");
                mainUI();
            }
        });
        builder.create().show();
    }

    /**
     * 安装apk
     */
    private void installAPK(File file) {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.fromFile(file),
                "application/vnd.android.package-archive");
        finish();
        startActivity(intent);
    }

    /**
     * 下载APK
     */
    private class DownLoadFileThreadTask implements Runnable {
        String apkurl;
        String fileurl;

        public DownLoadFileThreadTask(String apkurl, String fileurl) {
            this.apkurl = apkurl;
            this.fileurl = fileurl;
        }

        public void run() {
            DownLoadFileTask down = new DownLoadFileTask();
            try {
                File file = down.getFile(apkurl, fileurl, pd);
                System.out.println("下载完成，进行安装");
                pd.dismiss();
                installAPK(file);
            } catch (Exception e) {
                e.printStackTrace();
                Toast.makeText(getApplicationContext(), "下载文件失败", 0).show();
                pd.dismiss();
                mainUI();
            }
        }
    }

    /**
     * 获得版本号
     */
    private String getVession() {

        try {
            PackageManager pm = getPackageManager();
            // 第一个参数获得包的名字
            PackageInfo info = pm.getPackageInfo(getPackageName(), 0);
            return info.versionName;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

package cn.itcast.mobilesafe.engine;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import android.app.ProgressDialog;

public class DownLoadFileTask {

    /**
     * 
     * @param path
     *            服务器文件路径
     * @param filepath
     *            本地文件路径
     * @return 本地文件对象
     * @throws Exception
     */
    public static File getFile(String path, String filepath, ProgressDialog pd)
            throws Exception {
        URL url = new URL(path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setConnectTimeout(5000);
        if (conn.getResponseCode() == 200) {
            int total = conn.getContentLength();
            pd.setMax(total);
            InputStream is = conn.getInputStream();
            File file = new File(filepath);
            FileOutputStream fos = new FileOutputStream(file);
            byte[] buffer = new byte[1024];
            int len = 0;
            int process = 0;
            while ((len = is.read(buffer)) != -1) {
                fos.write(buffer, 0, len);
                process += len;
                pd.setProgress(process);
                Thread.sleep(50);
            }
            fos.flush();
            fos.close();
            is.close();

            return file;
        }
        return null;
    }
}