Android项目中怎么实现一个检查更新、下载、安装功能

public class MainActivity extends BaseActivity{
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  CheckUpdateUtil.checkUpdate(this);//检查更新
 }
}

package com.monkey.monkeymushroom.util;

import android.app.AlertDialog;
import android.app.NotificationManager;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Environment;
import android.support.v4.app.NotificationCompat;
import android.text.TextUtils;
import android.view.Gravity;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.lidroid.xutils.HttpUtils;
import com.lidroid.xutils.exception.HttpException;
import com.lidroid.xutils.http.ResponseInfo;
import com.lidroid.xutils.http.callback.RequestCallBack;
import com.umeng.analytics.MobclickAgent;

import java.io.File;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 检查更新工具类
 */
public class CheckUpdateUtil {
 private static NotificationCompat.Builder builder;
 private static NotificationManager manager;
 private static final int UPDATE_ID = "0";

 /**
  * 检查更新
  *
  * @param context
  * @return
  */
 public static boolean checkUpdate(Context context) {
  // 获取友盟在线参数（要更新的版本号）
  String force_version = MobclickAgent.getConfigParams(context, "version");
  if (StringUtils.isEmpty(version)) {
   version = "1.0";
  }
  // 版本号转换为数组
  String[] mUpdateVersionArray = version.split(",");
  String curr_version_name = SysInfoUtils.getVersionName(context);

  for (int i = 0; i < mUpdateVersionArray .length; i++) {//循环获取在线参数上设置的版本号
   if (curr_version_name.equals(mUpdateVersionArray [i])) {//如果有，代表要更新
    if ((mUpdateVersionArray .length > i + 1) && ("Y".equals(mUpdateVersionArray [i + 1]))) {//判断是否强更
     showUpdateDialog(true, context);
    } else {//不强更
     showUpdateDialog(false, context);
    }
    return true;// 只要找到对应的版本号，即有更新，结束循环
   }
  }
  return false;//无更新
 }

 /**
  * 显示更新对话框
  *
  * @param isForceUpdate 是否强制更新
  */
 public static void showUpdateDialog(final boolean isForceUpdate, final Context context) {
  // 获取更新日志
  String update_log = MobclickAgent.getConfigParams(context, "update_log");
  // 最新版本
  String new_version = MobclickAgent.getConfigParams(context, "new_version");
  // 获取下载地址
  final String download_path = MobclickAgent.getConfigParams(context, "new_version_path");
  if (TextUtils.isEmpty(update_log) || TextUtils.isEmpty(download_path) || TextUtils.isEmpty(new_version)) {
   return;
  }
  LogMessage.e("monkey", "更新日志--> " + update_log + " 最新版本--> " + new_version + " 下载地址--> " + download_path);
  //弹框提示
  final AlertDialog mAlertDialog = new AlertDialog.Builder(context).create();
  mAlertDialog.show();
  mAlertDialog.setCancelable(false);
  Window window = mAlertDialog.getWindow();
  window.setGravity(Gravity.BOTTOM);
  window.setLayout(WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.MATCH_PARENT);
  View view = View.inflate(context, R.layout.dialog_update, null);
  window.setContentView(view);

  TextView log_head = (TextView) view.findViewById(R.id.log_head);
  TextView msg_tv = (TextView) view.findViewById(R.id.msg_tv);
  log_head.setText("v" + new_version + "更新日志：");
  msg_tv.setText(update_log);
  Button update = (Button) view.findViewById(R.id.yes_btn);
  Button notNow = (Button) view.findViewById(R.id.no_btn);
  update.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
    download(context, download_path);
    mAlertDialog.dismiss();
   }
  });
  notNow.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
    mAlertDialog.dismiss();
   }
  });
  if (isForceUpdate) {//如果是强制更新，则不显示“以后再说”按钮
   notNow.setVisibility(View.GONE);
  }
 }

 /**
  * 下载apk
  */
 private static void download(final Context context, String download_path) {
  if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
   String apkName = download_path.substring(download_path.lastIndexOf("/") + 1);
   String target = Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + apkName;
   LogMessage.e("monkey", "apk target -->" + target);
   if (NetUtils.isNetConnect(context)) {
    HttpUtils httpUtils = new HttpUtils(1000 * 10);//为了方便使用了xUtils
    httpUtils.download(download_path, target, false, true, new RequestCallBack<File>() {
     @Override
     public void onStart() {
      super.onStart();
      ToastUtil.show(context, "正在下载……");
      //创建通知栏下载提示
      builder = new NotificationCompat.Builder(context);
      builder.setSmallIcon(R.drawable.ic_launcher)
        .setOngoing(true)
        .setContentTitle("猴菇先生");
      manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
     }

     @Override
     public void onLoading(long total, long current, boolean isUploading) {
      super.onLoading(total, current, isUploading);
      LogMessage.e("monkey", "--> total " + total + " current " + current);
      int cur = (int) (current * 100 / total);
      LogMessage.e("monkey", "cur--> " + cur + "%");
      builder.setProgress(100, cur, false)//更新进度
        .setContentText(cur + "%");
      manager.notify(UPDATE_ID, builder.build());
     }

     @Override
     public void onSuccess(ResponseInfo<File> responseInfo) {
      manager.cancel(UPDATE_ID);//取消通知栏下载提示
      //下载成功后自动安装apk并打开
      File file = responseInfo.result;
      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);
     }

     @Override
     public void onFailure(HttpException e, String s) {
      ToastUtil.show(context, "当前网络不可用，请检查网络设置");
     }
    });
   } else {
    ToastUtil.show(context, "当前网络不可用，请检查网络设置");
   }
  } else {
   ToastUtil.show(context, "SD卡没有插好");
  }
 }
}

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent">

 <RelativeLayout
  android:layout_width="310dp"
  android:layout_height="wrap_content"
  android:layout_centerInParent="true"
  android:background="@color/base_white"
  android:paddingBottom="20dp">

  <TextView
   android:id="@+id/title"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerHorizontal="true"
   android:layout_marginBottom="20dp"
   android:layout_marginTop="20dp"
   android:text="发现新版本"
   android:textSize="20sp" />

  <View
   android:id="@+id/line"
   android:layout_width="match_parent"
   android:layout_height="1dp"
   android:layout_below="@+id/title"
   android:background="#4a7acd" />

  <TextView
   android:id="@+id/log_head"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@+id/line"
   android:layout_marginLeft="20dp"
   android:layout_marginTop="20dp" />

  <TextView
   android:id="@+id/msg_tv"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@+id/log_head"
   android:layout_centerHorizontal="true"
   android:layout_marginLeft="32dp"
   android:layout_marginRight="32dp"
   android:text="更新日志"
   android:textSize="16sp" />

  <LinearLayout
   android:layout_width="match_parent"
   android:layout_height="35dp"
   android:layout_below="@+id/msg_tv"
   android:layout_marginTop="30dp"
   android:orientation="horizontal">

   <Button
    android:id="@+id/yes_btn"
    android:layout_width="0dp"
    android:layout_height="35dp"
    android:layout_marginLeft="20dp"
    android:layout_marginRight="20dp"
    android:layout_weight="1"
    android:background="#4a7acd"
    android:gravity="center"
    android:text="立即更新"
    android:textColor="@color/base_white"
    android:textSize="16sp" />

   <Button
    android:id="@+id/no_btn"
    android:layout_width="0dp"
    android:layout_height="35dp"
    android:layout_marginRight="20dp"
    android:layout_weight="1"
    android:background="#4a7acd"
    android:gravity="center"
    android:text="以后再说"
    android:textColor="@color/base_white"
    android:textSize="16sp" />
  </LinearLayout>
 </RelativeLayout>
</RelativeLayout>