为程序添加版本自动更新功能(转)

OverView :
程序 通过后台每天检查是否有最新版本，如果需要更新当前版本，将弹出对话框让用户选择是否在当前通过Market来更新软件 。
Knowledge Points:

SharedPreferences: 一个轻量级的存储方法，类似于经常使用的.ini文件 ，它也是通过检索关键字来取得相应的数值。之所以是成为轻量级，是因为它所能应用 的数值类型有限，对于存储较大数值，效率相对较低。官方参考
System.currentTimeMillis:将当前时间以毫秒作为单位来表示，用于比较两个时间的先后顺序。（其数值表示从1970-01-01 00:00:00直到当前时间的总毫秒数）官方参考
通过网络 来读取信息：在checkUpdate()方法中包含了通过制定的URL来读取网络资源 。具体操作步骤，请参考源代码 。
Runnable: 在其内部的Run()方法中实现所要执行的任何代码，当这个runnable interface被调用后可以视作为新的线程。
Source Code：

public class hello extends Activity  { 
        /** Called when the activity is first created. */ 
        private Handler mHandler; 
          
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
         
        mHandler = new Handler(); 

        /* Get Last Update Time from Preferences */ 
        SharedPreferences prefs = getPreferences(0); 
        long lastUpdateTime =  prefs.getLong("lastUpdateTime", System.currentTimeMillis()); 

        int curVersion = 0; 
                try { 
                        curVersion = getPackageManager().getPackageInfo("linhai.com.hello", 0).versionCode; 
                } catch (NameNotFoundException e) { 
                        // TODO Auto-generated catch block 
                        e.printStackTrace(); 
                } 
        Log.i("DEMO",String.valueOf(curVersion)); 
        /* Should Activity Check for Updates Now? */ 
        if ((lastUpdateTime + (24 * 60 * 60 * 1000)) < System.currentTimeMillis()) { 

            /* Save current timestamp for next Check*/ 
           lastUpdateTime = System.currentTimeMillis(); 
            SharedPreferences.Editor editor = getPreferences(0).edit(); 
            editor.putLong("lastUpdateTime", lastUpdateTime); 
            editor.commit();       

            /* Start Update */ 
         //   checkUpdate.start(); 
        } 
    } 

    /* This Thread checks for Updates in the Background */ 
    private Thread checkUpdate = new Thread() 
    { 
        public void run() { 
            try { 
                URL updateURL = new URL("http://my.company.com/update"); 
                URLConnection conn = updateURL.openConnection(); 
                InputStream is = conn.getInputStream(); 
                BufferedInputStream bis = new BufferedInputStream(is); 
                ByteArrayBuffer baf = new ByteArrayBuffer(50); 

                int current = 0; 
                while((current = bis.read()) != -1){ 
                     baf.app end((byte)current); 
                } 

                /* Convert the Bytes read to a String. */ 
                final String s = new String(baf.toByteArray());         

                /* Get current Version Number */ 
                int curVersion = getPackageManager().getPackageInfo("your.app.id", 0).versionCode; 
                int newVersion = Integer.valueOf(s); 

                /* Is a higher version than the current already out? */ 
                if (newVersion > curVersion) { 
                    /* Post a Handler for the UI to pick up and open the Dialog */ 
                    mHandler.post(showUpdate); 
                } 
            } catch (Exception e) { 
            } 
        } 
    }; 

    /* This Runnable creates a Dialog and asks the user to open the Market */ 
    private Runnable showUpdate = new Runnable(){ 
           public void run(){ 
            new AlertDialog.Builder(hello.this) 
            .setIcon(R.drawable.ok) 
            .setTitle("Update Available") 
            .setMessage("An update for is available!\n\nOpen Android Market and see the details?") 
            .setPositiveButton("Yes", new DialogInterface.OnClickListener() { 
                    public void onClick(DialogInterface dialog, int whichButton) { 
                            /* User clicked OK so do some stuff */ 
                            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("market ://search?q=pname:your.app.id")); 
                            startActivity(intent); 
                    } 
            }) 
            .setNegativeButton("No", new DialogInterface.OnClickListener() { 
                    public void onClick(DialogInterface dialog, int whichButton) { 
                            /* User clicked Cancel */ 
                    } 
            }) 
            .show(); 
           } 
    }; 
   
} 

分为三个部分：

置于onCreate()方法中的程序用于判断当前时间是否需要检查更新（如果距离上次更新时间大于1天，将启动检查更新）
当以上条件满足时，启动checkUpdate来检查当前程序是否为最新版本。
如果确定版本已过期，那么将登录market，并直接指向当前程序页面。
*******************************************************************************************
向上言：
     本人在论坛 曾经发过一关于此问题的求助 帖，虽然大至的思路和上文差不多，关键点是在于程序如何更新，现在看到它这里指出的更新方法居然是登录market。不过以后发布的程序都是在market中，问题就不存在。

                         

  Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("market://search?q=pname:your.app.id")); 
                            startActivity(intent); 

大家都是在eclipse上开发 吧，在每次更新代码，运行 模拟 器时，大家是否有注意到console的提示信息：

[2009-06-06 19:53:50 - Hello] Android Launch! 
[2009-06-06 19:53:50 - Hello] adb is running normally. 
[2009-06-06 19:53:50 - Hello] Performing linhai.com.hello.hello activity launch 
[2009-06-06 19:53:50 - Hello] Automatic Target Mode: using existing emulator 'emulator-5554' running compatible AVD 'avd' 
[2009-06-06 19:53:50 - Hello] WARNING: Application does not specify an API level requirement! 
[2009-06-06 19:53:50 - Hello] Device API version is 3 (Android 1.5) 
[2009-06-06 19:53:50 - Hello] Uploading Hello.apk onto device 'emulator-5554' 
[2009-06-06 19:53:50 - Hello] Installing Hello.apk... 
[2009-06-06 19:54:05 - Hello] Application already exists. Attempting to re-install instead... 
[2009-06-06 19:54:31 - Hello] Success! 

分析：
1。android 正常运行
2。通过配置文件AndroidManifest.xml中运行我们的程序
3。Uploading Hello.apk onto device 'emulator-5554' 这句是关键，更新我们的程序
4。Installing Hello.apk...
5。Application already exists. Attempting to re-install instead... //程序已经存在，尝试重新安装

所以如果我们的程序要自动 更新，本人初步猜想是和上面的步骤是一样的。
详看logcat中的log

06-06 11:54:02.567: DEBUG/PackageParser(582): Scanning package: /data/app/vmdl12464.tmp 
06-06 11:54:08.048: INFO/PackageManager(582): Removing non-system package:linhai.com.hello 
06-06 11:54:08.187: DEBUG/PackageManager(582): Removing package linhai.com.hello 
06-06 11:54:08.286: DEBUG/PackageManager(582):   Activities: linhai.com.hello.hello 
06-06 11:54:11.136: DEBUG/PackageManager(582): Scanning package linhai.com.hello 
06-06 11:54:11.301: INFO/PackageManager(582): /data/app/vmdl12464.tmp changed; unpacking 
06-06 11:54:11.626: DEBUG/installd(555): DexInv: --- BEGIN '/data/app/vmdl12464.tmp' --- 
06-06 11:54:12.987: DEBUG/dalvikvm(7756): DexOpt: load 224ms, verify 265ms, opt 1ms 
06-06 11:54:13.047: DEBUG/installd(555): DexInv: --- END '/data/app/vmdl12464.tmp' (success) --- 
06-06 11:54:13.057: DEBUG/PackageManager(582):   Activities: linhai.com.hello.hello 
06-06 11:54:15.608: INFO/installd(555): move /data/dalvik-cache/data@[e-mail]@classes.dex -> /data/dalvik-cache/data@[e-mail]@classes.dex 
06-06 11:54:15.737: DEBUG/PackageManager(582): New package installed in /data/app/linhai.com.hello.apk 

关于此类的自动更新的第三方管理软件已经有了叫aTrackDog ,其原理就是使用上面的方式。
关于得到版本号，使用：

int curVersion = getPackageManager().getPackageInfo("your.app.id", 0).versionCode; 

程序版本号的是放在AndroidManifest.xml文件中：

<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
        package="linhai.com.hello" android:versionCode="2" android:versionName="2.0.1"> 

主点是关于：getPackageManager()在这个下面有很多方法，你可以通过它得，得到当前终端安装的程序等。关于安装包的函数是：getPackageManager().installPackage(packageURI)

动手试验：
在dos状态下运行：

查看logcat下的信息,大致和刚才相同，分析流程：

06-06 12:18:58.827: INFO/jdwp(8368): received file descriptor 20 from ADB 
06-06 12:19:02.546: DEBUG/PackageParser(582): Scanning package: /data/app/vmdl12465.tmp 
06-06 12:19:07.738: INFO/PackageManager(582): /data/app/vmdl12465.tmp changed; unpacking 
06-06 12:19:07.978: DEBUG/installd(555): DexInv: --- BEGIN '/data/app/vmdl12465.tmp' --- 
06-06 12:19:09.617: DEBUG/dalvikvm(8378): DexOpt: load 254ms, verify 564ms, opt 3ms 
06-06 12:19:09.697: DEBUG/installd(555): DexInv: --- END '/data/app/vmdl12465.tmp' (success) --- 
06-06 12:19:11.907: INFO/installd(555): move /data/dalvik-cache/data@[e-mail]@classes.dex -> /data/dalvik-cache/data@[e-mail]@classes.dex 
06-06 12:19:11.956: DEBUG/PackageManager(582): New package installed in /data/app/com.example.android.snake.apk 
06-06 12:19:14.746: DEBUG/dalvikvm(8368): VM cleaning up 
06-06 12:19:14.857: DEBUG/dalvikvm(8368): LinearAlloc 0x0 used 628420 of 4194304 (14%) 
06-06 12:19:15.897: DEBUG/dalvikvm(582): GC freed 17704 objects / 903984 bytes in 615ms 
06-06 12:19:15.936: DEBUG/HomeLoaders(625): application intent received: android.intent.action.PACKAGE_ADDED, replacing=false 
06-06 12:19:15.936: DEBUG/HomeLoaders(625):   --> package:com.example.android.snake 
06-06 12:19:15.936: DEBUG/HomeLoaders(625):   --> add package 

1。接收数据 ，保存到临时文件中/data/app/vmdl12465.tmp
2。解压此文件，注意路径/data/dalvik-cache/data@[e-mail] @classes.dex
它是在data下的dalvik-cache下
3.安装文件[这个步骤还包括查找程序是否已经安装等]
4.使用GC清理内存

查看DDMS中的结构

看到此文件结构，应该可以想起linux下的文件系统 和它的权限管理，也就可以理解，为什么我们的程序无法在data下创建文件之类的问题了。