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为 Android 程序添加版本自动更新功能
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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。
    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.append((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@app@vmdl12464.tmp@classes.dex -> /data/dalvik-cache/data@app@linhai.com.hello.apk@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@app@vmdl12465.tmp@classes.dex -> /data/dalvik-cache/data@app@com.example.android.snake.apk@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@app@vmdl12465.tmp@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。
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