查找应用程序是否已安装..？

Question

我浏览了很多链接和教程，例如 Check if application is installed - Android 和 How to check programmatically if an application is installed or not in Android?，但我没有找到我的问题的确切解决方案。当我尝试安装启动程序包为 com.test.app 的应用程序时，我想在安装时检查此程序包，或者您可以说我们的应用程序是否已安装？ 当我尝试按照上面的链接进行操作时，无论是否已安装，它总是为我显示“已安装”。那么我将如何管理它。

Answer 1

这是一个想法。我已经实现了

     1. Create a Web Service which our app can pull whenever the app
        launches or based on some time limit that can check if there is new version out there.
     2. This Web service should return the latest Version of the apk file that is hosted on the
        Server along with the URI of the application file that has the new version.
     3. When your app gets the response from the Web Service, it will parse the JSON and
        check our app version to the latest version that is available
        on the server.
     4. If our app version is lower than the latest version it will prompt
        the user to start the download process.
     5. Today i manage download process by the Download Manager and day before
        yesterday I do same thing by Package Manager. I will update which mechanism is
        most optimal to download .apk file with size of more than 10MB.
     6. The download manager will notify our app using Broadcast receiver when the  download
        is complete.
     7. Upon completion of the latest version of the application file the we can  
        start the activity to install that file.

然后我们可以通过版本比较

    private static int compare(String v1, String v2) {   
        String s1 = normalisedVersion(v1);
        String s2 = normalisedVersion(v2);
        int cmp = s1.compareTo(s2);
        System.out.println("cmp int  "+cmp);

        return cmp;
       /* String cmpStr = cmp < 0 ? "<" : cmp > 0 ? ">" : "==";

        System.out.printf("'%s' %s '%s'%n", v1, cmpStr, v2);*/
    }

然后

    public static String normalisedVersion(String version) {
        return normalisedVersion(version, ".", 4);
    }

    public static String normalisedVersion(String version, String sep, int maxWidth) {
        String[] split = Pattern.compile(sep, Pattern.LITERAL).split(version);
        StringBuilder sb = new StringBuilder();
        for (String s : split) {
            sb.append(String.format("%" + maxWidth + 's', s));
        }
        return sb.toString();
    }