有个需求，想判断手机里是否安装指定的app，没找到现成的代码，参考Delphi代码实现了一个，当返回空串时，表示没有安装app。

function GetVersionString(APackageName:string): string;

//uses Androidapi.JNI.GraphicsContentViewText,Androidapi.Helpers,androidapi.jni.javatypes;

var

  PackageInfo: JPackageInfo;

  PackageManager: JPackageManager;

  AppContext: JContext;

begin

  AppContext := TAndroidHelper.Context;

  if AppContext <> nil then

  begin

    PackageManager := AppContext.getPackageManager;

    if PackageManager <> nil then

    begin

      try

        PackageInfo := AppContext.getPackageManager.getPackageInfo(StringToJString(APackageName), 0);

      except

        Exit(string.Empty);

      end;

      if PackageInfo <> nil then

         Exit(JStringToString(PackageInfo.versionName));

    end;

  end;

  Result := string.Empty;

end;

调用代码：

if GetVersionString('com.kinglandsoft.xmyt')='' then

begin

//没有安装app

...

end

https://www.cnblogs.com/kinglandsoft/p/12389276.html