Qt安装程序框架。如何启用覆盖安装

function Controller() {
    installer.autoRejectMessageBoxes();
    installer.installationFinished.connect(function() {
        if (installer.status == QInstaller.Success) {
            console.log("Installation succeeded.");
        }
    });
}

Controller.prototype.IntroductionPageChanged = function(page) {
    if (page.id == "introduction") {
        var existingVersion = installer.fileExists("/opt/myapp/myapp.conf");
        if (existingVersion) {
            var currentVersion = installer.value("Version");
            var installedVersion = installer.fileInfo("/opt/myapp/myapp.conf").version;
            if (currentVersion == installedVersion) {
                installer.messageBox({
                    type: "question",
                    buttons: "yesno",
                    title: "Existing Installation",
                    message: "An existing installation of the same version was found. Do you want to proceed?"
                }).then(function(button) {
                    if (button == "yes") {
                        // 用户选择继续安装，执行卸载脚本
                        var process = new QProcess();
                        process.start("maintenancetool.exe", ["--script", "uninstallscript.qs"]);
                        process.waitForFinished();
                        if (process.exitCode() == 0) {
                            // 卸载成功，继续安装新版本
                            installer.continueInstallation();
                        } else {
                            installer.abortInstallation();
                        }
                    } else {
                        // 用户选择不覆盖现有安装，终止安装
                        installer.abortInstallation();
                    }
                });
            }
        }
    }
}

<Installer>
    <description>
        <!-- 安装描述 -->
    </description>
    <version>1.0.0</version>
    <targetDirectory>/opt/myapp</targetDirectory>
    <allowUninstall>true</allowUninstall>
    <checkExistingInstallation>
        <fileExists>myapp.conf</fileExists>
        <compareVersion>
            <versionString>1.0.0</versionString>
            <operator>ge</operator>
        </compareVersion>
    </checkExistingInstallation>
    <installScript>installscript.qs</installScript>
</Installer>