优化需求：更安全的卸载系统应用的方式，动态的设置应用的安装状态

[neoblackxt]

动态设置的好处在于，模块本身故障时，其对系统的修改也随之消失或是自动还原，是一种失效安全机制。

在MIUI系统的services.jar中：

package com.android.server.pm;
public class PackageManagerServiceInjector {
//...
    public static void checkPackageInstallerStatus(PackageManagerService pms, Settings curPkgSettings) {
        if (VERSION.SDK_INT >= 23 && !Build.IS_INTERNATIONAL_BUILD && !Build.IS_TABLET) {
            PackageSetting miuiInstaller = (PackageSetting) curPkgSettings.mPackages.get(MIUI_INSTALLER_PACKAGE);
            PackageSetting googleInstaller = (PackageSetting) curPkgSettings.mPackages.get(PACKAGE_INSTALLER_NAME);
            PackageSetting androidInstaller = (PackageSetting) curPkgSettings.mPackages.get("com.android.packageinstaller");
            boolean isCtsBuild = AppOpsUtils.isXOptMode();
            if (isCtsBuild) {
                if (miuiInstaller != null) {
                    miuiInstaller.setInstalled(!isCtsBuild, 0);
                }
                mMiuiInstallerPackageSetting = (PackageSetting) curPkgSettings.mPackages.get(MIUI_INSTALLER_PACKAGE);
                mMiuiInstallerPackage = (Package) pms.mPackages.get(MIUI_INSTALLER_PACKAGE);
                curPkgSettings.mPackages.remove(MIUI_INSTALLER_PACKAGE);
                if (curPkgSettings.isDisabledSystemPackageLPr(MIUI_INSTALLER_PACKAGE)) {
                    curPkgSettings.removeDisabledSystemPackageLPw(MIUI_INSTALLER_PACKAGE);
                }
                pms.mPackages.remove(MIUI_INSTALLER_PACKAGE);
            } else {
                if (mMiuiInstallerPackageSetting != null) {
                    mMiuiInstallerPackageSetting.setInstalled(!isCtsBuild, 0);
                    curPkgSettings.mPackages.put(MIUI_INSTALLER_PACKAGE, mMiuiInstallerPackageSetting);
                    if ((mMiuiInstallerPackageSetting.pkgFlags & 128) != 0) {
                        curPkgSettings.disableSystemPackageLPw(MIUI_INSTALLER_PACKAGE, true);
                    }
                }
                if (mMiuiInstallerPackage != null) {
                    pms.mPackages.put(MIUI_INSTALLER_PACKAGE, mMiuiInstallerPackage);
                }
            }
            if (googleInstaller != null) {
                googleInstaller.setInstalled(isCtsBuild, 0);
            }
            if (androidInstaller != null) {
                androidInstaller.setInstalled(isCtsBuild, 0);
            }
        }
    }
//...
}

可以仿照这个思路动态的设置一个包的安装状态，上面代码伴随持久化过程，不可直接利用。
可以考虑拦截掉相关持久化过程。在读取包安装状态时注入自定义包安装配置。
做这些之前必须详细弄清楚包安装状态的完整处理流程。