Android 緩存策略demo

packageinstaller\permission\model\PermissionApps.java

 

/** * Class used to reduce the number of calls to the package manager. * This caches app information so it should only be used across parallel PermissionApps * instances, and should not be retained across UI refresh. */
    public static class PmCache { private final SparseArray<List<PackageInfo>> mPackageInfoCache = new SparseArray<>(); private final PackageManager mPm; public PmCache(PackageManager pm) { mPm = pm; } public synchronized List<PackageInfo> getPackages(int userId) { List<PackageInfo> ret = mPackageInfoCache.get(userId); if (ret == null) { ret = mPm.getInstalledPackagesAsUser(PackageManager.GET_PERMISSIONS, userId); mPackageInfoCache.put(userId, ret); } return ret; } }

 

private final PmCache mCache; List<PackageInfo> apps = mCache != null ? mCache.getPackages(user.getIdentifier()) : mPm.getInstalledPackagesAsUser(PackageManager.GET_PERMISSIONS, user.getIdentifier());

 

/**

* Class used to reduce the number of calls to the package manager.

* This caches app information so it should only be used across parallel PermissionApps

* instances, and should not be retained across UI refresh.

*/

public static class PmCache {

private final SparseArray< List< PackageInfo>> mPackageInfoCache = new SparseArray<>();

private final PackageManager mPm;

public PmCache( PackageManager pm) {

mPm = pm;

}

public synchronized List< PackageInfo> getPackages( int userId) {

List< PackageInfo> ret = mPackageInfoCache.get(userId);

if (ret == null) {

ret = mPm.getInstalledPackagesAsUser(PackageManager.GET_PERMISSIONS, userId);

mPackageInfoCache.put(userId, ret);

}

return ret;

}

}