Difference between GetCacheDir() and button "clear the cache"

Question

I need to programmatically delete all caches of my Xamarin.Forms application called MyXFApp, the same way as the button 'Clear Cache' of the Setting/Apps/MyXFApp/Storage page.

I read the Android and Xamarin.Forms official documentations, and used the methods getGetCacheDir() and GetExternalCacheDir() to retrieve the cache directories, and I delete both of them. After deleting both directories, I expect to see the cache size to 0 byte within the Setting/Apps/MyXFApp/Storage page. But the cache size displayed in the Setting/Apps/MyXFApp/Storage page has indeed diminished, but is not strictly equal to 0 byte, and I do not understand why?

Is there any other directory I must delete in order to fully clear my Xamarin.Forms cache? Or is it a bug of the Setting/Apps/MyXFApp/Storage displayed cache size?

And otherwise, what is the correct way or difference(s) between these two methods?

I tried to delete directories obtained from methods getGetCacheDir() and GetExternalCacheDir(). Expected to see cache size of 0B in the Setting/Apps/MyXFApp/Storage page, but I see 20KB and not 0B.

Answer 1

Thanks for your answers My code is:

            var cachePath = this.ApplicationContext.CacheDir.Path;
            var cachePath2 = this.ApplicationContext.ExternalCacheDir.Path;

            // If exist, delete the cache directory and everything in it recursivly
            if (System.IO.Directory.Exists(cachePath))
                System.IO.Directory.Delete(cachePath, true);

            // If exist, delete the cache directory and everything in it recursivly
            if (System.IO.Directory.Exists(cachePath2))
                System.IO.Directory.Delete(cachePath2, true);

            // If not exist, restore just the directory that was deleted
            if (!System.IO.Directory.Exists(cachePath))
                System.IO.Directory.CreateDirectory(cachePath);

            // If not exist, restore just the directory that was deleted
            if (!System.IO.Directory.Exists(cachePath2))
                System.IO.Directory.CreateDirectory(cachePath2);`

I try the response of @Liyun Zhang

Answer 2

I have done a sample and use the following code to clear the cache:

        public static bool DeleteCache(File file)
        {
            if(file != null && file.IsDirectory )
            {
                string[] children = file.List();
                for(int i = 0; i < children.Length; i++)
                {
                    bool success = DeleteCache(new File(file,children[i]));
                    if (!success)
                    {
                        return false;
                    }
                }
            }
            return file.Delete();
        }

And call the method in the MainActivity:

var file = this.CacheDir;
var file1 = this.ExternalCacheDir;
DeleteCache(file);
DeleteCache(file1);

When I called the method, I checked the cache size still had 20KB. And then I tapped App info and cleared cache. I also saw the cache size be 0KB. But when I reload the app storage page by going back and into the storage page again, I saw the cache size be 20KB again.

Expected to see cache size of 0B in the Setting/Apps/MyXFApp/Storage page, but I see 20KB and not 0B.

So you saw the 0B was not really 0B, when you reload the storage page, it will be 20KB. It seems the 20KB cache must exist for each app on the android device.

I also try to clear the cache app's cache on the really device. When the app restart, the cache be 28KB on the xiaomi device. So when you use the code in your app to clear the cache, your app is still running. The cache can't be clear as 0KB.