I am using TTPhotoViewController to show photo coming from remote repository. If I change the content of the photo on remote repository but still use the same url, on my iPhone client, the original phone will still be shown when load up the TTPhotoViewController. So the image is somehow cached, is there way to not do that?
I also noticed the same problem with one of the TTTableStyledTextItem that have url to an image.
So is there anyway to clear cache or auto refresh if the target image is changed?
Three20 uses an internal cache called TTURLCache that supports all kinds of caches including ETag and such.
Manually disable cache to disk via:
[TTURLCache sharedCache].disableDiskCache = YES;
I wouldn't recommend disabling the cache and instead you should look at your http cache header on your images - Three20 by default is respecting it. One way I do recommend you to handle it is adding a dummy parameter to your image urls (assuming you get the image url through some kind of an api). then simply append a dummy version number to it. Each time the version chages your app will get a new version of the image.
instead of:
http://yoururl.com/image.png
use
http://yoururl.com/image.png?dummyversion=232
Related
I am making android app that must show a lot of images from my REST API. I want to download images, and the next time check for images' name. If the image exists show them from the phone otherwise download from server.
Now I'm using Retrofit for my network requests and Glide for show images. But I have not good idea for solve this issue.
If needed I can change the network library or image loading library.
Thanks in advance
NOTE: This question might be too broad for the liking of S.O.
What you want to do is make what is known as a cache. The idea is that you have a unique identifier (often refered to as a key) for each object in the cache, such as an md5 sum of the image data, or original name + date of creation.
When you want to display an image, you first check if the image exists in the cache. If it exists simply return with the image from cache. if it does not exist, start the download and upon completion you insert the image into the cache.
Here is an example implementation that does what you want. I cannot vouch for it's quality because I never tried it.
I need to create, for a specific project, an image manager that works via Ajax (to get the list of images, display them, ...).
The upload of new images, or image modification, is done via an Ajax script (using the new javascript File API).
The upload works fine, but I encounter a problem in case of image modification : the image displayed by the browser after upload is the cached one and not the uploaded one !!
I know it's a classic cache problem, that can be solved via the 'imagesrc?new Date.getTime()' hack, but I can't use it here.
in fact, this hack doesn't really reload the image, it only create a new instance of the image into the cache, associated to the image url 'imagesrc?new Date.getTime()'.
So, if at any moment, into the image manager, I retry to display the image, without adding the '?new Date.getTime()' to the src, it will display again the old image.
And I either cannot add this hack systematically (because, for example, if the image manager needs to display a lot of very heavy images, it's usefull to get them from the browser cache until they are modified).
I searched a way to solve this problem on internet (really replace the cached image after a javascript upload instead of using the above hack), but I found nothing.
Is there a way to do this, or is it totally impossible ?
Any help or suggestion would be greatly appreciated.
Many thanks in advance
Olivier
Configure your server to send ETag-headers for the images.
An ETag is a hash-value of the file that changes when the file is modified. If an ETag is sent, the browser will add an If-None-Match-header containing the last received ETag of that ressource on its next request and the server will respond with 304: not modified to save traffic if nothing has changed or send the new file if there is one.
I have some image urls which I want to cache locally and save so that I don't need to make a web request again and again as needed.
Now, I am confused whether there is any significant benefit of using webclient's openreadasync method over bitmap for fetching the image for first time for saving it to IsolatedStorage.
For me, I think bitmap would be a better option as I would be able to get a event for progress.
This post gives good info on various image caching options.
http://blogs.msdn.com/b/swick/archive/2011/04/07/image-tips-for-windows-phone-7.aspx
Matt mentioned the fact that default image caching only works per session. So if you are implementing your own Image caching, then you will have to implement a image downloader for which the WebClient OpenReadAsync provides a way to store file locally
If you were't considering a local cache, UriSource would have been the choice.
If you want to cache images beyond the current application instance lifetime, have a look at http://blogs.msdn.com/b/delay/archive/2010/10/04/there-s-no-substitute-for-customer-feedback-improving-windows-phone-7-application-performance-now-a-bit-easier-with-lowprofileimageloader-and-deferredloadlistbox-updates.aspx which will show a way of saving the images to IsolatedStorage and then display it from there. This means you won't have to get it over the network each time the app is run.
If you're using this for lots of images be sure to manage the images you save as well so you don't fill up the disk with lots of old images you'll never need again.
I'm using the high performance image serving feature in App Engine to serve up images from the blobstore. However, I'd like users to be able to modify those images (e.g. rotate, crop etc.) and then write those change back to the blobstore, overwriting the original blob. I know I can write to new blobs in the blobstore, as documented here: http://code.google.com/appengine/docs/python/blobstore/overview.html#Writing_Files_to_the_Blobstore
but I don't see a way to overwrite existing blobs. Is this possible in App Engine?
My use case is as follows:
User uploads image, and app engine generates a link via
get_serving_url
The user may then use that link outside of my app, e.g. link to it
on their blog to display the image
If that image is changed later on in my app (rotation, etc.) , I'd
like their image link to reflect those changes
Files stored in blobstore are immutable, once they have been written than can not be changed (only served or deleted).
I think you should try to build your own controller for generate file serving url
- In Datastore each blobFile record have own ID (you manage it) and version ID
- for first upload , set new ID and version
- When user change your image, save new blobstore, keep ID and set new version field
In serving controller generate link by iD, when user call it, get the newest version for serving
It's just my opinion, hope it helpful !
I need a way for cache images and html files in PhoneGap from my site. I'm planning that users will see site without internet connection like it will be with it. But I see information only about sql data storing, but how can I store images (and use later).
To cache images check out this library -of which I'm the creator-:
imgcache.js
. It's designed for the very purpose of caching images using the local filesystem. If you check out the examples you will see that it can also detect when an image fails to be loaded (because you're offline or you have a very bad connection) and then replaces it automatically with the cached image. The user of the webapp doesn't even notice it's offline.
As for html pages.. if they're html static files, they could be stored locally in the web app (file:// in phonegap).
If they're dynamically generated pages, check the localStorage API if you have a small amount of data, otherwise the filesystem API.
For my web app I retrieve only json data from my server (and process/render it using Backbone+Underscore). The json payload is stored into the localStorage. If the application gets offline, it will fetch json data from the localStorage instead of the server (home-baked fork of Backbone.dualStorage)
You then get the full offline experience: pages+images.
Caching like you might need for simple offline operation is not exactly that easy.
Your first option is the cache manifest. It has some limitations (like the size of the cache) but might work for you since it was designed to do what you want.
Another options is that you can store content on the disk of the device using the file system APIs. This has some drawbacks like security and the fact that you have to load the file from a path / url that is different than you might normally load it from on the web. Check out the hydra plugin for an example of this.
One final option might be to store stuff in localStorage (which has the benefit of being private on all platforms) and then pull it out of there when needed ... that means base64'ing all your images tho so that is a pretty big departure from just standard caching.
Caching is very much possible on Android OS. but on Apple as stated above there are limitations with the size of the images and cache size etc.
If you are willing to integrate and allow the caching on iOS you can use "cache manifest" to do so. but keep the draw backs and limitations in mind.
Also
if you want to save the file to Documents folder under my App, Apple will reject your App. The reason is the system backup all data under Documents folder to iCould after iOS6, so Apple does not allow big data like images or JSON file which could sync from your server again to keep in this folder.
So there is another work around which is good So one can use LocalFileSystem.TEMPORARY instead. It does not save the data to Library/Cache, but it save data to temp folder of App, which does not been auto backup to iCloud and not auto deleted either.
Regards
Rajeev