I should hook UIResponder of every app, including SpringBoard and any others. In the hooking, I will write something to the specified file. If I set the path to /var/mobile/Library/MyApp, recommended by Cydia, I found that only the SpringBoard and MyApp could write successfully.
So is there a place every app can write and read?
I admit that I'm not 100% sure on this one, but my guess would be no, there is not a path that every app can writes files to on a jailbroken iPhone.
Certainly, jailbreak apps (installed in /Applications/) on a jailbroken phone can write to locations that can be shared between those jailbreak apps. But, as I understand your question, you would like to inject code into normal, App Store apps, so that those apps can also read and write to the shared location. That part I don't think is possible, because jailbreaking does not completely disable the sandbox for 3rd-party apps installed normally, under /var/mobile/Applications/.
Now, there might be a workaround. There are some shared folders that are accessible to all apps for certain purposes. For example, any app can write images to the saved photos album. What you could try is to take the content of the file you want to write, and encode it as fake image data, in a UIImage (e.g. with [UIImage imageWithData:]). You'd probably need to add a valid image header to the data. Then, you save the file to the photos album, using something like
writeImageToSavedPhotosAlbum:orientation:completionBlock:.
Another app could then find the fake photo by enumerating the saved photos album, and then converting the asset back to image representation to pull the real data back out.
However, this seems quite complicated, and possibly wouldn't work (I haven't tried it). Perhaps you could tell us why you want this shared file. Maybe there's a better way to share the data, without using a globally-accessible file?
Notifications can help you with this. Every app will send interprocess notifications about the events. You could start a daemon that will listen for this notifications and save them in a file. Or you could listen for them in SpringBoard as he can write, for example, to /var/mobile/Media. Depends on what you want to do with this file. Check out my answer here How to create a global environment variable that can be accessed by SpringBoard or other applications in the jailbroken iPhone?
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I am after some suggestions on how to reduce the final app size that gets submitted to apple?
Or is there any way to have stuff download after the app is isntalled? so that we can keep the app under 20 meg, but then the app downloads the rest of the program after the user has installed it and run the application?
ta
Daz
If your application uses a lot of image resources, your application could download those images instead of building them into the application.
Theoretically possible. Your app can access the file system, so it can make and save, and later read files.
The deal-breaker I see is that for most purposes, Apple probably wouldn't allow it.
They test the program as-is when you submit it, and they'll notice that it just sits there and tries to download a bunch of stuff from your server. If this takes more than, say, 30 seconds, they'll reject it for usability problems.
If the content downloaded could have been bundled with the program, they'll probably have a problem with that. If you could argue that the downloaded content changes rapidly and is a feature of your app, it might fly, but only if you keep it small..
Sure this is totally possible. Since it is most likely some sort of media that is causing a large file size, either images, video, or audio, you could definitely download them after the fact or supply a download button for users to add these features as "extra" content, if they are not critical to the operation of your app.
One thing to consider is that some users are not on an unlimited data plan. So for politeness, they should know what you are doing.
Also, if you are just over the limit, you might also be able to ship the application with the resources in a zip archive and then decompress the archive in the Documents directory.
In many applications images take lion share of the download size, and they can be greatly reduced with ImageAlpha and ImageOptim.
Check out this case study halving download size of Tweetbot by converting images to a more efficient PNG variant.
I want to make an app that runs in the background so that if a user is reading a web page or PDF file on an iPhone or iPad, he can mark some words, see the meaning of those words, and then have those words stored in the app's database. He can then afterwards look for the words which he has learnt and increase his vocabulary.
Does the iOS 4 API allow that? What are the limitations? Advantages? Disadvantages?
Thanks in advance
No is does not, you can only run voip. audio or navigation apps in the background.
Only one app can run at a time, and installing one app cannot effect any built in app. So no, there is no way to achieve what you are trying for here.
Your best bet is to instruct users to copy the word, open the app, and then you can snag whatever is on the clipboard then.
(Note there are multitasking APIs, but you still cant access anything outside of your app even if you convince the OS to let you run in the background for a little while)
What I'm building is simply an application that fetches data over the web and displays them on the iOS views. Data are text and, sometimes, images / music files / movies.
I'd like to use some caching solution for the media. What it needs to do is:
get an url of the file
check if it's alredy downloaded in the cache storage, if it is, serve it
if not, download it
while also checking how much of the storage the current cache uses, and, if it's over the quota, delete oldest files
Best would be to have a simple interface for this - so I can just give an url and get the file of it (while files can change over time and reside on the same URL, so this should be handled too, in a perfect case).
Anyone knows a library to do it, on iPhone/iPad application?
ASIHttpRequest has a DownloadCache option that may work for you. From their documentation:
* You want to have access to the data when there is no internet connection and you can't download it again
* You want to download something only if it has changed since you last downloaded it
* The content you are working with will never change, so you only want to download it once
This is what I used in my iPad app and it works pretty well.
You could try looking at using a UIWebview for the view. If I am understanding this correctly, you will be hosting your content on a web server and would simply like the iOS device to pull the content from the URL. This is what UIWebview is. It is essentially programmable access to Safari.
I have been asked to write a compliment website/service for an iPhone app.
The app creates images. The author wants these images to be uploaded onto the server, into their personal storage area. These images need to be able to be pulled down to the iPhone later for editing. The user will be able to use the website as well to see these images.
I have yet to decide (or understand) what the best way of implementing this would be. And with no experience with iPhone development I have no idea what it can actually handle.
Uploading and downloading images is trivial using NSURL and associated classes. You just open the URL, write/read the file and you're done.
See The URL Loading System to get started.
Is there a way to have an app write a into a file and then have another app read from that file?
I mean writting into the file system of the iPhone.
I want to do this without using an internet connection. So uploading the file and then downloading from the other app is not what i mean.
Thanks!
It appears that there are ways you can, but it won't get approved by Apple if you do.
See http://blogs.oreilly.com/iphone/2008/09/sandbox-think-like-apple.html for more information.
The current sand boxing of applications does not allow this, however it appears that this may be available in future iPhone OS versions. Reference
I'm not sure exactly what circumstances you're in here, but you could register app B as a handler for a particular protocol, and have app A try to open such a link (e.g. appB://yourinfohere). It depends on how much data you want to transfer and many other things, but it might work.