I just finished reading few some sparse tutorials on caching/offline and about making an Apps responsive when the user is not connected to the internet. It was quite interesting cause I have being wondering how some Apps have being doing that cause I was thinking it was some database manipulation.
I am relatively new to the caching mechanism and I really want to implement it in my next project cause I am still learning.
The few tutorials I have read talks about caching static files like pictures, .css files, .js files etc
My question is this;
**Question 1**
How do I cache Dynamic Files e.g I have an Apps when a User want to view their profile, I normally implement it by sending an Ajax request to the server to populate the profile page with pictures and other profile details (texts). How Do I cache these texts and pictures since they are dynamic?
**Question 2**
I am using different page (index.html, profile.html) JQuery Mobile mechanism, will this affect caching in any way because I have to refresh the page every time I am navigating to a new page so as to show my styling correctly?
This question may sound really noob but I really want to learn and I have read a lot about caching but these question were not addressed. I just hope somebody helps. thanks...
Answer is given based on my knowledge so far.
1) You can store / cache things with localStorage It's preety basic so won't take a lot of time or coding or mechanism to implement. Profile data, image as encoded string can be saved in localSorage. First you will save the profile data in localStorage. Then next time after app starts you can load data from the localStorage and also in the mean time you can make a async ajax call to server to check if data is modified. If so, then you can bring that data again and update localStorage.
2) If you use localStorage then page transitions won't be a matter until you reach the localStorage size limit of 5 mb.
Related
I'm developing an android app using Firebase back-end. Everything works fine, I have no problem whatsoever. The only problem is that, the data loading speed. Because it's a cloud-based system, sometimes it takes 4-5 (or even longer) seconds to load a user profile picture or simply to pull username from the database to display user. Now, you might say, well we don't even know how your data structure is stored in the no-SQL table but really I can't go wrong with that. I just structured it in a way that it's just a simple one read query. Or is it normal? Maybe Firebase loads data with some delay.
How you as other developers, get over this loading time? For example, I have a user picture, where the pic should be loaded from the Firebase database, but till pic is loaded, the image-view is just staying as a black view.
All of this depends on several factors that you can check.
Internet speed
Programming type
The size of the files (you probably need a lot of time to load for a
high volume file)
And another solution is to store the information you've previously received into the phone's memory(cache).
i have a question which i know its answers vary from one app to another.
consider an app like Telegram which you have a noticeably amount of data there like your contacts and chats. when you close the app and later you relaunch that, even if you don't have any connection to internet, app loads your contacts and chats and this is done in fraction of second. i want to know how these works are done and implemented?
for example they store all the data in disk in a file(storing that amount of data on disk can take long time moreover they cache images too), or we save each part of app in different files and we load them whenever user opens them.
You have two commonly used ways to store data in Android. SharedPreferences and local databases.
Before I continue, you should check out other articles regarding storing data on android. There are loads of them explaining it better and in-depth than what I can, I will just give some examples what you can use.
Start here or just google it!
SharedPreferences
SharedPreferences works in a Key -> Value, used for saving basic types of data. Good for storing user tokens, settings and similar things.
See more
Databases
Android uses SQLite for local data storage, and there are many libraries that can help you with this.
More notably Room, but there are other ones as well that are very popular to use. Databases are good for storing large amounts of data, like conversations and contacts in the example you are talking about.
Caching
You also have access to caching data, but keep in mind that it's meant as a temporary storage, and if you want to store something like user information or other complex data, you should stick to a database. Caching is useful for images.
This is called api data caching. It is important that we should know which data to be cached and which data should not be cached.
There is a library from NYtimes you can use it for api level caching with retrofit.
I'm developing a simple Android App where the user must fill in a very complex form, for which I believe it's much easier to use an HTML form than an Android Activity with tons of TextViews.
The data collected by the form must be sent to some remote database, and the application must be able to work offline.
I thought of two alternatives, the question is: which one would be better?
Let a WebView load a remote website with an offline manifest
Let a WebView load a local website in assets folder
My second question is related to the storage when offline, and once again I have two options, and I don't know which one is better:
Using the HTML5 local storage, and let HTML + javascript send data to the server when online again
Let my Android app catch the form data, and handle everything the Android way.
Any input will be very helpful. Thanks in advance.
Regarding the first question: depends on how often will you need to update your form. An online cached form can be updated quickly, while bundled pages are only updateable together with the app, and you will need to consider that both legacy and new clients can connect to your server at the same time (users will procrastinate updating).
Another aspect is portability. Do you envision an iOS version of your app, or perhaps a mobile site? If yes, then an HTML5 solution is definitely more portable. Also, debugging an app which is entirely HTML or entirely native is usually easier than a hybrid one -- you can stay within a single debugger.
Perhaps, one drawback of using HTML local storage inside WebView is that the data you save will be in a kind of a "black box" -- you will not be able to back it up easily.
[Added later] OK -- one drawback of putting your site into assets folder is that you'll have to use file: scheme in order to access it. This can lead to some cross-origin loading access related issues if you will try to mix your bundled content with content from the web. Check these WebView settings for example: setAllowFileAccessFromFileURLs, setAllowUniversalAccessFromFileURLs, setMixedContentMode.
My DataBase contains 1000's of images on server , I have to display these images in ListView in Android.
I have to develop similar List like that in the Flipcart app(If User Scroll then download Images) and store a local copy in SQlite and display from that SQlite database.
(In future if connectivity would not be there then also I would be able to run my app)
because Images will be available in SQlite.
Please suggest proper Solution for that.
Use of loaderManager or something else please suggest
I don't advise towards storing the images themselves in the SQLite database. The database will become slower to use and more cumbersome. Also, I think you should not implement such complex functionality yourself as there are many ready to use open source solutions.
There are a lot of solutions that allow you to cache the images on the file storage. They work transparently - when you request url they first check the local cache and only if this check does not exist they will make network call. Most of them also will display default thumbnail until the network call succeeds. Basically I think this is the best you can do.
I, myself have used Universal Image loader for what I describe, but out of this thread you can find many alternatives.
I'm a Webdev beginner, have been learning some Python/PHP/Javascript and want to help a friend of mine with a project.
She's conducting a large scale survey of old houses/windows, and fills in forms (similar to Google Forms). However, she doesnt always have 3G coverage on her phone, so she wants some way of uploading the data when she gets online, and she wants to be able to upload photos and attach these to the forms.
I've found a javascript-library which makes use of html5 localstorage, but I havent understood if localstorage also accepts file uploads? Also, when you have submitted one form you would need internet access to open up the form again to submit another form.
Are there libraries or projects around that would help me with some of this, so I dont have to reinvent the wheel?
This is going to be very difficult to do with a web app. Your going to have to rely on something like AJAX to send the data and if it times out store in local storage and keep retrying every few minutes, because a web app has no access to anything like checking the wifi status etc.
Also that there is a limit to the size you can use in html5 local storage:
What is the max size of localStorage values?
, this is not going to work if you want to hold onto photos.
This would require a native or minimum a hybrid app (like phonegap) to store the data on the actual device in a file or SQLite database. This way you can store what you like, have access to the status of the internet connection and even have prompts to appear on the screen (when the app is in the background) to remind her that there are still some that need to be uploaded.
It will be much more reliable and stable this way
You can create an app which stores the data (form) in the Local DB (ie SQLite) of the App.
Once she is online (mostly wifi) she can start uploading the data.