When one of your project requirements is to have an offline mode where users can still use the app and information even without a connection, there are different ways to go about this. In this article we will build an Ionic 4 app with offline mode that caches API data so it can be used as a fallback later. Also, we create an offline manager which stores requests made during that time so we can later send out the calls one by one when we are online again.
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To test our API calls we will simply use the service reqres. First of all we need to know whether we are currently connected to a network or not. At this point you can also show a toast like we do or use any other mechanism to inform the user that the connection has changed.
The base for this service comes actually from one old Ionic Forum thread and I just made some additions to it! Now we can see if we are online right now or not, and we will use this information to store important requests made during the time when we are offline. But if the user wants to perform other CRUD like operations you might want to keep track of that.
The difficulty here is of course that you would not only store the request but also perform the operation locally already upfront which might or might not work for your. Our next service can store a request which will be called from another service later as an object with some information that you decide right to our Ionic storage. This means, while we are offline an array of API calls is created that we need to work off later.
This task is done by the checkForEvents function that will later be called whenever the user is back online. I tried to keep this service as general as possible you can stick it into your own projects! Within our check function we basically get the array from the storage and send out all the requests one by one and finally delete the stored requests again.
The function will return a result once every operation is finished so if you need to wait for the historic data to be sent, you can subscribe to the check and be sure that everything is finished when you continue!
The goal was to make API calls, return locally cached data when we are offline and also store some requests that you identify as important locally with our offline manager and requests queue until we are back online. First of all we can check the internet connection inside our functions to see if we are maybe offline in which case we either directly return the cached result from our storage or otherwise store the PUT request within our offline manager so it can be performed later on.
They basically help us to transform our Observable data because we are often working with the Ionic Storage which returns a Promise and not an Observable. Back to topic. If we are online, our requests run through as desired and for a GET we store that information to our storage, for the important PUT we might want to catch any error case and store it locally then. This is a general assumption and of course you should not store any failed request! Quite a lot of code for not seeing any results on the screen.
But those 3 services are more or less a blueprint for your offline mode app so you can plug it in as easy as possible. Again, once the Observable of checkForEvents returns we can be sure that all local requests have been processed. Now we just need to get the real data by building tiny view and a simple page that makes the API calls.
There are not really any more words needed, we just use our service to get data or update data. We add a refresher to have some force refresh mechanism in place still, returning cached data when offline! You can kill the app and start it again, the results will be retrieved from the storage and your offline manager requests queue just grows whenever you try to make the PUT request when your are offline until you come back online again.
In general caching is a bit tricky and there are not super many out of the box plugins that work for everyone. Share Load our packages into the app module. HttpClientModule ]. StatusBar. SplashScreen .One of the most common things that I see people get tripped up on when learning Ionic is the difference between synchronous and asynchronous tasks and how to appropriately handle results from an asynchronous task.
In this article, I am going to discuss the difference between asynchronous and synchronous code, and some common situations that you might run into in an Ionic application.
That means that if you had a program that looked like this:. These functions would be called in the order that they appear, but since someAsynchronousFunction will be executing some asynchronous code, both of the synchronous functions will finish their tasks before someAsynchronousFunction finishes executing its tasks.
Any asynchronous tasks are placed in the event queue to be executed later and any synchronous tasks are placed in the stack to be executed right away. The end result is that asynchronous tasks in your application will finish after synchronous tasks, even if they were called first. One of the first times people run into issues with asynchronous code is with the Ionic Storage service. When retrieving data from storage using the get method, an asynchronous request is made to load the data.
Instead of returning the data directly, the get method will return a Promise that resolves with the data when the asynchronous task has completed. This adds a handler for when the Promise that get returns resolves, and it will log the data that the promise resolves with to the console.
This will work because the console. However, this can lead to more confusion. Once people understand that they need to handle the response in this manner, they may try to do something like this:. The promise is being handled correctly and the result is being assigned to this.
Since the get call is asynchronous, and the console. So, even though there is some appropriate handling of the asynchronous function, we are still attempting to access it in a synchronous manner which will not work no matter how you structure it. In order for it to work, whatever it is that is making use of the result must be triggered from inside of the.
You may also run into this situation with Observables, the concept is pretty much the same but it looks a little different. In this case, people run into trouble with observables initially when attempting to use the Http service. For example, people may do something like this:. Again, it looks reasonable enough but the get method is asynchronous and it will return an Observable, not the data that is being loaded in from the server.
The correct way to handle an observable is like this:. The way in which this is handled is very similar to a promise, except that we subscribe to the Observable. There are a few more differences between Observables and Promises, but not much more you need to know in the context of this tutorial. This is the same situation where the get call is asynchronous, but the console. So, even though the get request is launched first, the console.
I think the example of making HTTP requests is a little more obvious because it is somewhat intuitive to know that you are not going to instantly be able to access something that you are loading from a server. However, even code you execute completely locally can still be asynchronous and it may not be so obvious that the code is being executed later. Follow me on Twitter or subscribe to me on YouTube for more web development content. Angular Tutorials Ionic Tutorials.
That means that if you had a program that looked like this: someSynchronousFunction ; someAsynchronousFunction ; someOtherSynchronousFunction. Check out my latest videos:.This time we will build an expense management app, which stores income and expense data. The table will look like this. We assume that you have installed Node. To make sure everything is up to date, type this command in the terminal or Node command line. As usual, we start tutorial from scratch or from zero.
In the terminal or Node command line type this command to create a new Ionic 3 and Angular 4 app with the name "ionic3-sqlite". Make sure you are in your projects folder. Two imports of Add and Edit data required new pages for add and edit data that will be added later. Add this variable for an array of expenses, total income, total expense and balance before the constructor.
The add button is presented by a plus button on the navigation bar. The Edit and Delete button will show by sliding list item to the left. Before running the Ionic 3, Angular 4 and SQLite app on the device, remove and add the platforms first. That it's, We know this tutorial using unclean code. Maybe you can write better code than this example. You can get the full source code on our GitHub.
We know that building beautifully designed Ionic apps from scratch can be frustrating and very time-consuming. That just the basic. If you need more deep learning about Ionic, Angular, and Typescript, you can find the following books:. Toggle navigation. NET Core. All Articles.Offline data sync is a client and server SDK feature of Azure Mobile Apps that makes it easy for developers to create apps that are functional without a network connection.
When your app is in offline mode, you can still create and modify data, which are saved to a local store. When the app is back online, it can synchronize local changes with your Azure Mobile App backend. The feature also includes support for detecting conflicts when the same record is changed on both the client and the backend.HOW TO SYNC SQLite DATA TO MySQL DATABASE ONLINE IN ANDROID
Conflicts can then be handled either on the server or the client. The following tutorials show how to add offline sync to your mobile clients using Azure Mobile Apps:. These APIs connect directly to the Azure Mobile App backend and fail if the client device does not have a network connection. Before any sync table operations can be performed, the local store must be initialized. A local store is the data persistence layer on the client device.
On iOS, it is based on Core Data. For more information, see Universal Windows Platform: Enable offline sync. Developers can also implement their own local store. For instance, if you wish to store data in an encrypted format on the mobile client, you can define a local store that uses SQLCipher for encryption.
Android Sync SQLite Database with Server using PHP and MySQL
A sync context is associated with a mobile client object such as IMobileServiceClient or MSClient and tracks changes that are made with sync tables. The sync context maintains an operation queuewhich keeps an ordered list of CUD operations Create, Update, Delete that is later sent to the server.
A local store is associated with the sync context using an initialize method such as IMobileServicesSyncContext. InitializeAsync localstore in the. When using sync tables, your client code controls when local changes are synchronized with an Azure Mobile App backend. Nothing is sent to the backend until there is a call to push local changes.
Similarly, the local store is populated with new data only when there is a call to pull data. Push : Push is an operation on the sync context and sends all CUD changes since the last push. Note that it is not possible to send only an individual table's changes, because otherwise operations could be sent out of order. Pull : Pull is performed on a per-table basis and can be customized with a query to retrieve only a subset of the server data.
Implicit Pushes : If a pull is executed against a table that has pending local updates, the pull first executes a push on the sync context. This push helps minimize conflicts between changes that are already queued and new data from the server.
Incremental Sync : the first parameter to the pull operation is a query name that is used only on the client. Each time a pull operation returns a set of results, the latest updatedAt timestamp from that result set is stored in the SDK local system tables. Subsequent pull operations retrieve only records after that timestamp.
To use incremental sync, your server must return meaningful updatedAt values and must also support sorting by this field. However, since the SDK adds its own sort on the updatedAt field, you cannot use a pull query that has its own orderBy clause. The query name can be any string you choose, but it must be unique for each logical query in your app.Free and open source, Ionic offers a library of mobile-optimized UI components, gestures, and tools for building fast, highly interactive apps.
Start with ready-made components, typography, and a gorgeous base theme that adapts to each platform. Ionic enables web developers to ship apps to the app stores and as a PWA with a single shared code base. Create, build, test, and deploy your app with a powerful CLI. Access features like Live Reload, cross-platform deployments, and integrations. Ionic is built to perform and run fast on the all of the latest mobile devices.
Build out-of-the-box blazing fast apps with a small footprint and built-in best practices like hardware accelerated transitions, touch-optimized gestures, pre-rendering, and AOT compiling.
Power-up your app workflow with integrations into your favorite stacks. We just need some basic information so we can send the eBook your way. Log in Sign up. Toggle navigation. Ionic Framework 5 Design. Learn the differences between hybrid and native apps. We break down all the myths and misconceptions.
Read our Book. Performance obsessed Build fast appsfaster than before. Native Power Access core native device functionality.Assume we have to send some information from the application to our webserver and internet is not available on the device at a particular time. So instead of giving error to the user that internet is not available we can store the data to SQLite and send it later automatically when the internet is available.
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Ionic 3, Angular 4 and SQLite CRUD Offline Mobile App
In this blog I write tutorials and articles related to coding, app development, android etc. Hi there! I tried your code. I was able to launch the app on my ADV on android studio and to save data in local on sqllite but I was not able to sync data from sqlite to my mysql server. Maybe I wrong something…. What should I verify? I am still unable to find the problem.
Data is getting saved only in sqlite. I have also changed the url to my php file. Fix following constants according to your hosting params. Thanks for the code, Its work on my localhost but why can not work when i am upload to cpanel server the data can not update can you tell me why sir?? I have a situation where I want to initialize my app with data from mysql only when the app is installed for the first time.
The problem I run into however is that, when using volley in the onCreate of SQLiteOpenHelper class, the app starts before the network request completes. This results in blank screen for the first time. What can I do to make sure the UI only runs after network request is complete? Why is it not working in me?GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. Automatic data sync when a connection becomes available can create its own issues. What is needed is a simple and controlled method for performing Bi-Directional Synchronisation.
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Sign up. With this framework your application can work completely offline Airplane Modethen perform an automated Bidirectional Synchronization when an internet connection becomes available.
Java Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. Latest commit. Latest commit 2be Feb 24, The time has come for mobile app developers to accept reality. You signed in with another tab or window. Reload to refresh your session.