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How to Use Android Data Binding - www.tumblr.com
Apr 11, · Android DataBinding provides a way to tie the UI with business logic allowing the UI values to update automatically without manual intervention. This reduces lot of boilerplate code in your business logic that you usually write to sync the UI when new data is available. DataBinding is one of the android architecture components suggested by android. Nov 01, · Traditionally, data binding involved inflating XML layout in the activity, finding the element in the layout by using a method such as findViewbyID, assigning the element to a local variable, getting value from the data, and, finally, assigning value to an element property. If you want to use two-way data binding with custom attributes, you need to work with the @InverseBindingAdapter and @InverseBindingMethod annotations. For example, if you want to enable two-way data binding on a "time" attribute in a custom view called MyView, complete the following steps.
Steps to download databinding android
The Data Binding Library is an Android Jetpack library that allows you to bind UI components in your XML layouts to data sources in your app using a declarative format rather than programmatically, steps to download databinding android.
This can reduce boilerplate code. In this codelab you'll learn how to:. The app has a single screen that shows some static data and some observable data, meaning that when the data changes, the UI will be automatically updated. The data is provided by a ViewModel. Here's a diagram:. If you're not yet familiar with the ViewModel class from the Architecture Components libraries, you can check out the official documentation. In summary, it's a class that provides UI state to the view Activity, Fragment, etc.
It survives orientation changes and acts as an interface to the rest of the layers in your app. Once the project is open, click in the toolbar to run the app. Once the build is complete and the app is deployed to your device or emulator, the default activity opens and looks like this:. This screen shows some data and lets the user click on a button to increment a counter and update a progress bar.
It uses SimpleViewModel. Open it and take a look. SimpleViewModel also lets the user increment the number of likes with the onLike method. While it doesn't have the most interesting functionality, SimpleViewModel is sufficient for this exercise.
On the other hand, the UI implementation found in the PlainOldActivity class has a number of problems:. With the Data Binding Steps to download databinding android you can fix all of these problems by moving logic out of the activity into places where it's reusable and easier to test. This project already has Data Binding enabled, but when you want to use it in your own projects the first step is to enable the library in the modules that will use it:.
It is a regular layout with a ConstraintLayout as the root element. You'll also have to move the namespace definitions the attributes that start with xmlns: to the new root element. Android Studio offers a handy way to do this automatically: Right-click on the root element, select Show Context Actionsthen Convert to data binding layout :.
Layout variables are used to write layout expressions. Here are some examples:. Check out a complete description of the language here. You'll learn how to deal with different layout expression types and attributes later on. The layout is ready but it's necessary to some changes in the activity. Open PlainOldActivity. What is the purpose of this variable? Binding classes are generated automatically by the library. To see what a generated steps to download databinding android looks like, open PlainActivitySolutionBindingand take a look around.
So far you've learned how to show data to the user, but with the Data Binding Library you can also handle user events and invoke actions on layout variables. The former onClick attribute used an unsafe mechanism in which the onLike method in the activity or fragment is called when the view is clicked. If a method with that exact signature doesn't exist, the app crashes. The new way is much safer because it's checked at compile time and uses a lambda expression to call the onLike method of the view model.
If you run the app you'll see that the button doesn't do anything. That's because you're not calling updateLikes anymore. In the next section, you'll learn to implement that properly. In the previous step, you created a static binding. If you open the ViewModel you'll find that name and lastName are just Strings, which is fine because they are not steps to download databinding android to change.
However, steps to download databinding android is modified by the user. Instead of explicitly updating the UI when this value changes, steps to download databinding android, make it observable. There are multiple ways to implement observability. You can use observable classesobservable fieldsor, the preferred way, LiveData. The full documentation on that is here. As you can see, a LiveData's value is set with the value property, and you can make one LiveData depend on another using Transformations.
This mechanism allows the library to update the UI when the value changes. LiveData is a lifecycle-aware observable so you need to specify what lifecycle owner to use, steps to download databinding android. You do this in the binding object, steps to download databinding android. If you rebuild the project you'll find that the activity is not compiling. We're accessing likes directly from the activity, which we don't need anymore:. Open PlainOldActivity and remove all the private methods in the activity and their calls.
The activity is now as simple as it gets. Let's bind the TextView showing the number of likes to the observable integer. Thus far, you've used attributes like android:onClick and android:text.
In the next section, you'll learn about other properties and create your own. When you bind a string or an observable string to an android:text attribute it's pretty obvious what's going to happen but how is it happening?
The library provides a huge amount of Steps to download databinding android Adapters. Check them out here. Here's an example for the android:text attribute:. There's no magic in Data Binding. Everything is resolved at compilation time steps to download databinding android it's accessible for you to read in the generated code. Open the BindingAdapters. It doesn't matter where you create them, the library will find them. In Kotlin, steps to download databinding android, static methods can be created by adding functions to the top level of a Kotlin file or as extension functions on the class.
Run the app and you'll see that the progress bar shows up when you click for the first time on the button. However, we still need to change its value and color:. For the progress value, we're going to use a Binding Adapter that takes the maximum value and the number of likes. Open the BindingAdapters file and look for this one:. This Binding Adapter is not used if any of the attributes are missing. This happens at compile time. The method takes 3 parameters now the view it applies to plus the number of attributes defined in the annotation.
We're binding the progressScaled attribute to the number of likes and we're just passing a literal integer to the max attribute. You'll find solutions in the BindingAdapters. You completed the codelab, so you should know how to create Data Binding layouts, add variables and expressions to it, use observable data, and make your XML layouts more meaningful with custom attributes via custom Binding Adapters.
Now check out the samples for more advanced usages and the documentation for the complete picture, steps to download databinding android.
5 Basic steps: Android Data Binding Tutorial in Kotlin
, time: 5:18Steps to download databinding android
The Android Support Library includes the Architecture Components, which you can use to design robust, testable, and maintainable apps. You can use the Architecture Components with the Data Binding Library to further simplify the development of your UI. Two-way data binding The Data Binding Library supports two-way data binding. Nov 01, · Traditionally, data binding involved inflating XML layout in the activity, finding the element in the layout by using a method such as findViewbyID, assigning the element to a local variable, getting value from the data, and, finally, assigning value to an element property. Jan 12, · If you want to use data binding and Kotlin, here are a few things to keep in mind: Data binding is a support library, so it can be used with all Android platform versions all the way back to Android (API level 7+). To use data binding, you need Android .
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