Kotlin findviewbyid in fragment

How to fetch resource id in fragment using kotlin in android?

In Android development, accessing resources such as string, drawable, etc. from a fragment can sometimes be challenging. One of the methods to access the resource is by fetching its id. This id can then be used to retrieve the resource. In this case, you are asking for the method to fetch resource id in a fragment using Kotlin in Android.

Method 1: Using Resources.getIdentifier()

To fetch a resource id in a fragment using Kotlin in Android, you can use the Resources.getIdentifier() method. This method takes three parameters: the resource name, the resource type, and the package name.

Here’s an example of how to use Resources.getIdentifier() to fetch a string resource in a fragment:

val resourceId = resources.getIdentifier("my_string_resource", "string", activity?.packageName) val myString = getString(resourceId)

In this example, we’re fetching a string resource with the name «my_string_resource». The second parameter, «string», indicates that we’re fetching a string resource. The third parameter is the package name, which we get from the fragment’s activity.

Here’s another example of how to use Resources.getIdentifier() to fetch a drawable resource in a fragment:

val resourceId = resources.getIdentifier("my_drawable_resource", "drawable", activity?.packageName) val myDrawable = ContextCompat.getDrawable(requireContext(), resourceId)

In this example, we’re fetching a drawable resource with the name «my_drawable_resource». The second parameter, «drawable», indicates that we’re fetching a drawable resource. We then use ContextCompat.getDrawable() to get a Drawable object from the resource id.

Overall, using Resources.getIdentifier() is a convenient way to fetch resource ids in a fragment using Kotlin in Android.

Method 2: Using R.id.resource_name

To fetch a resource ID in a fragment using Kotlin in Android, you can use the findViewById method with the R.id.resource_name syntax. Here are the steps to do it:

class MyFragment : Fragment()  override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?  return inflater.inflate(R.layout.fragment_my, container, false) > >

1. Inside the onCreateView method, you can use the findViewById method to get a reference to your view:

class MyFragment : Fragment()  override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?  val view = inflater.inflate(R.layout.fragment_my, container, false) val textView = view.findViewByIdTextView>(R.id.my_text_view) return view > >

class MyFragment : Fragment()  override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?  return inflater.inflate(R.layout.fragment_my, container, false).apply  val textView = findViewByIdTextView>(R.id.my_text_view) > > >

1. If you need to access the resource ID outside of the onCreateView method, you can store it as a property of your fragment class:

class MyFragment : Fragment()  private lateinit var textView: TextView override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?  return inflater.inflate(R.layout.fragment_my, container, false).apply  textView = findViewById(R.id.my_text_view) > > fun doSomethingWithTextView()  textView.text = "Hello, world!" > >

That’s it! With these steps, you can fetch a resource ID in a fragment using Kotlin in Android with the R.id.resource_name syntax.

Источник

Debugging Kotlin findViewById: The Essential Handbook

In Android development, UI design happens in an XML layout file. Then, the business logic code is written in a Kotlin or Java file. As a result, a basic activity (a single screen) is made up of two files. First is the activity layout XML file, and then there’s a Kotlin file that contains the business logic code.

To further explain the last statement, let’s take a look at an example. When you start the process for creating a new empty activity in Android Studio, you’ll get the following dialog:

Now, let’s walk through the above screenshot. The first field is where the name for the Kotlin file that’ll be associated with the new activity is specified. The second field specifies the name of the layout XML file. Once you click the Finish button, Android Studio will generate both files in their respective folders.

With all that said, what is findViewById()? And how’s it related to the XML and Kotlin files of an activity?

Well, the simple answer to both questions is that the findViewById() method provides a way for you to make reference to a View from within your Kotlin code. In other words, it binds Views to the Kotlin code. For example, you can use the method to get a reference to a TextView and then use that reference to change the text content of the View from your Kotlin code.

The Kotlin findViewById() method has been an important feature for working with Android activities for many years. And in this post, we’ll look at a comprehensive guide on how to debug Kotlin findViewById().

We’ll start by taking a look at an example of the findViewById() method in action.

Code Example of findViewById()

To demonstrate the findViewById() method in action, let’s walk through some code snippets for a layout XML and the associated Kotlin code.

First, we’ll start with the XML code.

The above code adds two Views to an activity. The first View is a TextView that displays the text “Hello World!” while the second is a button. Note down the IDs for both Views, as they’ll be used in the associated Kotlin code.

Next, we’ll look at some Kotlin code that interacts with the XML Views.

 lateinit var textView: TextView lateinit var button: Button override fun onCreate(savedInstanceState: Bundle?)

Here, there’s a reference to the two Views present in the XML layout. This was done using the findViewById() method and the correct ID for each View. For example, findViewById(R.id.button1) has the ID for the button as a parameter in findViewById. We also set the text value for the TextView to “Hi there!” using the reference. This was made possible thanks to the findViewById method.

Now that you’ve seen how Kotlin findViewById works, let’s dive into debugging the method.

Debugging Kotlin findViewById

In this section, we’ll look at common issues with the Kotlin findViewById method and how to debug them.

1. Invalid ID

Supplying an invalid ID as the parameter for the findViewById method can lead to critical errors, including crashes. Or in some cases, it can cause your app to behave in an unexpected way.

Android Studio will usually catch this type of error while compiling your code. The Android Studio IDE will also show an unresolved reference error message in the Kotlin file.

You can debug this error by cross-checking the layout file and verifying that the value of ID for the affected View is the same as what you entered in findViewById. If you notice any difference, you have two options for resolving the issue.

• The first option is to update the value for ID in your XML to the value in your Kotlin code.
• The second option is to change the reference for ID in findViewById to whatever value you have in the XML layout. In the case where there’s no ID specified for the View, the fix will be to set an ID property to it.

2. Referencing ID From Wrong XML File

The next error is referencing the wrong ID. This is different from the previous case in two ways:

1. In this case, the ID actually exists in your project.
2. Therefore, Android Studio won’t display any error message in the Kotlin file.

A wrong ID here means referencing an ID for Views from different layout XML files. For example, if activity_main.xml is the content View for MainActivity.kt, referencing a View from another XML file by default will cause this type of error. To reduce the chances of this error occurring, you should ensure that you’re referencing the correct View in the findViewById() method.

This type of error usually passes the compilation stage. As a result, you’re going to detect it while debugging your app on a device or emulator.

While running the app on a device or emulator, you’ll want to switch to the Logcat tab of Android Studio. Logcat will display information related to the error in a stack trace.

The above screenshot shows the Logcat after a crash caused by making reference to a wrong ID. The stack trace shows a NullPointerException and a very helpful message that specifies the line of code causing the error.

3. Referencing Views in Fragments

The third issue, which is also very common, occurs in Fragments. A fragment is a component for representing reusable parts of an app. It has its own layout file, a Kotlin file, and a life cycle. We can see fragments as mini activities because they can be inside an activity. It’s even possible to have multiple fragments in a single activity.

Although fragments and activities share some similarities, they implement the findViewById() differently. This difference makes the findViewById() method throw an unresolved reference error when used in the onCreate() method of a fragment. The screenshot below shows this error.

How can you resolve this issue? Place your code that uses the findViewById() method in the onViewCreated() method instead. This method isn’t present in the fragment class by default. For this reason, you’ll need to insert it by pressing CTRL + O, and then select onViewCreated from the options.

Below is an example code snippet showing the right way to use findViewById() in the onViewCreated method of a fragment.

 override fun onViewCreated(view: View, savedInstanceState: Bundle?)

4. False Positive Unresolved Reference

The last but not the least issue to debug is false positive errors and warnings. The ID parameter for findViewById is set using the “R” class. R is an auto-generated class, and it’s responsible for generating the actual integer value for a View’s ID.

Sometimes, Android Studio may experience issues synchronizing the current state of R. This leads to a false positive unresolved reference error. For example, it may happen after you add a new library to a project.

A quick fix is to navigate to Build -> Clean Project in Android Studio. This will initiate a Gradle task that cleans your project.