Add an Input Filter to the TextField in Android using Jetpack Compose
In Jetpack Compose, a TextField is a UI element that lets users type in text as an input. This input can then be stored and used for various desired functions. As TextField has no character restrictions, users can type in any character. However, there can be a system where the application would accept only certain characters as input. In such a case, we need to filter out those characters using the regex function. So in this article, we will show you how you could add an input filter to the TextField in Android using Jetpack Compose. Follow the below steps once the IDE is ready.
Step by Step Implementation
Step 1: Create a New Project in Android Studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. While choosing the template, select Empty Compose Activity. If you do not find this template, try upgrading the Android Studio to the latest version. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.
Step 2: Working with the MainActivity.kt file
Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.
Kotlin
package com.w3wiki.jcinputfilters import android.os.Bundle import androidx.activity.ComponentActivity import androidx.activity.compose.setContent import androidx.compose.foundation.layout.Arrangement import androidx.compose.foundation.layout.Column import androidx.compose.foundation.layout.fillMaxSize import androidx.compose.material.* import androidx.compose.runtime.* import androidx.compose.ui.Alignment import androidx.compose.ui.Modifier import androidx.compose.ui.graphics.Color class MainActivity : ComponentActivity() { override fun onCreate(savedInstanceState: Bundle?) { super .onCreate(savedInstanceState) setContent { // Creating a Simple Scaffold // Layout for the application Scaffold( // Creating a Top Bar topBar = { TopAppBar(title = { Text( "GFG | Input Filter" , color = Color.White) }, backgroundColor = Color( 0xff0f9d58 )) }, // Creating Content content = { // Creating a Column Layout Column(Modifier.fillMaxSize(), horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.Center) { // Creating a variable to remember text value var text by remember { mutableStateOf( "" ) } // Calling the function FilteredTextField FilteredTextField( text = text, onChanged = { text = it }, ignoredRegex = Regex( "[qwerty123]" ) ) } } ) } } } // Creating a function to create Filtered Text Field @Composable fun FilteredTextField( text: String, onChanged: (String) -> Unit, ignoredRegex: Regex ) { TextField(value = text, onValueChange = { if (!it.contains(ignoredRegex)) onChanged(it) } ) } |
Output:
You can see that we are able to filter out the programmed characters.