A Toolbar in Android is an element present on the top of the application screen which generally displays the application name. In our example, we are creating a modified Toolbar i.e., Collapsing Toolbar that collapses when the application is scrolled down and holds up when scrolled up to the top. Below is the animation of how Collapsing Toolbar appears:
In this article, we will show you how you could create a Collapsing Toolbar 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.
package com.geeksforgeeks.jccollapsingtoolbar
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.Image
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.graphicsLayer
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.unit.dp
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 | Collapsing Toolbar" , color = Color.White) }, backgroundColor = Color( 0xff0f9d58 )) },
// Creating Content
content = {
// Creating a Column Layout
Column(Modifier.fillMaxSize(), horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.Center) {
// Creating a Scrollable list of 100 items
val items = ( 1 .. 100 ).map { "Item $it" }
val lazyListState = rememberLazyListState()
var scrolledY = 0f
var previousOffset = 0
LazyColumn(
Modifier.fillMaxSize(),
lazyListState,
) {
// Setting the Image as the first
// item and making it collapsible
item {
Image(
painter = painterResource(id = R.drawable.sample_image),
contentDescription = null ,
contentScale = ContentScale.FillWidth,
modifier = Modifier
.graphicsLayer {
scrolledY += lazyListState.firstVisibleItemScrollOffset - previousOffset
translationY = scrolledY * 0 .5f
previousOffset = lazyListState.firstVisibleItemScrollOffset
}
.height( 240 .dp)
.fillMaxWidth()
)
}
// Displaying the remaining 100 items
items(items) {
Text(
text = it,
Modifier
.background(Color.White)
.fillMaxWidth()
.padding( 8 .dp)
)
}
}
}
}
)
}
}
} |
Output:
In the below-recorded video, you can see that the Toolbar collapses when scrolled down and holds up when scrolled back to the top.