Thursday, April 1, 2021

jetpack compose - LazyColumn scroll to position

MainActivity.kt

package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.lazy.*
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import kotlinx.coroutines.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            MainContent()
        }
    }


    @Composable
    fun MainContent(){
        val list = (1..100).map { it.toString() }
        val listState = rememberLazyListState()
        val coroutineScope = rememberCoroutineScope()

        Box(
            modifier = Modifier.fillMaxSize()
        ) {
            LazyColumn(
                state = listState,
                modifier = Modifier
                    .background(Color(0xFFFFFFFF))
                    .wrapContentHeight()
                    .fillMaxWidth(),
                contentPadding = PaddingValues(12.dp),
                verticalArrangement = Arrangement.spacedBy(8.dp)
            ) {
                items(list){ txt ->
                    Card(
                        backgroundColor = Color(0xFF88540B),
                        modifier = Modifier
                            .fillMaxWidth(),
                        elevation = 8.dp,
                        shape = RoundedCornerShape(16.dp)
                    ) {
                        Text(
                            text = txt,
                            fontWeight = FontWeight.Bold,
                            fontSize = 40.sp,
                            fontFamily = FontFamily.Cursive,
                            color = Color(0xFFFFFFFF),
                            textAlign = TextAlign.Center,
                            modifier = Modifier.padding(16.dp)
                        )
                    }
                }
            }

            Column(
                modifier = Modifier
                    .padding(16.dp)
                    .align(Alignment.CenterEnd),
                verticalArrangement = Arrangement.spacedBy(8.dp)
                ) {
                FloatingActionButton(
                    onClick = {
                        coroutineScope.launch {
                            listState.animateScrollToItem(24)
                        }
                    },
                    shape = RoundedCornerShape(50),
                    backgroundColor = Color(0xFF7BB661),
                ) {
                    Text(text = "25", color = Color.White)
                }
                FloatingActionButton(
                    onClick = {
                        coroutineScope.launch {
                            listState.animateScrollToItem(74)
                        }
                    },
                    shape = RoundedCornerShape(50),
                    backgroundColor = Color(0xFF7BB661),
                ) {
                    Text(text = "75", color = Color.White)
                }
            }
        }
    }


    @Preview
    @Composable
    fun ComposablePreview(){
        //MainContent()
    }
}