MainActivity.kt

package com.lahsuak.apps.jetpackcomposebasic

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.animation.core.LinearEasing
import androidx.compose.animation.core.animateFloat
import androidx.compose.animation.core.infiniteRepeatable
import androidx.compose.animation.core.rememberInfiniteTransition
import androidx.compose.animation.core.tween
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.drawBehind
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Brush
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.TileMode
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.text.TextStyle
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.sp
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.JetPackComposeBasicTheme
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.lightBlue
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.lightGreen
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.lightPink
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.lightPurple
import com.lahsuak.apps.jetpackcomposebasic.ui.theme.lightYellow

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            JetPackComposeBasicTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    Box(modifier = Modifier.fillMaxSize()) {
                        Greeting("Android", modifier = Modifier.align(Alignment.Center))
                    }
                }
            }
        }
    }
}

@Composable
fun Greeting(name: String, modifier: Modifier) {
    val fontSize = 48.sp
    val currentFontSizePx = with(LocalDensity.current) { fontSize.toPx() }
    val currentFontSizeDoublePx = currentFontSizePx * 2

    val infiniteTransition = rememberInfiniteTransition(label = "text animation")
    val offset by infiniteTransition.animateFloat(
        initialValue = 0f,
        targetValue = currentFontSizeDoublePx,
        animationSpec = infiniteRepeatable(tween(3000, easing = LinearEasing)),
        label = "text animate"
    )
    val brush = Brush.linearGradient(
        colors = listOf(lightGreen, lightBlue, lightPink, lightPurple),
        start = Offset(offset, offset),
        end = Offset(offset + currentFontSizePx, offset + currentFontSizePx),
        tileMode = TileMode.Mirror
    )
    Text(
        text = "Hello $name Dev!, What are you doing?",
        style = TextStyle(
            fontFamily = FontFamily.Serif,
            brush = brush
        ),
        fontSize = fontSize,
        modifier = modifier,
        textAlign = TextAlign.Center
    )
}

@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
    JetPackComposeBasicTheme {
        Greeting("Android", modifier = Modifier)
    }
}