Hello World

Jetpack Compose刚推出不久，其应用前景还不明朗，在未来的很长一段时间内应该会和目前基于XML的UI并存，这里仅以一个小Demo作简单介绍。

删除原@Composable相关的代码，添加下面的代码。

package com.funcun.mobile.android.helloworld

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.sp
import com.funcun.mobile.android.helloworld.ui.theme.HelloWorldTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            HelloWorldTheme {

            }
        }
    }
}

@Composable
fun GreetingText(message: String, from: String, modifier: Modifier = Modifier) {
    Text(
        text = message,
        fontSize = 62.sp,
        lineHeight = 100.sp,
    )
    Text(
        text = from,
        fontSize = 36.sp
    )
}

@Preview(showBackground = true)
@Composable
fun GreetingPreview() {
    HelloWorldTheme {
        GreetingText(message = "Happy Birthday Bear！", from = "From Tom")
    }
}

修改后的代码

然后给GreetingText()方法中的两个Text()添加新的布局。

使用快捷方式

添加Row()布局

经过修改完善后，最终实现的代码如下。

package com.funcun.mobile.android.helloworld

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.res.stringResource
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 com.funcun.mobile.android.helloworld.ui.theme.HelloWorldTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            HelloWorldTheme {
                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
                    GreetingImage(
                        message = stringResource(R.string.hello_world),
                        from = stringResource(R.string.from_bear),
                        modifier = Modifier.padding(innerPadding)
                    )
                }
            }
        }
    }
}

@Composable
fun GreetingText(message: String, from: String, modifier: Modifier = Modifier) {
    // Column布局
    Column(verticalArrangement = Arrangement.Center, modifier = modifier) {
        Text(
            text = message,
            fontSize = 100.sp,
            lineHeight = 120.sp,
            textAlign = TextAlign.Center
        )
        Text(
            text = from,
            fontSize = 40.sp,
            // 仅应用于“from”
            modifier = Modifier
                .padding(20.dp)
                // align单独控制子级可组合项的位置，使其不受父布局强制执行的对齐布局规则的约束
                // .align(alignment = Alignment.End)
                .align(alignment = Alignment.CenterHorizontally)
        )
    }
}

@Composable
fun GreetingImage(message: String, from: String, modifier: Modifier = Modifier) {
    val image = painterResource(R.drawable.launcher_background)
    Box(modifier) {
        Image(
            painter = image,
            contentDescription = null,
            contentScale = ContentScale.Crop,
            alpha = 0.5F
        )
        GreetingText(
            message = stringResource(R.string.hello_world),
            from = stringResource(R.string.from_bear),
            // 应用于整个GreetingText()
            modifier = Modifier
                .fillMaxSize()
                .padding(8.dp)
        )
    }
}

@Preview(showBackground = true)
@Composable
fun GreetingPreview() {
    HelloWorldTheme {
        // GreetingText(message = "Happy Birthday Bear！", from = "From Tom")
        GreetingImage(
            message = stringResource(R.string.happy_birthday_sam),
            from = stringResource(R.string.from_bear)
        )
    }
}

完工之后，效果是这样的。

完工后的效果

---

感谢支持

更多内容，请移步《超级个体》。