Jetpack Compose是什么?

Jetpack Compose 是安卓用于构建UI的一种新方式,采用代码而非xml文件方式，写法与Flutter非常相似。

官方主页：https://developer.android.google.cn/jetpack/compose

官方Demo：https://github.com/android/compose-samples/tree/master/JetNews

官方入门指导: https://developer.android.google.cn/jetpack/compose/tutorial

约束条件

1. Android Studio: 4.0及以上
2. 支持安卓版本:Android API 21(即5.0)及以上
3. 必须使用kotlin语言

优点

1. 代码更少 少了xml,少了activity和xml之间的关联.
2. 双向绑定 数据变化了,UI就自动变化.

缺点

1. 含有参数的Composable函数不能直接预览.
2. Composable函数必须添加@Preview注解才能预览.
3. 代码修改后,需要重新编译才能预览.
4. 目前还不完善,相比于Flutter,还处于幼儿园水平.
5. 相比于xml画页面布局,效率会有降低.

常见控件使用样例

1. 文本显示

Text(text = "众鸟高飞尽，孤云独去闲。相看两不厌，只有敬亭山。")

1. 文本输入框

val state = +state { "Text Field to input" }
TextField(
value = state.value,
onValueChange = { state.value = it }
)

1. 按钮

Button(text = "咬我啊", onClick = { Log.v("test", "被咬了") })

4.弹出框

MaterialTheme {
Column {
val openDialog = +state { false }

Button("Click me", onClick = {
openDialog.value = true
})

if (openDialog.value) {
AlertDialog(
onCloseRequest = {
openDialog.value = false
},
title = {
Text(text = "Alert Dialog Title")
},
text = {
Text("Alert Dialog content")
},
confirmButton = {
Button(
"Confirm",
onClick = {
openDialog.value = false
})
},
dismissButton = {
Button(
"Cancel",
onClick = {
openDialog.value = false
})
},
buttonLayout = AlertDialogButtonLayout.Stacked
)
}
}
}

1. 开关

MaterialTheme {
val checkedState = +state { true }
Switch(
checked = checkedState.value,
onCheckedChange = { checkedState.value = it }
)
}

1. 单选框

MaterialTheme {
RadioButton(selected = true,
onSelect = { }
)
}

1. 复选框

MaterialTheme {
val checkedState = +state { true }
Checkbox(
checked = checkedState.value,
onCheckedChange = { checkedState.value = it }
)
}

1. 单选框组

MaterialTheme {
val radioOptions = listOf("A", "B", "C")
val (selectedOption, onOptionSelected) = +state { radioOptions[0] }
RadioGroup(
options = radioOptions,
selectedOption = selectedOption,
onSelectedChange = onOptionSelected
)
}

9.图片

Container(modifier = Height(300.dp) wraps Expanded) {
Clip(shape = RoundedCornerShape(4.dp)) {
DrawImage(+imageResource(R.drawable.img_0))
}
}

源代码

https://github.com/cxyzy1/Jetpack-Compose-Demos

文章不易，如果大家喜欢这篇文章，或者对你有帮助希望大家多多，点赞，转发，关注 哦。文章会持续更新的。绝对干货！！！