android Jetpack Compose何时推出重组，重组内容是什么？

nxowjjhe  于 2022-11-27  发布在  Android
关注(0)|答案(1)|浏览(241)

在question中，色雷斯人告诉我 “如果你需要范围重组，你需要创建范围”。
我好像在官方文件上找不到这个政策。
代码A是基于色雷斯人的答案。当我运行代码A时，我得到结果A。
1：MyColumn(Calendar.getInstance().time.toSeconds())将于何时推出？
2：为什么CallMyColumn()只推出一次？

代码A

class SoundViewModel(): ViewModel() {
    var i = 0
    val a1: Flow<Int> = flow {
        while (true) {
            emit(i++)
            delay(500)
        }
    }

    val a2: Flow<Int> = flow {
        while (true) {
            emit(i)
            delay(2000)
        }
    }
}

@Composable
fun ScreenDetail(   
    mViewMode: SoundViewModel   
) {
    Column() {
        val b1=mViewMode.a1.collectAsState(initial = 0)
        val b2=mViewMode.a2.collectAsState(initial = 0)

        MyColumn("A: "+ b1.value.toString())
        MyColumn("B: "+ b2.value.toString())
        MyColumn("C: "+ "Hello")                          //It's only fired one time
        Log.e("My","D: World")
        MyColumn(Calendar.getInstance().time.toSeconds()) //I don't know when it is fired
        CallMyColumn()                                    //It's only fired one time
    }
}

@Composable
private fun MyColumn(counter:String){
    Column(modifier= Modifier.background(color =getRandomColor()).fillMaxWidth()) {
        Text(counter)
        Log.e("My",counter)
    }
}

@Composable
private fun CallMyColumn() {
     MyColumn("Call "+ Calendar.getInstance().time.toSeconds())
//    Column(modifier = Modifier.background(color = getRandomColor()).fillMaxWidth()) {
//        val s = "Call " + Calendar.getInstance().time.toSeconds()
//        Text(s)
//        Log.e("My", s)
//    }
}

fun getRandomColor() =  Color(
    red = Random.nextInt(256),
    green = Random.nextInt(256),
    blue = Random.nextInt(256),
    alpha = 255
)

fun Date.toSeconds():String{
    return SimpleDateFormat("yyyy/MM/dd HH:mm:ss", Locale.US).format(this)
}

结果A

2022-06-21 12:02:34.761 19237-19237/info.dodata.soundmeter E/My: A: 0
2022-06-21 12:02:34.761 19237-19237/info.dodata.soundmeter E/My: B: 0
2022-06-21 12:02:34.762 19237-19237/info.dodata.soundmeter E/My: C: Hello
2022-06-21 12:02:34.762 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:34.764 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:34
2022-06-21 12:02:34.765 19237-19237/info.dodata.soundmeter E/My: Call 2022/06/21 04:02:34
2022-06-21 12:02:34.849 19237-19237/info.dodata.soundmeter E/My: B: 1
2022-06-21 12:02:34.849 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:35.230 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:35.231 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:35
2022-06-21 12:02:35.365 19237-19237/info.dodata.soundmeter E/My: A: 1
2022-06-21 12:02:35.366 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:35.869 19237-19237/info.dodata.soundmeter E/My: A: 2
2022-06-21 12:02:35.870 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:36.365 19237-19237/info.dodata.soundmeter E/My: A: 3
2022-06-21 12:02:36.365 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:36.367 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:36
2022-06-21 12:02:36.871 19237-19237/info.dodata.soundmeter E/My: A: 4
2022-06-21 12:02:36.873 19237-19237/info.dodata.soundmeter E/My: B: 4
2022-06-21 12:02:36.873 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:37.368 19237-19237/info.dodata.soundmeter E/My: A: 5
2022-06-21 12:02:37.368 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:37.369 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:37
2022-06-21 12:02:37.872 19237-19237/info.dodata.soundmeter E/My: A: 6
2022-06-21 12:02:37.873 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:38.371 19237-19237/info.dodata.soundmeter E/My: A: 7
2022-06-21 12:02:38.371 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:38.373 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:38
2022-06-21 12:02:38.873 19237-19237/info.dodata.soundmeter E/My: A: 8
2022-06-21 12:02:38.873 19237-19237/info.dodata.soundmeter E/My: B: 8
2022-06-21 12:02:38.873 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:39.375 19237-19237/info.dodata.soundmeter E/My: A: 9
2022-06-21 12:02:39.375 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:39.377 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:39
2022-06-21 12:02:39.875 19237-19237/info.dodata.soundmeter E/My: A: 10
2022-06-21 12:02:39.875 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:40.375 19237-19237/info.dodata.soundmeter E/My: A: 11
2022-06-21 12:02:40.375 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:40.377 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:40
2022-06-21 12:02:40.861 19237-19237/info.dodata.soundmeter E/My: B: 12
2022-06-21 12:02:40.861 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:40.882 19237-19237/info.dodata.soundmeter E/My: A: 12
2022-06-21 12:02:40.882 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:41.401 19237-19237/info.dodata.soundmeter E/My: A: 13
2022-06-21 12:02:41.402 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:41.405 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:41
2022-06-21 12:02:41.898 19237-19237/info.dodata.soundmeter E/My: A: 14
2022-06-21 12:02:41.898 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:42.404 19237-19237/info.dodata.soundmeter E/My: A: 15
2022-06-21 12:02:42.404 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:42.408 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:42
2022-06-21 12:02:42.869 19237-19237/info.dodata.soundmeter E/My: B: 16
2022-06-21 12:02:42.869 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:42.895 19237-19237/info.dodata.soundmeter E/My: A: 16
2022-06-21 12:02:42.895 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:43.401 19237-19237/info.dodata.soundmeter E/My: A: 17
2022-06-21 12:02:43.401 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:43.402 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:43
2022-06-21 12:02:43.908 19237-19237/info.dodata.soundmeter E/My: A: 18
2022-06-21 12:02:43.908 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:44.426 19237-19237/info.dodata.soundmeter E/My: A: 19
2022-06-21 12:02:44.426 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:44.431 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:44
2022-06-21 12:02:44.873 19237-19237/info.dodata.soundmeter E/My: B: 20
2022-06-21 12:02:44.874 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:44.925 19237-19237/info.dodata.soundmeter E/My: A: 20
2022-06-21 12:02:44.925 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:45.426 19237-19237/info.dodata.soundmeter E/My: A: 21
2022-06-21 12:02:45.427 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:45.428 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:45
2022-06-21 12:02:45.927 19237-19237/info.dodata.soundmeter E/My: A: 22
2022-06-21 12:02:45.927 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:46.429 19237-19237/info.dodata.soundmeter E/My: A: 23
2022-06-21 12:02:46.429 19237-19237/info.dodata.soundmeter E/My: D: World
2022-06-21 12:02:46.430 19237-19237/info.dodata.soundmeter E/My: 2022/06/21 04:02:46
2022-06-21 12:02:46.878 19237-19237/info.dodata.soundmeter E/My: B: 24
2022-06-21 12:02:46.878 19237-19237/info.dodata.soundmeter E/My: D: World

新增内容：

色雷斯人：谢谢你！
我运行代码B并得到结果B。
我不知道为什么Log.e("My","Canvas "+ Calendar.getInstance().time.toSeconds())可以反复推出，请问？

代码B

//The other codes are same as Code A.

@Composable
private fun CallMyColumn() {
    MyColumn("Call "+ Calendar.getInstance().time.toSeconds())

    Canvas(
        modifier = Modifier
            .fillMaxSize()
            .padding(10.dp)
    ) {
        Log.e("My","Canvas "+ Calendar.getInstance().time.toSeconds())
    }
}

结果B

2022-06-21 17:38:53.026 11931-11931/info.dodata.soundmeter E/My: A: 0
2022-06-21 17:38:53.027 11931-11931/info.dodata.soundmeter E/My: B: 0
2022-06-21 17:38:53.028 11931-11931/info.dodata.soundmeter E/My: C: Hello
2022-06-21 17:38:53.028 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:53.030 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:53
2022-06-21 17:38:53.032 11931-11931/info.dodata.soundmeter E/My: Call 2022/06/21 09:38:53
2022-06-21 17:38:53.594 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:53
2022-06-21 17:38:54.171 11931-11931/info.dodata.soundmeter E/My: B: 1
2022-06-21 17:38:54.171 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:54.181 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:54
2022-06-21 17:38:54.239 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:54
2022-06-21 17:38:54.585 11931-11931/info.dodata.soundmeter E/My: A: 1
2022-06-21 17:38:54.585 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:54.593 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:54
2022-06-21 17:38:55.175 11931-11931/info.dodata.soundmeter E/My: A: 2
2022-06-21 17:38:55.175 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:55.176 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:55
2022-06-21 17:38:55.184 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:55
2022-06-21 17:38:55.423 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:55
2022-06-21 17:38:55.683 11931-11931/info.dodata.soundmeter E/My: A: 3
2022-06-21 17:38:55.684 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:55.711 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:55
2022-06-21 17:38:56.100 11931-11931/info.dodata.soundmeter E/My: B: 4
2022-06-21 17:38:56.100 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:56.104 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:56
2022-06-21 17:38:56.122 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:56
2022-06-21 17:38:56.183 11931-11931/info.dodata.soundmeter E/My: A: 4
2022-06-21 17:38:56.183 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:56.190 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:56
2022-06-21 17:38:56.692 11931-11931/info.dodata.soundmeter E/My: A: 5
2022-06-21 17:38:56.692 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:56.712 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:56
2022-06-21 17:38:57.195 11931-11931/info.dodata.soundmeter E/My: A: 6
2022-06-21 17:38:57.195 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:57.197 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:57
2022-06-21 17:38:57.207 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:57
2022-06-21 17:38:57.695 11931-11931/info.dodata.soundmeter E/My: A: 7
2022-06-21 17:38:57.695 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:57.704 11931-11931/info.dodata.soundmeter E/My: Canvas 2022/06/21 09:38:57
2022-06-21 17:38:58.118 11931-11931/info.dodata.soundmeter E/My: B: 8
2022-06-21 17:38:58.119 11931-11931/info.dodata.soundmeter E/My: D: World
2022-06-21 17:38:58.122 11931-11931/info.dodata.soundmeter E/My: 2022/06/21 09:38:58
android

1条答案

按热度按时间
enyaitl3

enyaitl31#

当State被读取时，它会触发最近作用域中的重组。作用域是一个没有用inline标记的函数，并返回Unit。列、行和框是inline函数，因此它们不会创建作用域。
来源
https://dev.to/zachklipp/scoped-recomposition-jetpack-compose-what-happens-when-state-changes-l78
https://www.jetpackcompose.app/articles/donut-hole-skipping-in-jetpack-compose
https://twitter.com/intelligibabble/status/1435676765725224964?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1435676765725224964%7Ctwgr%5E%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fwww.jetpackcompose.app%2Farticles%2Fdonut-hole-skipping-in-jetpack-compose
Jetpack Compose Smart Recomposition
Why does mutableStateOf without remember work sometimes?
修饰符也是如此。当它们读取没有lambda的状态时，它们也会被重组。
例如，当Modifier.offset()读取的状态发生变化时，Modifier.offset{}会重新组合，但是Modifier.offset{}会调用布局和绘制阶段。当您链接修饰符时，它们会创建一个CombinedModifier，任何链接的修饰符在组合阶段读取状态时，都会导致CombinedModifier的子部分发生变化，并在您的Composable中使用更新的Modifier进行重新组合。
https://developer.android.com/jetpack/compose/performance
我也有教程，涵盖了重组，智能重组，修改器重组和阶段。你可以检查出来，并发挥它太多，并看到效果。国家部分涵盖了这些主题。
https://github.com/SmartToolFactory/Jetpack-Compose-Tutorials

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