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compose逆向分析1

2022-12-13 by zhangyong

compose相关问题思考

compose函数为什么只能在compose函数中调用

Compose不是一个注解处理器。Compose 在 Kotlin 编译器的类型检测与代码生成阶段依赖 Kotlin 编译器插件工作，所以无需注解处理器即可使用 Compose。
这一注解更接近于一个语言关键字。作为类比，可以参考 Kotlin 的 suspend 关键 字。

Kotlin 的 suspend 关键字 适用于处理函数类型：您可以将函数、lambda 或者函数类型声明为 suspend。Compose 与其工作方式相同：它可以改变函数类型。

这里的重点是，当您使用 @Composable 注解一个函数类型时，会导致它类型的改变：未被注解的相同函数类型与注解后的类型互不兼容。同样的，挂起 (suspend) 函数需要调用上下文作为参数，这意味着您只能在其他挂起函数中调用挂起函数。

通过逆向解析compose的状态变化

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@Preview
@Composable
fun Counter() {
    Column() {
        println("1111")
        var count by remember { mutableStateOf(0) }
        println("2222")
        Button(
            onClick = {
                count++
            }
        ) {
            println("3333")
            Text(
                text = "$count"
            )
        }
        println("4444")
    }
}

启动输出

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I/System.out: 1111
I/System.out: 2222
I/System.out: 3333
I/System.out: 4444

点击按钮输出

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I/System.out: 3333

逆向代码

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public final class CounterKt {
  public static final void Counter(Composer paramComposer, int paramInt) {
    Composer composer = paramComposer.startRestartGroup(-2095581453);
    ComposerKt.sourceInformation(composer, "C(Counter)17@390L332:Counter.kt#ptgicz");
    if (paramInt != 0 || !composer.getSkipping()) {
      composer.startReplaceableGroup(-483455358);
      ComposerKt.sourceInformation(composer, "C(Column)P(2,3,1)76@3834L61,77@3900L133:Column.kt#2w3rfo");
      Modifier modifier = (Modifier)Modifier.Companion;
      MeasurePolicy measurePolicy = ColumnKt.columnMeasurePolicy(Arrangement.INSTANCE.getTop(), Alignment.Companion.getStart(), composer, 0 >> 3 & 0xE | 0 >> 3 & 0x70);
      composer.startReplaceableGroup(-1323940314);
      ComposerKt.sourceInformation(composer, "C(Layout)P(!1,2)74@2915L7,75@2970L7,76@3029L7,77@3041L460:Layout.kt#80mrfh");
      CompositionLocal compositionLocal1 = (CompositionLocal)CompositionLocalsKt.getLocalDensity();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object1 = composer.consume(compositionLocal1);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object1 = object1;
      CompositionLocal compositionLocal2 = (CompositionLocal)CompositionLocalsKt.getLocalLayoutDirection();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object2 = composer.consume(compositionLocal2);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object2 = object2;
      CompositionLocal compositionLocal3 = (CompositionLocal)CompositionLocalsKt.getLocalViewConfiguration();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object3 = composer.consume(compositionLocal3);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object3 = object3;
      Function0 function0 = ComposeUiNode.Companion.getConstructor();
      Function3 function3 = LayoutKt.materializerOf(modifier);
      int i = (0 << 3 & 0x70) << 9 & 0x1C00 | 0x6;
      if (!(composer.getApplier() instanceof androidx.compose.runtime.Applier))
        ComposablesKt.invalidApplier(); 
      composer.startReusableNode();
      if (composer.getInserting()) {
        composer.createNode(function0);
      } else {
        composer.useNode();
      } 
      composer.disableReusing();
      Composer composer1 = Updater.constructor-impl(composer);
      Updater.set-impl(composer1, measurePolicy, ComposeUiNode.Companion.getSetMeasurePolicy());
      Updater.set-impl(composer1, object1, ComposeUiNode.Companion.getSetDensity());
      Updater.set-impl(composer1, object2, ComposeUiNode.Companion.getSetLayoutDirection());
      Updater.set-impl(composer1, object3, ComposeUiNode.Companion.getSetViewConfiguration());
      composer.enableReusing();
      function3.invoke(SkippableUpdater.box-impl(SkippableUpdater.constructor-impl(composer)), composer, Integer.valueOf(i >> 3 & 0x70));
      composer.startReplaceableGroup(2058660585);
      composer.startReplaceableGroup(-1163856341);
      ComposerKt.sourceInformation(composer, "C78@3948L9:Column.kt#2w3rfo");
      if ((i >> 9 & 0xE & 0xB) != 2 || !composer.getSkipping()) {
        ColumnScope columnScope = (ColumnScope)ColumnScopeInstance.INSTANCE;
        composer.startReplaceableGroup(-125081623);
        ComposerKt.sourceInformation(composer, "C19@446L30,22@539L39,21@509L183:Counter.kt#ptgicz");
        if (((0 >> 6 & 0x70 | 0x6) & 0x51) != 16 || !composer.getSkipping()) {
          String str = LiveLiterals$CounterKt.INSTANCE.String$arg-0$call-println$fun-$anonymous$$arg-3$call-Column$fun-Counter();
          System.out.println(str);
          composer.startReplaceableGroup(-492369756);
          ComposerKt.sourceInformation(composer, "C(remember):Composables.kt#9igjgp");
          Object object = composer.rememberedValue();
          if (object == Composer.Companion.getEmpty()) {
            object = SnapshotStateKt.mutableStateOf$default(Integer.valueOf(LiveLiterals$CounterKt.INSTANCE.Int$arg-0$call-mutableStateOf$fun-$anonymous$$arg-0$call-remember$val-count$delegate$fun-$anonymous$$arg-3$call-Column$fun-Counter()), null, 2, null);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          object1 = object;
          object = LiveLiterals$CounterKt.INSTANCE.String$arg-0$call-println-1$fun-$anonymous$$arg-3$call-Column$fun-Counter();
          System.out.println(object);
          composer.startReplaceableGroup(1157296644);
          ComposerKt.sourceInformation(composer, "C(remember)P(1):Composables.kt#9igjgp");
          boolean bool = composer.changed(object1);
          object = composer.rememberedValue();
          if (bool || object == Composer.Companion.getEmpty()) {
            object = new CounterKt$Counter$1$1$1((MutableState<Integer>)object1);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          ButtonKt.Button((Function0)object, null, false, null, null, null, null, null, null, (Function3)ComposableLambdaKt.composableLambda(composer, 1051517913, true, new CounterKt$Counter$1$2((MutableState<Integer>)object1)), composer, 805306368, 510);
          object = LiveLiterals$CounterKt.INSTANCE.String$arg-0$call-println-2$fun-$anonymous$$arg-3$call-Column$fun-Counter();
          System.out.println(object);
        } else {
          composer.skipToGroupEnd();
        } 
        composer.endReplaceableGroup();
      } else {
        composer.skipToGroupEnd();
      } 
      composer.endReplaceableGroup();
      composer.endReplaceableGroup();
      composer.endNode();
      composer.endReplaceableGroup();
      composer.endReplaceableGroup();
    } else {
      composer.skipToGroupEnd();
    } 
    ScopeUpdateScope scopeUpdateScope = composer.endRestartGroup();
    if (scopeUpdateScope != null)
      scopeUpdateScope.updateScope(new CounterKt$Counter$2(paramInt)); 
  }
  
  private static final int Counter$lambda-4$lambda-1(MutableState<Integer> paramMutableState) {
    return ((Number)((State)paramMutableState).getValue()).intValue();
  }
  
  private static final void Counter$lambda-4$lambda-2(MutableState<Integer> paramMutableState, int paramInt) {
    paramMutableState.setValue(Integer.valueOf(paramInt));
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class CounterKt$Counter$1$1$1 extends Lambda implements Function0<Unit> {
    final MutableState<Integer> $count$delegate;
    
    CounterKt$Counter$1$1$1(MutableState<Integer> param1MutableState) {
      super(0);
    }
    
    public final void invoke() {
      int i = CounterKt.Counter$lambda-4$lambda-1(this.$count$delegate);
      CounterKt.Counter$lambda-4$lambda-2(this.$count$delegate, i + 1);
    }
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class CounterKt$Counter$1$2 extends Lambda implements Function3<RowScope, Composer, Integer, Unit> {
    final MutableState<Integer> $count$delegate;
    
    CounterKt$Counter$1$2(MutableState<Integer> param1MutableState) {
      super(3);
    }
    
    public final void invoke(RowScope param1RowScope, Composer param1Composer, int param1Int) {
      Intrinsics.checkNotNullParameter(param1RowScope, "$this$Button");
      ComposerKt.sourceInformation(param1Composer, "C27@631L51:Counter.kt#ptgicz");
      if ((param1Int & 0x51) != 16 || !param1Composer.getSkipping()) {
        String str = LiveLiterals$CounterKt.INSTANCE.String$arg-0$call-println$fun-$anonymous$$arg-9$call-Button$fun-$anonymous$$arg-3$call-Column$fun-Counter();
        System.out.println(str);
        TextKt.Text-fLXpl1I(String.valueOf(CounterKt.Counter$lambda-4$lambda-1(this.$count$delegate)), null, 0L, 0L, null, null, null, 0L, null, null, 0L, 0, false, 0, null, null, param1Composer, 0, 0, 65534);
        return;
      } 
      param1Composer.skipToGroupEnd();
    }
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class CounterKt$Counter$2 extends Lambda implements Function2<Composer, Integer, Unit> {
    final int $$changed;
    
    CounterKt$Counter$2(int param1Int) {
      super(2);
    }
    
    public final void invoke(Composer param1Composer, int param1Int) {
      CounterKt.Counter(param1Composer, this.$$changed | 0x1);
    }
  }
}

这里很乱，我们可以先看一个关键字 System.out.println ，我们打印日志的地方。
第一个关键字的位置

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composer.startReplaceableGroup(-492369756);
ComposerKt.sourceInformation(composer, "C(remember):Composables.kt#9igjgp");
Object object = composer.rememberedValue();
if (object == Composer.Companion.getEmpty()) {
object = SnapshotStateKt.mutableStateOf$default(Integer.valueOf(LiveLiterals$CounterKt.INSTANCE.Int$arg-0$call-mutableStateOf$fun-$anonymous$$arg-0$call-remember$val-count$delegate$fun-$anonymous$$arg-3$call-Column$fun-Counter()), null, 2, null);
composer.updateRememberedValue(object);
} 
composer.endReplaceableGroup();

startReplaceableGroup和endReplaceableGroup明显是一对组合，中间的代码貌似是执行了count的remember初始化动作。

第二个print的位置进行了button的onclick匿名内部类的初始化操作，也有一对start和end。
在end之后和最后一个print之前绘制button。

现在能分析出来的东西很少，感觉start和end做了一个标记，remember动作转化成了每次从composer读取内容，内容为空时进行一次初始化操作。

最后的scopeUpdateScope.updateScope执行了compose的刷新操作，这个刷新是怎么做的呢：

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@Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class CounterKt$Counter$2 extends Lambda implements Function2<Composer, Integer, Unit> {
    final int $$changed;
    
    CounterKt$Counter$2(int param1Int) {
      super(2);
    }
    
    public final void invoke(Composer param1Composer, int param1Int) {
      CounterKt.Counter(param1Composer, this.$$changed | 0x1);
    }
  }

原来就是重新执行一遍这个compose方法。Count的第二个参数表现奇怪，暂时不知道什么作用。

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composer.startReusableNode();
if (composer.getInserting()) {
composer.createNode(function0);
} else {
composer.useNode();
} 
composer.disableReusing();

node貌似是用来复用的。

接下来我们再看count这个state是怎么触发Text变化的。我们先找到CounterKt$Counter$1$2，Button的匿名内部类。发现

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TextKt.Text-fLXpl1I(String.valueOf(CounterKt.Counter$lambda-4$lambda-1(this.$count$delegate)), null, 0L, 0L, null, null, null, 0L, null, null, 0L, 0, false, 0, null, null, param1Composer, 0, 0, 65534);

继续

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private static final int Counter$lambda-4$lambda-1(MutableState<Integer> paramMutableState) {
    return ((Number)((State)paramMutableState).getValue()).intValue();
  }

这是什么逻辑呢？转化成这样大家应该能看懂了

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@Preview
@Composable
fun Counter3() {
    Column() {
        val count = remember { mutableStateOf(0) }
        LaunchedEffect(key1 = Unit) {
            delay(5000)
            count.value = 10
        }
        test3 { count.value }
    }
}

@Composable
fun test3(provider: () -> Int) {
    Text(
        text = "${provider.invoke()}"
    )
}

这里就能看出by的作用，它能减少state的影响范围。之前刘建分享的例子里state变化引起整个方法重组，这里通过by，把重组控制在了button内部。后面大家写的时候也可以观察下是不是这样。

第二个例子

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@Preview
@Composable
fun Counter1() {
    Column() {
        println("1111")
        var count by remember { mutableStateOf(0) }
        println("2222")
        Button(
            onClick = {
                count++
            }
        ) {
            println("3333")
            Text(
                text = "$count"
            )
        }
        println("4444")

        var count2 by remember { mutableStateOf(0) }
        println("5555")
        Button(
            onClick = {
                count2++
            }
        ) {
            println("6666")
            Text(
                text = "click"
            )
        }
        println("7777")
        Text(
            text = "$count2"
        )
        println("8888")
    }
}

count1的变化只会影响第一个button，count2呢，点击时输出的是：

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I/System.out: 1111
I/System.out: 2222
I/System.out: 3333
I/System.out: 4444
I/System.out: 5555
I/System.out: 7777
I/System.out: 8888

结论是引起整个方法重组，和scopeUpdateScope.updateScope是一致的。
贴一下逆向结果：

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public final class Counter1Kt {
  public static final void Counter1(Composer paramComposer, int paramInt) {
    Composer composer = paramComposer.startRestartGroup(-717625547);
    ComposerKt.sourceInformation(composer, "C(Counter1)17@391L703:Counter1.kt#ptgicz");
    if (paramInt != 0 || !composer.getSkipping()) {
      composer.startReplaceableGroup(-483455358);
      ComposerKt.sourceInformation(composer, "C(Column)P(2,3,1)76@3834L61,77@3900L133:Column.kt#2w3rfo");
      Modifier modifier = (Modifier)Modifier.Companion;
      MeasurePolicy measurePolicy = ColumnKt.columnMeasurePolicy(Arrangement.INSTANCE.getTop(), Alignment.Companion.getStart(), composer, 0 >> 3 & 0xE | 0 >> 3 & 0x70);
      composer.startReplaceableGroup(-1323940314);
      ComposerKt.sourceInformation(composer, "C(Layout)P(!1,2)74@2915L7,75@2970L7,76@3029L7,77@3041L460:Layout.kt#80mrfh");
      CompositionLocal compositionLocal1 = (CompositionLocal)CompositionLocalsKt.getLocalDensity();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object1 = composer.consume(compositionLocal1);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object1 = object1;
      CompositionLocal compositionLocal2 = (CompositionLocal)CompositionLocalsKt.getLocalLayoutDirection();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object2 = composer.consume(compositionLocal2);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object2 = object2;
      CompositionLocal compositionLocal3 = (CompositionLocal)CompositionLocalsKt.getLocalViewConfiguration();
      ComposerKt.sourceInformationMarkerStart(composer, 2023513938, "C:CompositionLocal.kt#9igjgp");
      Object object3 = composer.consume(compositionLocal3);
      ComposerKt.sourceInformationMarkerEnd(composer);
      object3 = object3;
      Function0 function0 = ComposeUiNode.Companion.getConstructor();
      Function3 function3 = LayoutKt.materializerOf(modifier);
      int i = (0 << 3 & 0x70) << 9 & 0x1C00 | 0x6;
      if (!(composer.getApplier() instanceof androidx.compose.runtime.Applier))
        ComposablesKt.invalidApplier(); 
      composer.startReusableNode();
      if (composer.getInserting()) {
        composer.createNode(function0);
      } else {
        composer.useNode();
      } 
      composer.disableReusing();
      Composer composer1 = Updater.constructor-impl(composer);
      Updater.set-impl(composer1, measurePolicy, ComposeUiNode.Companion.getSetMeasurePolicy());
      Updater.set-impl(composer1, object1, ComposeUiNode.Companion.getSetDensity());
      Updater.set-impl(composer1, object2, ComposeUiNode.Companion.getSetLayoutDirection());
      Updater.set-impl(composer1, object3, ComposeUiNode.Companion.getSetViewConfiguration());
      composer.enableReusing();
      function3.invoke(SkippableUpdater.box-impl(SkippableUpdater.constructor-impl(composer)), composer, Integer.valueOf(i >> 3 & 0x70));
      composer.startReplaceableGroup(2058660585);
      composer.startReplaceableGroup(-1163856341);
      ComposerKt.sourceInformation(composer, "C78@3948L9:Column.kt#2w3rfo");
      if ((i >> 9 & 0xE & 0xB) != 2 || !composer.getSkipping()) {
        ColumnScope columnScope = (ColumnScope)ColumnScopeInstance.INSTANCE;
        composer.startReplaceableGroup(-1147866453);
        ComposerKt.sourceInformation(composer, "C19@447L30,22@540L39,21@510L183,33@741L30,36@834L40,35@804L183,46@1020L44:Counter1.kt#ptgicz");
        if (((0 >> 6 & 0x70 | 0x6) & 0x51) != 16 || !composer.getSkipping()) {
          String str = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(str);
          composer.startReplaceableGroup(-492369756);
          ComposerKt.sourceInformation(composer, "C(remember):Composables.kt#9igjgp");
          Object object = composer.rememberedValue();
          if (object == Composer.Companion.getEmpty()) {
            object = SnapshotStateKt.mutableStateOf$default(Integer.valueOf(LiveLiterals$Counter1Kt.INSTANCE.Int$arg-0$call-mutableStateOf$fun-$anonymous$$arg-0$call-remember$val-count$delegate$fun-$anonymous$$arg-3$call-Column$fun-Counter1()), null, 2, null);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          MutableState<Integer> mutableState = (MutableState)object;
          object = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println-1$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(object);
          composer.startReplaceableGroup(1157296644);
          ComposerKt.sourceInformation(composer, "C(remember)P(1):Composables.kt#9igjgp");
          boolean bool = composer.changed(mutableState);
          object = composer.rememberedValue();
          if (bool || object == Composer.Companion.getEmpty()) {
            object = new Counter1Kt$Counter1$1$1$1(mutableState);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          ButtonKt.Button((Function0)object, null, false, null, null, null, null, null, null, (Function3)ComposableLambdaKt.composableLambda(composer, -12111205, true, new Counter1Kt$Counter1$1$2(mutableState)), composer, 805306368, 510);
          object = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println-2$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(object);
          composer.startReplaceableGroup(-492369756);
          ComposerKt.sourceInformation(composer, "C(remember):Composables.kt#9igjgp");
          object = composer.rememberedValue();
          if (object == Composer.Companion.getEmpty()) {
            object = SnapshotStateKt.mutableStateOf$default(Integer.valueOf(LiveLiterals$Counter1Kt.INSTANCE.Int$arg-0$call-mutableStateOf$fun-$anonymous$$arg-0$call-remember$val-count2$delegate$fun-$anonymous$$arg-3$call-Column$fun-Counter1()), null, 2, null);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          mutableState = (MutableState<Integer>)object;
          object = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println-3$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(object);
          composer.startReplaceableGroup(1157296644);
          ComposerKt.sourceInformation(composer, "C(remember)P(1):Composables.kt#9igjgp");
          bool = composer.changed(mutableState);
          object = composer.rememberedValue();
          if (bool || object == Composer.Companion.getEmpty()) {
            object = new Counter1Kt$Counter1$1$3$1(mutableState);
            composer.updateRememberedValue(object);
          } 
          composer.endReplaceableGroup();
          ButtonKt.Button((Function0)object, null, false, null, null, null, null, null, null, ComposableSingletons$Counter1Kt.INSTANCE.getLambda-1$app_debug(), composer, 805306368, 510);
          object = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println-4$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(object);
          TextKt.Text-fLXpl1I(String.valueOf(Counter1$lambda-8$lambda-5(mutableState)), null, 0L, 0L, null, null, null, 0L, null, null, 0L, 0, false, 0, null, null, composer, 0, 0, 65534);
          object = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println-5$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
          System.out.println(object);
        } else {
          composer.skipToGroupEnd();
        } 
        composer.endReplaceableGroup();
      } else {
        composer.skipToGroupEnd();
      } 
      composer.endReplaceableGroup();
      composer.endReplaceableGroup();
      composer.endNode();
      composer.endReplaceableGroup();
      composer.endReplaceableGroup();
    } else {
      composer.skipToGroupEnd();
    } 
    ScopeUpdateScope scopeUpdateScope = composer.endRestartGroup();
    if (scopeUpdateScope != null)
      scopeUpdateScope.updateScope(new Counter1Kt$Counter1$2(paramInt)); 
  }
  
  private static final int Counter1$lambda-8$lambda-1(MutableState<Integer> paramMutableState) {
    return ((Number)((State)paramMutableState).getValue()).intValue();
  }
  
  private static final void Counter1$lambda-8$lambda-2(MutableState<Integer> paramMutableState, int paramInt) {
    paramMutableState.setValue(Integer.valueOf(paramInt));
  }
  
  private static final int Counter1$lambda-8$lambda-5(MutableState<Integer> paramMutableState) {
    return ((Number)((State)paramMutableState).getValue()).intValue();
  }
  
  private static final void Counter1$lambda-8$lambda-6(MutableState<Integer> paramMutableState, int paramInt) {
    paramMutableState.setValue(Integer.valueOf(paramInt));
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class Counter1Kt$Counter1$1$1$1 extends Lambda implements Function0<Unit> {
    final MutableState<Integer> $count$delegate;
    
    Counter1Kt$Counter1$1$1$1(MutableState<Integer> param1MutableState) {
      super(0);
    }
    
    public final void invoke() {
      int i = Counter1Kt.Counter1$lambda-8$lambda-1(this.$count$delegate);
      Counter1Kt.Counter1$lambda-8$lambda-2(this.$count$delegate, i + 1);
    }
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class Counter1Kt$Counter1$1$2 extends Lambda implements Function3<RowScope, Composer, Integer, Unit> {
    final MutableState<Integer> $count$delegate;
    
    Counter1Kt$Counter1$1$2(MutableState<Integer> param1MutableState) {
      super(3);
    }
    
    public final void invoke(RowScope param1RowScope, Composer param1Composer, int param1Int) {
      Intrinsics.checkNotNullParameter(param1RowScope, "$this$Button");
      ComposerKt.sourceInformation(param1Composer, "C27@632L51:Counter1.kt#ptgicz");
      if ((param1Int & 0x51) != 16 || !param1Composer.getSkipping()) {
        String str = LiveLiterals$Counter1Kt.INSTANCE.String$arg-0$call-println$fun-$anonymous$$arg-9$call-Button$fun-$anonymous$$arg-3$call-Column$fun-Counter1();
        System.out.println(str);
        TextKt.Text-fLXpl1I(String.valueOf(Counter1Kt.Counter1$lambda-8$lambda-1(this.$count$delegate)), null, 0L, 0L, null, null, null, 0L, null, null, 0L, 0, false, 0, null, null, param1Composer, 0, 0, 65534);
        return;
      } 
      param1Composer.skipToGroupEnd();
    }
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class Counter1Kt$Counter1$1$3$1 extends Lambda implements Function0<Unit> {
    final MutableState<Integer> $count2$delegate;
    
    Counter1Kt$Counter1$1$3$1(MutableState<Integer> param1MutableState) {
      super(0);
    }
    
    public final void invoke() {
      int i = Counter1Kt.Counter1$lambda-8$lambda-5(this.$count2$delegate);
      Counter1Kt.Counter1$lambda-8$lambda-6(this.$count2$delegate, i + 1);
    }
  }
  
  @Metadata(k = 3, mv = {1, 7, 1}, xi = 48)
  static final class Counter1Kt$Counter1$2 extends Lambda implements Function2<Composer, Integer, Unit> {
    final int $$changed;
    
    Counter1Kt$Counter1$2(int param1Int) {
      super(2);
    }
    
    public final void invoke(Composer param1Composer, int param1Int) {
      Counter1Kt.Counter1(param1Composer, this.$$changed | 0x1);
    }
  }
}

更加复杂了，而且也看不出来为什么范围不一样。那么上第三个例子。

第三个例子

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@Preview
@Composable
fun Counter2() {
    Column() {
        println("1111")
        var count by remember { mutableStateOf(0) }
        println("2222")
        Button(
            onClick = {
                count++
            }
        ) {
            println("3333")
            Text(
                text = "$count"
            )
        }
        println("4444")
        test()
    }
}

@Composable
fun test() {
    var count2 by remember { mutableStateOf(0) }
    println("5555")
    Button(
        onClick = {
            count2++
        }
    ) {
        println("6666")
        Text(
            text = "click"
        )
    }
    println("7777")
    Text(
        text = "$count2"
    )
    println("8888")
}

这里单看test的逆向代码

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public static final void test(Composer paramComposer, int paramInt) {
    Composer composer = paramComposer.startRestartGroup(-981726729);
    ComposerKt.sourceInformation(composer, "C(test)38@785L30,41@866L32,40@840L147,51@1012L36:Counter2.kt#ptgicz");
    if (paramInt != 0 || !composer.getSkipping()) {
      composer.startReplaceableGroup(-492369756);
      ComposerKt.sourceInformation(composer, "C(remember):Composables.kt#9igjgp");
      Object object = composer.rememberedValue();
      if (object == Composer.Companion.getEmpty()) {
        object = SnapshotStateKt.mutableStateOf$default(Integer.valueOf(LiveLiterals$Counter2Kt.INSTANCE.Int$arg-0$call-mutableStateOf$fun-$anonymous$$arg-0$call-remember$val-count2$delegate$fun-test()), null, 2, null);
        composer.updateRememberedValue(object);
      } 
      composer.endReplaceableGroup();
      MutableState<Integer> mutableState = (MutableState)object;
      object = LiveLiterals$Counter2Kt.INSTANCE.String$arg-0$call-println$fun-test();
      System.out.println(object);
      composer.startReplaceableGroup(1157296644);
      ComposerKt.sourceInformation(composer, "C(remember)P(1):Composables.kt#9igjgp");
      boolean bool = composer.changed(mutableState);
      object = composer.rememberedValue();
      if (bool || object == Composer.Companion.getEmpty()) {
        object = new Counter2Kt$test$1$1(mutableState);
        composer.updateRememberedValue(object);
      } 
      composer.endReplaceableGroup();
      ButtonKt.Button((Function0)object, null, false, null, null, null, null, null, null, ComposableSingletons$Counter2Kt.INSTANCE.getLambda-1$app_debug(), composer, 805306368, 510);
      object = LiveLiterals$Counter2Kt.INSTANCE.String$arg-0$call-println-1$fun-test();
      System.out.println(object);
      TextKt.Text-fLXpl1I(String.valueOf(test$lambda-6(mutableState)), null, 0L, 0L, null, null, null, 0L, null, null, 0L, 0, false, 0, null, null, composer, 0, 0, 65534);
      object = LiveLiterals$Counter2Kt.INSTANCE.String$arg-0$call-println-2$fun-test();
      System.out.println(object);
    } else {
      composer.skipToGroupEnd();
    } 
    ScopeUpdateScope scopeUpdateScope = composer.endRestartGroup();
    if (scopeUpdateScope != null)
      scopeUpdateScope.updateScope(new Counter2Kt$test$2(paramInt)); 
  }

也有scopeUpdateScope.updateScope，执行结果也是只会在compose方法内重组。

几个想法，欢迎反驳

  1. 触发了重组不一定表示所有的组件重新绘制，print不是compose组件所以会打印，compose组件有记忆，value不变的情况下不会重复绘制。参考下方的位置记忆法。
  2. 非compose方法尽量在副作用代码块中执行，避免多次执行造成耗时。
  3. state.value的使用Laziness，减少state作用域。

用到了什么理论

Positional Memoization (位置记忆化)

https://effectiveandroid.substack.com/p/positional-memoization-in-jetpack

这块我的理解还不足，大家可以先看引用的文档尝试理解下，后面继续交流。

引用

https://juejin.cn/post/7103336251645755429
https://juejin.cn/post/6889797083667267598