此函数具有具体化类型参数，因此只能在编译时内联，不能直接调用

Question

我有以下编译代码，但运行时崩溃

@Composable
fun Launcher() {
    val context = LocalContext.current
    LazyColumn(modifier = Modifier.fillMaxWidth(),
        horizontalAlignment = Alignment.CenterHorizontally) {
        item {
            context.StartActivityButton<LaunchedEffectActivity>()
        }
    }
}

@Composable
private inline fun <reified T : Activity>Context.StartActivityButton() {
    Button(onClick = {
        startActivity(Intent(this, T::class.java))
    }) {
        Text(T::class.toString())
    }
}

错误是

     Caused by: java.lang.UnsupportedOperationException: This function has a reified type parameter and thus can only be inlined at compilation time, not called directly.
        at kotlin.jvm.internal.Intrinsics.throwUndefinedForReified(Intrinsics.java:207)
        at kotlin.jvm.internal.Intrinsics.throwUndefinedForReified(Intrinsics.java:201)
        at kotlin.jvm.internal.Intrinsics.needClassReification(Intrinsics.java:219)
        at com.example.composesideeffects.ComposableSingletons$MainActivityKt.<clinit>(MainActivity.kt:52)
        at com.example.composesideeffects.MainActivity.onCreate(MainActivity.kt:25) 
        at android.app.Activity.performCreate(Activity.java:7994) 
        at android.app.Activity.performCreate(Activity.java:7978) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

我已经为我的 reified 使用了 inline。我错过了什么？

Answer 1

这似乎是一个错误，我建议你report it。

内联操作效果很好：

private inline fun <reified T : Activity> Context.startActivity() {
    startActivity(Intent(this, T::class.java))
}
// ..
Button(onClick = {
    context.startActivity<MainActivity>()
}) {

}

创建可组合函数作为 Context 的扩展对我来说似乎很奇怪：您可以在任何可组合项中获得 LocalContext.current。

以下是无需内联即可执行相同操作的方法：

@Composable
private fun StartActivityButton(activityClass: Class<*>) {
    val context = LocalContext.current
    Button(onClick = {
        context.startActivity(Intent(context, activityClass))
    }) {
    }
}

用法：

StartActivityButton(LaunchedEffectActivity::class.java)

此函数具有具体化类型参数，因此只能在编译时内联，不能直接调用

This function has a reified type parameter and thus can only be inlined at compilation time, not called directly

android

kotlin

kotlin-reified-type-parameters

android-jetpack-compose