Navigation in Jetpack Compose. Button onClick issue-CodePudding

I have some program with 2 screens made in Compose. One of this screen have a button that makes transmission to another screen. All works good, if I put only this action on this Button's onClick method. But if I try to add something else, that should be made before changing screen, this navigate function no work anymore.

This way works:

Button(
    onClick = onNavigateToListUser
) {
    Text(text = "Add")
}

This way does not:

        Button(
            onClick = {
                if (firstName != "" && lastName != "") {
                    val user = User(uid = 555, firstName, lastName)
                    userDao.insert(user)
                    Log.d("MyDebug", ":"   user.firstName   " "   user.lastName)
                }
                Log.d("MyDebug", "Hey. Second Line")
                onNavigateToListUser
            }
        ) {
            Text(text = "Add")
        }

What is onNavigate...:

composable(route = DatabaseScreens.AddData.name) {
                AddDataScreen(
                    userDao,
                    onNavigateToListUser = { navController.navigate(DatabaseScreens.UserList.name) }
                )
            }

Any help would be appreciated.

CodePudding user response：

If you have defined the function doSomething: () -> Unit, you can use:

   onClick = doSomething
   onClick = { doSomething() }

In your 2nd case you have to use:

    onClick = {
          //if () { /* ... */ }
          onNavigateToListUser() //instead of onNavigateToListUser
    }

CodePudding user response：

In your second code

onClick = {
    ...
    onNavigateToListUser
}

Kotlin's lambda function regards the last line as the returned value, so this one actually returns a lambda function(onNavigateToListUser) instead of executing it. You need to call it dirictly.

onClick = {
    ...
    onNavigateToListUser()
    // or onNavigateToListUser.invoke()
}