Android compose onClick being called before click

Question

I'm having issues whit the onClick on Jetpack compose, it performs the click as soon as I run the app and after returning to this activity the button stops working. Any insights?

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            val context = LocalContext.current
            linkButton("Go to text views", goTo(context, TextViewActivity::class.java))
        }
    }
}

@Composable
fun linkButton(msg: String, link: Unit) {
    Button(onClick = {
        link
    }) {
        Text(msg)
    }
}

@Preview
@Composable
fun PreviewMessageCard() {
    val context = LocalContext.current

    linkButton(
        msg = "Sample",
        link = goTo(context, TextViewActivity::class.java)
    )
}

private fun goTo(context: Context, clazz: Class<*>) {
    context.startActivity(Intent(context, clazz))
}

Your parameter type in linkButton is wrong. You are getting a Unit but you need a () -> Unit. The way you have written it causes the goto to be called immediately in setContent. In other words, you are calling the function instead of passing it. — momvart
– momvart, Commented Oct 21, 2021 at 9:14
@momt99 so if I undestand you correctly I should change the method parameter to "fun linkButton(msg: String, link: () -> Unit)" and then call it this way? linkButton("Go to text views") { goTo(context, TextViewActivity::class.java) } — Jose Gonzalez
– Jose Gonzalez, Commented Oct 21, 2021 at 10:08
I've been testing that, but the goTo Method never gets called — Jose Gonzalez
– Jose Gonzalez, Commented Oct 21, 2021 at 11:00
Have you updated your linkButton method? You should call the parameter in onClick like link(). — momvart
– momvart, Commented Oct 21, 2021 at 11:02

momvart · Accepted Answer · 2021-10-21 12:50:38Z

1

You are actually calling the method at the moment you are composing the linkButton, not passing it as a callback to be called on click. And on click, it is just returning a Unit which causes the unexpected behavior.

To fix that, you should change the parameter type in your composable function to () -> Unit, which represents a function type.

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            val context = LocalContext.current
            linkButton("Go to text views") {
                goTo(context, TextViewActivity::class.java)
            }
        }
    }
}

@Composable
fun LinkButton(msg: String, link: () -> Unit) {
    Button(onClick = {
        link()
    }) {
        Text(msg)
    }
}

answered Oct 21, 2021 at 12:50

momvart

2,0391 gold badge23 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Android compose onClick being called before click

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related