Using Conditional Rendering in Jetpack Compose

In Jetpack Compose, you can use conditional rendering to control which parts of your UI are displayed based on certain conditions. This allows you to create dynamic and responsive user interfaces that can adapt to different states and user interactions.

Using if Statements

One way to implement conditional rendering in a Composable function is by using if statements. Here's an example that shows how to use an if statement to conditionally display a Text composable:

Copycopy code to clipboard
1@Composable
2fun MyComposable(showText: Boolean) {
3    if (showText) {
4        Text("Hello, World!")
5    } else {
6        Text("Goodbye, World!")
7    }
8}

In this example, we define a showText parameter for our MyComposable function that determines whether or not the Text composable should display "Hello, World!" or "Goodbye, World!". If showText is true, the Text composable displays "Hello, World!". If showText is false, the Text composable displays "Goodbye, World!".

Using when Expressions

Another way to implement conditional rendering in a Composable function is by using when expressions. Here's an example that shows how to use a when expression to conditionally display different composables based on the value of an enum:

Copycopy code to clipboard
1enum class MyState {
2    LOADING, SUCCESS, ERROR
3}
4
5@Composable
6fun MyComposable(state: MyState) {
7    when (state) {
8        MyState.LOADING -> CircularProgressIndicator()
9        MyState.SUCCESS -> Text("Data loaded successfully!")
10        MyState.ERROR -> Text("An error occurred while loading data.")
11    }
12}

In this example, we define a state parameter for our MyComposable function that determines which composable should be displayed. We use a when expression to match the value of state against different cases and add the appropriate composable to the composition based on the current state.

Using let Expressions

You can also use Kotlin's let expression to implement conditional rendering in a Composable function. Here's an example that shows how to use a let expression to conditionally display a Text composable based on the value of a nullable string:

Copycopy code to clipboard
1@Composable
2fun MyComposable(text: String?) {
3    ~~~
4    text?.let {
5        Text(it)
6    }
7    ~~~
8}

In this example, we define a nullable text parameter for our MyComposable function. We use a let expression to check if the value of text is not null. If it is not null, we add a Text composable to the composition and pass the value of text as its text.

Summary

In summary, you can use conditional rendering in Jetpack Compose to control which parts of your UI are displayed based on certain conditions. This allows you to create dynamic and responsive user interfaces that can adapt to different states and user interactions. You can use various control structures such as if statements, when expressions or Kotlin's scope functions like let, to implement conditional rendering in your Composable functions. I also think it's personally a lot more fun than using XML for layouts!