Any code improvement in adding/replacing fragment

Question

I have started to study Kotlin and do not know all the functionality of the language.

The function is used to show the fragment in the FrameLayout. The logic is so that the first time it should always add() the fragment and next times it will replace(). Also in some cases I need to use addToBackStack() and also in the same situations to disable the left-side menu.

fun showFragment(fragment : Fragment,
                 isReplace: Boolean = true,
                 backStackTag: String? = null,
                 isEnabled: Boolean = true)
{
    /* Defining fragment transaction */
    val fragmentTransaction = supportFragmentManager
            .beginTransaction()

    /* Select if to replace or add a fragment */
    if(isReplace)
        fragmentTransaction.replace(R.id.frameLayoutContent, fragment, backStackTag)
    else
        fragmentTransaction.add(R.id.frameLayoutContent, fragment)

    /* Select if to add to back stack */
    if(backStackTag != null)
        fragmentTransaction.addToBackStack(fragment.javaClass.name)

    fragmentTransaction.commit()
    enableDrawer(isEnabled)
}

Question: Are there some possible improvements of the function code related to the specifications of Kotlin language to make code cleaner as for now the function looks as a mass.

Answer 1

I have posted a blog about the below answer.

I will write an Extension function to the FragmentManager which accepts a Lambda with Receiver as an argument.

inline fun FragmentManager.inTransaction(func: FragmentTransaction.() -> Unit) {
    val fragmentTransaction = beginTransaction()
    fragmentTransaction.func()
    fragmentTransaction.commit()
}

To add a fragment, we can call like this from the Activity now:

supportFragmentManager.inTransaction {
    add(R.id.frameLayoutContent, fragment)
}

The advantage of this is we don't have to call beginTransaction() and commit() every time we add or replace a Fragment now. How many hours have you wasted debugging only to find out that you have missed calling commit() in Java?

Next, I will write Extension functions to AppCompatActivity:

fun AppCompatActivity.addFragment(fragment: Fragment, frameId: Int, backStackTag: String? = null) {
    supportFragmentManager.inTransaction {
        add(frameId, fragment)
        backStackTag?.let { addToBackStack(fragment.javaClass.name) }
    }
}

fun AppCompatActivity.replaceFragment(fragment: Fragment, frameId: Int, backStackTag: String? = null) {
    supportFragmentManager.inTransaction {
        replace(frameId, fragment)
        backStackTag?.let { addToBackStack(fragment.javaClass.name) }
    }
}

So that now we can add/ replace Fragment from any Activity in a single line, without any additional qualifiers:

addFragment(yourFragment, R.id.frameLayoutContent, "tag")

replaceFragment(yourFragment, R.id.frameLayoutContent, "tag")

Answer 2

I like to use with and let when I have some code related to using a lot some variable and null checks

So I'd do something like this:

fun showFragment(fragment : Fragment,
                 isReplace: Boolean = true,
                 backStackTag: String? = null,
                 isEnabled: Boolean = true)
{
    /* Defining fragment transaction */
    with(supportFragmentManager.beginTransaction()) {

        /* Select if to replace or add a fragment */
        if(isReplace)
            replace(R.id.frameLayoutContent, fragment, backStackTag)
        else
            add(R.id.frameLayoutContent, fragment)

        /* Select if to add to back stack */
        backStackTag?.let { addToBackStack(it) }

        commit()
    }
    enableDrawer(isEnabled)
}