Android中的activity和fragment之外的函数如何使用布局组件？

Question

I have a layout and I want to use its component in a function. How can I do that?

This is the XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
<com.google.android.material.textview.MaterialTextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:id="@+id/title"
    android:layout_gravity="center"
    android:textColor="#0055FF"
    android:textSize="30dp"/>
</LinearLayout>

And this is the function:

fun Context.Dialog(){
    title.setOnItemClickListener{
        Toast.makeText(this,"OK",Toast.LENGTH_LONG).show()
    }
}

But title is not recognized in the Dialog function. I don't want to use Dialog function in an activity or a fragment.

Answer 1

I wouldn't move initialization of OnCLickListener out of activity or fragment, because there (in activity or fragment) you have access to all views defined in the layout. But if you want to create a separate function out of activity or fragment you need to pass either views or activity or fragment as parameters:

// passing views
fun showDialog(title: View) {
    title.setOnClickListener { Toast.makeText(title.context, "OK", Toast.LENGTH_LONG).show() }
}

// passing activity
fun showDialog(activity: Activity) {
    val title: View = activity.findViewById(R.id.title);
    title.setOnClickListener { Toast.makeText(activity, "OK", Toast.LENGTH_LONG).show() }
}

// passing fragment
fun showDialog(fragment: Fragment) {
    val title: View? = fragment.view?.findViewById(R.id.title);
    title?.setOnClickListener { Toast.makeText(fragment.context, "OK", Toast.LENGTH_LONG).show() }
}

Also you can create an extension function on View :

fun View.showDialogWhenClick() {
    setOnClickListener { Toast.makeText(context, "OK", Toast.LENGTH_LONG).show() }
}

And use it in Activity or Fragment like this:

title.showDialogWhenClick()

Answer 2

First you need to get the reference to title first. Then set listeners and such.

in your activity

fun onCreate(savedInstanceState:Bundle){
setContentView(R.layout.activity_layout)
Context.Dialog(this);
}

in your Context.Dialog:

fun Context.Dialog(activity:Activity){
    var title = activity.findViewById(R.id.title);
    title?.setOnItemClickListener{
        Toast.makeText(this,"OK",Toast.LENGTH_LONG).show()
    }
}

or something like that