FullScreenFragment.kt

package com.thegar.helper

import android.annotation.SuppressLint
import android.graphics.PixelFormat
import android.os.Build
import android.os.Bundle
import android.view.*
import android.widget.FrameLayout
import android.widget.ScrollView
import androidx.annotation.CallSuper
import androidx.annotation.LayoutRes
import androidx.core.view.doOnLayout
import androidx.fragment.app.Fragment

abstract class FullScreenFragment(@LayoutRes private val layoutId : Int) : Fragment(){

    private val windowManager get() = requireActivity().windowManager

    @SuppressLint("ClickableViewAccessibility")
    @CallSuper
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        val mChildrenView = inflater.inflate(layoutId, null)

        val param = WindowManager.LayoutParams(
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.TYPE_APPLICATION_PANEL,
            0,
            PixelFormat.TRANSLUCENT
        )

        param.addFlag(WindowManager.LayoutParams.FLAG_FULLSCREEN)
        param.addFlag(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN)

        param.token = requireActivity().findViewById<View>(android.R.id.content).windowToken
        param.windowAnimations = android.R.style.Animation_Dialog
        updateLayoutParam(param)

        val mTopView : ViewGroup

        if(param.height == WindowManager.LayoutParams.MATCH_PARENT){
            mTopView = object : FrameLayout(inflater.context){

                override fun dispatchKeyEvent(event: KeyEvent?): Boolean {
                    return dispatchKeyUtil(event) xor super.dispatchKeyEvent(event)
                }
            }
        }else{
            mTopView = object : ScrollView(inflater.context){

                var childMeasurement = -1
                var scrollable = false

                init {
                    mChildrenView.doOnLayout {
                        childMeasurement = it.measuredHeight
                    }

                    viewTreeObserver.addOnGlobalLayoutListener {
                        scrollable = measuredHeight < childMeasurement
                    }
                }

                override fun dispatchKeyEvent(event: KeyEvent?): Boolean {
                    return dispatchKeyUtil(event) xor super.dispatchKeyEvent(event)
                }

                override fun onTouchEvent(ev: MotionEvent): Boolean {
                    return when (ev.action) {
                        MotionEvent.ACTION_DOWN ->  // if we can scroll pass the event to the superclass
                            scrollable && super.onTouchEvent(ev)
                        else -> super.onTouchEvent(ev)
                    }
                }

                override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {
                    // Don't do anything with intercepted touch events if
                    // we are not scrollable
                    return scrollable && super.onInterceptTouchEvent(ev)
                }
            }
        }

        mTopView.isFocusableInTouchMode = true
        mTopView.isClickable = true

        mTopView.setOnTouchListener { _, event ->
            val isConsumed = event.action == MotionEvent.ACTION_OUTSIDE
            if(isConsumed){
                finish()
            }
            false
        }

        // HAHA. THIS IS A GREAT FIND.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP_MR1) {
            param.addFlag(WindowManager.LayoutParams.FLAG_LAYOUT_ATTACHED_IN_DECOR)
        }


        mTopView.addView(mChildrenView, ViewGroup.LayoutParams(-1, -2))
        windowManager.addView(mTopView, param)

        return mTopView
    }

    private fun dispatchKeyUtil(event : KeyEvent?) : Boolean{
        if(event?.keyCode == KeyEvent.KEYCODE_BACK){
            finish()
            return true
        }
        return false
    }

    fun WindowManager.LayoutParams.addFlag(masks : Int){
        flags = flags and masks.inv() or masks
    }

    fun WindowManager.LayoutParams.clearFlag(masks : Int){
        flags = flags and masks.inv()
    }

    fun finish(){
        if (parentFragment != null) {
            requireParentFragment().childFragmentManager.popBackStack()
        } else {
            requireActivity().onBackPressed()
        }
    }

    protected open fun updateLayoutParam(param : WindowManager.LayoutParams) : WindowManager.LayoutParams = param

    @CallSuper
    override fun onDestroyView() {
        super.onDestroyView()
        windowManager.removeView(view)
    }

}