【Android】关于Activity压后台Fragment重叠的问题

How To Solve?

利用savedInstanceState,记录当前fragment的index

override fun onSaveInstanceState(outState: Bundle) {
    outState.putInt(SAVED_CURRENT_ID, _currentItemIndex)
    super.onSaveInstanceState(outState)
}

在onCreate中获取savedInstanceState中的index

companion object {
	private const val SAVED_CURRENT_ID = "SAVED_CURRENT_ID"
}

private val vb by lazy { ActivityTabkBottomFragmentBinding.inflate(layoutInflater) }
private var _currentItemIndex = 0

override fun onCreate(savedInstanceState: Bundle?) {
	super.onCreate(savedInstanceState)
    setContentView(vb.root)

    savedInstanceState?.let {
    	_currentItemIndex = savedInstanceState.getInt(SAVED_CURRENT_ID)//从savedInstanceState中获取index
	}

    ...
}

最后塞给adapter

/**
* 实例化以及显示指定位置的fragment
* @param container View
* @param position Int
*/
fun instantiateItem(container: View, position: Int) {
	val currentTransaction: FragmentTransaction = _fragmentManager.beginTransaction()
    if (_currentFragment != null) {
    	currentTransaction.hide(_currentFragment!!)
	}
    val name = container.id.toString() + ":" + position
    var fragment: Fragment? = _fragmentManager.findFragmentByTag(name)
    if (fragment != null) {
    	currentTransaction.show(fragment)
	} else {
	    fragment = getItem(position)
    	if (fragment != null && !fragment.isAdded) {
    		currentTransaction.add(container.id, fragment, name)
    	}
	}
    _currentFragment = fragment
    currentTransaction.commitAllowingStateLoss()
}