[英]Attempt to Invoke virtual method ... on a null object reference
I get a null object reference Exception message everytime I try filter data from Firebase Database and add them into my RecyclerView
.每次我尝试从 Firebase 数据库过滤数据并将它们添加到我的
RecyclerView
时,我都会收到 null object 参考异常消息。
If I pass when(id) { "" -> {...}}
everything is fine all Items which I want will be added to the RecyclerView
, but if I pass when(id) { else -> {...}}
it shows me a null object reference Exception.如果我通过
when(id) { "" -> {...}}
一切都很好,我想要的所有项目都将添加到RecyclerView
,但是如果我通过when(id) { else -> {...}}
它向我展示了when(id) { else -> {...}}
object 参考异常。
- Exception is below the code - - 异常在代码下方 -
fun fetchVideos(id: String?) {
if (id == currentFilter) {
currentFilter = null
return fetchSubs()
}
currentFilter = id
val uid = auth.uid
val ref = database.getReference("/content/videos")
ref.addListenerForSingleValueEvent(object: ValueEventListener {
@SuppressLint("NotifyDataSetChanged")
override fun onDataChange(p0: DataSnapshot) {
val adapter = GroupAdapter<GroupieViewHolder>()
p0.children.forEach {
val video = it.getValue(Video::class.java)
when(id) {
"" -> {
if (video != null && video.publisher_uid != uid) {
val user = database.getReference("users/$uid/subscriptions/${video.publisher_uid}")
user.addListenerForSingleValueEvent(object : ValueEventListener{
override fun onDataChange(p0: DataSnapshot) {
val sub = p0.getValue(Subscription::class.java) ?: return
if (sub.subscribed == true){
adapter.add(VideoItem(video))
}
}
override fun onCancelled(error: DatabaseError) {
}
})
}
}
else -> {
if (video != null && video.publisher_uid == id) {
adapter.add(VideoItem(video))
}
}
}
}
// New Bottom Sheet
adapter.setOnItemClickListener{ item, view ->
val videoItem = item as VideoItem
selectedVideo = videoItem.video.video_uid
HomeFragment.selectedVideo = selectedVideo
updateViewCount()
addRecentVideo()
showVideoPlayer()
createValues()
}
try {
sub_recyclerview_videos.adapter = adapter
}catch (e: Exception){
Log.d(TAG,"${e.message}")
}
adapter.notifyDataSetChanged()
}
override fun onCancelled(p0: DatabaseError) {
}
})
}
This is my Exception:这是我的例外:
Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)' on a null object reference
尝试在 null object 参考上调用虚拟方法 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)'
The Problem was not the adapter or my layout it was actually my class SubItem
.问题不是适配器或我的布局,它实际上是我的 class
SubItem
。
class SubItem(val channel: Channel) : Item<GroupieViewHolder>() {
@SuppressLint("ResourceAsColor")
override fun bind(viewHolder: GroupieViewHolder, position: Int) {
var selected_position = SubscriptionsFragment.selected_position
val profileImageUrl = channel.channel_logo
viewHolder.itemView.sub_item_name.text = channel.channel_name
viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.white)
viewHolder.itemView.sub_item_name.setTextColor(R.color.colorSecondaryText)
val targetImageView = viewHolder.itemView.sub_item_profile
try {
Picasso.get().load(profileImageUrl)
.placeholder(R.drawable.ic_baseline_account_circle_24)
.into(targetImageView)
}catch (e:Exception){
Log.d("SubItem","${e.message}")
// Toast.makeText(,e.message,Toast.LENGTH_SHORT).show()
}
/*viewHolder.itemView.sub_item_layout.setOnClickListener {
selected_position = position
// because I am calling here it doesn't know my recyclerview
SubscriptionsFragment().fetchVideos(channel.uid) // because I am calling here fetchVideos it blocked another clickListener for the same object
notifyChanged()
}*/
checkFilter(viewHolder,position)
if (SubscriptionsFragment.list[position]){
viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.colorSecondaryText)
viewHolder.itemView.sub_item_name.setTextColor(R.color.black)
}
else{
viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.white)
viewHolder.itemView.sub_item_name.setTextColor(R.color.colorSecondaryText)
}
}
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