CODEWITHSUNDEEP
firebaseandroid-studiofirebase-realtime-databasekotlin
evals
evals

Reputation: 1869

KotlinNullException when using query

i'm trying to build an app that shows images from FirebaseDatabase into RecyclerView, something like this tutorial but with Kotlin, now I have kotlin.KotlinNullPointerException and it points to this code line 

var options = FirebaseRecyclerOptions.Builder<Blog>()
        .setQuery(query!!, Blog::class.java)
        .build()

I couldn't solve it since tow days, this is the activity code :

class MainActivity : AppCompatActivity() {
    private var mDatabase:DatabaseReference? = null
    private var mBlogList:RecyclerView?=null
    private var query:Query?=null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        navBar.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
        mDatabase=FirebaseDatabase.getInstance().getReference().child("mall")
        mDatabase?.keepSynced(true)
        mBlogList = findViewById(R.id.recyclee)
        mBlogList?.setHasFixedSize(true)
        mBlogList?.layoutManager = LinearLayoutManager(this)
        query = mDatabase?.orderByKey()
    }
    var options = FirebaseRecyclerOptions.Builder<Blog>()
            .setQuery(query!!, Blog::class.java)
            .build()
    override fun onStart() {
        super.onStart()
        val mAdapter = object : FirebaseRecyclerAdapter<Blog, BlogViewHolder>(
                options) {
            override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BlogViewHolder {
                val view = LayoutInflater.from(parent.context)
                        .inflate(R.layout.cardview, parent, false)
                return BlogViewHolder(view)}

            override fun onBindViewHolder(holder: BlogViewHolder, position: Int, model: Blog) {
                holder.setTitle(model.title)
                holder.setDes(model.des)
                holder.setImage(applicationContext, model.image)
            }
        }
        mBlogList?.adapter = mAdapter
    }
    inner class BlogViewHolder : RecyclerView.ViewHolder{
        var mView:View?=null
        constructor(itemView: View?) : super(itemView) {
            this.mView = itemView
        }
        fun setTitle(title:String){
            var postTitle = mView?.findViewById<TextView>(R.id.post_title)
            postTitle?.text = title
        }
        fun setDes(des:String){
            var postDes = mView?.findViewById<TextView>(R.id.post_des)
            postDes?.text = des
        }
        fun setImage(ctx:Context, image:String){
            var postImage = mView?.findViewById<ImageView>(R.id.post_title)
            Picasso.get().load(image).into(postImage)
        }
    }
}

Blog class: 

class Blog(var title: String?, var des: String?, var image: String?)

My database looks like:

database

Upvotes: 0

Views: 73

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317467

You're trying to make use of query before it's initially assigned in onCreate. You should wait to create options only after query has a non-null value. Notice that your options is sitting at the class member level, which gets evaluated before Android calls your onCreate.

Upvotes: 2

Related Questions