带RecyclerView的黑屏未连接适配器 [英] Blank screen with RecyclerView No adapter attached
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问题描述
我想在recyclerview中解析JSON.应用编译正常,但输出空白/黑屏
I'm tying to parse JSON in recyclerview. App compiles fine but it's outputting empty/blank screen
BlogAdapter.kt
BlogAdapter.kt
class BlogAdapter(private val blogList: List<Blog>) : RecyclerView.Adapter<BlogAdapter.ViewHolder>() {
override fun getItemCount()= blogList.size
private var mContext: Context? = null
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
this.mContext=parent.context;
return ViewHolder(
LayoutInflater.from(parent.context).inflate(
R.layout.character_item,
parent,
false
)
)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val mBlog = this.blogList[position]
if (mBlog.img != null) {
Glide.with(mContext!!)
.load(mBlog.img)
.into(holder.ivThumbnail)
}
if (mBlog.name != null) {
holder.tvTitle.text = mBlog.name
println("Log: Kabe "+mBlog.name)
}
}
class ViewHolder(itemView:View):RecyclerView.ViewHolder(itemView){
val ivThumbnail:ImageView = itemView.findViewById(R.id.ivThumbnail);
val tvTitle:TextView = itemView.findViewById(R.id.tvTitle);
}
}
MainActivity.kt
MainActivity.kt
class MainActivity : AppCompatActivity() {
var mainViewModel: MainViewModel? = null
var mBlogAdapter: BlogAdapter? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
mainViewModel = ViewModelProvider(this).get(MainViewModel::class.java)
getPopularBlog()
swipe_refresh.setOnRefreshListener { getPopularBlog() }
}
private fun getPopularBlog() {
swipe_refresh.isRefreshing = false
mainViewModel!!.allBlog.observe(this, Observer { charactersList ->
prepareRecyclerView(charactersList)
})
}
private fun prepareRecyclerView(blogList: List<Blog>) {
mBlogAdapter = BlogAdapter(blogList)
if (this.resources.configuration.orientation == Configuration.ORIENTATION_PORTRAIT) {
blogRecyclerView.layoutManager = LinearLayoutManager(this)
} else {
blogRecyclerView.layoutManager = GridLayoutManager(this, 4)
}
blogRecyclerView.itemAnimator = DefaultItemAnimator()
blogRecyclerView.adapter = mBlogAdapter
}
}
我的Json文件如下:
My Json file looks like this:
[
{
"id": 1,
"name": "potter",
"img": "https://images.example.com/potter.jpg"
},
{ …}
]
I've created it based on this tutorial: https://itnext.io/kotlin-wrapping-your-head-around-livedata-mutablelivedata-coroutine-networking-and-viewmodel-b552c3a74eec
请提出任何建议
class BlogRepository() {
private var character = mutableListOf<ABCCharacters>()
private var mutableLiveData = MutableLiveData<List<ABCCharacters>>()
val completableJob = Job()
private val coroutineScope = CoroutineScope(Dispatchers.IO + completableJob)
private val thisApiCorService by lazy {
RestApiService.createCorService()
}
fun getMutableLiveData():MutableLiveData<List<ABCCharacters>> {
coroutineScope.launch {
val request = thisApiCorService.getPopularBlog()
withContext(Dispatchers.Main) {
try {
val response = request.await()
val mBlogWrapper = response;
if (/*mBlogWrapper != null &&*/ mBlogWrapper.isNotEmpty()) {
character = mBlogWrapper as MutableList<ABCCharacters>
mutableLiveData.value = character
}
} catch (e: HttpException) {
// Log exception //
} catch (e: Throwable) {
// Log error //)
}
}
}
return mutableLiveData;
}
}
推荐答案
尝试使用以下实现:
class MainActivity : AppCompatActivity() {
lateinit var mainViewModel: MainViewModel
var mBlogAdapter: BlogAdapter? = null
var blogList: List<Blog> = arrayListOf()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
mainViewModel = ViewModelProvider(this).get(MainViewModel::class.java)
// init your RV here
prepareRecyclerView()
getPopularBlog()
swipe_refresh.setOnRefreshListener { mainViewModel.getAllBlog() }
}
private fun getPopularBlog() {
swipe_refresh.isRefreshing = false
mainViewModel.getAllBlog().observe(this, Observer { charactersList ->
blogList = charactersList
mBlogAdapter?.notifyDataSetChanged()
})
}
private fun prepareRecyclerView() {
mBlogAdapter = BlogAdapter(blogList)
if (this.resources.configuration.orientation == Configuration.ORIENTATION_PORTRAIT) {
blogRecyclerView.layoutManager = LinearLayoutManager(this)
} else {
blogRecyclerView.layoutManager = GridLayoutManager(this, 4)
}
blogRecyclerView.itemAnimator = DefaultItemAnimator()
blogRecyclerView.adapter = mBlogAdapter
}
}
按如下所示修改视图模型:
Modify your view model like below:
class MainViewModel() : ViewModel() {
val characterRepository= BlogRepository()
fun getAllBlog(): MutableLiveData<List<ABCCharacters>> {
return characterRepository.getMutableLiveData()
}
override fun onCleared() {
super.onCleared()
characterRepository.completableJob.cancel()
}
}
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