基本上,我想使用适配器将数据绑定到我的RecyclerView,但似乎在定义适配器的Activity中看不到我的数据列表
listItems.adapter = FormRecyclerAdapter(this, TestFileManager.testForms) // testForms highlighted(unresloved reference)
似乎应该可以,但是可能存在一些误解或其他我无法解决的问题。
这是我的课程
MainActivity.kt
class MainActivity: AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(activity_main)
val toolbar: Toolbar = findViewById(R.id.toolbar)
setSupportActionBar(toolbar)
supportActionBar?.title = "Forms creator"
listItems.layoutManager = LinearLayoutManager(this)
listItems.adapter = FormRecyclerAdapter(this, TestFileManager.testForms) <- here is where the problem occurs
}
}
TestFileManager.kt
class TestFileManager {
private val testForms = ArrayList<TestForm>()
init {
initializeForms()
}
fun initializeForms() {
var testForm = TestForm("Form 1", "Created Jun 1 2020")
testForms.set(0, testForm)
testForm = TestForm("Form 2", "Created 5 Jan 2019")
testForms.set(1, testForm)
testForm = TestForm("Form 3", "Created 3 March 2020")
testForms.set(2, testForm)
}
}
TestForm.kt
class TestForm( var name: String, var description: String)
FormRecyclerAdapter.kt
class FormRecyclerAdapter(private val context: Context, private val forms: List<TestForm>) :
RecyclerView.Adapter<FormRecyclerAdapter.ViewHolder>() {
private val layoutInflater = LayoutInflater.from(context)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val itemView = layoutInflater.inflate(R.layout.item_form_list, parent, false)
return ViewHolder(itemView)
}
override fun getItemCount() = forms.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val form = forms[position]
holder.textTitle?.text = form.name
holder.textDescription?.text = form.description
}
class ViewHolder(itemView: View?) : RecyclerView.ViewHolder(itemView!!) {
val textTitle = itemView?.findViewById<TextView?>(R.id.textTitle)
val textDescription = itemView?.findViewById<TextView?>(R.id.textDescription)
}
}
可能是一些愚蠢的问题或误解,但我正在努力自己找到它。
不初始化
listItems.adapter = FormRecyclerAdapter(this, TestFileManager.testForms)
用途:
为适配器创建类变量
lateinit var formRecyclerAdapter: FormRecyclerAdapter
之后onCreate()做
formRecyclerAdapter = FormRecyclerAdapter(this, TestFileManager.testForms)
之后,将适配器初始化为回收站视图
listItems.adapter = formRecyclerAdapter
首先,您没有初始化类,请执行以下操作:
listItems.adapter = FormRecyclerAdapter(this, TestFileManager().testForms)
第二,您使用错误的运算符将项目添加到ArrayList中,请使用add()。 set()不会将项目添加到ArrayList中。
fun initializeForms() {
var testForm = TestForm("Form 1", "Created Jun 1 2020")
testForms.add(testForm)
testForm = TestForm("Form 2", "Created 5 Jan 2019")
testForms.add(testForm)
testForm = TestForm("Form 3", "Created 3 March 2020")
testForms.add(testForm)
}
尝试一下:
fun initializeForms() {
var testForm = TestForm("Form 1", "Created Jun 1 2020")
testForms.add(testForm)
testForm = TestForm("Form 2", "Created 5 Jan 2019")
testForms.add(testForm)
testForm = TestForm("Form 3", "Created 3 March 2020")
testForms.add(testForm)
}
ArrayList.set(int index,E element)用指定的元素替换此列表中指定位置的元素。
您的列表为空。
Call:TestFileManager()。testForms
所以我的主体现在看起来像这样:
class MainActivity: AppCompatActivity() {
lateinit var formRecyclerAdapter: FormRecyclerAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(activity_main)
val toolbar: Toolbar = findViewById(R.id.toolbar)
setSupportActionBar(toolbar)
supportActionBar?.title = "Forms creator"
listItems.layoutManager = LinearLayoutManager(this)
formRecyclerAdapter = FormRecyclerAdapter(this, TestFileManager.testForms)
listItems.adapter = formRecyclerAdapter
}
}
无法解决问题,因为:/仍然对.testForms不满意我看不到这节课的内容。不知道为什么