为什么 RecyclerView 在其余 Kotlin 之前加载 Android
Why is the RecyclerView loading before the rest Kotlin Android
你好，我正在为我的作业做一个小应用程序，我想在应用程序上显示来自 php api 的数据。但是 Recycler View 在适配器代码 运行 之前发送此消息 2022-04-25 00:41:36.662 13593-13593/net.robcorp.finalapp E/RecyclerView: No adapter attached; skipping layout，因为此消息 2022-04-25 00:41:36.907 13593-13593/net.robcorp.finalapp I/System.out: [Drivers(pos=1, name=Charles Leclerc, nb=16, points=71, title=Ferrari), Drivers(pos=2, name=Esteban Ocon, nb=31, points=20, title=Alpine)] 在前一个消息之后显示，并且假设在适配器之前 运行 。
这是 DriversFragment.kt:
package net.robcorp.finalapp
import android.content.Context
import android.graphics.Insets.add
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.view.OneShotPreDrawListener.add
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Observer
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.FragmentDriversBinding
import net.robcorp.finalapp.drivers.DriverFragmentAdapter
import net.robcorp.finalapp.drivers.Drivers
import org.json.JSONArray
class DriversFragment : Fragment(R.layout.fragment_drivers) {
private lateinit var recyclerView: RecyclerView
private lateinit var myAdapter: DriverFragmentAdapter;
lateinit var binding: FragmentDriversBinding
private val drivers = ArrayList<Drivers>()
val url = "https://robcorp.net/f1api/getdrivers.php"
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentDriversBinding.inflate(layoutInflater)
recyclerView = binding.driversRecyclerView
recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
recyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
fun downloadDrivers() {
val task = Volley.newRequestQueue(this.context)
val request = StringRequest(Request.Method.GET, url, {
response ->
val data = response.toString()
val jArray = JSONArray(data)
// Log.e("Error",response.toString())
for (i in 0..jArray.length()-1) {
val json_data = jArray.getJSONObject(i)
// Log.e("Jobject",json_data.toString())
val pos = i+1
val name = json_data.getString("Name")
val nb = json_data.getString("NB")
val points = json_data.getString("Points")
val title = json_data.getString("Title")
val driver = Drivers(pos, name, nb, points, title)
drivers.add(driver)
}
println(drivers)
myAdapter.notifyDataSetChanged()
}, {
error ->
println(error)
})
task.add(request)
}
}
这里是 DriverFragmentAdapter.kt:
package net.robcorp.finalapp.drivers
import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.RecyclerView
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.DriverListBinding
class DriverFragmentAdapter(private var driversList: List<Drivers>): RecyclerView.Adapter<DriverFragmentAdapter.MyViewHolder>() {
class MyViewHolder(val binding: DriverListBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(driver: Drivers) {
val context = itemView.context
val pos = itemView.findViewById<TextView>(R.id.driver_position)
val bar = itemView.findViewById<TextView>(R.id.driver_bar)
val name = itemView.findViewById<TextView>(R.id.driver_name)
val nb = itemView.findViewById<TextView>(R.id.driver_number)
val team = itemView.findViewById<TextView>(R.id.driver_team)
val points = itemView.findViewById<TextView>(R.id.driver_points)
pos.text = driver.pos.toString()
name.text = driver.name
nb.text = driver.nb
team.text = driver.title
points.text = driver.points
if (driver.title == "Ferrari") {
bar.background = ContextCompat.getDrawable(context, R.drawable.ferrari_bar)
} else if (driver.title == "Alpine") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alpine_bar)
} else if (driver.title == "Red Bull") {
bar.background = ContextCompat.getDrawable(context, R.drawable.redbull_bar)
} else if (driver.title == "Mercedes") {
bar.background = ContextCompat.getDrawable(context, R.drawable.mercedes_bar)
} else if (driver.title == "McLaren") {
bar.background = ContextCompat.getDrawable(context, R.drawable.mclaren_bar)
} else if (driver.title == "Alfa Romeo") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alfaromeo_bar)
} else if (driver.title == "AlphaTauri") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alphatauri_bar)
} else if (driver.title == "Williams") {
bar.background = ContextCompat.getDrawable(context, R.drawable.williams_bar)
} else if (driver.title == "Aston Martin") {
bar.background = ContextCompat.getDrawable(context, R.drawable.astonmartin_bar)
} else if (driver.title == "Haas") {
bar.background = ContextCompat.getDrawable(context, R.drawable.haas_bar)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
return MyViewHolder(DriverListBinding.inflate(LayoutInflater.from(parent.context)))
}
override fun getItemCount(): Int {
return driversList.size
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val driver = driversList[position]
holder.binding.apply {
println("je suis dans le binding")
holder.bind(driver)
}
}
fun setDriversList(driversList: List<Drivers>) {
this.driversList = driversList
notifyDataSetChanged()
}
}
fragment_drivers.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/primary"
android:orientation="vertical"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginBottom="10dp">
<TextView
android:id="@+id/calendar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="30dp"
android:layout_marginBottom="20dp"
android:fontFamily="@font/marianneb"
android:text="Pilotes"
android:textAlignment="center"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/drivers_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toBottomOf="@+id/header"/>
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
driver_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="20dp"
android:elevation="8dp"
android:orientation="horizontal"
android:padding="10dp"
android:background="@drawable/rectangle">
<TextView
android:id="@+id/driver_position"
android:layout_width="30dp"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="1"
android:textColor="@color/black"
android:textSize="25sp"
android:textAlignment="center"/>
<ImageView
android:id="@+id/driver_bar"
android:layout_width="20px"
android:layout_height="match_parent"
android:background="@drawable/ferrari_bar"/>
<LinearLayout
android:layout_width="250dp"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/driver_name"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="Charles Leclerc"
android:textColor="@color/black"
android:textSize="15sp"
android:layout_marginStart="10dp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/driver_number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="2.5dp"
android:fontFamily="@font/mariannem"
android:text="16"
android:textColor="@color/black"
android:textSize="10sp" />
<TextView
android:id="@+id/driver_team"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="2.5dp"
android:fontFamily="@font/mariannem"
android:text="Ferrari"
android:textColor="@color/black"
android:textSize="10sp" />
</LinearLayout>
</LinearLayout>
<TextView
android:id="@+id/driver_points"
android:layout_width="50dp"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="578"
android:textColor="@color/black"
android:textSize="25sp"/>
</LinearLayout>
这是一个无害的警告。由于您的 RecyclerView 已经在布局中，它会在您的视图层次结构变得可见时尝试绘制它，发现没有分配适配器，因此它只是发出警告而不绘制它。
也许创建您的适配器（使用空列表）并在膨胀视图后立即分配它，并在数据准备好时更新其列表可能会更干净。
顺便说一句，在 onCreate 中膨胀你的布局是不正确的。这应该在 onCreateView.
中完成
编辑：
此处的代码将布局膨胀两次，一次用于变量 v，一次用于 binding 属性。首先，没有理由给它充气两次。其次，由于您使用 v 作为 onCreateView 的 return 值，因此您对 binding 中的视图所做的任何操作都是毫无意义的，并且对实际的视图没有影响在屏幕上。
val v = inflater.inflate(R.layout.fragment_drivers, container, false)
binding = FragmentDriversBinding.inflate(layoutInflater)
// ...
return v
您应该只膨胀视图一次（使用绑定）并且 return 绑定的视图：
// DELETE THIS LINE: val v = inflater.inflate(R.layout.fragment_drivers, container, false)
binding = FragmentDriversBinding.inflate(layoutInflater)
// ...
return binding.root
此外，在 onViewCreated() 中设置视图比在 onCreateView() 中设置视图更合适。如果这样做，您实际上可以通过将视图 ID 传递给 Fragment 构造函数，将 inflation 移动到 super-constructor 调用中，然后绑定到现有视图，而不是扩充绑定。它看起来像这样：
class DriversFragment : Fragment(R.layout.fragment_drivers) {
private lateinit var recyclerView: RecyclerView
private lateinit var myAdapter: DriverFragmentAdapter;
lateinit var binding: FragmentDriversBinding
private val drivers = ArrayList<Drivers>()
val url = "https://robcorp.net/f1api/getdrivers.php"
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentDriversBinding.bind(view)
recyclerView = binding.driversRecyclerView
recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
recyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
//...
}
让@Tenfour04 的回答更加清晰。
您无法删除它。他们告诉你如何用 viewbinding
正确地膨胀它
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentDriversBinding.inflate(layoutInflater, container, false)
return binding.root
}
还有一点旁注：
你应该像这样销毁你的绑定以防止内存泄漏
override fun onDestroyView() {
super.onDestroyView()
binding = null
}
现在进入正题。
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//binding = FragmentDriversBinding.bind(view) this is not needed since its already been inflated
//recyclerView = binding.driversRecyclerView why keep recyclerview as another variable when you can access it with binding.driversRecyclerView?
binding.driversRecyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
binding.driversRecyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
最后，问题很可能是您的布局。
由于所有内容都包含在线性布局中，因此约束布局位置线不会做任何事情。
我删除了无用的线性布局。
希望这能解决任何问题。
抱歉格式化顺便说一句，只需使用 CTRL + ALT + L 自动格式化它
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/primary"
android:orientation="vertical"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginBottom="10dp">
<TextView
android:id="@+id/calendar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="30dp"
android:layout_marginBottom="20dp"
android:fontFamily="@font/marianneb"
android:text="Pilotes"
android:textAlignment="center"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/drivers_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toBottomOf="@+id/header"/>
</androidx.constraintlayout.widget.ConstraintLayout>
你好，我正在为我的作业做一个小应用程序，我想在应用程序上显示来自 php api 的数据。但是 Recycler View 在适配器代码 运行 之前发送此消息 2022-04-25 00:41:36.662 13593-13593/net.robcorp.finalapp E/RecyclerView: No adapter attached; skipping layout，因为此消息 2022-04-25 00:41:36.907 13593-13593/net.robcorp.finalapp I/System.out: [Drivers(pos=1, name=Charles Leclerc, nb=16, points=71, title=Ferrari), Drivers(pos=2, name=Esteban Ocon, nb=31, points=20, title=Alpine)] 在前一个消息之后显示，并且假设在适配器之前 运行 。
这是 DriversFragment.kt:
package net.robcorp.finalapp
import android.content.Context
import android.graphics.Insets.add
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.view.OneShotPreDrawListener.add
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Observer
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.FragmentDriversBinding
import net.robcorp.finalapp.drivers.DriverFragmentAdapter
import net.robcorp.finalapp.drivers.Drivers
import org.json.JSONArray
class DriversFragment : Fragment(R.layout.fragment_drivers) {
private lateinit var recyclerView: RecyclerView
private lateinit var myAdapter: DriverFragmentAdapter;
lateinit var binding: FragmentDriversBinding
private val drivers = ArrayList<Drivers>()
val url = "https://robcorp.net/f1api/getdrivers.php"
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentDriversBinding.inflate(layoutInflater)
recyclerView = binding.driversRecyclerView
recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
recyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
fun downloadDrivers() {
val task = Volley.newRequestQueue(this.context)
val request = StringRequest(Request.Method.GET, url, {
response ->
val data = response.toString()
val jArray = JSONArray(data)
// Log.e("Error",response.toString())
for (i in 0..jArray.length()-1) {
val json_data = jArray.getJSONObject(i)
// Log.e("Jobject",json_data.toString())
val pos = i+1
val name = json_data.getString("Name")
val nb = json_data.getString("NB")
val points = json_data.getString("Points")
val title = json_data.getString("Title")
val driver = Drivers(pos, name, nb, points, title)
drivers.add(driver)
}
println(drivers)
myAdapter.notifyDataSetChanged()
}, {
error ->
println(error)
})
task.add(request)
}
}
这里是 DriverFragmentAdapter.kt:
package net.robcorp.finalapp.drivers
import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.RecyclerView
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.DriverListBinding
class DriverFragmentAdapter(private var driversList: List<Drivers>): RecyclerView.Adapter<DriverFragmentAdapter.MyViewHolder>() {
class MyViewHolder(val binding: DriverListBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(driver: Drivers) {
val context = itemView.context
val pos = itemView.findViewById<TextView>(R.id.driver_position)
val bar = itemView.findViewById<TextView>(R.id.driver_bar)
val name = itemView.findViewById<TextView>(R.id.driver_name)
val nb = itemView.findViewById<TextView>(R.id.driver_number)
val team = itemView.findViewById<TextView>(R.id.driver_team)
val points = itemView.findViewById<TextView>(R.id.driver_points)
pos.text = driver.pos.toString()
name.text = driver.name
nb.text = driver.nb
team.text = driver.title
points.text = driver.points
if (driver.title == "Ferrari") {
bar.background = ContextCompat.getDrawable(context, R.drawable.ferrari_bar)
} else if (driver.title == "Alpine") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alpine_bar)
} else if (driver.title == "Red Bull") {
bar.background = ContextCompat.getDrawable(context, R.drawable.redbull_bar)
} else if (driver.title == "Mercedes") {
bar.background = ContextCompat.getDrawable(context, R.drawable.mercedes_bar)
} else if (driver.title == "McLaren") {
bar.background = ContextCompat.getDrawable(context, R.drawable.mclaren_bar)
} else if (driver.title == "Alfa Romeo") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alfaromeo_bar)
} else if (driver.title == "AlphaTauri") {
bar.background = ContextCompat.getDrawable(context, R.drawable.alphatauri_bar)
} else if (driver.title == "Williams") {
bar.background = ContextCompat.getDrawable(context, R.drawable.williams_bar)
} else if (driver.title == "Aston Martin") {
bar.background = ContextCompat.getDrawable(context, R.drawable.astonmartin_bar)
} else if (driver.title == "Haas") {
bar.background = ContextCompat.getDrawable(context, R.drawable.haas_bar)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
return MyViewHolder(DriverListBinding.inflate(LayoutInflater.from(parent.context)))
}
override fun getItemCount(): Int {
return driversList.size
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val driver = driversList[position]
holder.binding.apply {
println("je suis dans le binding")
holder.bind(driver)
}
}
fun setDriversList(driversList: List<Drivers>) {
this.driversList = driversList
notifyDataSetChanged()
}
}
fragment_drivers.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/primary"
android:orientation="vertical"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginBottom="10dp">
<TextView
android:id="@+id/calendar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="30dp"
android:layout_marginBottom="20dp"
android:fontFamily="@font/marianneb"
android:text="Pilotes"
android:textAlignment="center"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/drivers_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toBottomOf="@+id/header"/>
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
driver_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="20dp"
android:elevation="8dp"
android:orientation="horizontal"
android:padding="10dp"
android:background="@drawable/rectangle">
<TextView
android:id="@+id/driver_position"
android:layout_width="30dp"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="1"
android:textColor="@color/black"
android:textSize="25sp"
android:textAlignment="center"/>
<ImageView
android:id="@+id/driver_bar"
android:layout_width="20px"
android:layout_height="match_parent"
android:background="@drawable/ferrari_bar"/>
<LinearLayout
android:layout_width="250dp"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/driver_name"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="Charles Leclerc"
android:textColor="@color/black"
android:textSize="15sp"
android:layout_marginStart="10dp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/driver_number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="2.5dp"
android:fontFamily="@font/mariannem"
android:text="16"
android:textColor="@color/black"
android:textSize="10sp" />
<TextView
android:id="@+id/driver_team"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="2.5dp"
android:fontFamily="@font/mariannem"
android:text="Ferrari"
android:textColor="@color/black"
android:textSize="10sp" />
</LinearLayout>
</LinearLayout>
<TextView
android:id="@+id/driver_points"
android:layout_width="50dp"
android:layout_height="match_parent"
android:fontFamily="@font/marianneb"
android:text="578"
android:textColor="@color/black"
android:textSize="25sp"/>
</LinearLayout>
这是一个无害的警告。由于您的 RecyclerView 已经在布局中，它会在您的视图层次结构变得可见时尝试绘制它，发现没有分配适配器，因此它只是发出警告而不绘制它。
也许创建您的适配器（使用空列表）并在膨胀视图后立即分配它，并在数据准备好时更新其列表可能会更干净。
顺便说一句，在 onCreate 中膨胀你的布局是不正确的。这应该在 onCreateView.
编辑：
此处的代码将布局膨胀两次，一次用于变量 v，一次用于 binding 属性。首先，没有理由给它充气两次。其次，由于您使用 v 作为 onCreateView 的 return 值，因此您对 binding 中的视图所做的任何操作都是毫无意义的，并且对实际的视图没有影响在屏幕上。
val v = inflater.inflate(R.layout.fragment_drivers, container, false)
binding = FragmentDriversBinding.inflate(layoutInflater)
// ...
return v
您应该只膨胀视图一次（使用绑定）并且 return 绑定的视图：
// DELETE THIS LINE: val v = inflater.inflate(R.layout.fragment_drivers, container, false)
binding = FragmentDriversBinding.inflate(layoutInflater)
// ...
return binding.root
此外，在 onViewCreated() 中设置视图比在 onCreateView() 中设置视图更合适。如果这样做，您实际上可以通过将视图 ID 传递给 Fragment 构造函数，将 inflation 移动到 super-constructor 调用中，然后绑定到现有视图，而不是扩充绑定。它看起来像这样：
class DriversFragment : Fragment(R.layout.fragment_drivers) {
private lateinit var recyclerView: RecyclerView
private lateinit var myAdapter: DriverFragmentAdapter;
lateinit var binding: FragmentDriversBinding
private val drivers = ArrayList<Drivers>()
val url = "https://robcorp.net/f1api/getdrivers.php"
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentDriversBinding.bind(view)
recyclerView = binding.driversRecyclerView
recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
recyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
//...
}
让@Tenfour04 的回答更加清晰。
您无法删除它。他们告诉你如何用 viewbinding
正确地膨胀它override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentDriversBinding.inflate(layoutInflater, container, false)
return binding.root
}
还有一点旁注：
你应该像这样销毁你的绑定以防止内存泄漏
override fun onDestroyView() {
super.onDestroyView()
binding = null
}
现在进入正题。
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//binding = FragmentDriversBinding.bind(view) this is not needed since its already been inflated
//recyclerView = binding.driversRecyclerView why keep recyclerview as another variable when you can access it with binding.driversRecyclerView?
binding.driversRecyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
myAdapter = DriverFragmentAdapter(drivers)
binding.driversRecyclerView.adapter = myAdapter
println("adapter loaded")
downloadDrivers()
}
最后，问题很可能是您的布局。 由于所有内容都包含在线性布局中，因此约束布局位置线不会做任何事情。 我删除了无用的线性布局。 希望这能解决任何问题。
抱歉格式化顺便说一句，只需使用 CTRL + ALT + L 自动格式化它
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/primary"
android:orientation="vertical"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginBottom="10dp">
<TextView
android:id="@+id/calendar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="30dp"
android:layout_marginBottom="20dp"
android:fontFamily="@font/marianneb"
android:text="Pilotes"
android:textAlignment="center"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/drivers_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toBottomOf="@+id/header"/>
</androidx.constraintlayout.widget.ConstraintLayout>