我的问题1：我正在使用android studio构建一个回收器视图。但是，当我运行代码时，会弹出此通知。
我的问题2：在MainActivity.java中，弹出了一个错误，显示在第23行找不到系统变量Recyclerview。我可以知道怎么解决吗？因为我已经宣布了
以下是我的代码：
(MainActivity.java:(
package com.example.recyclerviewdemo;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
List <Details> detailsList;
MyAdapter myAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView=findViewById(R.id.recyclerView);
detailsList=new ArrayList<>();
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setHasFixedSize(true);
//passing data to model class
for (int i=0;i<=10;i++){
Details details=new Details("Java "+i,"This is description " +i);
detailsList.add(details);
}
myAdapter=new MyAdapter(detailsList);
recyclerView.setAdapter(myAdapter);
}
}
(activity_main.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">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="409dp"
android:layout_height="729dp"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>
MyAdapter.java:
package com.example.recyclerviewdemo;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.core.widget.TextViewOnReceiveContentListener;
import androidx.recyclerview.widget.RecyclerView;
import org.jetbrains.annotations.NotNull;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private List<Details> detailsList;
public MyAdapter(List<Details> detailsList) {
this.detailsList = detailsList;
}
@NonNull
@NotNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull @NotNull ViewGroup parent, int viewType) {
View view= LayoutInflater.from(parent.getContext()).inflate(
R.layout.rv_item_list,
parent,
false
);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull @NotNull MyAdapter.MyViewHolder holder, int
position) {
holder.tvTitle.setText(detailsList.get(position).getTitle());
holder.tvDesc.setText(detailsList.get(position).getTitle());
}
@Override
public int getItemCount() {
return detailsList.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tvTitle;
TextView tvDesc;
public MyViewHolder(@NonNull @org.jetbrains.annotations.NotNull View itemView) {
super(itemView);
tvTitle=itemView.findViewById(R.id.tvTitle);
tvDesc=itemView.findViewById(R.id.tvDescription);
}
}
}
Details.java:
package com.example.recyclerviewdemo;
public class Details {
private String title;
private String description;
public Details(String title, String description) {
this.title = title;
this.description = description;
}
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
}
rv_item_list.xml：
<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
app:cardCornerRadius="5dp"
app:cardElevation="5dp"
android:layout_margin="5dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imageView"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/a" />
<TextView
android:id="@+id/tvTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="24dp"
android:text="TextView"
app:layout_constraintStart_toEndOf="@+id/imageView"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvDescription"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:layout_marginEnd="200dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/imageView"
app:layout_constraintTop_toBottomOf="@+id/tvTitle" />
</androidx.constraintlayout.widget.ConstraintLayout>
</com.google.android.material.card.MaterialCardView>
您忘记在XML文件中声明id。。将此添加到您的活动xml 中
<?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">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="409dp"
android:layout_height="729dp"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>