Android studio Java回收器启动时查看错误

对不起，我说的是英语，我是法国人：

我试图学习如何在Android studio中编写代码，我从一个回收器视图开始，不幸的是，我有一个错误，我不知道如何修复它

提前感谢您的帮助

错误：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.mtoapp, PID: 4393
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mtoapp/com.example.mtoapp.Recycler.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View androidx.recyclerview.widget.RecyclerView.findViewById(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3450)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3602)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2067)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View androidx.recyclerview.widget.RecyclerView.findViewById(int)' on a null object reference
        at com.example.mtoapp.Recycler.MainActivity.onCreate(MainActivity.java:29)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1312)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3423)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3602) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2067) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7660) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975) 

MainActivity.java所有代码

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {


    String data1[], data2[];
    int images[];
    Context context;


    public MyAdapter(Context ct, String s1[], String s2[], int img[]){
    context = context;
    data1 = s1;
    data2 = s2;
    images = img;
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.my_row,parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.myText1.setText(data1[position]);
        holder.myText2.setText(data2[position]);
        holder.myImage.setImageResource(images[position]);
    }

    @Override
    public int getItemCount() {
        return images.length;
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {

        TextView myText1, myText2;
        ImageView myImage;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            myText1 = itemView.findViewById(R.id.myText1);
            myText2 = itemView.findViewById(R.id.myText2);
            myImage = itemView.findViewById(R.id.myImageView);

        }
    }
}

链接到的外部代码：

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.example.mtoapp.R;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {


    String data1[], data2[];
    int images[];
    Context context;


    public MyAdapter(Context ct, String s1[], String s2[], int img[]){
    context = context;
    data1 = s1;
    data2 = s2;
    images = img;
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.my_row,parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.myText1.setText(data1[position]);
        holder.myText2.setText(data2[position]);
        holder.myImage.setImageResource(images[position]);
    }

    @Override
    public int getItemCount() {
        return images.length;
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {

        TextView myText1, myText2;
        ImageView myImage;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            myText1 = itemView.findViewById(R.id.myText1);
            myText2 = itemView.findViewById(R.id.myText2);
            myImage = itemView.findViewById(R.id.myImageView);

        }
    }
}

再次感谢您，祝您度过愉快的一天：

首先，您应该启动recyclerview，如：

RecyclerView RecyclerView=findViewByIdR.id.recycler\u view\u id；

---

然后您可以使用recyclerview.findViewById

您好，谢谢您的帮助，但是我没有R.id.recycler\u view\u id在xml文件中为你的recyclerview添加一个android:id=@+id/recycler\u view\u id属性然后你有一个=注意：当然你可以使用除recycler\u view\u id之外的其他id。我遵循YouTube上的教程：这个人没有使用真正的recycler。。。我不知道为什么，但这对他和聊天中的人来说都是有用的。。。他使用了ConstraintLayout->CardView->ConstraintLayout->Img/text/…您可以在本视频的04:23中找到它。他在“回收者”视图中添加了一个id，并在04:41的活动中使用了该id哦，我的糟糕，谢谢你的帮助：我不知道你是否可以帮我再添加一个id，请注意，这是完全相同的错误，但不是在同一行上。。。如果出现以下情况，请提前向您表示感谢：

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.example.mtoapp.R;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {


    String data1[], data2[];
    int images[];
    Context context;


    public MyAdapter(Context ct, String s1[], String s2[], int img[]){
    context = context;
    data1 = s1;
    data2 = s2;
    images = img;
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.my_row,parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.myText1.setText(data1[position]);
        holder.myText2.setText(data2[position]);
        holder.myImage.setImageResource(images[position]);
    }

    @Override
    public int getItemCount() {
        return images.length;
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {

        TextView myText1, myText2;
        ImageView myImage;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            myText1 = itemView.findViewById(R.id.myText1);
            myText2 = itemView.findViewById(R.id.myText2);
            myImage = itemView.findViewById(R.id.myImageView);

        }
    }
}