android 提示没有初始化，但却无法正常初始化

我想用switch语句跳转到其它activity,从而实现底部导航栏的效果，但当我在发布运行的时候编译器一直提示

    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

我看了其他帖子，有的说是我没有初始化。但我却无法在代码中按正常初始化

这是我的MainActivity代码

package com.example.prolife;

import androidx.appcompat.app.AppCompatActivity;
import android.view.View.OnClickListener;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity implements OnClickListener {
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.home).setOnClickListener(this);
        findViewById(R.id.shop).setOnClickListener(this);
        findViewById(R.id.user).setOnClickListener(this);


    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.home:
                Intent intent=new Intent();
                intent.setClass(this,MainActivity.class);
                startActivity(intent);
                break;
            case R.id.shop:
                Intent intent1=new Intent();
                intent1.setClass(this,shopActivity2.class);
                startActivity(intent1);
                break;
            case R.id.user:
                Intent intent2=new Intent();
                intent2.setClass(this,userActivity2.class);
                startActivity(intent2);
                break;
        }
    }
}

XML

<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="match_parent"
    android:layout_margin="5dp"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_margin="5dp"
            android:text="@string/home_page"
            android:textSize="30sp" />

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:scaleType="fitXY"
            android:src="@drawable/ic_line" />
        
    LinearLayout>
    

    <RelativeLayout
        android:id="@+id/ll_function_btn"
        android:layout_width="match_parent"
        android:layout_height="414dp"
        android:gravity="center"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_take"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/btn_take"
            android:textSize="50sp" />

        <Button
            android:id="@+id/btn_put"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="72dp"
            android:layout_toRightOf="@id/btn_take"
            android:text="@string/btn_put"
            android:textSize="50sp" />

    RelativeLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="149dp">LinearLayout>


        <com.google.android.material.tabs.TabLayout
            android:id="@+id/menu"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_gravity="bottom"
            app:tabGravity="fill"
            app:tabIndicatorGravity="bottom"
            >

            <com.google.android.material.tabs.TabItem
                android:id="@+id/home"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:icon="@drawable/ic_home"
                android:text="@string/ic_home" />

            <com.google.android.material.tabs.TabItem
                android:id="@+id/shop"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:icon="@drawable/ic_shop"
                android:text="@string/ic_shop" />

            <com.google.android.material.tabs.TabItem
                android:id="@+id/user"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:icon="@drawable/ic_user"
                android:text="@string/ic_user" />
        com.google.android.material.tabs.TabLayout>


LinearLayout>

请问怎么解决

应该是tablayout的使用方法不对，你查一下

这样写

TabLayout tabLayout = findViewById(R.id.tab);
        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                switch (tab.getPosition()){
                    case 0://第一个TabItem
                        Log.d("onTabSelected","Home");
                        break;
                    case 1://第二个TabItem
                        Log.d("onTabSelected","Shop");
                        break;
                    case 2://第三个TabItem
                        Log.d("onTabSelected","User");
                        break;
                }
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });