java - 为什么会出现空对象引用错误？

Question

顶部 profilebar.xml

merge xmlns:android="http://schemas.android.com/apk/res/android"
>

<com.google.android.material.appbar.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:background="@drawable/white_grey_border_bottom"
    >

    <androidx.appcompat.widget.Toolbar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/profileToolBar">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:text="mitch.tabian"
                android:textSize="20sp"
                android:textColor="@color/black"
                android:layout_marginStart="15dp"
                android:id="@+id/username"/>

            <ImageView
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:layout_alignParentRight="true"
                android:layout_marginEnd="20dp"
                android:layout_centerVertical="true"
                android:id="@+id/profile_Menu"
                android:src="@drawable/ic_ellipses"/>



        </RelativeLayout>


    </androidx.appcompat.widget.Toolbar>



</com.google.android.material.appbar.AppBarLayout>

</merge>
  null object reference error
  null object reference error
  null object reference error

代码：

  package com.example.myapplication.Profile;

  import android.content.Context;


 import android.content.Intent;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.ImageView;


 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;


 import com.example.myapplication.R;
 import com.example.myapplication.utils.BottomNavigationViewHelper;
 import com.ittianyu.bottomnavigationviewex.BottomNavigationViewEx;

public class ProfileActivity extends AppCompatActivity {
private static final String TAG = "SearchActivity";
private Context mContext = ProfileActivity.this;
private static final int ACTIVITY_NUM = 4;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_profile);
    Log.d(TAG, "onCreate: started.");

    setupBottomNavigationView();
    setupToolbar();

}

private void setupToolbar(){
    Toolbar toolbar = findViewById(R.id.profileToolBar);
    setSupportActionBar(toolbar);

    ImageView profileMenu = findViewById(R.id.profile_Menu);
    profileMenu.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d(TAG, "onClick: navigating to account settings.");
            Intent intent = new 
  Intent(mContext,AccountSettingsActivity.class);
        }
    });



     }
    }

我附上了xml和java文件。profileMenu 将编译错误显示为空引用。请帮忙

 Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
 Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

标签： javaandroid