TextView NullPointerException，在android中使用setText（value）期间获取空对象引用？

问：

我在对 TextView 使用 setText（value） 时遇到错误。我正在使用 dataBinding 绑定布局并从 xml 中查找 id。任何解决方案。我已经启用了数据绑定。 请参阅下面的代码。

<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="10dp"
    android:orientation="horizontal"
    android:background="@color/green">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/icon_cart"
        android:layout_centerVertical="true"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_centerInParent="true">

        <TextView
            android:id="@+id/textTotal"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="Total : "
            android:textColor="@color/black"
            android:textSize="16sp"
            android:textStyle="bold" />
        <TextView
            android:id="@+id/cartValue"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toRightOf="@id/textTotal"
            android:text=""
            android:textSize="16sp"
            android:textColor="@color/black"
            android:textStyle="bold"/>

    </LinearLayout>

    <TextView
        android:id="@+id/textcontinue"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:background="@drawable/drawable_addtocart_background"
        android:padding="8dp"
        android:text="Continue"
        android:textColor="@color/white"
        android:textSize="16sp"
        android:textStyle="bold" />

</RelativeLayout>
</layout>

CartActivity 类

        package com.example.rangeela_cart.Activity;
    
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.databinding.DataBindingUtil;
    
    import android.content.Context;
    import android.os.Bundle;
    import android.util.Log;
    import android.widget.TextView;
    import android.widget.Toast;
    
    import com.example.rangeela_cart.R;
    import com.example.rangeela_cart.databinding.ActivityCartBinding;
    
    public class CartActivity extends AppCompatActivity {
        private ActivityCartBinding binding;
        Context context;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            binding = DataBindingUtil.setContentView(this, R.layout.activity_cart);
            initView();
        }
    
        private void initView() {
    //        updateCart("50");
        }
    
        public void updateCart(Context context, String cartValue) {
            Log.e("cart cart value ", cartValue);
            try {
                if (cartValue != null) {
                    binding.textTotal.setText(cartValue);
                    Toast.makeText(context, "Cart Value is not null", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(context, "Cart Value is null", Toast.LENGTH_SHORT).show();
                }
            } catch (Exception e) {
                Toast.makeText(context, "exception " + e, Toast.LENGTH_LONG).show();
                Log.e("Exception ", String.valueOf(e));
    
            }
        }
    }

适配器类

            package com.example.rangeela_cart.Adapter;
        
        import android.content.Context;
        import android.view.LayoutInflater;
        import android.view.View;
        import android.view.ViewGroup;
        
        import androidx.annotation.NonNull;
        import androidx.databinding.DataBindingUtil;
        import androidx.recyclerview.widget.RecyclerView;
        
        import com.bumptech.glide.Glide;
        import com.example.rangeela_cart.Activity.CartActivity;
        import com.example.rangeela_cart.R;
        import com.example.rangeela_cart.databinding.ItemHomePopularProBinding;
        import com.example.rangeela_cart.models.HomePopularProModel;
        
        import java.util.List;
        
        public class HomeFragPopularProAdapter extends RecyclerView.Adapter<HomeFragPopularProAdapter.myViewHolder> {
            private Context context;
            private List<HomePopularProModel> list;
        
            public HomeFragPopularProAdapter(Context context, List<HomePopularProModel> list) {
                this.context = context;
                this.list = list;
            }
        
            public HomeFragPopularProAdapter(Context context) {
                this.context = context;
            }
        
            @NonNull
            @Override
            public myViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                ItemHomePopularProBinding binding = DataBindingUtil.inflate(LayoutInflater.from(context), R.layout.item_home_popular_pro, parent, false);
                return new myViewHolder(binding);
            }
        
            @Override
            public void onBindViewHolder(@NonNull myViewHolder holder, int position) {
                HomePopularProModel model = list.get(position);
                Glide.with(context).load(model.getPro_image_url()).into(holder.binding.imagePopProduct);
                holder.binding.textAvailability.setText(model.getPro_availability());
                holder.binding.textCompanyName.setText(model.getPro_company_name());
                holder.binding.textPopProductPrice.setText(model.getPro_price());
                holder.binding.layoutAddToCart.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        CartActivity cartActivity = new CartActivity();
                        cartActivity.updateCart(context, model.getPro_price());
                    }
                });
        
            }
        
            @Override
            public int getItemCount() {
                return list.size();
            }
        
            public class myViewHolder extends RecyclerView.ViewHolder {
                ItemHomePopularProBinding binding;
                public myViewHolder(ItemHomePopularProBinding binding) {
                    super(binding.getRoot());
                    this.binding = binding;
                }
            }
        
            onItemClickListner onItemClickListner;
        
            public void setOnItemClickListner(HomeFragPopularProAdapter.onItemClickListner onItemClickListner) {
                this.onItemClickListner = onItemClickListner;
            }
        
            public interface onItemClickListner{
                void onClick(String str);//pass your object types.
            }
        }

我正在从适配器类调用 updateCart（） 方法并从那里获取值，我和 cartValue 不为 null。将此 （cartValue） 设置为 TextView-> textTotal 时，会发生 NullPointerException。 错误如下 - >

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference