想着有段时间了再写一次、报空指针的时候我检查了好几遍还搬出之前的写过的代码看了好几遍感觉跟之前的没差啊就是报空指针找不到头脑这个debug不太会用啊瞎定点瞎看希望老师可以讲一下debug怎么用就是提一下老师觉得有可以话就可以出一期视频说回重点怎么解这

用androidViewModel里面的application执行application.getSharedPreferences会出现空指针异常，想知道为什么？

模式会写一点点并在我的项目上用上了但领券联盟里的大多数知识点还是不懂的被老师牵着绳子走的没有老师牵根本就不可能自己再写一遍出来知识储备不够很难吃下那些知识点这回我在我自己的期末作业里引用了自定义FlowLayout可是要搜索记录储存就要用JsonCacheUtil因为不会写嘛就去领券联盟里面扒想着不会写至少会用吧不然白学了可是我就遇到问题了而且摸不到头脑的那种这种......在自身类里面空指针怎么回事呢还有这个

https://images.sunofbeaches.com//images/2023_03_05/1632257292343894017.png">

跟着B站视频做到请求分类数据，但是遇到空指针异常

如图：运行之后出现请问：为什么会是空的呢？是因为activity生命周期的问题吗？如何解决？以下是代码

log已经打印出来result的内容了，为何setdatas那会报空指针异常呢？

和视频中写的一模一样，但是总报空指针异常是怎么回事？

错误提示是空指针异常，尝试调用接口，如果在成员变量处重新实现接口是可以的，测试ServiceConnection无法连接packagecom.example.bankservice;importandroid.content.ComponentName

不带头结点#include<stdio.h>typedefstructLNode{//定义单链表结构intdata;//每个节点存放一个数据structLNode*next;//指针指向下一个节点

而Kotlin通过空指针检查基本解决了这一问题，今天就来学习一下空指针检查。空指针检查通常情况，我们在安卓开发中总是需要对某个控件或变量进行判空，以确保他不会造成空指针异常。

}//判断栈空boolStackEmpty(SqStackS){if(S.top==-1){//栈空returntrue;}else{returnfalse;}}//新元素入栈boolPush(SqStack

删除队头元素，并用x返回GetHead(Q,&x):读队头元素，若队列Q非空，则将队头元素赋给x其他操作QueueEmpty(Q):判断列空，若队列Q为空返回true，否则返回false普通队列

Q.front=Q.rear=(LinkNode*)malloc(sizeof(LinkNode));Q.front->next=NULL;}//判断队列是否为空boolQueueEmpty(LinkQueueQ

扫描到右括号且栈空，右括号单身处理完所有括号后，栈非空，左括号单身实现代码#include<stdio.h>#defineMaxSize10//定义栈中元素最大个数typedefstruct

编写数据缓存工具类时，利用先前自定义的BaseApplication获取context，从而在缓存工具类的初始化过程中利用context创建SharedPreference，但创建SharedPreference时报空指针异常

(this);}@OverrideprotectedvoidloadData(){//加载数据mHomePresenter.getCategories();//---------------这里会爆出空指针异常

空指针异常！提示TabLayout是一个空引用，但是我上面是有绑定了吧？对于安卓的语法不是很懂，麻烦大佬们帮忙指正下，感谢！

这是GsonFormat自动生成的bean类publicclassCellDataBean{/***code:200*message:获取模块列表成功*success:true*data:[{"id":906,"name":"通风系统","sign":"ventilation_sys","hex_start":4,"model":[{"id":1168,"cell_id":906,"name":"风扇","unit":"","sign":"fan","hex_start":0,"data_type":"3","data_type_str":"布尔型"}]},{"id":908,"name":"照明系统","sign":"lighting_sys","hex_start":3,"model":[{"id":1169,"cell_id":908,"name":"照明灯","unit":"","sign":"floodlight","hex_start":0,"data_type":"3","data_type_str":"布尔型"}]},{"id":909,"name":"温湿度监测系统","sign":"temp_hum_det_system","hex_start":1,"model":[{"id":1170,"cell_id":909,"name":"温度","unit":"℃","sign":"temperature","hex_start":0,"data_type":"2","data_type_str":"浮点型"},{"id":1171,"cell_id":909,"name":"湿度","unit":"%","sign":"humidity","hex_start":1,"data_type":"1","data_type_str":"整数型"}]},{"id":910,"name":"烟雾监测系统","sign":"smoke_detection_sys","hex_start":0,"model":[{"id":1172,"cell_id":910,"name":"烟雾感知","unit":"","sign":"smoke","hex_start":0,"data_type":"2","data_type_str":"浮点型"}]},{"id":911,"name":"环境异常监测系统","sign":"abnormal_environ_sys","hex_start":2,"model":[{"id":1173,"cell_id":911,"name":"环境音","unit":"db","sign":"environmental_sound","hex_start":0,"data_type":"1","data_type_str":"整数型"}]}]*/privateintcode;privateStringmessage;privatebooleansuccess;privateList<DataBean>data;publicintgetCode(){returncode;}publicvoidsetCode(intcode){this.code=code;}publicStringgetMessage(){returnmessage;}publicvoidsetMessage(Stringmessage){this.message=message;}publicbooleanisSuccess(){returnsuccess;}publicvoidsetSuccess(booleansuccess){this.success=success;}publicList<DataBean>getData(){returndata;}publicvoidsetData(List<DataBean>data){this.data=data;}publicstaticclassDataBean{/***id:906*name:通风系统*sign:ventilation_sys*hex_start:4*model:[{"id":1168,"cell_id":906,"name":"风扇","unit":"","sign":"fan","hex_start":0,"data_type":"3","data_type_str":"布尔型"}]*/privateintid;privateStringname;privateStringsign;privateinthex_start;privateList<ModelBean>model;publicintgetId(){returnid;}publicvoidsetId(intid){this.id=id;}publicStringgetName(){returnname;}publicvoidsetName(Stringname){this.name=name;}publicStringgetSign(){returnsign;}publicvoidsetSign(Stringsign){this.sign=sign;}publicintgetHex_start(){returnhex_start;}publicvoidsetHex_start(inthex_start){this.hex_start=hex_start;}publicList<ModelBean>getModel(){returnmodel;}publicvoidsetModel(List<ModelBean>model){this.model=model;}publicstaticclassModelBean{/***id:1168*cell_id:906*name:风扇*unit:*sign:fan*hex_start:0*data_type:3*data_type_str:布尔型*/privateintid;privateintcell_id;privateStringname;privateStringunit;privateStringsign;privateinthex_start;privateStringdata_type;privateStringdata_type_str;publicintgetId(){returnid;}publicvoidsetId(intid){this.id=id;}publicintgetCell_id(){returncell_id;}publicvoidsetCell_id(intcell_id){this.cell_id=cell_id;}publicStringgetName(){returnname;}publicvoidsetName(Stringname){this.name=name;}publicStringgetUnit(){returnunit;}publicvoidsetUnit(Stringunit){this.unit=unit;}publicStringgetSign(){returnsign;}publicvoidsetSign(Stringsign){this.sign=sign;}publicintgetHex_start(){returnhex_start;}publicvoidsetHex_start(inthex_start){this.hex_start=hex_start;}publicStringgetData_type(){returndata_type;}publicvoidsetData_type(Stringdata_type){this.data_type=data_type;}publicStringgetData_type_str(){returndata_type_str;}publicvoidsetData_type_str(Stringdata_type_str){this.data_type_str=data_type_str;}}}}发个图片吧，图片是不是更容易看我一调用就出现这个错误

数据判空，运行之后，可以显示账号为空，但密码为空为什么不显示

stdio.h>#include<stdlib.h>typedefstructLNode{//定义单链表结构intdata;//每个节点存放一个数据structLNode*next;//指针指向下一个节点

管理中心获取文章详情API--getArticle()其中需要把标签labels从形如"java-spring-后端"的格式,拆散填入列表List中,在修改getLabels()方法时,需要判空,

刚才打开项目，出现空指针异常，昨天还可以用

和视频敲的一样，但是运行的时候闪退了，说registerViewCallback方法空指针

\n");}LNode*p;//指针p指向当前扫描到的节点intj=0;//当前p指向的是第几个节点p=L;//L指向头结点，头结点是第0个节点（不存数据）while(p!