android

Graphical Flutter Widgets architecture and practice

Overview The widgets architecture is the first difficult point in learning Flutter. This article does not want to elaborate on the architecture of widges, because it is too theoretical. The main purpose is to let readers understand the following points through theory and practice. The answers to these points will be given at the end of the article From a theoretical level, know how Flutter is laid out? At the application level, quickly screen out the best and optimal layout from the many achieva

Grayson

schedule 25 min read

android

Solution to the conflict, incomplete display and focus problem of NestedScrollView and ScrollView nested Recyclerview

Recently, there are many nested controls in the project, and many problems have been encountered. Yesterday, I solved it. Hurry up and record it. The scene is ViewPager2 nested NestedScrollView nested RecyclerView waterfall flow Effect picture: No way, the compression is too serious, just do it The main issues are as follows: NestedScrollView / ScrollView nested RecyclerView conflict, no scrolling, incomplete display, or no display problem NestedScrollView / ScrollView nested RecyclerView water

Ashley

schedule 9 min read

android

[Path planning] Robot dynamic obstacle avoidance path planning based on matlab A_star algorithm [including Matlab source code 1033]

1. Introduction A algorithm A algorithm is a typical heuristic search algorithm, based on the Dijkstra algorithm. It is widely used in game maps and the real world to find the shortest path between two points. The main thing of the A algorithm is to maintain a heuristic evaluation function, as shown in equation (1). f(n)=g(n)+h(n)(1) Among them, f(n) is the corresponding heuristic function when the algorithm searches for each node. It consists of two parts. The first part g(n) is the actual trav

Hailey

schedule 11 min read

android

Use Threejs and D3 to visualize the global new crown epidemic

Not much to say, let s look at the overall effect first. This article mainly explains the realization of the earth Core demand The earth is translucent, you can see the back Dot matrix global map Generate the corresponding column according to the latitude and longitude of the data The larger the value, the darker and longer the color and height of the column Introduce Threejs and D3 < script src = "https://cdn.staticfile.org/three.js/r125/three.min.js" > </ script > < script src =

Cooper

schedule 8 min read

android

15.23 #include <iostream> #include <vector> using namespace std; template < typename X > bool palindrome(const vector< X >& vec) { typename vector< X >::const_reverse_iterator r = vec.rbegin(); typename vector< X >::const_iterator i = vec.begin(); while (r != vec.rend() && i != vec.end()) { if (*r != *i) return false; ++r; ++i; } return true; } template < typename Y > void printVector(const vector< Y >& vec) { typename vector< Y

Paige

schedule 14 min read

coder_life

Cattle! Ali interviewer suspected that the interviewer had poor skills, so he was angry all night. JSP Interview Customs Manual

Hello, today I will share the JSP with you children's shoes, and quickly take out a small book and write it down! 1. Introduction to JSP The full name of JSP is Java Server Pages, java server page. JSP is a text-based program, its characteristic is that HTML and Java code coexist! JSP itself is a kind of Servlet. When Tomcat accesses any resource, it is accessing Servlet! JSP is a java program that encapsulates Servlet Compilation principle: When the browser requests 1.jsp for the first time, To

Richard

schedule 14 min read

coder_life

Spring Cloud Distributed Configuration Center (Spring Cloud Config) (6)

Copyright statement: This article is the original article of the blogger, welcome to reprint, please indicate the author, the hyperlink of the original text, and the blogger address: blog.csdn.net/forezp. https://blog.csdn.net/forezp/article/details/70037291 Please indicate the source for reprinting:  blog.csdn.net/forezp/arti This  article comes from Fang Zhipeng s blog The latest version of: The simplest Spring Cloud tutorial in history | Part 6: Distributed Configuration Center (Spr

Blake

schedule 6 min read

coder_life

How does Android call back the encoded audio and video data

Some developers mentioned that on the basis of the RTMP push terminal, they hope to call back the encoded audio and video data so that developers can connect to third-party systems, such as GB28181. To this end, we have added some interfaces: 1. Set audio and video callback Corresponding interface: /** * Set Audio Encoded Data Callback. * * @param audio_encoded_data_callback: Audio Encoded Data Callback. * * @return {0} if successful */ public native int SmartPublisherSetAudioEncodedDataCallback

Eli

schedule 6 min read

coder_life

ListView optimization

** Familiar with listview optimization, asynchronous loading of network pictures, batch loading, paging display, picture caching and other optimization methods ** First, let's understand the working principle of ListView (see mobile.51cto.com/abased-4108... ), as shown in the figure: ListView For each item, the adapter is required to "return a view" (getView), which means that the ListView is in When starting to draw, the system first calls the getCount() function to get the length of the ListVi

Jayden

schedule 17 min read

coder_life

Cross-site scripting (XSS) cheat sheet-2019 version

This is a cross-site scripting (XSS) memo that collects a large number of XSS attack vectors, including various event handling, communication protocols, special attributes, restricted characters, encoding methods, sandbox escape and other techniques, which can help penetration testers Bypass WAF and filtering mechanisms. Translator's Note: The original text is updated regularly in 2019 by Portswigger's Web Security Academy. Yes, it is the company that developed the famous penetration tool Burp s

Cameron

schedule 25 min read

dev_tools

Implementation of LASSO regression, Ridge regression and Elastic Net model in r language

Original link: tecdat.cn/?p=3795 Original source: Tuoduan Data Tribe Official Account   Glmnet is a software package for fitting generalized linear models by penalizing the maximum likelihood relationship. The regularization path is calculated for the lasso or Elastic Net (elastic network) penalty value at the value grid of the regularization parameter . The algorithm is very fast and can take advantage of the sparsity in the input matrix x. It is suitable for linear, logistic and poly

Melody

schedule 25 min read

dev_tools

Source code analysis: Spring Boot startup process (1)

Write in front Because I also watched some corresponding Spring-related source code reading videos and articles first, but I still know a little about this part, and I am relatively lazy, so I urge myself to read it in a record way. There will definitely be many omissions. Please excuse me. My ultimate goal is to cover the comments in every line of code in all the startup processes. If you think there is a redundant place, please point it out in the comments. Whole reading Because I am also the

Sydney

schedule 13 min read

dev_tools

Autumn move! Friends, you don t even know about generics now! No way, no way!

One, the basic concept of generics Definition of generic type: Generic type is a new feature of JDK 1.5, its essence is the application of parameterized type (Parameterized Type), that is to say, the data type that is operated is designated as a parameter, when it is used in Specify the specific type. This parameter type can be used in the creation of classes, interfaces, and methods. They are called generic classes, generic interfaces, and generic methods, respectively. The idea of generics be

Braxton

schedule 14 min read

dev_tools

Apache Griffin debugging process bug record

1. The database reports an error Table'quartz.DATACONNECTOR' doesn't exist 2021 -01 -18 14 : 54 is : 54.135 ERROR 122 541 --- [ HTTP - NiO - 8081 - Exec - . 8 ] oaccC [ . [ . [ . [ DispatcherServlet ] [ 175 ]: Servlet.service () for the servlet [ DispatcherServlet ] in context with path [] threw exception [ Request processing failed; nested exception is org.springframework.transaction.TransactionSystemException : Could not commit JPA transaction ; nested exception is javax.persistence.RollbackEx

Madison

schedule 21 min read

dev_tools

Spring Security authentication process

<Core filter loading> This article has been analyzed, FilterChainProxyAfter obtaining the filter chain, start to follow the logic of the filter chain. As shown in the figure, these filter chains include the following <Core Filter Introduction> section, which talks about the authentication logic of the form authentication method.UsernamePasswordAuthenticationFilterProceeded, so let's start to analyzeUsernamePasswordAuthenticationFilter, Before analyzing it, let s analyze its parent cl

Aaron

schedule 14 min read

programming

Summary of Operating System Interview Questions Consolidate your computer foundation

I have not studied computer operating system courses systematically. I was preparing for an interview and found that Dachang would like to take this aspect of the question. So based on the questions faced by some friends, I searched for some good articles and summarized them. a bit. Which is likeThe difference between process and thread, synchronous and asynchronous, blocking, non-blocking, deadlockTo understand these concepts, I think it is very helpful to deepen some knowledge of the front-en

Jackson

schedule 26 min read

programming

(Essence) Detailed explanation of computer operating system network model on September 1, 2020

One, the system structure The collection of various layers of computer networks and their protocols is called the network architecture. According to different dimensions, it is often divided into seven-layer, five-layer, and four-layer network structures: 1.1 Seven-layer network model The Open System Interconnection Model (OSI model for short) is a conceptual model proposed by the International Organization for Standardization and trying to become a standard framework for computers to be interco

Camden

schedule 42 min read

programming

MySQL database-MySql index & view & stored procedure

MySQL index What is an index In the database table, indexing the fields can greatly improve the query speed. By making good use of these indexes, MySQL queries and operations can be made more efficient. If the MySQL with a reasonable design and use of indexes is a Lamborghini, then the MySQL without the design and use of indexes is a human tricycle. Take the directory page (index) of a Chinese dictionary for example, we can quickly find the word we need in the directory (index) sorted by pinyin,

Emmett

schedule 17 min read

programming

amount! Is there such a big difference between user threads and daemon threads in Java?

Threads in the Java language are divided into two categories: user threads and daemon threads, and the difference between the two is rarely known, so this article Lei Ge will take you to see the difference between the two, as well as some of the daemon threads need to pay attention to matter. 1. The default user thread In the Java language, whether it is a thread or a thread pool, it is a user thread by default , so user threads are also called ordinary threads. Take the thread as an example, if

Bentley

schedule 14 min read

programming

Alipay payment access finishing

This is the first day I participated in the Wenwen Challenge. For details of the event, please view: Wenwen Challenge background Generally companies will have related requirements for access to Alipay and WeChat Pay. Record the relevant content of the document and personal records here Pay with Ali-Pay Special note: Alipay has two versions of the interface, and the historical system may use the old interface Old version (mapi) New version (openapi) The payment purposes supported by Alipay are as

Kendall

schedule 20 min read