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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Margin布局</title>
    <style>
        .box{
            width: 100%;
            height: 1155px;
            background-color: aqua;
        }
        .wrap{
            width: 1240px;
            height: 1150px;
            background-color: red;
            /* (父元素宽度-子元素宽度)/2 */
            margin: 0 auto;
        }
        .wrap>div{
            width: 303px;
            height: 375px;
            background-color: seagreen;
            float: left;
            margin-top: 10px;
            margin-right: 9px;
        }
        .four{
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="wrap">
            <div></div>
            <div></div>
            <div></div>
            <div class="four"></div>
            <div></div>
            <div></div>
            <div></div>
            <div></div>
            <div></div>
            <div></div>
            <div></div>
            <div></div>
        </div>
    </div>
</body>
</html>

image.png老师我想请问一下在这个布局下我想测试第四个测试是否被挤下一行的第一个,但是在内联样式设置第四个div背景为粉红色为什么没有显示出来呢?    

WEB前端全系列/第一阶段:HTML5+CSS3模块/初识CSS 23298楼
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JAVA 全系列/第六阶段:项目管理与SSM框架/Mybatis 23301楼

# coding=utf-8
"""开发记事本软件的菜单"""

from tkinter.filedialog import *
from tkinter.colorchooser import *
from tkinter import *


class Application(Frame):

    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.textpad = None
        self.pack()
        self.createWidget()

    def createWidget(self):
        # 创建主菜单栏
        menubar = Menu(root)

        # 创建主菜单三个
        menuFile = Menu(menubar)
        menuEdit = Menu(menubar)
        menuHelp = Menu(menubar)

        # 将三个主菜单加入主菜单栏中
        menubar.add_cascade(text="文件[F]", menu=menuFile)
        menubar.add_cascade(text="编辑[E]", menu=menuEdit)
        menubar.add_cascade(text="帮助[H]", menu=menuHelp)

        # 为文件[F]增加子菜单项
        menuFile.add_command(label="新建", accelerator="ctrl+n", command=self.newfile)
        menuFile.add_command(label="打开", accelerator="ctrl+o", command=self.openfile)
        menuFile.add_command(label="保存", accelerator="ctrl+s", command=self.savefile)
        menuFile.add_separator()  # 添加分行符
        menuFile.add_command(label="退出", accelerator="ctrl+q", command=self.exit)

        # 将主菜单添加到窗口中
        root["menu"] = menubar

        # 增加快捷键的处理
        root.bind("<Control-n>", lambda event: self.newfile())
        root.bind("<Control-o>", lambda event: self.openfile())
        root.bind("<Control-s>", lambda event: self.savefile())
        root.bind("<Control-q>", lambda event: self.exit())

        # 文本编辑区
        self.textpad = Text(root, width=50, height=30)
        self.textpad.pack()

        # 创建上下菜单
        self.contextMenu = Menu(root)
        self.contextMenu.add_command(label="背景颜色", command=self.openAskColor)

        # 为右键绑定事件
        root.bind("Button-3", self.createContextMenu)

    def newfile(self):
        self.textpad.delete("1.0", "end")  # 把text中的所有的内容清空
        self.filename = asksaveasfilename(title="另存为", initialfile="未命名.txt",
                                          filetypes=[("文本文档", "*.txt")], defaultextension=".txt")
        self.savefile()

    def openfile(self):
        self.textpad.delete("1.0", "end")  # 把text中的所有的内容清空
        with askopenfile(title="打开文本文件") as f:
            self.textpad.insert(INSERT, f.read())
            self.filename = f.name

    def savefile(self):
        self.textpad.delete("1.0", "end")  # 把text中的所有的内容清空
        with open(self.filename, "w") as f:
            c = self.textpad.get(1.0, END)
            f.write(c)

    def exit(self):
        root.quit()

    def openAskColor(self):
        s1 = askcolor(color="red", title="选择背景色")
        self.textpad.config(bg=s1[1])
        pass

    def createContextMenu(self, event):
        # 菜单在鼠标右键单击的座标处显示
        self.contextMenu.post(event.x_root, event.y_root)


if __name__ == '__main__':
    root = Tk()
    root.geometry("500x400+200+300")
    root.title("私用记事本")
    app = Application(master=root)
    root.mainloop()

屏幕截图 2021-03-29 190337.png

Python 全系列/第二阶段:Python 深入与提高/GUI编程(隐藏) 23302楼

"""开发画图软件的菜单"""

from tkinter.colorchooser import *
from tkinter import *

# 窗口的宽度和高度
win_width = 900
win_height = 450


class Application(Frame):

    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.bgcolor = "#000000"
        self.x = 0
        self.y = 0
        self.fgcolor = "#ff0000"
        self.lastDraw = 0  # 表示最后绘制的图形的id
        self.startDrawFlag = False
        self.pack()
        self.createWidget()

    def createWidget(self):
        # 创建绘图区
        self.drawpad = Canvas(root, width=win_width, height=win_height * 0.9, bg=self.bgcolor)
        self.drawpad.pack()

        # 创建按钮
        btn_start = Button(root, text="开始", name="start")
        btn_start.pack(side="left", padx="10")
        btn_pen = Button(root, text="笔画", name="pen")
        btn_pen.pack(side="left", padx="10")
        btn_rect = Button(root, text="矩形", name="rect")
        btn_rect.pack(side="left", padx="10")
        btn_clear = Button(root, text="清屏", name="clear")
        btn_clear.pack(side="left", padx="10")
        btn_erasor = Button(root, text="橡皮擦", name="erasor")
        btn_erasor.pack(side="left", padx="10")
        btn_line = Button(root, text="直线", name="line")
        btn_line.pack(side="left", padx="10")
        btn_lineArrow = Button(root, text="箭头直线", name="lineArrow")
        btn_lineArrow.pack(side="left", padx="10")
        btn_color = Button(root, text="颜色", name="color")
        btn_color.pack(side="left", padx="10")

        # 事件处理
        btn_pen.bind_class("<ButtonRelease-1>", self.eventManager)
        self.drawpad.bind("<ButtonRelease-1>", self.stopDraw)

        # 增加颜色切换快捷键处理
        root.bind("<KeyPress-r>", self.kuaijiejian)
        root.bind("<KeyPress-g>", self.kuaijiejian)
        root.bind("<KeyPress-y>", self.kuaijiejian)

    def eventManager(self, event):
        name = event.widget.winfo_name()
        print(name)
        if name == "line":
            self.drawpad.bind("<B1-Motion>", self.myline)
        elif name == "lineArrow":
            self.drawpad.bind("<B1-Motion>", self.mylineArrow)

        elif name == "rect":
            self.drawpad.bind("<B1-Motion>", self.myRect)

        elif name == "pen":
            self.drawpad.bind("<B1-Motion>", self.myPen)

        elif name == "erasor":
            self.drawpad.bind("<B1-Motion>", self.myErasor)

        elif name == "clear":
            self.drawpad.delete("all")

        elif name == "color":
            c = askcolor(color=self.fgcolor, title="选择笔画颜色")
            self.fgcolor = c[1]

    def stopDraw(self, event):
        self.startDrawFlag = False
        self.lastDraw = 0

    def startDraw(self, event):
        self.drawpad.delete(self.lastDraw)

        if not self.startDrawFlag:
            self.startDrawFlag = True
            self.x = event.x
            self.y = event.y

    def myline(self, event):
        self.startDraw(event)
        self.lastDraw = self.drawpad.create_line(self.x, self.y, event.x, event.y, fill=self.fgcolor)

    def mylineArrow(self, event):
        self.startDraw(event)
        self.lastDraw = self.drawpad.create_line(self.x, self.y, event.x, event.y, arrow=LAST, fill=self.fgcolor)

    def myRect(self, event):
        self.startDraw(event)
        self.lastDraw = self.drawpad.create_rectangle(self.x, self.y, event.x, event.y, outline=self.fgcolor)

    def myPen(self, event):
        self.startDraw(event)
        self.drawpad.create_line(self.x, self.y, event.x, event.y, fill=self.fgcolor)
        self.x = event.x
        self.y = event.y

    def myErasor(self, event):
        self.startDraw(event)
        self.drawpad.create_rectangle(event.x-4, event.y-4, event.x+4, event.y+4, fill=self.bgcolor)
        self.x = event.x
        self.y = event.y

    def kuaijiejian(self, event):
        if event.char == "r":
            self.fgcolor = "#ff0000"
        elif event.char == "g":
            self.fgcolor = "#00ff00"
        elif event.char == "y":
            self.fgcolor = "#ffff00"


if __name__ == '__main__':
    root = Tk()
    root.geometry(str(win_width) + "x" + str(win_height) + "+200+300")
    root.title("画图软件项目")
    app = Application(master=root)
    root.mainloop()

老师,这代码能运行,但是,点击组件按钮画画,没反映,可能事件获取有问题,还是什么的?

Python 全系列/第二阶段:Python 深入与提高/GUI编程(隐藏) 23303楼
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JAVA 全系列/第一阶段:AI驱动的JAVA编程/IDEA的使用和第一个java项目 23307楼

老师,帮我看看我的代码,和老师的核对了一下是正确的,但是还是报错image.png

java.lang.NullPointerException: Cannot invoke "com.bjsxt.springboot.jdbc.service.UsersService.addUser(com.bjsxt.springboot.jdbc.pojo.Users)" because "this.usersService" is null
	at com.bjsxt.springboot.jdbc.Controller.UsersController.addUser(UsersController.java:26)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:831)

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JAVA 全系列/第九阶段:Spring Boot实战/Spring Boot 23308楼
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