pywebview桌面程序开发(技术路线:前端+Python,全网独一份!!!!!!)

pywebview桌面程序开发(技术路线:前端+Python,全网独一份!!!!!!)

一、pywebview

官网:https://pywebview.flowrl.***/

1、简介

pywebview声称Build GUI for your python program with JavaScript, HTML, and CSS。就是可以使用web技术来实现桌面应用程序开发。其内核我理解仍然是浏览器,只不过将浏览器封装成系统窗口,这样就可以将web无缝切换到桌面应用,相比pyQt等重武器还是比较方便的。

对于目前比较火的electron,Python的加入给应用程序提供了上限,据说打包的大小也比electron小。

2、安装

pip install pywebview

Hello world 的demo:

import webview
webview.create_window('Hello world', 'https://pywebview.flowrl.***/')
webview.start()

3、依赖

windows程序依赖python***(要求 > .*** 4.0),python***可以让python调用.***代码。

为了使用最新版本的 Chromium(Chromium是谷歌的开源项目,国产的所有 “双核浏览器”,都是基于 Chromium 开发的,甚至 Chrome 也是基于它。),需要安装WebView2。

选择Web应用还是原生应用来开发是一种在通用性和本地权限之前的权衡。WebApp兼容的范围很广,而且Web前端代码基于浏览器天生跨平台,而且前端框架多好开发。而原生应用有很大本地权限,可以进行各种文件和操作系统接口的调用。WebView可以结合这两者的优点进行开发。WebView2允许你在本地App里面嵌入web相关的技术(例如HTML,CSS和JavaScript)。WebView2控件使用微软的Edge作为渲染引擎,你可以嵌入一部分或者整个App都用WebView来做。

WebView2下载地址:https://developer.microsoft.***/en-us/microsoft-edge/webview2/?form=MA13LH

4、使用

4.1、最简单示例

import webview

window = webview.create_window('Woah dude!', 'https://pywebview.flowrl.***')
webview.start()
  • create_window:

    返回窗口实例,该实例可以使用许多窗口操作和DOM函数,可创建任意数量窗口,在GUI循环启动后创建的窗口会立即显示。所有打开的窗口都以列表形式存储在webview.windows中。create_window第二个参数可以是url(远程url或本地url),也可设置html来加载html。html与url同时存在,html优先级高。

4.2、http server示例

pywebview提供一个与WSGI兼容的http服务器。

import webview

webview.create_window('Woah dude!', 'index.html')
webview.start(http_server=True)

将http_server设为true

一般使用外部WSGI兼容的http服务器,将服务器对象作为url传递

from flask import Flask
import webview

server = Flask(__name__, static_folder='./assets', template_folder='./templates')
webview.create_window('Flask example', server)
webview.start()

4.3、线程模型

webview.start会开启一个GUI循环,并且它是一个阻塞函数。当GUI循环被阻塞时,必须在一个单独的线程和进程中执行后端逻辑

。可以通过手动开启线程/进程,或者将函数作为要启动的第一个参数来启动。第二个参数设置函数的参数。这种方法会在后台启动一个线程,与手动起一个线程相同。

import webview

def custom_logic(window):
    window.evaluate_js('alert("wel***e")')

window = webview.create_window('Woah dude!', html='<h1>Woah dude!<h1>')
webview.start(custom_logic, window)
# anything below this line will be executed after program is finished executing
print(2)#只有窗口关闭了才能打印

4.4、Python与evaluate_js通信

  • 在Python调用Javascript

    使用evaluate_js可以在Python中调用Javascript 函数,如:window.evaluate_js(‘alert(“wel***e”)’)

  • 在Javascript 中调用Python

    方法1(十分反人类):在一个Python类中先写一个html网页,在其中的Javascript 使用pywebview.api.方法名来调用Python函数,方法名不能以下划线开头。示例如下:

    import random
    import sys
    import threading
    import time
    
    import webview
    
    html = """
    <!DOCTYPE html>
    <html>
    <head lang="en">
    <meta charset="UTF-8">
    
    <style>
        #response-container {
            display: none;
            padding: 3rem;
            margin: 3rem 5rem;
            font-size: 120%;
            border: 5px dashed #***c;
        }
    
        label {
            margin-left: 0.3rem;
            margin-right: 0.3rem;
        }
    
        button {
            font-size: 100%;
            padding: 0.5rem;
            margin: 0.3rem;
            text-transform: uppercase;
        }
    
    </style>
    </head>
    <body>
    
    <h1>JS API Example</h1>
    <p id='pywebview-status'><i>pywebview</i> is not ready</p>
    
    <button onClick="initialize()">Hello Python</button><br/>
    <button id="heavy-stuff-btn" onClick="doHeavyStuff()">Perform a heavy operation</button><br/>
    <button onClick="getRandomNumber()">Get a random number</button><br/>
    <label for="name_input">Say hello to:</label><input id="name_input" placeholder="put a name here">
    <button onClick="greet()">Greet</button><br/>
    <button onClick="catchException()">Catch Exception</button><br/>
    
    <div id="response-container"></div>
    <script>
        window.addEventListener('pywebviewready', function() {
            var container = document.getElementById('pywebview-status')
            container.innerHTML = '<i>pywebview</i> is ready'
        })
    
        function showResponse(response) {
            var container = document.getElementById('response-container')
    
            container.innerText = response.message
            container.style.display = 'block'
        }
    
        function initialize() {
            pywebview.api.init().then(showResponse)
        }
    
        function doHeavyStuff() {
            var btn = document.getElementById('heavy-stuff-btn')
    
            pywebview.api.doHeavyStuff().then(function(response) {
                showResponse(response)
                btn.onclick = doHeavyStuff
                btn.innerText = 'Perform a heavy operation'
            })
    
            showResponse({message: 'Working...'})
            btn.innerText = 'Cancel the heavy operation'
            btn.onclick = cancelHeavyStuff
        }
    
        function cancelHeavyStuff() {
            pywebview.api.cancelHeavyStuff()
        }
    
        function getRandomNumber() {
            pywebview.api.getRandomNumber().then(showResponse)
        }
    
        function greet() {
            var name_input = document.getElementById('name_input').value;
            pywebview.api.sayHelloTo(name_input).then(showResponse)
        }
    
        function catchException() {
            pywebview.api.error().catch(showResponse)
        }
    
    </script>
    </body>
    </html>
    """
    
    class Api:
        def __init__(self):
            self.cancel_heavy_stuff_flag = False
    
        def init(self):
            response = {'message': 'Hello from Python {0}'.format(sys.version)}
            return response
    
        def getRandomNumber(self):
            response = {
                'message': 'Here is a random number courtesy of randint: {0}'.format(
                    random.randint(0, 100000000)
                )
            }
            return response
    
        def doHeavyStuff(self):
            time.sleep(0.1)  # sleep to prevent from the ui thread from freezing for a moment
            now = time.time()
            self.cancel_heavy_stuff_flag = False
            for i in range(0, 1000000):
                _ = i * random.randint(0, 1000)
                if self.cancel_heavy_stuff_flag:
                    response = {'message': 'Operation cancelled'}
                    break
            else:
                then = time.time()
                response = {
                    'message': 'Operation took {0:.1f} seconds on the thread {1}'.format(
                        (then - now), threading.current_thread()
                    )
                }
            return response
    
        def cancelHeavyStuff(self):
            time.sleep(0.1)
            self.cancel_heavy_stuff_flag = True
    
        def sayHelloTo(self, name):
            response = {'message': 'Hello {0}!'.format(name)}
            return response
    
        def error(self):
            raise Exception('This is a Python exception')
    
    if __name__ == '__main__':
        api = Api()
        window = webview.create_window('JS API example', html=html, js_api=api)
        webview.start()
    

    方法二:将Python函数公开到Javascript域,示例如下:

    import webview
    
    def lol():
        print('LOL')
    
    def wtf():
        print('WTF')
    
    def echo(arg1, arg2, arg3):
        print(arg1)
        print(arg2)
        print(arg3)
    
    def expose(window):
        window.expose(echo)  # expose a function during the runtime
    
        window.evaluate_js('pywebview.api.lol()')
        window.evaluate_js('pywebview.api.wtf()')
        window.evaluate_js('pywebview.api.echo(1, 2, 3)')
    
    if __name__ == '__main__':
        window = webview.create_window(
            'JS Expose Example', html='<html><head></head><body><h1>JS Expost</body></html>'
        )
        window.expose(lol, wtf)  # expose functions beforehand
    
        webview.start(expose, window, debug=True)
    

    方法三(最实用)

    运行一个PythonWeb服务,让前端代码对其API进行调用。对于将Web一直到应用程序非常便捷。

4.5、事件

Windows对象有许多声明周期事件,订阅事件使用+=语法,即windows.events.loaded+=函数名,事件触发时会调用该函数,不能重复订阅,多次订阅也只调用一次。取消订阅使用windows.events.loaded-=函数名。

  • events.closed:窗口关闭后触发的事件
  • events.closing:窗口正在关闭,在确认时候触发的事件
  • events.loaded:DOM准备就绪时触发的事件
  • events.minimized:窗口最小化触发的事件
  • events.restore:窗口恢复时触发的事件
  • events.maximized:窗口最大化触发的事件
  • events.resized:窗口大小变化时触发的事件
  • events.shown:窗口显示时触发的事件

5、常用示例

5.1、10秒后改变加载的url

import time

import webview

def change_url(window):
    # wait a few seconds before changing url:
    time.sleep(10)

    # change url:
    window.load_url('https://pywebview.flowrl.***/hello')

if __name__ == '__main__':
    window = webview.create_window('URL Change Example', 'http://www.google.***')
    webview.start(change_url, window)

5.2、带有确认对话框的窗口

import webview

def open_confirmation_dialog(window):
    result = window.create_confirmation_dialog('Question', 'Are you ok with this?')
    if result:
        print('User clicked OK')
    else:
        print('User clicked Cancel')

if __name__ == '__main__':
    window = webview.create_window(
        'Confirmation dialog example', 'https://pywebview.flowrl.***/hello'
    )
    webview.start(open_confirmation_dialog, window)

5.3、常用事件

import webview

def on_closed():
    print('pywebview window is closed')

def on_closing():
    print('pywebview window is closing')

def on_shown():
    print('pywebview window shown')

def on_minimized():
    print('pywebview window minimized')

def on_restored():
    print('pywebview window restored')

def on_maximized():
    print('pywebview window maximized')

def on_resized(width, height):
    print(
        'pywebview window is resized. new dimensions are {width} x {height}'.format(
            width=width, height=height
        )
    )

def on_loaded():
    print('DOM is ready')

    # unsubscribe event listener
    webview.windows[0].events.loaded -= on_loaded
    webview.windows[0].load_url('https://pywebview.flowrl.***/hello')

def on_moved(x, y):
    print('pywebview window is moved. new coordinates are x: {x}, y: {y}'.format(x=x, y=y))

if __name__ == '__main__':
    window = webview.create_window(
        'Simple browser', 'https://pywebview.flowrl.***/', confirm_close=True
    )

    window.events.closed += on_closed
    window.events.closing += on_closing
    window.events.shown += on_shown
    window.events.loaded += on_loaded
    window.events.minimized += on_minimized
    window.events.maximized += on_maximized
    window.events.restored += on_restored
    window.events.resized += on_resized
    window.events.moved += on_moved

    webview.start(debug=True)

5.4、文件打开

import webview

def open_file_dialog(window):
    file_types = ('Image Files (*.bmp;*.jpg;*.gif)', 'All files (*.*)')

    result = window.create_file_dialog(
        webview.OPEN_DIALOG, allow_multiple=True, file_types=file_types
    )
    print(result)#result为文件的绝对路径

if __name__ == '__main__':
    window = webview.create_window('Open file dialog example', 'https://pywebview.flowrl.***/hello')
    webview.start(open_file_dialog, window)

5.5、文件保存

import webview

def save_file_dialog(window):
    import time

    time.sleep(5)
    result = window.create_file_dialog(
        webview.SAVE_DIALOG, directory='/', save_filename='test.file'
    )
    print(result)

if __name__ == '__main__':
    window = webview.create_window('Save file dialog', 'https://pywebview.flowrl.***/hello')
    webview.start(save_file_dialog, window)
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