如何将 Python 的日志输出重定向到 Kivy 标签？

Question

正如标题中所写，我需要以尽可能简单的方式将日志记录模块输出重定向到 Kivy 标签。我在网上搜索了一个解决方案，我认为最好的方法是以某种方式覆盖 StreamHandler 或 MemoryHandler （但我不知道该怎么做点）。

有人可以帮我实现吗？

我使用 python 2.7

谢谢

Answer 1

我总是为此类情况制作自己的 logging.Handler。

这是一个工作示例：

main.py:

import kivy
from kivy.app import App
from kivy.clock import Clock
from kivy.uix.label import Label
import logging
import thread
import time

def my_thread(log):

    for i in range(2**20):
        time.sleep(1)
        log.info("WOO %s", i)

class MyLabelHandler(logging.Handler):

    def __init__(self, label, level=logging.NOTSET):
        logging.Handler.__init__(self, level=level)
        self.label = label

    def emit(self, record):
        "using the Clock module for thread safety with kivy's main loop"
        def f(dt=None):
            self.label.text = self.format(record) #"use += to append..."
        Clock.schedule_once(f)


class MyApp(App):
    def build(self):
        label = Label(text="showing the log here")

        log = logging.getLogger("my.logger")
        log.level = logging.DEBUG
        log.addHandler(MyLabelHandler(label, logging.DEBUG))

        thread.start_new(my_thread, (log,))

        return label


if __name__ == '__main__':
    MyApp().run()

注意这里的简单线程来测试日志记录。

Answer 2

您可以将日志写入文件，然后在单独的线程中使用您的应用程序读取它。如果没有单独的线程，GUI 将被冻结。

test.kv:

#:kivy 1.9.1

GridLayout:
    cols: 1

    LogButton:
        text: 'log me'
        on_press: self.log_me()

    ScrollView:

        GridLayout:
            cols: 1
            size_hint_y: None
            height: self.minimum_height

            LogLabel:
                size_hint_y: None
                height: self.texture_size[1]
                text_size: self.width, None
                halign: 'center'

main.py:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
import logging
import threading
import time


class LogButton(Button):
    def __init__(self, **kwargs):
        super(LogButton, self).__init__(**kwargs)
        self.set_logger()

    def set_logger(self):
        self.logger = logging.getLogger('example')
        hdlr = logging.FileHandler('example.log')
        formatter = logging.Formatter(
            '%(asctime)s %(levelname)s %(message)s'
        )
        hdlr.setFormatter(formatter)
        self.logger.addHandler(hdlr)
        self.logger.setLevel(logging.DEBUG)

    def log_me(self, *x):
        self.logger.debug('logger text')


class LogLabel(Label):
    def __init__(self, **kwargs):
        super(LogLabel, self).__init__(**kwargs)
        thread = threading.Thread(target=self.read_log)
        thread.daemon = True  # kill thread on app close
        thread.start()

    def read_log(self):
        with open('example.log', 'r') as file:
            while 1:
                where = file.tell()
                line = file.readline()
                if not line:
                    time.sleep(0.1)
                    file.seek(where)
                else:
                    # newest logs on top
                    self.text = '%s%s' % (line, self.text)


class Test(App):
    def build(self):
        return self.root


Test().run()