如何在 PyQt 中启动“绘图循环”？

class Library(QtCore.QObject):
    def __init__(self):
        QtCore.QObject.__init__(self)
​
    def importUrls(self, url_list):
        # 创建一个进度对话框
        self.ui_progress = AddUrlsProgressDialog()
        self.ui_progress.show()
        self.ui_progress.raise_()
​
        # 创建添加文件线程对象
        self.add_files_thread = AddFilesThread()
​
        # 连接线程和对话框
        self.connect(self.add_files_thread, QtCore.SIGNAL('updateDialog'), self.ui_progress.setDialog)
        self.connect(self.add_files_thread, QtCore.SIGNAL('updateValue'), self.ui_progress.setValue)
        self.connect(self.add_files_thread, QtCore.SIGNAL('finished'), self.ui_progress.setFinished)
        self.connect(self.add_files_thread, QtCore.SIGNAL('canceled'), self.ui_progress.closeNow)
​
        # 连接对话框和线程
        self.connect(self.ui_progress, QtCore.SIGNAL('cancel'), self.add_files_thread.cancelRequest)
​
        # 启动线程
        self.add_files_thread.start()
​
​
class AddFilesThread(QtCore.QThread):
    def __init__(self, parent=None):
        QtCore.QThread.__init__(self, parent)
        self.cancel_request = False
​
    def __del__(self):
        self.wait()
​
    def run(self):
        try:
            self.main()
        except:
            print('AddFilesThread broke yo.')
            self.cancelNow(force=True)
            traceback.print_exc()
​
    def main(self):
        num_added = 0
        for local_path in self.path_list:
            # 首先设置对话框
            status_label = 'Finding files to add . . .'
            dialog_update = (status_label, (0, 0), 0)
            self.emit(QtCore.SIGNAL('updateDialog'), dialog_update)
​
            # 执行递归搜索
            all_files = hystrix_file.getFiles()
            num_files = len(all_files)
​
            if self.cancelNow():
                return
​
            status_label = '%d files found.\nExtracting tags . . .' % (num_files)
            dialog_update = (status_label, (0, num_files), 0)
            self.emit(QtCore.SIGNAL('updateDialog'), dialog_update)
​
            num_added = 0
            for index, filename in enumerate(all_files):
                try:
                    metadata = hystrix_tags.getMetadata(filename)
                    # 在这里，我将元数据添加到我的库中
                except:
                    traceback.print_exc()
                    print('Could not extract Metadata from file.')
                    continue
​
                # 应该将其发送到进度小部件
                if index % 1 == 0:
                    self.emit(QtCore.SIGNAL('updateValue'), index)
​
                # 检查是否收到取消信号
                if self.cancelNow():
                    return
​
        status_label = 'Finished. Added %d files.' % (num_added)
        dialog_update = (status_label, (0, num_added), num_added)
        self.emit(QtCore.SIGNAL('updateDialog'), dialog_update)
​
        self.emit(QtCore.SIGNAL('finished'))
​
    def cancelRequest(self):
        self.cancel_request = True
​
    def cancelNow(self, force=False):
        if self.cancel_request or force:
            self.emit(QtCore.SIGNAL('canceled'))
            return True
        else:
            return False

# 创建一个 Library 对象
library = Library()
​
# 将 URL 列表传递给 Library 对象
library.importUrls(url_list)