如何在非主線程QObject中開始工作

Question

基於Qt文檔和其他Web上的例子，我會認爲下面的程序使用QThread.started信號，將啓動非工程線程。但是，這是不是這樣，而是每個work插槽從主線程調用：

import time 
import sys 

from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot 
from PyQt5.QtWidgets import QApplication, QPushButton, QTextEdit, QVBoxLayout, QWidget 


def trap_exc_during_debug(*args): 
    # when app exits, put breakpoint in next line when run in debugger, and analyse args 
    pass 


sys.excepthook = trap_exc_during_debug 


class Checker(QObject): 
    sig_step = pyqtSignal(int, str) 
    sig_done = pyqtSignal(int) 

    def __init__(self, id: int): 
     super().__init__() 
     self.__id = id 

    @pyqtSlot() 
    def work(self): 
     thread_name = QThread.currentThread().objectName() 
     thread_id = int(QThread.currentThreadId()) 
     print('running work #{} from thread "{}" (#{})'.format(self.__id, thread_name, thread_id)) 

     time.sleep(2) 
     self.sig_step.emit(self.__id, 'step 1') 
     time.sleep(2) 
     self.sig_step.emit(self.__id, 'step 2') 
     time.sleep(2) 
     self.sig_done.emit(self.__id) 


class MyWidget(QWidget): 
    NUM_THREADS = 3 

    sig_start = pyqtSignal() 

    def __init__(self): 
     super().__init__() 

     self.setWindowTitle("Thread Example") 
     form_layout = QVBoxLayout() 
     self.setLayout(form_layout) 
     self.resize(200, 200) 

     self.push_button = QPushButton() 
     self.push_button.clicked.connect(self.start_threads) 
     self.push_button.setText("Start {} threads".format(self.NUM_THREADS)) 
     form_layout.addWidget(self.push_button) 

     self.log = QTextEdit() 
     form_layout.addWidget(self.log) 
     # self.log.setMaximumSize(QSize(200, 80)) 

     self.text_edit = QTextEdit() 
     form_layout.addWidget(self.text_edit) 
     # self.text_edit.setMaximumSize(QSize(200, 60)) 

     QThread.currentThread().setObjectName('main') 
     self.__threads_done = None 
     self.__threads = None 

    def start_threads(self): 
     self.log.append('starting {} threads'.format(self.NUM_THREADS)) 
     self.push_button.setDisabled(True) 

     self.__threads_done = 0 
     self.__threads = [] 
     for idx in range(self.NUM_THREADS): 
      checker = Checker(idx) 
      thread = QThread() 
      thread.setObjectName('thread_' + str(idx)) 
      self.__threads.append((thread, checker)) # need to store checker too otherwise will be gc'd 
      checker.moveToThread(thread) 
      checker.sig_step.connect(self.on_thread_step) 
      checker.sig_done.connect(self.on_thread_done) 

      # self.sig_start.connect(checker.work) # method 1 works: each work() is in non-main thread 
      thread.started.connect(checker.work) # method 2 doesn't work: each work() is in main thread 
      thread.start() 

     self.sig_start.emit() # this is only useful in method 1 

    @pyqtSlot(int, str) 
    def on_thread_step(self, thread_id, data): 
     self.log.append('thread #{}: {}'.format(thread_id, data)) 
     self.text_edit.append('{}: {}'.format(thread_id, data)) 

    @pyqtSlot(int) 
    def on_thread_done(self, thread_id): 
     self.log.append('thread #{} done'.format(thread_id)) 
     self.text_edit.append('-- Thread {} DONE'.format(thread_id)) 
     self.__threads_done += 1 
     if self.__threads_done == self.NUM_THREADS: 
      self.log.append('No more threads') 
      self.push_button.setEnabled(True) 


if __name__ == "__main__": 
    app = QApplication([]) 

    form = MyWidget() 
    form.show() 

    sys.exit(app.exec_()) 

如果我使用一個自定義的信號，相反，它工作正常。要看到這一點，註釋掉「方法2」行並取消註釋「方法1」行並重復運行。

這肯定會是更好的開始，工人無需創建一個自定義的信號，是有辦法做到這一點（而堅持呼籲moveToThread對工人的設計）？

注：QThread.started信號的文檔不太多幫助：

這個信號是從相關線程發出它開始執行

對我來說這意味着started將發射時在非主線程中，這樣它連接到的work插槽將在非主線程中調用，但顯然不是這種情況。即使我的解釋是不正確的信號是，實際上在主線程發出，連接類型是兩種方法默認Qt.AutoConnection，在插槽上QObject移動到另一個線程，所以started信號應該異步傳輸（即通過每個檢查器的QThread事件循環），但顯然不是這種情況。

Answer 1

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