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Anki 使卡片能够使用 JavaScript。例如，一张卡片可以包含以下内容：

<script>
//JavaScript code here
</script>

当卡片显示时，JavaScript 代码将被执行。

为了通过启用此类脚本与 Anki 后端交互来提供更大的灵活性（例如，为了更改注释字段的值、添加标签、影响调度等），我想写一个插件- 用于 Anki（第 2 版），它将实现一些后端功能并启用卡片的 JavaScript 脚本来调用它们。

例如，假设我的插件中有一个（Python）函数与 Anki 的对象交互：

def myFunc():
# use plug-in's ability to interact with Anki's objects to do stuff

我希望能够允许卡片的 JavaScript 调用该函数，例如在卡片中有这样的东西：

<script>
myFunc(); // This should invoke the plug-in's myFunc().
</script>

我知道如何添加钩子，以便各种 Anki 事件调用我的插件的功能，但我希望允许卡内的 JavaScript 这样做。这完全可以做到吗，如果可以，那怎么做？谢谢！

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1 回答 1

13

阅读了@Louis链接的帖子，并与一些同事讨论了这个问题，并尝试了各种尝试，我终于设法想出了一个解决方案：

思路可以概括为这两个关键点（以及两个子关键点）：

  • 该插件可以创建一个或多个对象，这些对象将“公开”给卡片的 JavaScript 脚本，以便卡片脚本可以访问这些对象——它们的字段和方法——就好像它们是脚本范围的一部分一样。

    • 为了做到这一点，对象必须是特定类（或其子类）的实例，并且要公开给卡片脚本的每个方法和属性都必须使用适当的 PyQt 装饰器进行声明。

和

  • PyQt 提供了将此类对象“注入”到 webview 的功能。

    • 插件必须确保每次 Anki 的审阅者的 web 视图（重新）初始化时都会发生这种注入。

以下代码显示了如何实现这一点。它为卡片脚本提供了一种检查当前状态（“问题”或“答案”）的方法，以及一种访问（读取，更重要的是 - 写入）笔记字段的方法。

from aqt import mw              # Anki's main window object
from aqt import mw QObject      # Our exposed object will be an instance of a subclass of QObject.
from aqt import mw pyqtSlot     # a decorator for exposed methods
from aqt import mw pyqtProperty # a decorator for exposed properties

from anki.hooks import wrap     # We will need this to hook to specific Anki functions in order to make sure the injection happens in time.

# a class whose instance(s) we can expose to card scripts
class CardScriptObject(QObject):
    # some "private" fields - card scripts cannot access these directly 
    _state = None
    _card = None
    _note = None

    # Using pyqtProperty we create a property accessible from the card script.
    # We have to provide the type of the property (in this case str).
    # The second argument is a getter method.
    # This property is read-only. To make it writeable we would add a setter method as a third argument.
    state = pyqtProperty(str, lambda self: self._state)

    # The following methods are exposed to the card script owing to the pyqtSlot decorator.
    # Without it they would be "private".
    @pyqtSlot(str, result = str) # We have to provide the argument type(s) (excluding self),
                                 # as well as the type of the return value - with the named result argument, if a value is to be returned.
    def getField(self, name):
        return self._note[name]

    # Another method, without a return value:
    @pyqtSlot(str, str)
    def setField(self, name, value):
        self._note[name] = value
        self._note.flush()

    # An example of a method that can be invoked with two different signatures -
    # pyqtSlot has to be used for each possible signature:
    # (This method replaces the above two.
    # All three have been included here for the sake of the example.)
    @pyqtSlot(str, result = str)
    @pyqtSlot(str, str)
    def field(self, name, value = None): # sets a field if value given, gets a field otherwise
        if value is None: return self._note[name]
        self._note[name] = value
        self._note.flush()

cardScriptObject = CardScriptObject() # the object to expose to card scripts
flag = None # This flag is used in the injection process, which follows.

# This is a hook to Anki's reviewer's _initWeb method.
# It lets the plug-in know the reviewer's webview is being initialised.
# (It would be too early to perform the injection here, as this method is called before the webview is initialised.
# And it would be too late to do it after _initWeb, as the first card would have already been shown.
# Hence this mechanism.)
def _initWeb():
    global flag
    flag = True

# This is a hook to Anki's reviewer's _showQuestion method.
# It populates our cardScriptObject's "private" fields with the relevant values,
# and more importantly, it exposes ("injects") the object to the webview's JavaScript scope -
# but only if this is the first card since the last initialisation, otherwise the object is already exposed.
def _showQuestion():
    global cardScriptObject, flag
    if flag:
        flag = False
        # The following line does the injection.
        # In this example our cardScriptObject will be accessible from card scripts
        # using the name pluginObject.
        mw.web.page().mainFrame().addToJavaScriptWindowObject("pluginObject", cardScriptObject)
    cardScriptObject._state = "question"
    cardScriptObject._card = mw.reviewer.card
    cardScriptObject._note = mw.reviewer.card.note()

# The following hook to Anki's reviewer's _showAnswer is not necessary for the injection,
# but in this example it serves to update the state.
def _showAnswer():
    global cardScriptObject
    cardScriptObject._state = "answer"

# adding our hooks
# In order to already have our object injected when the first card is shown (so that its scripts can "enjoy" this plug-in),
# and in order for the card scripts to have access to up-to-date information,
# our hooks must be executed _before_ the relevant Anki methods.
mw.reviewer._initWeb = wrap(mw.reviewer._initWeb, _initWeb, "before")
mw.reviewer._showQuestion = wrap(mw.reviewer._showQuestion, _showQuestion, "before")
mw.reviewer._showAnswer = wrap(mw.reviewer._showAnswer, _showAnswer, "before")

就是这个！安装了这样的插件后，卡片中的 JavaScript 脚本可以使用 pluginObject.state 检查它是作为问题的一部分还是作为答案的一部分运行（也可以通过将问题部分包装在答案模板中来实现使用设置变量的脚本，但这更简洁），pluginObject.field(name) 从注释中获取字段的值（也可以通过使用 Anki 的预处理器将字段直接注入 JavaScript 代码来实现）和 pluginObject.field(name, value) 设置注释中字段的值（据我所知，目前还不能完成）。当然，许多其他功能可以编程到我们的 CardScriptObject 中，以允许卡片脚本做更多的事情（读取/更改配置，实现另一个问答机制，与调度程序交互等。

如果有人可以提出改进建议，我很想听听。具体来说，我感兴趣的是：

  • 是否有更简洁的方式来公开方法和属性，从而允许更多的签名灵活性；和
  • 是否有不那么繁琐的注入方式。
于 2014-04-26T11:57:40.830 回答