Question

我正在用kivy构建一个简单的计算器，如何使光标自动开始从右向左输入

Answer 1

不幸的是，这不是那么简单。不知道这是否正是您要查找的内容，但这是我为类似情况编写的TextInput的扩展名。它可以使文本正确调整。请注意，这是希望文本为合法的浮点数。如果您不希望使用该限制，只需删除调用float的代码：

class FloatInputRight(TextInput):

    def __init__(self, **kwargs):
        super(FloatInputRight, self).__init__(**kwargs)
        self.multiline = False

    def right_adjust(self, text):
        if text == '':
            return text
        max_width = self.width - self.padding[0] - self.padding[2]
        new_text = text
        text_width = self._get_text_width(new_text, self.tab_width, self._label_cached)
        while text_width < max_width:
            new_text = ' ' + new_text
            text_width = self._get_text_width(new_text, self.tab_width, self._label_cached)
        while text_width >= max_width:
            if new_text[0] != ' ':
                break
            else:
                new_text = new_text[1:]
                text_width = self._get_text_width(new_text, self.tab_width, self._label_cached)
        return new_text

    def on_size(self, instance, value):
        super(FloatInputRight, self).on_size(instance, value)
        if len(self._lines) == 0:
            return True
        cc, cr = self.cursor
        cur_text = self._lines[cr]
        initial_len = len(cur_text)
        super(FloatInputRight, self)._refresh_text(self.right_adjust(cur_text))
        final_len = len(self._lines[cr])
        self.cursor = self.get_cursor_from_index(final_len - (initial_len - cc))
        return True

    def delete_selection(self, from_undo=False):
        if not self._selection:
            return
        cr = self.cursor[1]
        initial_len = len(self._lines[cr])
        a, b = self._selection_from, self._selection_to
        if a > b:
            a, b = b, a
        super(FloatInputRight, self).delete_selection(from_undo=from_undo)
        cur_text = self._lines[cr]
        super(FloatInputRight, self)._refresh_text(self.right_adjust(cur_text))
        final_len = len(self._lines[cr])
        self.cursor = self.get_cursor_from_index(final_len - (initial_len - b))

    def do_backspace(self, from_undo=False, mode='bkspc'):
        cc, cr = self.cursor
        initial_len = len(self._lines[cr])
        super(FloatInputRight, self).do_backspace(from_undo=from_undo, mode=mode)
        cc, cr = self.cursor
        cur_text = self._lines[cr]
        super(FloatInputRight, self)._refresh_text(self.right_adjust(cur_text))
        final_len = len(self._lines[cr])
        self.cursor = self.get_cursor_from_index(final_len - (initial_len-cc) + 1)

    def insert_text(self, the_text, from_undo=False):
        cc, cr = self.cursor
        cur_text = self._lines[cr]
        initial_len = len(cur_text)
        new_text = self.right_adjust(cur_text[:cc] + the_text + cur_text[cc:])
        try:
            num = float(new_text) # throw exception if new_text is invalid float
        except ValueError:
            return
        self._lines[cr] = ''
        super(FloatInputRight, self).insert_text(new_text, from_undo=from_undo)
        final_len = len(self._lines[cr])
        self.cursor = self.get_cursor_from_index(final_len - (initial_len-cc))

    def set_right_adj_text(self, text):
        num = float(text)  # throws exception if text is invalid float
        self._refresh_text(self.right_adjust(text))

Kivy TextInput如何从右侧开始输入

1 个答案: