＆＃34; Grabbing touch事件＆＃34;这条线的重点是什么？部分。 （Kivy）

Question

我对touch.grab感到困惑

Documentation说

  

触摸坐标未转换为窗口小部件空间，因为触摸直接来自窗口。将坐标转换为本地空间是你的工作。

但是当我运行下面的代码时

# -*- coding: utf-8 -*-

from kivy.base import runTouchApp
from kivy.lang import Builder
from kivy.factory import Factory


class DragRecognizer(Factory.Widget):

    def on_touch_down(self, touch):
        if self.collide_point(*touch.pos):
            touch.grab(self)
            print('on_drag_begin', touch.pos)
            return True
        else:
            return super().on_touch_down(touch)

    def on_touch_up(self, touch):
        if touch.grab_current is self:
            touch.ungrab(self)
            print('on_drag_end', touch.pos, '(grab)')
            return True
        else:
            print('on_drag_end', touch.pos)
            return super().on_touch_up(touch)


root = Builder.load_string(r'''
<Widget>:
    canvas.after:
        Line:
            rectangle: self.x+2,self.y+2,self.width-3,self.height-3
            dash_offset: 5
            dash_length: 3

BoxLayout:
    Widget:
    RelativeLayout
        DragRecognizer:
            size_hint: 0.8, 0.8
            pos_hint: {'center_x': 0.5, 'center_y': 0.5, }
''')

runTouchApp(root)

并按下鼠标按钮。

screenshot

我期待这样

on_drag_begin (88, 111)
on_drag_end (88, 111)
on_drag_end (488, 111) (grab)

但我得到的是

on_drag_begin (88, 111)
on_drag_end (88, 111)
on_drag_end (88, 111) (grab)

抓取触摸不是窗口坐标！所以我不明白文档的重点。对不起，我的英语不好。如果你帮助我，我真的很感激。

Answer 1

https://github.com/kivy/kivy/pull/5925
该文档是错误的。抱歉回复太晚。

Answer 2

您必须使用* instance.to_window（ instance.pos）将坐标转换为本地空间。有关详细信息，请参阅示例。

段

to_window = instance.to_window(*instance.pos)

实施例

main.py

# -*- coding: utf-8 -*-

from kivy.base import runTouchApp
from kivy.lang import Builder
from kivy.factory import Factory
from kivy.properties import ListProperty


class DragRecognizer(Factory.Widget):
    pressed = ListProperty([0, 0])

    def on_touch_down(self, touch):
        if self.collide_point(*touch.pos):
            touch.grab(self)
            self.pressed = touch.pos
            print('on_touch_down: on_drag_begin', touch.pos)
            return True

    def on_touch_up(self, touch):
        if touch.grab_current is self:
            touch.ungrab(self)
            print('on_touch_up: on_drag_end', touch.pos, '(grab)')
            return True

    def on_pressed(self, instance, pos):
        print("Pressed at {}".format(pos))
        to_window = instance.to_window(*instance.pos)
        print("to_window = {}".format(to_window))
        to_widget = instance.to_widget(*to_window)
        print("to_widget = {}".format(to_widget))


root = Builder.load_string(r'''
<Widget>:
    canvas.after:
        Line:
            rectangle: self.x+2,self.y+2,self.width-3,self.height-3
            dash_offset: 5
            dash_length: 3

BoxLayout:
    Widget:
    RelativeLayout
        DragRecognizer:
            size_hint: 0.8, 0.8
            pos_hint: {'center_x': 0.5, 'center_y': 0.5, }
''')

runTouchApp(root)

输出