KivyMD：如何更改 MDSegmentedControl 的活动项目

Question

我不知道如何在 KivyMD 中更改

MDSegmentedControl

的活动（选定）段而不触摸它（例如，在从数据库加载数据并打开屏幕后）。我可以将

current_active_segment

属性设置为

MDSegmentedControlItem

之一，但它对 UI 没有影响。示例代码如下：

from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.metrics import dp
from kivy.input.providers.mouse import MouseMotionEvent
from kivy.clock import Clock

kvFloatLayout = """
MDScreen:
    id: mdscr
    
    MDBoxLayout:
        orientation: "vertical"
        adaptive_height: True
        pos_hint: {"top": 1}
        spacing: "12dp"
        
        MDTopAppBar:
            id: top_app_bar
            pos_hint: {"top": 1}
            title: "Test App"
            elevation: 4
                        
        MDBoxLayout:
            orientation: "vertical"
            adaptive_height: True
            pos_hint: {"top": 1}
            padding: "12dp", "0dp", "12dp", "12dp"
            spacing: "12dp"
            
            MDRaisedButton:
                id: btn_resize
                text: "Resize"
                on_release: app.seg_resize()
               
            MDRaisedButton
                id: btn_change
                text: "Change selection"
                on_release: app.seg_change_selection()
                
            MDSegmentedControl:
                id: seg_options
                MDSegmentedControlItem:
                    id: sci_option1
                    text: "Option left"
                MDSegmentedControlItem:
                    id: sci_option2
                    text: "Option right"
                    
"""

class TestApp(MDApp):
    
    def build(self):
        return Builder.load_string(kvFloatLayout)

    def seg_resize(self):
        #Workaround from stackoverflow (size not working in .kv - https://stackoverflow.com/questions/74999000/kivymd-mdsegmentedcontrol-size)
        self.root.ids.seg_options.ids.segment_panel.width = (Window.width - dp(24))
        
    def seg_change_selection(self):
        sc = self.root.ids.seg_options
        print("---sc:")
        print(sc)
        sci = self.root.ids.sci_option2
        print("---sci:")
        print(sci)
        print("---sc.current_active_segment before:")
        print(sc.current_active_segment)
        sc.current_active_segment = sci
        print("---sc.current_actilve_segment after:")
        print(sc.current_active_segment.text)
        #A poor workaround with mouse click:
        #Clock.schedule_once(self.simulate_mouse_click, 1)
     
    def simulate_mouse_click(self, *args):
        x = 0.75*Window.width
        y = Window.height - \
            self.root.ids.top_app_bar.height - \
            self.root.ids.btn_resize.height - \
            self.root.ids.btn_change.height - \
            dp(12) * 3 - 40
        touch = MouseMotionEvent(None, 0, (x,y))  # args are device, id, spos
        touch.button = 'left'
        touch.pos = (x,y)
        touch.x = touch.px = touch.ox = x
        touch.y = touch.py = touch.oy = y
        print("---touch")
        print(str(touch))
        Window.dispatch('on_touch_down', touch)
        #1/0
        
TestApp().run()

有什么想法或解决方法吗？

我能够使其工作的唯一方法是在右侧的分段项目上单击鼠标，但这当然远不是一个良好且可靠的解决方案。就是这部分代码：

#Clock.schedule_once(self.simulate_mouse_click, 1)

Answer 1

不幸的是，

MDSegmentedControl

的设计者似乎并没有考虑到您想要的实用程序。另一种欺骗

MDSegmentedControl

使其认为已被单击的方法是创建一个

FakeTouch

类：

class FakeTouch(object):
    pass

然后，在您的

seg_change_selection()

方法中使用该类：

def seg_change_selection(self):
    sc = self.root.ids.seg_options
    print("---sc:")
    print(sc)
    sci = self.root.ids.sci_option2
    print("---sci:")
    print(sci)
    print("---sc.current_active_segment before:")
    print(sc.current_active_segment)
    # sc.current_active_segment = sci
    touch = FakeTouch()
    touch.x = sci.center_x
    touch.y = sci.center_y
    sc.on_press_segment(sci, touch)
    print("---sc.current_actilve_segment after:")
    print(sc.current_active_segment.text)
    # A poor workaround with mouse click:
    # Clock.schedule_once(self.simulate_mouse_click, 1)

与模拟鼠标点击类似，但可能更简单。