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kivy chapter1~chapter3

2015-05-29 17:21 218 查看

Kivy

rootwidget&childwidgets

WeatherRoot:

<WeatherRoot>:
AddLocationForm

<AddLocationForm>:
orientation:"vertical"
search_input:search_box
search_results:search_results_list
BoxLayout:
height:"40dp"
size_hint_y:None
TextInput:
id:search_box
size_hint_x:50
Button:
text:"Search"
size_hint_x:25
on_press:root.search_location()
Button:
text:"CurrentLocation"
size_hint_x:25
ListView:
id:search_results_list
adapter:
ListAdapter(data=[],cls=main.LocationButton)

　<LocationButton>:
　　　on_press:app.root.show_current_weather(self.text)

rootwidget形如WeatherRoot

childwidgets形如AddLocationForm,LocationButton

其中比较重要的区别定义当中root和app.root的使用,这分别引用（refersto）不懂的对象(object)在KVlanguagefile.

app.root始终关联rootwidget,root则关联‘当前’的widget

Becarefulnottoconfusetherootmagicvariable,whichreferstotheleftmostruleinthecurrentindentationblock,withapp.root,whichalwaysreferstotherootwidgetoftheapp.app.rootreferstothesameobjectanywhereintheKVlanguagefile,butrootreferstoadifferentthingdependingonwhatruleitisfoundin.

3.值得注意的是AddLocationForm中ListViewAdapter中的main,这里的main指的是类似‘模块’,main.LocationButton则是传递一个‘类模板'给adpter用于初始化ListView的对象。以下贴出Pythoncode的代码（即main.py）:

　　对应rootwidget的class:

classWeatherRoot(BoxLayout):
defshow_current_weather(self,location):
fromkivy.uix.labelimportLabel
self.clear_widgets()
#self.add_widget(Label(text=location))
current_weather=Factory.CurrentWeather()
current_weather.location=location
self.add_widget(current_weather)

defshow_add_location_form(self):
self.clear_widgets()
self.add_widget(AddLocationForm())

　　对应childwidget的class:

classAddLocationForm(BoxLayout):
search_input=ObjectProperty()
search_results=ObjectProperty()

defsearch_location(self):
search_template="http://api.openweathermap.org/data/2.5/find?q={}&type=like"
search_url=search_template.format(self.search_input.text)
request=UrlRequest(search_url,self.found_location)

deffound_location(self,request,data):
data=json.loads(data.decode())ifnotisinstance(data,dict)elsedata
cities=["{}({})".format(d['name'],d['sys']['country'])fordindata['list']]
self.search_results.item_strings=cities
delself.search_results.adapter.data[:]
self.search_results.adapter.data.extend(cities)
self.search_results._trigger_reset_populate()

　　以及用于生成按钮风格的ListView的class：

classLocationButton(ListItemButton):
pass

　　LocationButton只是单纯地继承ListItemButton.其中LiteItemButton源自:

fromkivy.uix.listviewimportListItemButton

　　

　　值得注意的的是rootwidgetWeatherRoot的“属性”(property)设置貌似没有。

WeatherRoot: <WeatherRoot>: AddLocationForm

properties

　　通常在网页里面,比如一个文本输入框里面的值是怎么获取的,这就不得不了解property.

　　还是以childwidgetAddLocationForm为栗子:

<AddLocationForm>:
orientation:"vertical"
search_input:search_box
search_results:search_results_list
BoxLayout:
height:"40dp"
size_hint_y:None
TextInput:
id:search_box
size_hint_x:50
Button:
text:"Search"
size_hint_x:25
on_press:root.search_location()
Button:
text:"CurrentLocation"
size_hint_x:25
ListView:
id:search_results_list
adapter:
ListAdapter(data=[],cls=main.LocationButton)

　　oritation,search_input,height,id,size_hint_x等都是property.

　　其中oritation不同于search_input和search_results,search_input和search_results是Pythoncode代码里面的逻辑产生的,KVlanguagefile里面引用,只在界面与布局里面简单使用。

　　以下是AddLocationForm的对应的Pythoncode,为了阅读简洁,我略去了一个method:

classAddLocationForm(BoxLayout):
search_input=ObjectProperty()
search_results=ObjectProperty()

defsearch_location(self):
search_template="http://api.openweathermap.org/data/2.5/find?q={}&type=like"
search_url=search_template.format(self.search_input.text)
request=UrlRequest(search_url,self.found_location)

　　对于不同的widget,形如文本输入框或者按钮,对应的属性不同。特别地,还有独有的eventproperty.

Widget

<CurrentWeather@BoxLayout>:
location:""
orientation:"vertical"
Label:
text:root.location
BoxLayout:
orientation:"horizontal"
height:"40dp"
size_hint_y:None
Button:
text:"AddLocation"
on_press:app.root.show_add_location_form()
Button:
text:"ForeCast"

　　CurrentWeathor是一个Layoutclasses.按《creatingappinkivy》作者的说法,Widget有如下分类：

Widgets
Kivyusesthewordwidgettodescribeanyuserinterfaceelement.Justafewexamplesofwidgetsinclude:
•ThelabelyourenderedinExample1-3
•Thetextinputfieldandbuttonsyou’llrendershortly
•Layoutclassesthatcompriseotherwidgetsanddeterminewheretheyshouldbedisplayed
•Complicatedtreeviewssuchasfilepickers
•Movieandphotorenderers
•Tabbedboxesthatdisplaydifferentwidgetsdependingontheselectedtab

Ifinditconvenienttothinkofawidgetasasortofboxthathasbehaviorsandcancontainotherboxes.TheWidgetclassisthemostbasicsuchbox.

event

　　借助上面的代码,首先聚焦Button,text表名这个button的名称,on_press的值指明了当这个按钮被按下的事件由rootwidget对应的class的方法来具体响应。再来看看PythonCode代码,看看事件具体是如何响应的:

classWeatherRoot(BoxLayout):
defshow_current_weather(self,location):
fromkivy.uix.labelimportLabel
self.clear_widgets()
#self.add_widget(Label(text=location))
current_weather=Factory.CurrentWeather()
current_weather.location=location
self.add_widget(current_weather)

defshow_add_location_form(self):
self.clear_widgets()
self.add_widget(AddLocationForm())

　　1.首先调用clear_widgets方法清除所有widgets(按函数的名称字面上来理解至少是这样的)

　　2.然后rootwidget调用add_widget方法来创建一个新的AddLocationForm'页面'(views)

最后形如clear_widget和add_widget方法如同extend、_trigger_reset_populate方法一样,似飞来之物。所以要多看手册文档，甚至作者说的，_trigger_reset_populate方法是一个undocumentedmethod,需要看源代码才能获悉这样的函数(data变化来forceanupdatehere),这毋庸置疑需要看ListViews.

self.search_results.adapter.data.extend(cities)
self.search_results._trigger_reset_populate()

2015/05/29

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