我想在导航视图中更改所选项目的背景颜色。
我尝试使用选择器颜色文件并且也可以绘制,但是没有任何效果。 当我在itemBackground属性上运行所有时间异常时。.
background_color_tab.xml
package main
import (
"fmt"
)
// a simple type, with two methods : one with a value receiver, one with a pointer receiver
type Item struct {
name string
}
func (i Item) GetNameByValue() string {
return i.name
}
func (i *Item) GetNameByRef() string {
return i.name
}
func main() {
{
// in this map, we store *pointers* to Item values
mapByRef := make(map[int]*Item)
mapByRef[0] = &Item{"I am stored as a pointer"}
// GetNameByRef will work on a *Item : "mapByRef[0]" is already a pointer
fmt.Println("GetByRef :", mapByRef[0].GetNameByRef())
// GetNameByValue will work on a *Item : go automatically turns this into '(*mapByRef[0]).GetNameByValue()', and this is valid
fmt.Println("GetByValue :", mapByRef[0].GetNameByValue())
}
{
// in this map, we store Item values (no pointers)
mapByValue := make(map[int]Item)
mapByValue[0] = Item{"I am stored as a value"}
// GetNameByValue will work on a Item : "mapByValue[0]" has the right type
fmt.Println("GetByValue :", mapByValue[0].GetNameByValue())
// GetNameByRef will not work : go tries to turn this into : (&mapByValue[0]).GetNameByRef(),
// and go refuses to let you take the address of a value inside a map
// fmt.Println("GetByRef :", mapByValue[0].GetNameByRef())
// compiler error :
// ./prog.go:47:46: cannot call pointer method on mapByValue[0]
// ./prog.go:47:46: cannot take the address of mapByValue[0]
// you will need some way to copy the value before taking its address :
item := mapByValue[0]
fmt.Println("item.GetByRef :", item.GetNameByRef())
// same as :
fmt.Println("(&item).GetByRef :", (&item).GetNameByRef())
}
}
// Output :
//
// GetByRef : I am stored as a pointer
// GetByValue : I am stored as a pointer
// GetByValue : I am stored as a value
// item.GetByRef : I am stored as a value
// (&item).GetByRef : I am stored as a value
底部导航 第49行是(app:itemBackground)
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:color="@color/blue" android:state_checked="true" />
<item android:color="@android:color/black"/>
</selector>
错误
java.lang.RuntimeException:无法启动活动 ComponentInfo {com.example.ccms / com.example.ccms.MainActivity}: android.view.InflateException:二进制XML文件第49行:二进制XML 文件行#49:错误放大类 android.support.design.widget.BottomNavigationView
答案 0 :(得分:0)
您不能在app:itemBackground
中设置颜色资源,必须在此属性中设置可绘制资源
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@color/blue" android:state_checked="true" />
<item android:drawable="@android:color/black" android:state_checked="false" />
</selector>