例說過如果需要構造一些較復雜的類的實例,通常的方法是使用@Provides 方法。這個方法必須定義在模塊中(Module),而且必須使用@Provides 標註,在個方法的返回類型則綁定到這個方法返回的對象實例。
如果這個方法帶有binding Annotation 或是@Named(“xxx”),Guice則將@Provides方法返回的對象綁定到這個annotated 類型。
本例使用@Provides創建三個圓,然後再屏幕上顯示出來,圖形庫的使用可以參見Android簡明開發教程十二:引路蜂二維圖形庫簡介及顏色示例 。其實創建圓並不復雜,這裡隻是用來說明@Provides 方法的用法。
在Graphics2DModule 在添加三個@Provides方法:
[java] @Provides @Named("Circle1")
IShape provideCircle1(){
return new Ellipse(30,60,80,80);
}
@Provides @Named("Circle2")
IShape provideCircle2(){
return new Ellipse(60,30,80,80);
}
@Provides @Named("Circle3")
IShape provideCircle3(){
return new Ellipse(90,60,80,80);
}
@Provides @Named("Circle1")
IShape provideCircle1(){
return new Ellipse(30,60,80,80);
}
@Provides @Named("Circle2")
IShape provideCircle2(){
return new Ellipse(60,30,80,80);
}
@Provides @Named("Circle3")
IShape provideCircle3(){
return new Ellipse(90,60,80,80);
}
分別綁定到IShape帶有標註@Named(“Circle1″),@Named(“Circle2″),@Named(“Circle3″).
創建ProvidesMethodsDemo,有如下代碼
[java] public class ProvidesMethodsDemo extends Graphics2DActivity{
@Inject @Named("Circle1") IShape circle1;
@Inject @Named("Circle2") IShape circle2;
@Inject @Named("Circle3") IShape circle3;
protected void drawImage(){
// The solid (full opaque) red color in the ARGB space
Color redColor = new Color(0xffff0000);
// The semi-opaque green color in the ARGB space (alpha is 0x78)
Color greenColor = new Color(0x7800ff00,true);
// The semi-opaque blue color in the ARGB space (alpha is 0x78)
Color blueColor = new Color(0x780000ff,true);
// The semi-opaque yellow color in the ARGB space ( alpha is 0x78)
Color yellowColor = new Color(0x78ffff00,true);
// The dash array
int dashArray[] = { 20 ,8 };
graphics2D.clear(Color.WHITE);
graphics2D.Reset();
SolidBrush brush=new SolidBrush(redColor);
graphics2D.fill(brush,circle1);
brush=new SolidBrush(greenColor);
graphics2D.fill(brush,circle2);
Pen pen=new Pen(yellowColor,10,Pen.CAP_BUTT,Pen.JOIN_MITER,dashArray,0);
brush=new SolidBrush(blueColor);
graphics2D.setPenAndBrush(pen,brush);
graphics2D.fill(null,circle3);
graphics2D.draw(null,circle3);
}
}
public class ProvidesMethodsDemo extends Graphics2DActivity{
@Inject @Named("Circle1") IShape circle1;
@Inject @Named("Circle2") IShape circle2;
@Inject @Named("Circle3") IShape circle3;
protected void drawImage(){
// The solid (full opaque) red color in the ARGB space
Color redColor = new Color(0xffff0000);
// The semi-opaque green color in the ARGB space (alpha is 0x78)
Color greenColor = new Color(0x7800ff00,true);
// The semi-opaque blue color in the ARGB space (alpha is 0x78)
Color blueColor = new Color(0x780000ff,true);
// The semi-opaque yellow color in the ARGB space ( alpha is 0x78)
Color yellowColor = new Color(0x78ffff00,true);
// The dash array
int dashArray[] = { 20 ,8 };
graphics2D.clear(Color.WHITE);
graphics2D.Reset();
SolidBrush brush=new SolidBrush(redColor);
graphics2D.fill(brush,circle1);
brush=new SolidBrush(greenColor);
graphics2D.fill(brush,circle2);
Pen pen=new Pen(yellowColor,10,Pen.CAP_BUTT,Pen.JOIN_MITER,dashArray,0);
brush=new SolidBrush(blueColor);
graphics2D.setPenAndBrush(pen,brush);
graphics2D.fill(null,circle3);
graphics2D.draw(null,circle3);
}
}
@Provides方法通常用來創建將復雜的類對象,可以帶參數,參數也可以通過註入傳入比如:
[java] @Provides @Named("Circle1")
IShape provideCircle1(@Named("width") int width){
return new Ellipse(30,60,width,width);
}
本例下載:http://up.aiwalls.com/2012/0504/20120504095832813.zip
摘自 引路蜂移動軟件