Android RoboGuice User Guide (7): @ Provides Methods

For example, if you need to construct instances of complex classes, the common method is to use the @ Provides method. This method must be defined in the Module and marked with @ Provides. The return type of each method is bound to the object instance returned by this method.

If this method has binding Annotation or @ Named ("xxx"), Guice binds the object returned by the @ Provides method to this annotated type.

In this example, use @ Provides to create three circles and display them on the screen. For details about how to use the graphics library, see tutorial 12 of simplified Android development: Introduction to the two-dimensional graphics library of the Web tracking bee and color samples. In fact, it is not complex to create a circle. Here it is only used to describe the use of the @ Provides method.

Add three @ Provides methods in Graphics2DModule:

[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 );
}

 

Bind to IShape with annotation @ Named ("Circle1"), @ Named ("Circle2"), @ Named ("Circle3") respectively ″).

Create ProvidesMethodsDemo with the following code:

[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 );
 
}
 
}
The @ Provides method is usually used to create complex class objects, which can contain parameters or input parameters through injection. For example:

[Java] @ Provides @ Named ("Circle1 ")
IShape provideCircle1 (@ Named ("width") int width ){
Return new Ellipse (30,60, width, width );
}






Download this example: http://www.bkjia.com/uploadfile/2012/0504/20120504095832813.zip





Excerpted from the mobile app