iOS Development Foundation-uiscrollview for picture scaling

When the user uses the pinch gesture on uiscrollview , uiscrollview sends a message to the uiscrollviewdelegate protocol and invokes the proxy's Viewforzoominginscrollview: method, the control that the method returns is the control that needs to be scaled.

Steps to implement the Zoom feature:

1) Let the controller comply with Uiscrollview Agent Protocol uiscrollviewdelegate ;

2) Set the agent for Uiscrollview , _scrollview.  Delegate = self; ；

3) Call the Proxy method Viewforzoominginscrollview: , return the child controls that need to implement the Zoom function;

4) Set the zoom range, _scrollview.maximumzoomscale, _scrollview.minimumzoomscale .

Instance

Create a new single View application, let the Viewcontroller class comply with the uiscrollviewdelegate protocol, and add Uiscrollview to the class extension and Uiimageview properties, as follows:

1 // VIEWCONTROLLER.M 2 @interface Viewcontroller () 3 {4     Uiscrollview *_scrollview; 5     Uiimageview *_imageview; 6 }

The overloaded viewdidload method is as follows:

1- (void) Viewdidload {2 [Super Viewdidload];3     //Add Uiscrollview4_scrollview =[[Uiscrollview alloc] initWithFrame:self.view.bounds];5 [Self.view Addsubview:_scrollview];6     7     //Add a picture8    UIImage *image = [UIImage imagenamed:@ "beauty4.jpg"]; 9     //Initwithimage: Method creates the width of the _imageview and the same as the pictureTen     _imageview = [[Uiimageview alloc] initwithimage:image];  One [_scrollview Addsubview:_imageview]; A_scrollview.contentsize =image.size; -      -     //Set proxy Object the_scrollview.Delegate=Self ; -     //Set the maximum zoom-in ratio -_scrollview.maximumzoomscale =2.0; -_scrollview.minimumzoomscale =0.5; +}

Implement the Viewforzoominginscrollview: method to tell _scrollview that _imageview is a child control that needs to be scaled:

1 // VIEWCONTROLLER.M 2 -(UIView *) Viewforzoominginscrollview: (Uiscrollview *) ScrollView {3     NSLog (@ "  Achieve the zoom of the picture "); 4     return _imageview; 5 }

Add

The Code underline section above, the method of instantiating Uiimageview can be replaced by:

1 _imageview = [[Uiimageview alloc] init]; 2 UIImage *image = [UIImage imagenamed:@ "beauty4.jpg"]; 3 _imageview.image = image; 4 _imageview.frame = CGRectMake (00, Image.size.width, image.size.height);

Other proxy methods related to scaling:

-(void) scrollviewwillbeginzooming: (Uiscrollview *) ScrollView Withview: (UIView *) View Called when the zoom is complete.

-(void) Scrollviewdidzoom: (Uiscrollview *) called when ScrollView is scaling.

Add the following code to the original code:

1 -(void) scrollviewwillbeginzooming: (Uiscrollview *) ScrollView Withview: (UIView *) View { 2     NSLog (@ "%s", __function__); 3 }45 -(void) Scrollviewdidzoom: (Uiscrollview *) ScrollView { 6     NSLog (@ "%s", __function__); 7 }

To debug on a real machine, use pinch gestures to enlarge the image and output the following:

1  .- Geneva- -  -: *:07.780wjqscrollviewdemo[189:3549] -[Viewcontroller Viewforzoominginscrollview:]2  .- Geneva- -  -: *:07.781wjqscrollviewdemo[189:3549] -[Viewcontroller Scrollviewwillbeginzooming:withview:]3  .- Geneva- -  -: *:07.798wjqscrollviewdemo[189:3549]-[viewcontroller Scrollviewdidzoom:]

Reference Blog: iOS Development UI Chapter-uiscrollview controls for picture scaling

Code Download: http://vdisk.weibo.com/s/DiY98QyXCNtD9

iOS Development Foundation-uiscrollview for picture scaling