(7/18) Re-learning Standford_ios7 Development _ View, drawing, gesture recognition _ Course notes

Seventh Lesson:

1. View

In general, a view is a building block that represents a rectangular area on the screen, defines a coordinate space, draws and adds touch events in it, and so on.

Hierarchical relationship of ① views

A view can have only one parent view, with multiple child views

1 -(void) Addsubview: (UIView *) Aview; // Parent View Add child view 2 -(void) Removefromsuperview; // child views remove themselves from the parent view

②uiwindow

Top-level view of UIView: In general, there is only one UIWindow in the iOS app, which refers to the screen content that is currently displayed.

Initialization of the ③uiview

A. Initializing from storyboard: awakefromnib

B. Code initialization: Alloc initwithframe:

-(void) Setup {...} -(void) awakefromnib {[Self setup];} -(ID) initwithframe: (cgrect) arect{    = [Super Initwithframe:arect];    [Self setup];     return Self ;}

④ classes related to views

A.cgfloat

B.cgpoint: (cgfloat) x, (cgfloat) y

C.cgsize: (cgfloat) width, (cgfloat) height

D.cgrect: (Cgpoint) origin, (cgsize) size

⑤ coordinate system

A. Pixel-to-point concept: Each view has a read-only property contentscalefactor that identifies how many pixels a point contains

B. Coordinate System Properties: (CGRect) bounds, (cgpoint) center, (cgrect) frame

　　　　　　　　

For view B:bounds = ((0,0), (200,250))

frame = ((140,65), (320,320))

Center = (300,225)

Here you understand the concept that a view can be rotated in a parent view.

Creating a ⑥ View

Storyboard:drag

Code:alloc initWithFrame (directly initialized to frame = Cgrectzero by using init)

1 cgrect labelrect = CGRectMake (a); 2 UILabel *label =3 label.text = @ "hello! "; 4 [Self.view Addsubview:label];

⑦ a custom view

By implementing-(void) DrawRect: (CGRect) Arect; method to draw the content, Arect refers to the area that needs to be optimized for drawing, related to the final performance of the view (not required here)

　　　　　　Note: The DrawRect: Method cannot be called actively, and if it needs repainting, it can call-(void) setneedsdisplay; or-(void) Setneedsdisplayinrect: (CGRect) Arect; The system will call DrawRect at the appropriate time:

The implementation process of A.drawrect

Use Coregraphics: * Gets the context of the drawing content

* Create drawing path (Uibezierpath)

* Set drawing properties (Color,font,textures,linewidth,linecaps)

* Strokes (Strok), padding (fill), etc.

Use of B.uibezierpath

Uibezierpath encapsulates contextual content (context: refers to the location of the drawing, the content, and other information)

Uikit calls DrawRect before processing the context content, need to get the current context content when used: cgcontextref context = Uigraphicsgetcurrentcontext ();

Uibezierpath *path = [[Uibezierpath alloc] init];//Create//Draw Path[Path Movetopoint:cgpointmake ( the,Ten)]; [Path Addlinetopoint:cgpointmake ( the, Max)]; [Path Addlinetopoint:cgpointmake (Ten, Max]);//Closed Path[path Closepath];//set strokes and fills[[Uicolor Greencolor] setfill]; [[Uicolor Redcolor] setstroke];//strokes and fills[path fill]; [path stroke];

// Other usage 2.0; // set Drawing path width  *roundedrect = [Uibezierpath bezierpathwithroundedrect: (cgrect) Bounds Cornerradius: (cgfloat) radius]; // Draw rounded rectangles // Draw Ellipse Uibezierpath *oval = [Uibezierpath bezierpathwithovalinrect: (cgrect) bounds]; // Crop View [Roundedrect Addclip]; // the clipped view can only be drawn within its path area, beyond which the part will not be drawn

C. Transparency-related

*uicolor: Attribute Alpha (0.0-1.0)

*uiview: (BOOL) opaque (opaque), alpha (0.0-1.0), Hidden (hidden view)

See the difference: http://blog.csdn.net/martin_liang/article/details/40739845

D. Issues with context content changes when the child view and parent view are converted

Press-in (push), remove (pop) status

- (void) Drawgreencircle: (cgcontextref) ctxt{cgcontextsavegstate (ctxt);//Save Current context[[Uicolor Greencolor] setfill]; //Draw My CircleCgcontextrestoregstate (Ctxt);//recovering a saved context}- (void) DrawRect: (cgrect) arect{cgcontextref context=Uigraphicsgetcurrentcontext ();    [[Uicolor Redcolor] setfill]; //Do some stuff[self drawgreencircle:context]; //Do more stuff and expect fill color to be red}

E. Drawing text

Using nsattributestring

Nsattributedstring *text = ...; // Create drawing content Cgsize textSize = [Text Size]; // get text size size [Text drawatpoint: (Cgpoint) p]; // draw the text to the specified position (upper-left corner), or use Drawinrect to

F. Drawing pictures

UIImage *image =[UIImage imagenamed:@ "foo.jpg"];//UIImage *image = [[UIImage alloc] Initwithcontentsoffile: (NSString *) FullPath];//UIImage *image = [[UIImage alloc] Initwithdata: (NSData *) imageData];//Drawing with ContextUigraphicsbeginimagecontext (cgsize);//draw with Cgcontext functionsUIImage *myimage =Uigraphicsgetimagefromcurrentcontext (); Uigraphicsendimagecontext ();//Standard Drawing[Image drawatpoint: (Cgpoint) p];//[Image drawinrect: (CGRect) r];//[Image drawaspatterninrect: (cgrect) patrect;

Redraw the view when the g.bounds changes

UIView Properties: @property (nonatomic) Uiviewcontentmode Contentmode;

// position Redraw Uiviewcontentmode{left,right,top,right,bottomleft,bottomright,topleft,topright} // Zoom Redraw //  //bounds change when called DrawRect redraw //  It is quite often , that's what you want

2. Gesture Recognition

Step: A. Create a gesture recognizer, add to view

B. Invoking methods when implementing gesture triggering

①uigesturerecognizer

Abstract superclass, parent class for all specific gesture classes

② adding gesture control

-(void//  Maybe-a setter in a Controller          {= pannableview;           *pangr =              [[Uipangesturerecognizer alloc] Initwithtarget:pannableview action: @selector (pan:)]; // Target is also the view controller, and the pan is the calling method for the trigger, implemented          by the target class [Pannableview Addgesturerecognizer:pangr]; // tell gestures to add to view }

Examples of ③pan gestures

-(Cgpoint) Translationinview: (UIView *) Aview; // Touch Moving Distance -(cgpoint) Velocityinview: (UIView *) Aview; // Movement Speed -(void) Settranslation: (cgpoint) Translation InView: (UIView *) Aview;

④ the State property provided by the abstract superclass

//uigesturerecognizerstatebegin continuous gesture start//uigesturerecognizerstatechanged Mobile//uigesturerecognizerstateended//uigesturerecognizerstatecancelled//uigesturerecognizerstatefailed//uigesturerecognizerstaterecognized recognition to gestures//Examples of Use- (void) Pan: (Uipangesturerecognizer *) recognizer{if((recognizer.state = = uigesturerecognizerstatechanged) | |(Recognizer.state==uigesturerecognizerstateended)) {Cgpoint translation=[recognizer Translationinview:self]; //move something in myself (I ' m a UIView) by translation.x and TRANSLATION.Y//For example, if I were a graph and my origin is set by an @property calledOrigin self.origin = Cgpointmake (self.origin.x+translation.x, self.origin.y+TRANSLATION.Y); [Recognizer Settranslation:cgpointzero inview:self];//Resume gesture Move distance, initialize for next gesture recognition call? }}

⑤ Other Gesture Properties

//Uipinchgesturerecognizer pinch gesture@property CGFloat Scale;//Zoom ratio@property (ReadOnly) CGFloat Velocity;//speed (readonly)Uirotationgesturerecognizer rotation gesture @property cgfloat rotation;//Rotate radians@property (ReadOnly) CGFloat Velocity;//speed (readonly)uiswipegesturerecognizer Slide gesture @property uiswipegesturerecognizerdirection direction;//direction (4)@property Nsuinteger numberoftouchesrequired;//number of touch controlsUITapGestureRecognizer Click Gesture @property nsuinteger numberoftapsrequired;//Click Count@property Nsuinteger numberoftouchesrequired;//number of touch controls

3. Other

#pragma mark-example

compiler tags, grouping methods, with the following results

5. Demo

Supercard:https://github.com/nslogmeng/stanford_ios7_study/commit/1505f50229e875776c323fcd08d4b80e04cfcff0

Course Video Address: NetEase Open class: Http://open.163.com/movie/2014/1/2/A/M9H7S9F1H_M9H80ED2A.html

or itunes U search Standford Course

(7/18) Re-learning Standford_ios7 Development _ View, drawing, gesture recognition _ Course notes