(7/18) re-learn Standford_iOS7 development _ views, plotting, gesture recognition _ course notes, standford_ios7 gestures

(7/18) re-learn Standford_iOS7 development _ views, plotting, gesture recognition _ course notes, standford_ios7 gestures

Lesson 7:

1. View

Generally, a view is a construction block that represents a rectangular area on the screen, defines a coordinate space, and draws and adds touch events.

① Hierarchical relationship of views

A view can have only one parent view and multiple child views.

1-(void) addSubview :( UIView *) aView; // Add the child View to the parent view; 2-(void) removeFromSuperview; // remove the child view from the parent View

② UIWindow

The top-level view of the UIView: Generally, there is only one UIWindow In the iOS application, which indicates the screen content currently displayed.

③ Initialize UIView

A. initialize from storyboard: awakeFromNib

B. Code initialization: alloc initWithFrame:

- (void)setup { ... }- (void)awakeFromNib { [self setup]; }- (id)initWithFrame:(CGRect)aRect{    self = [super initWithFrame:aRect];    [self setup];    return self;}

④ View-related classes

A. CGFloat

B. CGPoint :( CGFloat) x, (CGFloat) y

C. CGSize :( CGFloat) width, (CGFloat) height

D. CGRect :( CGPoint) origin, (CGSize) size

⑤ Coordinate System

A. Concept of pixels and points: each View has a read-only attribute contentScaleFactor to identify how many pixels a point contains.

B. Coordinate System attributes: (CGRect) bounds, (CGPoint) center, (CGRect) frame

　　　　　　　　

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

Frame = (320,320 ))

Center = (300,225)

Here we understand the concept that a view can rotate in the parent view.

6. Create a view

Storyboard: drag

Code: alloc initWithFrame (use init to initialize frame = CGRectZero by default)

1 CGRect labelRect = CGRectMake(20, 20, 50, 30);2 UILabel *label = [[UILabel alloc] initWithFrame:labelRect]; 3 label.text = @”Hello!”;4 [self.view addSubview:label];

7. Custom View

Through implementation-(void) drawRect :( CGRect) aRect; Method to draw content, aRect refers to the area to be optimized and is related to the final performance of the view (not required here)

Note: drawRect: The method cannot be called actively. If you need to re-paint, you can call-(void) setNeedsDisplay; or-(void) setNeedsDisplayInRect :( CGRect) aRect ;, the system will call drawRect at the appropriate time:

A. Implementation Process of drawRect

Use CoreGraphics: * to obtain the context of the drawn content

* Create a drawing path (UIBezierPath)

* Set the painting attributes (color, font, textures, lineWidth, linecaps)

* Stroke, fill, and so on

B. Use of UIBezierPath

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

UIKit processes the context content before calling DrawRect. To obtain the current context, use CGContextRef context = UIGraphicsGetCurrentContext ();

UIBezierPath * path = [[UIBezierPath alloc] init]; // create // draw path [path moveToPoint: CGPointMake (75, 10)]; [path addLineToPoint: CGPointMake (160,150)]; [path addLineToPoint: CGPointMake (10,150]); // close path [path closePath]; // set stroke and fill [[UIColor greenColor] setFill]; [[UIColor redColor] setStroke]; // stroke and fill in [path fill]; [path stroke];

// Other usage path. lineWidth = 2.0; // set the drawing path width UIBezierPath * roundedRect = [UIBezierPath bezierPathWithRoundedRect :( CGRect) bounds cornerRadius :( CGFloat) radius]; // draw the rounded rectangle // draw the oval UIBezierPath * oval = [UIBezierPath bezierPathWithOvalInRect :( CGRect) bounds]; // crop the view [roundedRect addClip]; // The cropped view can only be drawn in its path area.

C. Transparency

* UIColor: attribute alpha (0.0-1.0)

* UIView: (BOOL) opaque (opaque), alpha (0.0-1.0), and hidden (hidden view)

Difference please see: http://blog.csdn.net/martin_liang/article/details/40739845

D. Context content changes during conversion between child views and parent views

Push and pop status

-(Void) drawGreenCircle :( CGContextRef) ctxt {CGContextSaveGState (ctxt); // Save the current context [[UIColor greenColor] setFill]; // draw my circle CGContextRestoreGState (ctxt ); // restore the saved context}-(void) drawRect :( CGRect) aRect {CGContextRef context = UIGraphicsGetCurrentContext (); [[UIColor redColor] setFill]; // do some stuff [self drawGreenCircle: context]; // do more stuff and keep CT fill color to be red}

E. Draw text

Use NSAttributeString

NSAttributedString * text = ...; // create the drawing content CGSize textSize = [text size]; // obtain the text size [text drawAtPoint :( CGPoint) p]; // draw the text to the specified position (upper left corner ), or use drawInRect.

F. Draw an image

UIImage * image = [UIImage imageNamed: @“foo.jpg "]; // UIImage * image = [[UIImage alloc] initWithContentsOfFile :( NSString *) fullPath]; // UIImage * image = [[UIImage alloc] initWithData :( NSData *) imageData]; // use context to draw UIGraphicsBeginImageContext (CGSize ); // draw with CGContext functionsUIImage * myImage = drawing (); UIGraphicsEndImageContext (); // standard drawing [image drawAtPoint :( CGPoint) p]; // [image drawInRect :( CGRect) r]; // [image drawAsPatternInRect :( CGRect) patRect;

G. redraw of the view chart when the bounds changes

UIView attributes: @ property (nonatomic) UIViewContentMode contentMode;

// Position re-painting UIViewContentMode {Left, Right, Top, Right, BottomLeft, BottomRight, TopLeft, TopRight} // zoom and re-paint UIViewContentModeScale {ToFill, AspectFill, aspectFit} // bit stretching/shrinking // when bounds changes, call drawRect to re-paint UIViewContentModeRedraw // it is quite often that this is what you want

2. Gesture Recognition

Step: a. Create a gesture reader and add it to the view

B. Call methods for gesture triggering

① UIGestureRecognizer

Abstract superclass, the parent class of all specific gesture classes

② Add gesture control

-(Void) setPannableView :( UIView *) pannableView // maybe this is a setter in a Controller {_ pannableView = pannableView; optional * pangr = [paialloc] initWithTarget: pannableView action: @ selector (pan :)]; // target is also a view controller. pan is the call Method for triggering. It is implemented by the target class [pannableView addGestureRecognizer: pangr]; // Add gestures to the view}

③ Example of pan gesture

-(CGPoint) translationInView :( UIView *) aView; // The distance from the touch movement-(CGPoint) velocityInView :( UIView *) aView; // The moving speed-(void) setTranslation :( CGPoint) translation inView :( UIView *) aView;

④ State attribute provided by abstract superclass

// Begin continuous gesture start // UIGestureRecognizerStateChanged move // done // The Consumer recognizes the gesture // use example-(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 was set by an @ property called origin self. origin = CGPointMake (self. origin. x + translation. x, self. origin. y + translation. y); [recognizer setTranslation: CGPointZero inView: self]; // restore the gesture movement distance and initialize the callback for the next Gesture Recognition call }}

⑤ Other gesture attributes

// UIPinchGestureRecognizer kneading gesture @ property CGFloat scale; // scaling ratio @ property (readonly) CGFloat velocity; // speed (readonly) UIRotationGestureRecognizer rotation gesture @ property CGFloat rotation; // rotate radians @ property (readonly) CGFloat velocity; // speed (readonly) UISwipeGestureRecognizer sliding gesture @ property direction ction; // direction (4) @ property NSUInteger numberOfTouchesRequired; // touch count UITapGestureRecognizer click gesture @ property NSUInteger numberOfTapsRequired; // Number of clicks @ property NSUInteger numberOfTouchesRequired; // touch count

3. Others

# Pragma mark-example

The compiler flag groups the methods. The result is as follows:

5. demo

SuperCard: https://github.com/NSLogMeng/Stanford_iOS7_Study/commit/1505f50229e875776c323fcd08d4b80e04cfcff0

 

 

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