"Learning the path to iOS: UI series" Drawing (DrawRect)

The implementation code is as follows:
① defining 3 properties in a custom view

//记录线条的路径@property (nonatomicNSMutableArray *paths;//设置绘图过程中线条的颜色@property (nonatomicUIColor *pathColor;@property (nonatomicassignCGFloat pathWidth;//撤销功能- (void)undo;//清除功能- (void)clear;

② implementation, you need to process the operation during the move of your finger, that is, you need to operate in the following two methods.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;

Method is implemented in:

//Achieve the appropriate time- (void) Touchesbegan: (Nsset *) touches withevent: (Uievent *) Event {//Get Finger objectUitouch *touch = [touches anyobject];//Get finger current touch point    CgpointStartPoint = [Touch Locationinview:touch. View];//Create Path ObjectUibezierpath *path = [Uibezierpath Bezierpath];//Set the starting point of the path[Path Movetopoint:startpoint];//Configure path Properties    //Line widthPath. LineWidth= Self. Pathwidth;//Line Union stylePath. Linejoinstyle= Kcglinejoinround;//Line stylePath. Linecapstyle= Kcglinecapround;//Add a path to an array of paths[ Self. PathsAddobject:path];} - (void) touchesmoved: (Nsset *) touches withevent: (Uievent *) Event {//Get Finger objectUitouch *touch = [touches anyobject];//Get the position of the finger current touch    CgpointCurrentpoint = [Touch Locationinview:touch. View];//Get current pathUibezierpath *path = [ Self. PathsLastobject];//Set path end point[Path Addlinetopoint:currentpoint];//This method does not need to be implemented, but it automatically calls the DrawRect method[ SelfSetneedsdisplay];}

③ implementation view in the self-contained method (DrawRect), the code is as follows:

- (void)drawRect:(CGRect)rect {     [self.pathColor setStroke];    //遍历所有路径    forself.paths) {    path.usesEvenOddFillRuleYES;        [self.pathColor setFill];        //设置笔画的颜色        [self.pathColor setStroke];        //和所有的路径相连       [path stroke];    }}

④ Properties for lazy loading that eliminates and revokes operations

- (Nsmutablearray*) Paths {if(!_paths) { Self. Paths= [NsmutablearrayArraywithcapacity:1]; }return[[_paths retain] autorelease];} - (CGFloat) Pathwidth {if(!_pathwidth) {_pathwidth =1; }return_pathwidth;}//Undo function- (void) Undo {//Delete last piece of data, path[ Self. PathsRemovelastobject]; [ SelfSetneedsdisplay];}//Clear function- (void) Clear {//Delete all information[ Self. PathsRemoveallobjects]; [ SelfSetneedsdisplay];}

④ enables you to save graffiti pictures to your system albums.
1) Get graffiti pictures (uiimage), view is the current doodle

  + (UIImage *)saveImageFromDrawView:(UIView *)view {    //获取图形上下文(上下文在这两个Graphics之间有效或者在DracRect中有效)    UIGraphicsBeginImageContext(view.frame.size);    //2.将要保存的view的layer绘制到bitmap图形上下文中,完成拍照的功能    [view.layer renderInContext:UIGraphicsGetCurrentContext()];    //从当前上下文获取图片    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    //结束操作    UIGraphicsEndImageContext();    return image;

2) Save the picture (written in the trigger event of the button)

   //获取要保存的图片    UIImage *image = [UIImage saveImageFromDrawView:self.nameView];    //保存到相册    selfnilnil);

⑤ sliding the bottom of the slider implementation to change the line color, that is, the width of the line.

//设置颜色- (IBAction)colorAction:(UISlider *)sender {     //CGFloat value = sender.value;    self.nameView.pathColor = [UIColor colorWithHue:sender.value saturation:sender.value brightness:sender.value alpha:sender.value];}//设置线条的宽度- (IBAction)boldAction:(UISlider *)sender {    self.nameView.pathWidth = sender.value;}

"Learning the path to iOS: UI series" Drawing (DrawRect)