How to realize the label text dynamic change? For example,
labe.text = #"1";
the second is the :
label.text = #"2";
You can do this by extending UILabel class.
MyLable.h
#import <UIKit/UIKit.h>
#protocol MyLabelDelegate;
#interface MYLabel : UILabel
#property(nonatomic, unsafe_unretained) id<MyLabelDelegate> delegate;
#end
#protocol MyLabelDelegate <NSObject>
-(void) label:(UILabel *) label didChangeText:(NSString *) string;
#end
My label.m
#implementation MYLabel
#synthesize delegate = _delegate;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
}
*/
- (void)setText:(NSString *)text{
[super setText:text];
if([self.delegate respondsToSelector:#selector(label:didChangeText:)]){
[_delegate label:self didChangeText:text];
}
}
#end
and you can implement MyLabel delegate in your view controller if want to detect change there
Related
First of all, let me say that I am new to Objective C.
I'm basically trying to pass the originalPriceOnGraph variable from ViewController (UIViewController) to the original variable from GraphView (UIView). However, I keep getting 0.00 when I try and display original. I don't get what exactly is the problem. Here's some of my code:
GraphView.h
#interface GraphView : UIView
#property (nonatomic) double original;
#end
GraphView.m
#implementation GraphView
#synthesize original;
- (id)initWithFrame:(CGRect)frame
{
//some code here
}
- (void)drawRect:(CGRect)rect;
{
NSLog(#"%.2f", original);
//some more code here
}
#end
ViewController.m
#interface OtherViewController ()
#end
#implementation OtherViewController
#synthesize originalPriceOnGraph;
#synthesize graph;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
originalPriceOnGraph = 20.00;
graph = [[GraphView alloc] init];
graph.original = originalPriceOnGraph;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
ViewController.h
#interface OtherViewController : UIViewController
#property (strong, nonatomic) GraphView *graph;
#property (nonatomic) double originalPriceOnGraph;
#end
Thank you in advance!
EDIT: I was able to solve this by creating an IBOutlet between the OtherViewController and GraphView. I also got rid of the alloc init statement for GraphView in ViewController.m. Thank you all for your suggestions!
Are you sure the GraphView's drawRect: method isn't getting called before you set its 'original' property?
If so, try initializing any instance of a GraphView with a default value for original.
In GraphView.h:
-(id)initWithOriginal:(double)original;
In GraphView.m:
-(id)initWithOriginal:(double)original
{
self = [super init];
if (self) {
[self setOriginal:original];
}
return self;
}
In ViewController.m:
-(void)viewDidLoad
{
[super viewDidLoad];
originalPriceOnGraph = 20.00;
[self setGraph:[[GraphView alloc] initWithOriginal:originalPriceOnGraph]];
}
use :
self.graph = [[GraphView alloc] init];
self.graph.original = originalPriceOnGraph;
I have ARC enabled so I am unsure as to why my reference is null.
My view controller instantiates a UIView ‘theGrid’ as soon as the view is loaded.
Later I have switch inside another class (MyOtherClass) that calls the UIViewContoller - (void) updateTheGrid:(id)sender method, that method is called as per the NSLog, but when I output the UIView to see if it is there, its returns null.
What am I doing wrong? It was my impression that ARC keeps up with everything. I feel like my trouble is coming from mm "MyOtherClass" when I ViewController * vc = [[ViewController alloc] init]; because I feel like that is just creating a new instance. But if that is the case, how am i suppose to reference the old instance and call the method?
NSLOG OUTPUT
[28853:c07] Intial Grid: <GridView: 0x8e423b0; frame = (0 0; 768 1024); layer = <CALayer: 0x8e43780>>
[28853:c07] Update The Grid (null)
GridView.h
#import <UIKit/UIKit.h>
#interface GridView : UIView
- (void) gridUpdated;
#end
GridView.m
#import "GridView.h"
#implementation GridView
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code
NSLog(#"initWithFrame");
}
return self;
}
- (void)drawRect:(CGRect)rect{
NSLog(#"Grid Draw Rect");
}
- (void) gridUpdated {
NSLog(#"GRID VIEW.m : Grid update called");
[self setNeedsDisplay];
}
#end
ViewController.h
#import <UIKit/UIKit.h>
#import "GridView.h"
#interface ViewController : UIViewController {
GridView *theGrid;
}
#property (strong, retain) GridView * theGrid;
- (void) updateTheGrid : (id) sender;
#end
ViewController.m
#import "ViewController.h"
#import "GridView.h"
#interface ViewController () {}
#end
#implementation ViewController
#synthesize theGrid;
- (void)viewDidLoad {
[super viewDidLoad];
//draw the grid
theGrid = [[GridView alloc] initWithFrame:self.view.frame];
NSLog(#"Intial Grid: %#", theGrid);
[self.view addSubview:theGrid];
}
- (void) updateTheGrid : (id) sender{
NSLog(#"Update The Grid %#", theGrid);
[theGrid gridUpdated];
}
#end
MyOtherClass.m
- (void) mySwitch : (id) sender {
ViewController * vc = [[ViewController alloc] init];
[vc updateTheGrid:sender];
}
Do not allocate ViewController object again in your MyOtherClass.m because it will create an new instance of ViewController and your previous objects which holds ViewController wil get disposed including theGrid.
So please declare a weak property of ViewController inside the MyOtherClass.m and assign it while allocating MyOtherClass.m
Example:
ViewController class
moc = [[MyOtherClass alloc] initWithFrame:self.view.frame];
moc.vc = self;
MyOtherClass.h
#property(nonatomic,weak) ViewController *vc;
MyOtherClass.m
- (void) mySwitch : (id) sender {
[self.vc updateTheGrid:sender];
}
Note:Take care about the forward declarations :)
I know this is just a fundamental question but still somewhere I am missing something, I am playing with passing data to a textView from another class. For this I have created two classes one with xib file (ViewController) and another without(secondVC).
What I am trying to do is that I have a textview in ViewController class and wanted to pass the data to this textView from secondVC. This is how I am doing.
//ViewController.h
#import <UIKit/UIKit.h>
#import "secondVC.h"
#interface ViewController : UIViewController{
IBOutlet UITextView *textView;
}
#property (nonatomic, retain) UITextView *textView;
- (IBAction)go:(id)sender;
#end
//ViewController.m
- (IBAction)go:(id)sender{
secondVC *sec = [[secondVC alloc] init];
[sec print];
}
//secondVC.h
#import <UIKit/UIKit.h>
#import "ViewController.h"
#interface secondVC : UIViewController
- (void)print;
#end
//secondVC.m
- (void)print{
NSString *printThis = #"This works";
ViewController *vc = [[ViewController alloc] init];
[vc.textView setText:printThis];
//vc.textView.text = printThis //Tried both
}
Any suggestions would be appreciated.
Thanks
you can do like this :
//ViewController.h
#import <UIKit/UIKit.h>
#import "secondVC.h"
#interface ViewController : UIViewController{
IBOutlet UITextView *textView;
}
#property (nonatomic, retain) UITextView *textView;
- (IBAction)go:(id)sender;
#end
//ViewController.m
- (IBAction)go:(id)sender{
secondVC *sec = [[secondVC alloc] init];
sec.viewController = self;
[sec print];
}
//secondVC.h
#import <UIKit/UIKit.h>
#import "ViewController.h"
#interface secondVC : UIViewController {
ViewController *viewController;
}
#property(nonatomic, retain)ViewController *viewController;
- (void)print;
#end
//secondVC.m
#synthesize viewController;
- (void)print{
NSString *printThis = #"This works";
self.viewController.textView.text = printThis ;
}
Try with protocol... if you want to send string from textView(child) to other ViewController(parent)
You need a delegate method that is fired from the SecondVC and handled in the first one (ViewController).
There are a few issues here:
You've got a ViewController creating a new secondVC and sending it a print message. That's okay, but the implementation of -print creates a different instance of ViewController and tries to set the text of it's textView property. That's clearly not what you want -- you should instead be sending the text back to the original instance of ViewController.
That second instance of ViewController very likely has its textView property set to nil since textView is an outlet, but you haven't loaded its view from the .xib.
It's really not nice for one view controller to mess with the views of another view controller. The secondVC should be giving the text to the original ViewController object, not trying to set the text of one of its views.
To facilitate communication from secondVC to ViewController, give secondVC a property to keep track of the original ViewController. The usual thing to do here is to define a delegate protocol for secondVC and implement that protocol in ViewController. When ViewController creates secondVC, it sets the delegate of secondVC to itself. That gives secondVC a pointer to its delegate (it shouldn't care whether its a ViewController or some other kind of object, as long as the delegate implements the right methods).
.h file:
#import <UIKit/UIKit.h>
#protocol StringDelegate <NSObject>
-(void)getArrayOfStrings:(NSMutableArray*)strArray;
#end
#interface WWSettings : UIViewController{
}
#property(nonatomic,assign)id<StringDelegate>delegate;
#end
.m file:
#import "WWSettings.h"
#implementation WWSettings
#synthesize delegate;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
-(void)blablablaFunction{
[delegate getArrayOfStrings:yourArray];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
#end
if you dont understand how it works .. ask ! i'll make my best to help you )
your secondVC
#import <UIKit/UIKit.h>
#import "WWSettings.h"
#interface secondVC : UIViewController<StringDelegate>{
WWSettings *obj;
}
#end
and .m file :
#import "secondVC.h"
#implementation secondVC
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
-(void)getArrayOfStrings:(NSMutableArray *)strArray{
// here you get your array !!! it's a delegate function made by you in child viewController;
}
- (void)viewDidLoad
{
obj = [[WWSettings alloc]init];
[obj setDelegate:self];
[super viewDidLoad];
// Do any additional setup after loading the view.
}
first VC .h file :
#import <UIKit/UIKit.h>
#protocol textViewChildDelegate <NSObject>
-(void)getStrings:(NSString*)string;
#end
#interface textViewChild : UIViewController<UITextViewDelegate>{
UITextView *textView;
}
#property(nonatomic,assign)id<textViewChildDelegate>delegate;
#end
.m file:
#import "textViewChild.h"
#implementation textViewChild
#synthesize delegate;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
-(void)myWorkingMethod{
// get string from textView
[delegate getStrings:textView.text];
}
- (void)viewDidLoad
{
textView = [[UITextView alloc]initWithFrame:CGRectMake(0, 240, 320, 240)];
[super viewDidLoad];
// Do any additional setup after loading the view.
}
Now go to secondVC .h:
#import <UIKit/UIKit.h>
#import "textViewChild.h"
#interface TextViewViewController : UIViewController<textViewChildDelegate>{
UITextView * myfirstTextView;
}
#end
and to .m file:
#import "TextViewViewController.h"
#implementation TextViewViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
-(void)getStrings:(NSString *)string{
myfirstTextView.text = string; // finally we get string from child view controller
}
- (void)viewDidUnload
{
myfirstTextView = [[UITextView alloc]init];
[super viewDidUnload];
// Release any retained subviews of the main view.
}
I read in this same site how to inset and UILabel (subclass UILabel and override the required methods). Before adding it to my app I decided to test it out in a standalone test app. Code is shown below.
Here's MyUILabel.h
#import <UIKit/UIKit.h>
#interface MyUILabel : UILabel
#end
Here's MyUILabel.m
#import "MyUILabel.h"
#import <QuartzCore/QuartzCore.h>
#implementation MyUILabel
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
// for border and rounding
-(void) drawRect:(CGRect)rect
{
self.layer.cornerRadius = 4.0;
self.layer.borderWidth = 2;
[super drawRect:rect];
}
// for inset
-(void) drawTextInRect:(CGRect)rect
{
UIEdgeInsets insets = {0, 5, 0, 5};
[super drawTextInRect: UIEdgeInsetsInsetRect(rect, insets)];
}
Here's my ViewController.h
#import <UIKit/UIKit.h>
#import "MyUILabel.h"
#interface ViewController : UIViewController
{
MyUILabel *myDisplay;
}
#property (strong, nonatomic) IBOutlet MyUILabel *myDisplay;
#end
Here's ViewController.m:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize myDisplay;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
myDisplay.text = #"Hello World!";
}
- (void)viewDidUnload
{
[self setMyDisplay:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
#end
None of the methods in MyUILabel.m (that Im overriding) get called.
Insights into why are greatly appreciated.
Regards,
Ramon.
Ok. I did some further digging and in Xcode there is a field visible when looking at the nib file. Its the 'Identity Inspector' (3rd icon from left). This needed to be changed from UILabel to MyUILabel.
Now it works!
I'm new to iOS Dev, I'm following the Stanford CS193P classes for Fall 2010. I'm on assignment 3 and I'm setting my delegate to my view and by using the debugger I'm noticing the call to my delegate method won't happen, I don't understand what could be happening. My code is as follows:
GraphViewController.h:
#interface GraphViewController : UIViewController <GraphViewDelegate> {
GraphView *graphView;
float scale;
}
#property (retain) IBOutlet GraphView *graphView;
#property float scale;
- (IBAction)zoomIn;
- (IBAction)zoomOut;
#end
GraphViewController.m:
#implementation GraphViewController
#synthesize graphView, scale;
- (NSString *)functionForGraph:(GraphView *)requestor {
NSLog(#"%#", #"culo peluo");
return #"lol";
}
- (float)scaleForGraph:(GraphView *)requestor {
return self.scale;
}
- (IBAction)zoomIn {
}
- (IBAction)zoomOut {
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void)dealloc
{
[super dealloc];
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
#pragma mark - View lifecycle
- (void)viewDidLoad
{
[super viewDidLoad];
self.graphView.delegate = self;
self.scale = 20;
[self.graphView setNeedsDisplay];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
GraphView.h:
#class GraphView;
#protocol GraphViewDelegate
- (NSString *)functionForGraph:(GraphView *)requestor;
- (float)scaleForGraph:(GraphView *)requestor;
#end
#interface GraphView : UIView {
id <GraphViewDelegate> delegate;
}
#property (assign) id <GraphViewDelegate> delegate;
#end
GraphView.m:
#implementation GraphView
#synthesize delegate;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
- (void)drawRect:(CGRect)rect
{
CGFloat cgScale = [self.delegate scaleForGraph:self];
[AxesDrawer drawAxesInRect:self.bounds originAtPoint:self.center scale:cgScale];
}
- (void)dealloc
{
[super dealloc];
}
#end
Put a break point on the line where you set the graph view's delegate.
Inspect the graphView variable. Is it nil?
This happens to me all the time and it's always (well nearly always) because I have failed to connect the outlet to the view in interface builder.
Let's say class YourClass is a delegate for some other class. And delegate methods are not called, despite that delegate property is set up.
Most probably the problem is that your class instance, that is a delegate for your other class is released before the delegate method is called on it. Make it more persistent by making this class a property or instance variable of other class or by using dispatch_once. For example,
Change
YourClass *instance = [[YourClass alloc] init];
by
#property(nonatomic, strong) YourClass *instance;
self.instance = [[YourClass alloc] init];
This problem occurs because in ARC everything that is created inside a method (and is not an instance variable) is released, when method finishes. And delegate methods cannot be called, that are invoked by some background process.
I've written a big blog post on this problem. This is pretty common situation.
http://alwawee.com/wordpress/2013/07/31/on-xmppframework-delegate-method-not-being-called/
Ive got a few pointers for ya on this one:
You don't need an iVar (internal Variable) if you have the variable as a property, it will still work, I've never know it not to.
GraphView
#interface GraphView : UIView {
}
#property (assign) id <GraphViewDelegate> delegate;
#end
GraphViewController
#interface GraphViewController : UIViewController <GraphViewDelegate> {
}
#property (retain) IBOutlet GraphView *graphView;
#property float scale;
- (IBAction)zoomIn;
- (IBAction)zoomOut;
#end
You need to set your delegate in your view to be able to use it.
GraphViewController
#implementation GraphViewController
( ... )
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
self.delegate = self;
}
return self;
}
( ... )
#end
You are not calling the delegate functions anywhere in your GraphView.m. Try testing it out by placing this piece of code in your - (id)initWithFrame:(CGRect)frame method, right before you return.
[self.delegate functionForGraph:nil];
and see if it logs any message to the console.
Of course this is just to test the delegate implementation, you should actually be using this delegate call in some other method in your GraphView.m which is able to process your requestor