Today i’ll show you the best way to drag and drop or move objects using touch events , i’ll use this two functions that you can implement them in any ViewController:

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

touchesBegan : will be active at the first moment of moving object , it’s will be active once per moving operation .

touchesMoved : will be active all the time you do moving the object.

OK , Let’s see how to move drag and drop object by this touch functions:

1- my object is UIImageView “imageView” with name (imgTest)
2- the most important thing is to active UserInteraction in UIImageView to be active with touch events , you can do it in “viewDidLoad” function

[[self imgTest]setUserInteractionEnabled:YES];

3- implement or add the two touch event functions “touchesBegan , touchesMoved” in your ViewController

4- define the following variables as class scope variables:

//Save the first touch point
CGPoint firstTouchPoint;

//xd,yd destance between imge center and my touch center
float xd;
float yd;

5- in “touchesBegan” function check if the touched object is (imgTest) or not , and if(YES)– save touch point CGPoint , and calculate xd it’s the deference between touched point x-axes and object centre y-axes and yd deference y-axes

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* bTouch = [touches anyObject];
    if ([bTouch.view isEqual:[self imgTest]]) {
        firstTouchPoint = [bTouch locationInView:[self view]];
        xd = firstTouchPoint.x - [[bTouch view]center].x;
        yd = firstTouchPoint.y - [[bTouch view]center].y;
    }
}

 
6- in “touchesMoved” function , start moving the object (imgTest) after checking the touching object by change centre x,y as below :

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* mTouch = [touches anyObject];
    if (mTouch.view == [self imgTest]) {
        CGPoint cp = [mTouch locationInView:[self view]];
        [[mTouch view]setCenter:CGPointMake(cp.x-xd, cp.y-yd)];
    }
}

you can download fully GUI example here ” Xcode 4.6 “

in the header file copy and past the function definition below:

+(UIImage*)MergeImage:(UIImage*)img1 withImage:(UIImage*)img2;

MergeImage function with parameters UIImage,UIImage and return value is UIImage,
then past the function code in the .m source file

/**
 *Merge two Image @ 0,0
 */
+(UIImage*)MergeImage:(UIImage*)img1 withImage:(UIImage*)img2
{
    //return value
    UIImage* result = nil;

    //convert image1 from UIImage to CGImageRef to get Width and Height
    CGImageRef img1Ref = img1.CGImage;
    float img1W        = CGImageGetWidth(img1Ref);
    float img1H        = CGImageGetHeight(img1Ref);

    //convert image2 from UIImage to CGImage to get Width and Height
    CGImageRef img2Ref = img2.CGImage;
    float img2W        = CGImageGetWidth(img2Ref);
    float img2H        = CGImageGetHeight(img2Ref);

    //Create output image size
    CGSize size = CGSizeMake(MAX(img1W, img2W), MAX(img1H, img2H));

    //Start image context to draw the two images
    UIGraphicsBeginImageContext(size);

    //draw two images in the context
    [img1 drawInRect:CGRectMake(0, 0, img1W, img1H)];
    [img2 drawInRect:CGRectMake(0, 0, img2W, img2H)];

    //get the result of drawing as UIImage
    result = UIGraphicsGetImageFromCurrentImageContext();

    //End and close context
    UIGraphicsEndImageContext();

    //release All CGImageRef 's
    CGImageRelease(img2Ref);
    CGImageRelease(img1Ref);

    //return value :)
    return result;
}

this code is to merge two images only , if you want to merge more than two images you can use this function more than once , or you can add more parameters to the function as you want and repeat

CGImageRef imgXRef = imgX.CGImage;
    float imgXW        = CGImageGetWidth(imgXRef);
    float imgXH        = CGImageGetHeight(imgXRef);
   .
   .    
    //Create output image size
    CGSize size = CGSizeMake(MAX(all images widths), MAX(all images hieghts);

    //draw two images in the context
    [imgx drawInRect:CGRectMake(0, 0, imgxW, imgxH)];

in imgx mean image numbe x = (1,2,3,4,…)

another note
this function merge images at point x=0 and y=0 , so if you want to change this location on the final result image , you can change the 0,0 in the draw lines like this

[img1 drawInRect:CGRectMake(10, 25, imgxW, imgxH)];

if you want to build and install and use openCV in your iOS projects for iPhone, iPad or iPod Touch  so you can use this link to do this and get opencv2.framework to add it in your project.

but if you faced any error during building openCV for ios, so you want to use this easy way to build and compile it for iOS objective-c

1- install MacPorts
http://www.macports.org/install.php

2- open terminal and write

sudo port -v selfupdate

to update MacPorts
3- in terminal write

sudo port -v install opencv +python27

this line will download opencv with some requirements in /opt folder
4- after installing finished , go to path ” /opt/local/var/macports/distfiles/opencv “ you will find OpenCV-2.4.3.tar.bz2 file , extract it to ” OpenCV-2.4.3 ” folder on any place you want, and in terminal cd into this folder

cd OpenCV-2.4.3/ios
python build_framework.py iosFolder

, where iosFolder is the new folder that the python will build opencv2.framwork on it.
5- now after building finished , go to iosFolder you will find opencv2.framework folder , and that’s it , you can add it to your project

 
Adding opencv2.framework to ios project:

1- copy opencv2.framework to root folder or your project , then from xcode (click on project root —> Summary —> Linked Frameworks And Libraries —>(+) to add frameworks —-> Add Other… —> chose your opencv2.framework

2- and don’t forget adding important .framework dependencies from Summary —> Linked Frameworks And Libraries —>(+) to add frameworks and chose :

opencv2.framework  , Accelerate.framework , AssetsLibrary.framework , AVFoundation.framework ,CoreGraphics.framework , CoreImage.framework ,CoreMedia.framework, CoreVideo.framework ,QuartzCore.framework ,UIKit.framework ,Foundation.framework

3- if you face any “null std” error like this :

(null): "cv::CascadeClassifier::load(std::string const&)", referenced from:
(null): "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::compare(char const*) const", referenced from:
(null): "std::__1::__vector_base_common<true>::__throw_length_error() const", referenced from:
(null): "std::__1::locale::use_facet(std::__1::locale::id&) const", referenced from:
(null): "std::__1::ios_base::getloc() const", referenced from:
(null): "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long)", referenced from:
(null): "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long, unsigned long)", referenced from:
(null): "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(unsigned long, char)", referenced from:
(null): "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::append(char const*)", referenced from:

the solution is , -Goto project —moveTo–> Build Settings —slid down to–> Apple LLVM compiler 4.2 – Language
now change default  value of
“C++ Language Dialect” —to–> “C++ 11 [-std=c++11]“
“C++ Standard Library” —to–> “libc++(LLVM C++ standard library with C++ 11 support)”
now reBuild the project , the error must disappear , enjoy

Eng.Ahmed Al-Sadi

Hi;

How to make fade in or fade out animation for “or on” UIImageView object in Objective-c ” iOS”

you want to use UIVew class and UIImageView object “myImage”

1-    UIView : beginAnimations : context // to tell that the animation options will start !!

2- UIView setAnimationCurve // to set animation curve “fast then slow then fast etc..”

3- UIView setAnimationDuration // to set the time that the full animation will take ” from start to end”

4- UIView commitAnimations // start animating

//Fade Out
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationDuration:1];
    [[self myImage]setAlpha:0];
    [UIView commitAnimations];

    //Fade in
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationDuration:1];
    [[self myImage]setAlpha:1];
    [UIView commitAnimations];

the code below shows how to change UITableView ” table view ” cell or row height by using [ UITableView : heightForRowAtIndexPath ] ” Asks the delegate for the height to use for a row in a specified location “

//ExampleDB.com        by AlSadi
//heightForRowAtIndexPath
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 50;
}

or you can change cell “row” height by section number , or specific row

//ExampleDB.com       by AlSadi
//heightForRowAtIndexPath
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    switch (indexPath.section) {
        case 0:
        switch(indexPath.row){
        case 0:    return 40;break;
        default: return 35:break;
       }

            break;
        case 1:
            return 50;
            break;
        default:
            return 45;
            break;
    }
}

to edit ” delete or select ” rows or cells of table view , you can use [ UITableView : setEditing ] “A Boolean value that determines whether the receiver is in editing mode”

//ExampleDB.com     by AlSadi

[TableView setEditing:YES];

if you want to know my way of deleting selected rows from table view so maybe you choose the easiest way to delete selected rows or cells from UITableView :

firstly , my preferred way is use [[ UITableView : indexPathsForSelectedRows ]count] to get the count of selected rows only , and [ UITableView : indexPathForSelectedRow ] to get first selected row ” to delete ” , so if you have an array of values to list on tableView , you can do like below :

//ExampleDB.com by AlSadi

    int selectedCoun = [[tableView indexPathsForSelectedRows]count];       
    for (int i=0; i<selectedCoun; i++) {
        NSIndexPath* tmpIndexPath = [tableView indexPathForSelectedRow];
        [self tableView:tableView commitEditingStyle:UITableViewCellEditingStyleDelete forRowAtIndexPath:tmpIndexPath];
    }

and on [ tableView : commitEditingStyle : forRowAtIndexPath ] from UITableViewDataSource Protocol Reference under UITableViewCellEditingStyleDelete editing style do as below :

//ExampleDB.com   by AlSadi

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        [myArray removeObjectAtIndex:indexPath.row];
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {

    }   
}

Hi;
the method “function” below is an example how to delete file using file manager “NSFileManager” [ NSFileManager : removeItemAtPath: error ] “Removes the file or directory at the specified path.” , you can use this method “function” to do this.

//exampledb.com
//DeleteFile // By AlSadi
-(void)DeleteFile:(NSString*)filePath
{
    NSFileManager* fileMngr = [NSFileManager defaultManager];
    if ([fileMngr fileExistsAtPath:filePath]) {
        NSError* deletionError;
        bool isDeleted = [fileMngr removeItemAtPath:filePath error:&deletionError];
        if (isDeleted) {
            NSLog(@"file Deleted");
        }else {
            NSLog(@"Deleting Error : %@",[deletionError localizedDescription]);
        }
        deletionError = nil;
    }
    fileMngr = nil;
}

the example below show how to delete all rows cells from table view , but note that you must remove all objects of using array , and then use [UITableView : reloadData] “Reloads the rows and sections of the receiver”

//exampledb.com  - By AlSadi
//Remove all tableview rows or cells
-(void) DeleteAllList
{
    [arrayList removeAllObjects];
    [TableView reloadData];
}

the line code below show how to get or parse file name from full path using [NSString : lastPathComponent]

//get filename from path - alsadi
NSString* fileName = [fullFilePath lastPathComponent];