Usage of uiscrollview (occasionally updated)

Let's start with the most basic research and use an example to illustrate how to create a UIScrollView.

Create a view-based project in xcode, open the xib file of viewController in the project, add a uiscrollview to the view, and drag several buttons, textfield, and so on to the scrollview.

In this way, the basic ui framework is complete.

The following is the code:

UIScrollViewDemoViewController. h

#import <UIKit/UIKit.h>@interface UIScrollViewDemoViewController : UIViewController<UITextFieldDelegate,UIScrollViewDelegate> {    IBOutlet UIScrollView * myScrollView;    UITextField * activeField;    CGFloat oldContentOffsetValue;    IBOutlet UITextField * textFieldOne;    IBOutlet UITextField * textFieldTwo;    IBOutlet UITextField * textFieldThree;    IBOutlet UITextField * textFieldFour;    BOOL keyboardShown;    BOOL isNeedSetOffset;    }@property (nonatomic,retain) UITextField * activeField;@end

In the code above, I created five iboutlet variables in the xib file, which are four textfields and one scrollview. Then I can connect them to the xib file and connect them to the corresponding ui.

Other variables are used in the implementation file.

UIScrollViewDemoViewController. m

#import "UIScrollViewDemoViewController.h"@implementation UIScrollViewDemoViewController@synthesize activeField;- (void)dealloc{    [myScrollView release];    [activeField release];    [textFieldOne release];    [textFieldTwo release];    [textFieldThree release];    [textFieldFour release];    [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// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.- (void)viewDidLoad{    [super viewDidLoad];        textFieldOne.delegate = self;    textFieldTwo.delegate = self;    textFieldThree.delegate = self;    textFieldFour.delegate = self;            myScrollView.contentSize = CGSizeMake(myScrollView.frame.size.width, 1400.0f);    myScrollView.scrollEnabled = YES;    myScrollView.delegate = self;        keyboardShown = NO;    [self performSelector:@selector(registerForKeyboardNotifications)];    }- (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);}#pragma mark - UITextField Delegate-(void)textFieldDidBeginEditing:(UITextField *)textField{    activeField = textField;}-(void)textFieldDidEndEditing:(UITextField *)textField{    activeField = nil;}-(BOOL)textFieldShouldReturn:(UITextField *)textField{    [textField resignFirstResponder];    return YES;}#pragma mark -Keyboard Helper Method// Call this method somewhere in your view controller setup code.- (void)registerForKeyboardNotifications{    [[NSNotificationCenter defaultCenter] addObserver:self                                             selector:@selector(keyboardWasShown:)                                                 name:UIKeyboardDidShowNotification object:nil];        [[NSNotificationCenter defaultCenter] addObserver:self                                             selector:@selector(keyboardWasHidden:)                                                 name:UIKeyboardDidHideNotification object:nil];}// Called when the UIKeyboardDidShowNotification is sent.- (void)keyboardWasShown:(NSNotification*)aNotification{    NSLog(@"-------");    if (keyboardShown)        return;        NSDictionary* info = [aNotification userInfo];        // Get the size of the keyboard.    NSValue* aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];    CGSize keyboardSize = [aValue CGRectValue].size;        // Resize the scroll view (which is the root view of the window)    CGRect viewFrame = [myScrollView frame];    viewFrame.size.height -= keyboardSize.height;    myScrollView.frame = viewFrame;            // Scroll the active text field into view.    CGRect textFieldRect = [activeField frame];    [myScrollView scrollRectToVisible:textFieldRect animated:YES];        oldContentOffsetValue = [myScrollView contentOffset].y;            CGFloat value = (activeField.frame.origin.y+myScrollView.frame.origin.y+activeField.frame.size.height - self.view.frame.size.height + keyboardSize.height)+2.0f;    if (value > 0) {        [myScrollView setContentOffset:CGPointMake(0, value) animated:YES];        isNeedSetOffset = YES;    }    keyboardShown = YES;}// Called when the UIKeyboardDidHideNotification is sent- (void)keyboardWasHidden:(NSNotification*)aNotification{    NSDictionary* info = [aNotification userInfo];        // Get the size of the keyboard.    NSValue* aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];    CGSize keyboardSize = [aValue CGRectValue].size;        // Reset the height of the scroll view to its original value    CGRect viewFrame = [myScrollView frame];    viewFrame.size.height += keyboardSize.height;    myScrollView.frame = viewFrame;            if (isNeedSetOffset) {        [myScrollView setContentOffset:CGPointMake(0, oldContentOffsetValue) animated:YES];    }    isNeedSetOffset = NO;    keyboardShown = NO;}@end

The Code is a bit long. parse it step by step.

First, initialize the viewDidLoad method:

-(Void) viewdidload {[Super viewdidload]; textfieldone. delegate = self; // set the delegate of textfield, mainly to display and hide the textfieldtwo used by the pop-up keyboard. delegate = self; textfieldthree. delegate = self; textfieldfour. delegate = self; // It is very important to use scrollview. Set the contentsize, which is generally set by setting the size of your scrollview. The following height can be 300 ~ 400 myscrollview. contentsize = cgsizemake (myscrollview. Frame. Size. Width, 140020.f); myscrollview. scrollenabled = yes; // This is yes by default, which is redundant here. Myscrollview. delegate = self; // set the delegate of scrollview. If you want to listen to a rolling event, you can implement its delegate method keyboardshown = no; // a status flag, this method is mainly used to identify the display and hiding status of the keyboard [self defined mselector: @ selector (registerforkeyboardications ications)]; // This method is used to handle the problem when the textfield is blocked by the pop-up keyboard, scroll it to the appropriate position}

Then the corresponding

The registerforkeyboardconfigurications method is used to scroll textfield to an appropriate position.

-(Void) registerforkeyboardconfigurations {// Add yourself as the observer to obtain the notification [[nsicationicationcenter defaultCenter] addObserver: self selector: @ selector (keyboardWasShown :) name: Your object: nil]; // Add yourself as an observer to obtain the notification [[nsicationicationcenter defacenter center] addObserver: self selector: @ selector (keyboardWasHidden :) name: UIKeyboardDidHideNotification object: nil];} // call this method when the keyboard appears-(void) keyboardWasShown :( NSNotification *) aNotification {// if the keyboard is displayed, no repeated operations are required if (keyboardShown) return; // user information dictionary for obtaining keyboard notifications NSDictionary * info = [aNotification userInfo]; // obtain the keyboard size. NSValue * aValue = [info objectForKey: UIKeyboardBoundsUserInfoKey]; CGSize keyboardSize = [aValue CGRectValue]. size; // reset the size of the scrollView CGRect viewFrame = [myScrollView frame]; viewFrame. size. height-= keyboardSize. height; myScrollView. frame = viewFrame; // scroll the currently blocked text field to the appropriate visible position in the view. CGRect textFieldRect = [activeField frame]; [myScrollView scrollRectToVisible: textFieldRect animated: YES]; // records the offset of the current textField to hide the keyboard, restore textField to the original location oldContentOffsetValue = [myScrollView contentOffset]. y; // calculate the appropriate position for textField to scroll to CGFloat value = (activeField. frame. origin. y + myScrollView. frame. origin. y + activeField. frame. size. height-self. view. frame. size. height + keyboardSize. height) + 2.0f; // if the value is greater than 0, scroll is required. if the value is smaller than 0, the current textField is not blocked. if (value> 0) does not need to be rolled) {// scroll textField to the appropriate position [myScrollView setContentOffset: CGPointMake (0, value) animated: YES]; isNeedSetOffset = YES; // change the status flag to scroll} // change the keyboard status flag to show keyboardShown = YES;} // call this method when the keyboard is hidden-(void) keyboardWasHidden :( NSNotification *) aNotification {NSDictionary * info = [aNotification userInfo]; // Get the size of the keyboard. NSValue * aValue = [info objectForKey: UIKeyboardBoundsUserInfoKey]; CGSize keyboardSize = [aValue CGRectValue]. size; // Reset the height of the scroll view to its original value CGRect viewFrame = [myScrollView frame]; viewFrame. size. height + = keyboardSize. height; myScrollView. frame = viewFrame; // if the status flag is scroll, You need to perform the textFiled reset operation if (isNeedSetOffset) {// oldContentOffsetValue records the original position of textField. Reset it to [myScrollView setContentOffset: CGPointMake (0, oldContentOffsetValue) animated: YES];} // reset status flag isNeedSetOffset = NO; keyboardShown = NO ;}

This is a simple scrollview. It is also very common to scroll the blocked content to the appropriate location.