iphone - iOS，KERN_INVALID_ADDRESS [UITextField keyboardInputChangedSelection:]

我收到以下错误。

EXC_BAD_ACCESS
KERN_INVALID_ADDRESS
[UITextField keyboardInputChangedSelection:]

直到最新的崩溃报告为止，我一直无法重现此崩溃。

我根据自己的应用程序中是否设置了密码 / 密码，从didFinishLaunchingWithOptions和applicationWillEnterForeground调用此视图控制器。

现在这是奇怪的事情。

在以下情况下会发生崩溃。

我在没有设置密码的情况下运行我的应用程序，我设置了密码。

然后按主页按钮。

该视图控制器弹出，我输入图钉，然后视图被关闭。

然后我按下主页按钮。

我进入应用程序，出现图钉屏幕。

我按回家。

然后进入应用程序，我崩溃了。

我正在使用arc，并在iOS6上重现了崩溃。

这是下面的代码，我看不到问题了吗？

.h文件

#import <UIKit/UIKit.h>

#define PVSectionFooterDefault @"Enter your PIN"
#define PVSectionFooterInvalid @"Invalid!"
#define PVSectionFooterCorrect @"Correct!"

@interface PasscodeViewController : UIViewController <UITableViewDelegate,
       UITableViewDataSource, UITextFieldDelegate>{
    IBOutlet UITableView *passcodeTable;
    IBOutlet UILabel *lblMessage;
}
@property (nonatomic, strong) UITableView *passcodeTable;
@property (nonatomic, strong) UITextField   *txtPassword;
@property (nonatomic, strong) UILabel *lblMessage;
@end

.m文件

#import "PasscodeViewController.h"
#import "AppDelegate.h"

@implementation PasscodeViewController
@synthesize passcodeTable;
@synthesize txtPassword;
@synthesize lblMessage;
- (void)viewDidLoad {
    [super viewDidLoad];

    //[passcodeTable setBackgroundColor:[UIColor clearColor]];
    //[passcodeTable setBackgroundView:nil];
    self.view.backgroundColor = [UIColor groupTableViewBackgroundColor];

    lblMessage.shadowColor       = [UIColor whiteColor];
    lblMessage.shadowOffset      = CGSizeMake(0.0, 1.0);
    lblMessage.font              = [UIFont systemFontOfSize:14];
    lblMessage.textColor         = [UIColor darkGrayColor];
    lblMessage.text = PVSectionFooterDefault;

    txtPassword.isAccessibilityElement = YES;
    txtPassword.accessibilityLabel = @"Enter PIN";
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self
         selector:@selector(willShowKeyboard:)
             name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
         selector:@selector(didShowKeyboard:)
             name:UIKeyboardDidShowNotification object:nil];

}

- (void)viewWillDisappear:(BOOL)animated {
    [[NSNotificationCenter defaultCenter] removeObserver:self
             name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self
             name:UIKeyboardDidShowNotification object:nil];
}

- (void)willShowKeyboard:(NSNotification *)notification {
    [UIView setAnimationsEnabled:NO];
}

- (void)didShowKeyboard:(NSNotification *)notification {
    [UIView setAnimationsEnabled:YES];
}

#pragma mark - Table view methods
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView
              numberOfRowsInSection:(NSInteger)section {
    return 1;
}

- (UITableViewCell *)tableView:(UITableView *)tableView
                    cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView
                    dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc]
                    initWithStyle:UITableViewCellStyleDefault
                  reuseIdentifier:CellIdentifier];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;

        CGRect frame = CGRectMake(cell.frame.origin.x+205,
                    cell.frame.origin.y+7, 90, 31);

        txtPassword = [[UITextField alloc] initWithFrame:frame];
        txtPassword.delegate = self;
        txtPassword.borderStyle = UITextBorderStyleRoundedRect;
        txtPassword.font = [UIFont systemFontOfSize:17.0];
        txtPassword.backgroundColor = [UIColor whiteColor];
        txtPassword.contentVerticalAlignment =
                     UIControlContentVerticalAlignmentCenter;
        txtPassword.keyboardType = UIKeyboardTypeNumberPad;
        txtPassword.returnKeyType = UIReturnKeyDone;
        txtPassword.secureTextEntry = YES;
        txtPassword.clearButtonMode = UITextFieldViewModeAlways;

        cell.textLabel.text = @"Enter PIN";

        [cell addSubview:txtPassword];

        [txtPassword becomeFirstResponder];
    }
    return cell;
}
#pragma mark - UITextFieldDelegate
- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    return YES;
}

- (BOOL) textFieldShouldClear:(UITextField *)textField {
    lblMessage.text = PVSectionFooterDefault;
    return YES;
}

- (BOOL)textField:(UITextField *)textField
           shouldChangeCharactersInRange:(NSRange)range
                       replacementString:(NSString *)string {
    BOOL res = TRUE;
    NSString *newString = [textField.text
             stringByReplacingCharactersInRange:range
                                     withString:string];

    if ([newString length] == 4) {
        NSUserDefaults *myDefaults = [NSUserDefaults standardUserDefaults];
        NSString *strPassword = [myDefaults stringForKey:@"pass"];

        if (strPassword == nil) {
            strPassword = @"";
        }

        if (![newString isEqualToString:strPassword]) {
            lblMessage.text = PVSectionFooterInvalid;
        } else {
            lblMessage.text = PVSectionFooterCorrect;

            AppDelegate *appDel = (AppDelegate*)
                        [[UIApplication sharedApplication] delegate];
            appDel.gbooShowingGetStartedPasswordAsk = FALSE;
            [self.view removeFromSuperview];
        }
    } else if ([newString length] < 4) {
        lblMessage.text = PVSectionFooterDefault;
    }

    res = !([newString length] > 4);

    return res;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (void)viewDidUnload {
    [super viewDidUnload];
}
@end

应用程序委托确实启动了

if (![strPassword isEqualToString:@""]) {
        self.gbooShowingGetStartedPasswordAsk = TRUE;

        lvc = [[PasscodeViewController alloc]
               initWithNibName:@"PasscodeView" bundle:nil];

        lvc.view.frame = CGRectMake(0, 20, 320, 460);

        [window addSubview:lvc.view];
    }

和....

- (void)applicationWillEnterForeground:(UIApplication *)application {
    NSUserDefaults *myDefaults = [NSUserDefaults standardUserDefaults];

    if (self.gbooShowingGetStartedPasswordAsk == FALSE) {

        NSString *strPassword = [myDefaults stringForKey:@"pass"];
        if (strPassword == nil) {
            strPassword = @"";
        }

        if (![strPassword isEqualToString:@""]) {
            lvc = [[PasscodeViewController alloc]
                   initWithNibName:@"PasscodeView" bundle:nil];
            int th = self.window.frame.size.height;
            lvc.view.frame = CGRectMake(0, 20, 320, th);

            lvc.view.backgroundColor = [UIColor groupTableViewBackgroundColor];

            [window addSubview:lvc.view];
        }
    }
}

最佳答案

考虑何时lvc不是nil，并且具有 super 视图，并且applicationWillEnterForeground:被调用，并将分支带到那里的主要代码块中。您将lvc分配给PasscodeViewController的新实例，这很可能导致lvc的旧值被释放。但是，其view属性具有一个 super 视图，因此不会与其一起释放。这些 Activity 对象可能仍会产生释放的视图控制器仍在监听的通知或动作。我还注意到，您并非总是取消订阅文本字段的委托的dealloc或nil中的通知。

那么，我的建议是:1)确保在实例化另一个实例之前删除lvc的视图，以及2)确保您的PasscodeViewController的dealloc方法清除了NSNotificationCenter具有的可能悬挂的引用。

您的applicationWillEnterForeground:方法变为:

- (void)applicationWillEnterForeground:(UIApplication *)application {
    NSUserDefaults *myDefaults = [NSUserDefaults standardUserDefaults];

    if (self.gbooShowingGetStartedPasswordAsk == FALSE) {

        NSString *strPassword = [myDefaults stringForKey:@"pass"];
        if (strPassword == nil) {
            strPassword = @"";
        }

        if (![strPassword isEqualToString:@""]) {
            [lvc.view removeFromSuperview]; // This line prevents the view from persisting
            lvc = [[PasscodeViewController alloc]
                   initWithNibName:@"PasscodeView" bundle:nil];
            int th = self.window.frame.size.height;
            lvc.view.frame = CGRectMake(0, 20, 320, th);

            lvc.view.backgroundColor = [UIColor groupTableViewBackgroundColor];

            [window addSubview:lvc.view];
        }
    }
}

您的PasscodeViewController的dealloc应该如下所示:

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    if (txtPassword.delegate == self) {
        txtPassword.delegate = nil; //docs indicate this is still an `assign` property so is not auto-zeroing in ARC and iOS 5+
    }
}

进行了这些更改之后，就不应再有对已释放视图控制器的悬空引用，并且视图层次结构中也没有孤立的视图。

关于iphone - iOS，KERN_INVALID_ADDRESS [UITextField keyboardInputChangedSelection:]，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15085512/