当我尝试使用(void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)事件以捕获抖动事件时,我遇到了一些问题。问题是该函数甚至没有运行,即使我覆盖canBecomeFirstResponder并将其设置为返回YES。我已经看到其他人的帖子有这个问题,但我还没有找到答案。
感谢您的帮助!
第一个例子.h(继承自UIView的类 - 从app delegate类“调用”) {
@class TestApplicationView;
@interface TestApplicationView : UIView {
IBOutlet UIView *view;
}
}
第一个例子.m {
- (id)initWithCoder:(NSCoder *)coder
{
[self setUpView];
return self;
}
- (id)initWithFrame:(CGRect)frame
{
[self setUpView];
return self;
}
- (void)setUpView
{
[self becomeFirstResponder];
NSLog(@"First Responder - %d", [self isFirstResponder]);
}
}
第二个例子.h(继承自UIApplicationDelegate和UIScrollViewDelegate的类) {
#import <UIKit/UIKit.h>
@class TestApplicationViewController;
@interface TestApplicationAppDelegate : NSObject <UIApplicationDelegate, UIScrollViewDelegate> {
IBOutlet UIWindow *window;
IBOutlet UIScrollView *scrollView;
}
}
第二个例子.m {
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
[self becomeFirstResponder];
}
}
- 第二个示例返回以下警告:'TestApplicationAppDelegate'可能无法响应'-becomeFirstResponder'
答案 0 :(得分:31)
我假设你想在UIViewController
的子类中实现它。使UIViewController
能够成为第一响应者:
- (BOOL)canBecomeFirstResponder {
return YES;
}
让UIViewController
成为viewDidAppear:
中的第一响应者。
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
[self becomeFirstResponder];
}
如果视图包含可能成为第一响应者本身的任何元素(例如UITextField
),请确保该元素在某个时刻重新响应第一个响应者。例如,使用UITextField
,UIViewController
需要实现UITextFieldDelegate
协议,并且实际上是委托。然后,在textFieldShouldReturn:
- (BOOL)textFieldShouldReturn:(UITextField *)theTextField {
// Hides the keyboard
[theTextField resignFirstResponder];
// Returns first responder status to self so that shake events register here
[self becomeFirstResponder];
return YES;
}
实施motionEnded:withEvent:
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if ( event.subtype == UIEventSubtypeMotionShake ) {
// Do something
}
if ([super respondsToSelector:@selector(motionEnded:withEvent:)]) {
[super motionEnded:motion withEvent:event];
}
}
iPhone开发者论坛中有good post by Matt Drance of Apple(需要注册为开发人员)。
正如评论中所讨论的,这在UIView
的子类中也有效,并不令人惊讶。以下是构建最小示例的方法。
创建一个新的基于视图的应用程序项目,将其命名为ShakeTest
。创建UIView
的新子类,将其命名为ShakeView
。让ShakeView.h
看起来像这样:
#import <UIKit/UIKit.h>
@interface ShakeView : UIView {
}
@end
让ShakeView.m
看起来像这样:
#import "ShakeView.h"
@implementation ShakeView
- (BOOL)canBecomeFirstResponder {
return YES;
}
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if ( event.subtype == UIEventSubtypeMotionShake ) {
NSLog(@"Shake!");
}
if ([super respondsToSelector:@selector(motionEnded:withEvent:)]) {
[super motionEnded:motion withEvent:event];
}
}
@end
让ShakeTestViewController.h
看起来像这样:
#import <UIKit/UIKit.h>
#include "ShakeView.h"
@interface ShakeTestViewController : UIViewController {
ShakeView *s;
}
@end
让ShakeTestViewController.m
看起来像这样:
#import "ShakeTestViewController.h"
@implementation ShakeTestViewController
- (void)viewDidLoad {
[super viewDidLoad];
s = [[ShakeView alloc] init];
[[self view] addSubview:s];
[s becomeFirstResponder];
}
- (void)dealloc {
[s release];
[super dealloc];
}
@end
构建并运行。点击Cmd-Ctrl-Z来摇动iPhone模拟器。惊叹于日志消息。
答案 1 :(得分:0)
您是否实施了旧方法?如果您实现了旧的应用程序范围方法,则需要在调用新方法之前将其删除。