增加速度

Question

大家好，我正在制作一个应用程序，在这个应用程序中，你是一个蓝色的球，必须在不让红色球碰到你的情况下移动，我想知道我该怎么做才能让速度每增加一秒，我就有这样的东西：

- (void)viewDidLoad {
[super viewDidLoad];
//(X Speed, Y Speed)
pos = CGPointMake(13.0,8.0);
pos2 = CGPointMake(10.0,9.0);
}

- (IBAction)restart:(id)sender {
     [restartbutton setHidden:YES];
     [menubutton setHidden:YES];
     randomMain = [NSTimer scheduledTimerWithTimeInterval:(0.03) target:self selector:@selector(onTimer) userInfo:nil repeats:YES];
}
- (IBAction)start:(id)sender {    
     [startbutton setHidden:YES];
     [restartbutton setHidden:YES];
     [menubutton setHidden:YES];
     randomMain = [NSTimer scheduledTimerWithTimeInterval:(0.03) target:self selector:@selector(onTimer) userInfo:nil repeats:YES];
}
- (IBAction)menu:(id)sender {
     [self.navigationController popViewControllerAnimated:YES];
}
- (void)onTimer {
    [self checkCollision];
    enemy.center = CGPointMake(enemy.center.x+pos.x, enemy.center.y+pos.y);
    enemy2.center = CGPointMake(enemy2.center.x+pos2.x, enemy2.center.y+pos2.y);
    if (enemy.center.x > 320 || enemy.center.x < 0) 
        pos.x = -pos.x;
    if (enemy.center.y > 480 || enemy.center.y < 0) 
        pos.y = -pos.y;
    if (enemy2.center.x > 320 || enemy2.center.x < 0) 
        pos2.x = -pos2.x;
    if (enemy2.center.y > 480 || enemy2.center.y < 0) 
        pos2.y = -pos2.y;
}
- (void)checkCollision {
    if (CGRectIntersectsRect(player.frame, enemy.frame)) {
        [randomMain invalidate];
        [startbutton setHidden:YES];
        [restartbutton setHidden:NO];
        [menubutton setHidden:NO];
        CGRect frame = [player frame];
        frame.origin.x = 135.0f;
        frame.origin.y = 205.0f;
        [player setFrame:frame];
        CGRect frame2 = [enemy frame];
        frame2.origin.x = 135.0f;
        frame2.origin.y = 20.0f;
        [enemy setFrame:frame2];
        CGRect frame3 = [enemy2 frame];
        frame3.origin.x = 135.0f;
        frame3.origin.y = 390.0f;
        [enemy2 setFrame:frame3];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"You Lost!" 
                                                        message:[NSString stringWithFormat:@"Better Luck Next Time"]     
                                                       delegate:nil 
                                              cancelButtonTitle:@"Cancel" 
                                              otherButtonTitles:nil];
    [alert show];
    }
}
 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *myTouch = [[event allTouches] anyObject];
    player.center = [myTouch locationInView:self.view];
}
 - (void)viewDidUnload
 {
     [super viewDidUnload];
     // Release any retained subviews of the main view.
 }

@end

Answer 1

您给我们的唯一一个经常被调用的方法似乎是onTimer。你为什么不设定一个非常小的加速度常数，比如0.01。然后，创建一个名为accelerate的方法，并将其放入代码中以达到以下效果：

pos = CGPointMake(pos.x + ACC_CONSTANT, pos.y + ACC_CONSTANT);
pos2 = CGPointMake(pos2.x + ACC_CONSTANT, pos.y + ACC_CONSTANT);

〔self-checkCollision〕后调用accelerate；

然后使用加速度常数，直到得到想要的结果。

如果你希望它是一个阶跃函数，每秒只增加一次，你需要使用NSTimer iVar，这也相当容易。只需使用这个init函数以1秒的时间间隔实例化它

scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:

然后调用@selector（accelerate）作为目标选择器。