Objective C：从数组创建 uibuttons 时出错？

Question

我被困在以下代码中：

btn1 = [UIButton alloc];
btn2 = [UIButton alloc];
btn3 = [UIButton alloc];
btn4 = [UIButton alloc];
btn5 = [UIButton alloc];
btn6 = [UIButton alloc];
NSArray *myarray = [NSArray arrayWithObjects:btn1, btn2, btn3, btn4, btn5, btn6,nil];

for (int i =0; i < [myarray count]; i++)
{
    NSLog(@"What: %@", [myarray objectAtIndex:i]); // Result UIButton
    [myarray objectAtIndex:i].frame = CGRectMake(i* 110+25, 60, 100, 100);// error, cant build
    UIButton *b = (UIButton *)[myarray objectAtIndex:i];
    b.frame = CGRectMake(i* 110+25, 60, 100, 100);
    [b setTitle:@"my button" forState:UIControlStateNormal];
    b.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
    b.titleLabel.textAlignment = UITextAlignmentCenter;
    b.titleLabel.textColor = [UIColor colorWithRed:0x93/255.0 green:0x73/255.0 blue:0x47/255.0 alpha:1.0];
    b.tag = i+1;
    [b addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchDown];
    [self addSubview: b];
    [b release];
}

最初我使用 switch case，例如：

switch (i)
    case 0: {
        /*
        ..... 
        repeat this code
        .....
    }

因此，如果使用 switch case，代码会很长。我循环它的原因是：

• 位置
• 尽量不要重复代码，例如设置标题，背景，添加目标等

或者您有更简单/更短的代码吗？

Answer 1

您已分配 UIButton，但尚未初始化它们。

UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(10, 10, 10, 10)];

您还需要在循环中缓存 UIButton 指针

UIButton *currentButton = [myarray objectAtIndex:i];

，然后将 '[myarray objectAtIndex:i]' 的所有实例替换为 'currentButton'

Answer 2

btn1 = [UIButton alloc];

您需要在分配后初始化，否则您刚刚分配了垃圾内存

btn1 = [[UIButton alloc] init];

也会

[myarray objectAtIndex:i].frame = CGRectMake(i* 110+25, 60, 100, 100);// error, cant build

失败，因为它不知道该对象是什么类，因此它是否可以在其上调用 setFrame: ，这就是为什么您需要将其转换为按钮（这是UIView 子类）

UIButton *b = (UIButton *)[myarray objectAtIndex:i];
b.frame = CGRectMake(i* 110+25, 60, 100, 100);

Answer 3

你可以试试这个吗？

for (int i =0; i < [myarray count]; i++)
{
    UIButton *b = [[UIButton alloc] initWithFrame:CGRectMake(i* 110+25, 60, 100, 100)];
    [b setTitle:@"my button" forState:UIControlStateNormal];
    b.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
    b.titleLabel.textAlignment = UITextAlignmentCenter;
    b.titleLabel.textColor = [UIColor colorWithRed:0x93/255.0 green:0x73/255.0 blue:0x47/255.0 alpha:1.0];
    b.tag = i+1;
    [b addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchDown];
    [self addSubview: b];
    [b release];
}

我认为您忘记初始化按钮。有不同的方法来初始化它们。 init、initWithFrame 和 initWithCoder

Answer 4

[myarray objectAtIndex:i].frame = CGRectMake(i* 110+25, 60, 100, 100);// error, cant build 

给您一个错误，因为您无法使用点语法来访问强制转换（或在本例中为 id）对象。如果删除此行并在设置 b 之后添加以下内容：

b.frame = CGRectMake(i* 110+25, 60, 100, 100);

您将不再收到错误。

您还可以使用快速枚举来优化循环：

for (UIButton *b in myArray)

其他回答者正确地指出您一开始就没有正确创建按钮 - 使用 buttonWithType 或 alloc和initWithFrame。

Answer 5

UIButton *btn1 = [[UIButton alloc] init];
    UIButton *btn2 = [[UIButton alloc] init];
    UIButton *btn3 = [[UIButton alloc] init];
    UIButton *btn4 = [[UIButton alloc] init];
    UIButton *btn5 = [[UIButton alloc] init];
    UIButton *btn6 = [[UIButton alloc] init];
    NSArray *myarray = [NSArray arrayWithObjects:btn1, btn2, btn3, btn4, btn5, btn6,nil];

    for (int i =0; i < [myarray count]; i++)
    {
        NSLog(@"What: %@", [myarray objectAtIndex:i]);        
        UIButton *b = (UIButton *)[myarray objectAtIndex:i];
        b.frame = CGRectMake(i* 110+25, 60, 100, 100);
        [b setTitle:@"my button" forState:UIControlStateNormal];
        b.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
        b.titleLabel.textAlignment = UITextAlignmentCenter;
        float red = 0.33;
        float green = 0.82;
        float blue = 0.48;

        //Color values are float values between 0 and 1;

        b.titleLabel.textColor = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
        b.tag = i+1;
        [b addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchDown];
        [self.view addSubview: b];
        [b release];
    }