Question

对于学校作业，我被告知要制作一个计算器应用程序，就像聚光灯计算器一样。它实时工作，没有按钮可以开始。

到目前为止，这是我的代码。它写在文本字段中，其中包含事件编辑已结束。我很确定这是错的，但我找不到另一种解决方案。此外，我没有得到实时的工作，所以我有点恢复到按下文本字段时完成以下步骤。

- (IBAction)Didend_Action:(id)sender {
  NSString *list = [Sum_TextField text]; 
  NSArray *listItemsArray = [list componentsSeparatedByString:@" "];
  float firstNumber = [[listItemsArray objectAtIndex: 0] floatValue]; 
  NSString *symbol = [listItemsArray objectAtIndex: 1];
  float secondNumber = [[listItemsArray objectAtIndex: 2] floatValue];
  {   
    Calculator* calc = [[Calculator alloc] init];
    [calc setNum1:firstNumber];
    [calc setNum2:secondNumber];
    if ([symbol isEqualToString:@"-"])
    {
        [calc minus];
    }
    else if ([symbol isEqualToString:@"+"])
    {
        [calc add];
    } 
    if ([symbol isEqualToString:@"*"])
    {
        [calc multiply];
    }
    else if ([symbol isEqualToString:@"/"])
    {
        [calc divide];

    }
    [Answer_TextField setText:[NSString stringWithFormat:@"%d", [calc answer]]];  
  }
}

Answer 1

我认为更好的方法是实现像textViewDidChange:这样的UITextViewDelegate协议方法。例如，你可以这样做：

- (void)textViewDidChange:(UITextView *)textView {

    NSString *currentText = [textview text];
    NSArray *currentItems = [currentText componenetsSeparatedByString:@" "];
    float result = 0.0;

    //If a valid expression is in the text view
    if([currentItems count] > 2) {

        float num1 = [[currentItems objectAtIndex:0] floatValue];
        float num2 = [[currentItems objectAtIndex:2] floatValue];
        NSString *operator = [currentItems objectAtIndex:1];

        if([operator isEqualToString:@"+"]) {

            result = num1 + num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"-"]) {

            result = num1 - num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"*"]) {

            result = num1 * num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"/"]) {

            result = num1 / num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];            
        }
        else{

            answerTextField.text = @"Invalid Operation";
        }
    }
}

每次用户在文本视图中编辑文本时都会调用此方法。它应该工作，但我没有测试它。确保在此代码所在的任何文件的标题中，您执行以下操作：

@interface yourClassName : yourSuperclass <UITextViewDelegate> {

    //Your instance variables
}

//Your method and property declarations

修改

假设我将- (void)textViewDidChange:(UITextView *)textView代码放在名为MyClass.m的文件中。文件MyClass.m将如下所示：

@implementation MyClass - (void)textViewDidChange:(UITextView *)textView { //All the above code goes here } - (void)viewDidLoad { [super viewDidLoad]; //INCLUDE THESE LINES Sum_TextField.delegate = self; Answer_TextField.delegate = self; } - (void)viewDidUnload { [super viewDidUnload]; } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; } @end

在头文件（MyClass.h）中，我会把它放在：

@interface MyClass : UIViewController <UITextViewDelegate> //Note: you don't declare - (void)textViewDidChange:(UITextView *)textView in the header file because you are implementing //a protocol method. //MAKE SURE SUM_TEXTFIELD AND ANSWER_TEXTFIELD ARE UITEXTVIEWS NOT UITEXTFIELDS @property (strong, nonatomic) IBOutlet UITextView *Sum_TextField; @property (strong, nonatomic) IBOutlet UITextView *Answer_TextField; @end

希望这有帮助！

实时计算器

1 个答案: