UIButton 背景图片 点击更改

Question

I have a tableView showing some controls.Like options for the correct ans in UIButton.I want to change the buttons background image in the correct ans and the wrong ans in the click event.how can i do this?Can any one give me a idea? i am trying to change the background image as:

 [cell.ansBtn2 setImage:[UIImage imageNamed:@"option_red.png"]  forState:UIControlStateSelected];

and i have set the backgound as:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

     static NSString *CellIdentifier = @"BeginingCell";

     cell=(BeginingCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];


    if (cell == nil) {

               NSArray *topLevelObjects=[[NSBundle mainBundle] loadNibNamed:@"BeginingCell" owner:self options:nil ];

        for(id CurrentObject in topLevelObjects)
        {
            if ([CurrentObject isKindOfClass:[BeginingCell class]]) {

                cell=(BeginingCell *) CurrentObject;
                cell.selectionStyle = UITableViewCellSelectionStyleNone;


                break;
            }
        }

    }


    if(indexPath.row==0)
    {


                imageURL=[dictionary objectForKey:@"questionImage"];

        NSURL *url = [NSURL URLWithString:imageURL];
        NSData *data = [NSData dataWithContentsOfURL:(NSURL *)url];
        UIImage *img = [[UIImage alloc]  initWithData:data];



        cell.lblScoreCurrent.text=[NSString stringWithFormat:@"%d", reloader];

        cell.lblScore.text=@"/30";
        cell.myImageView.image = img;
        cell.SectionTitle.text=[dictionary objectForKey:@"question"];




        cell.ansBtn1.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
        cell.ansBtn2.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
        cell.ansBtn3.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
        cell.ansBtn4.titleLabel.lineBreakMode = UILineBreakModeWordWrap;



        cell.ansBtn1.titleLabel.textAlignment = UITextAlignmentCenter;
        cell.ansBtn2.titleLabel.textAlignment = UITextAlignmentCenter;
        cell.ansBtn3.titleLabel.textAlignment = UITextAlignmentCenter;
        cell.ansBtn4.titleLabel.textAlignment = UITextAlignmentCenter;


        [cell.ansBtn1 setTitle:[dictionary objectForKey:@"option1"] forState:UIControlStateNormal];
        [cell.ansBtn2 setTitle:[dictionary objectForKey:@"option2"] forState:UIControlStateNormal];
        [cell.ansBtn3 setTitle:[dictionary objectForKey:@"option3"] forState:UIControlStateNormal];
        [cell.ansBtn4 setTitle:[dictionary objectForKey:@"option4"] forState:UIControlStateNormal];


        [cell.ansBtn1 addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
        [cell.ansBtn2 addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
        [cell.ansBtn3 addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
        [cell.ansBtn4 addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];



    }


    return cell;

}

And here is the click Event:

      -(void) btnAction:(id) sender {

NSString *str =((UIButton*)sender).titleLabel.text;

NSLog(@"%@",str);
NSLog(@"%@",[dictionary objectForKey:@"option3"]);

correctAns=[dictionary objectForKey:@"answer"];

if(str==[dictionary objectForKey:@"option1"])
{
    selectedAns=@"1";

    if ([selectedAns compare:correctAns]==NSOrderedSame) 
    {

    [cell.ansBtn1 setBackgroundImage:[UIImage imageNamed:@"option_green.png"] forState:UIControlStateHighlighted];
     NSLog(@"this is correct");

     countCorrect++;
     cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];


    }

    else 
    {

        [cell.ansBtn1 setBackgroundImage:[UIImage imageNamed:@"option_red.png"] forState:UIControlStateHighlighted];
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }

}

else if(str==[dictionary objectForKey:@"option2"])
{
    selectedAns=@"2";
    if ([selectedAns compare:correctAns]==NSOrderedSame) 
    {
        [cell.ansBtn2 setBackgroundImage:[UIImage imageNamed:@"option_green.png"] forState:UIControlStateHighlighted];
        NSLog(@"this is correct");
        countCorrect++;
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }

    else 
    {
        [cell.ansBtn2 setBackgroundImage:[UIImage imageNamed:@"option_red.png"] forState:UIControlStateHighlighted];
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }
}


else if(str==[dictionary objectForKey:@"option3"])
{

    selectedAns=@"3";
    NSLog(@"selected ans is %@",selectedAns);
    NSLog(@"correct ans is %@",correctAns);

    if ([selectedAns compare:correctAns]==NSOrderedSame) 
    {
        [cell.ansBtn3 setBackgroundImage:[UIImage imageNamed:@"option_green.png"] forState:UIControlStateHighlighted];
        NSLog(@"this is correct");

        countCorrect++;
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }

    else 
    {
        [cell.ansBtn3 setBackgroundImage:[UIImage imageNamed:@"option_red.png"] forState:UIControlStateHighlighted];
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }

}

else if(str==[dictionary objectForKey:@"option4"])
{

    selectedAns=@"4";
    NSLog(@"selected ans is %@",selectedAns);
    NSLog(@"correct ans is %@",correctAns);

    if ([selectedAns compare:correctAns]==NSOrderedSame) 
    {

        [cell.ansBtn4 setBackgroundImage:[UIImage imageNamed:@"option_green.png"] forState:UIControlStateHighlighted];

        countCorrect++;
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];

    }

    else 
    {
        [cell.ansBtn4 setBackgroundImage:[UIImage imageNamed:@"option_red.png"] forState:UIControlStateHighlighted];
        cell.lblRating.text=[NSString stringWithFormat:@"%i", countCorrect];            

    }

}


else {
    NSLog(@"ERROR");
}


reloader++;

if (reloader>=[QuestionMutableArray count]) {



    NSString *str=[self GetSkill];
    NSString *totalTime=[NSString stringWithFormat:@"%i . %i minutes",7-timeMin,60-timeSecond];
    NSString *str2=[NSString stringWithFormat:@"Game Over :\n Knowlwdge Level : %@  \n Total Correct Answer :%i \n Total Time : %@ \n Total Question Answered : %i \n",str,countCorrect,totalTime,reloader];

    appAlert=[[UIAlertView alloc]initWithTitle:@"Game Over :\n" message:str2 
                                               delegate:self cancelButtonTitle:@"Exit" otherButtonTitles:nil];
    [appAlert addButtonWithTitle:@"PlayAgain"];



    UIImage *alertBoxImage = [UIImage imageNamed:@"first_look.jpg"];

    UIImageView *_backgroundImageView = [[UIImageView alloc] initWithImage:alertBoxImage];

    _backgroundImageView.frame = CGRectMake(0, 0, 282, 220);

    _backgroundImageView.contentMode = UIViewContentModeScaleToFill;

    [appAlert addSubview:_backgroundImageView];

    [appAlert sendSubviewToBack:_backgroundImageView]; 


    [appAlert show];        
    [dictionary release];
    [QuestionMutableArray release];
    countCorrect=0;


}
else {

    dictionary=[QuestionMutableArray objectAtIndex:reloader];
    [self.tableView reloadData];
}

}

problem is when i am clicking a button for the first time the background is not changing.but in the next click i am getting the change according to the change logic set(i mean green/red change)...what should i do in this case.What is the solution?

Answer 1

More Edit:
Don't use == to check if the strings are equal or not, instead use isEqualToString: or compare: function

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html

you can do

if([string1 compare:string2] == NSOrderedSame)
{
    //Do something...
}

because == will check 2 pointers address in memory location and not the contents of those pointers.

OLD

You can use

http://developer.apple.com/library/ios/#documentation/uikit/reference/UIButton_Class/UIButton/UIButton.html#//apple_ref/occ/instm/UIButton/setBackgroundImage:forState :

or

http://developer.apple.com/library/ios/#documentation/uikit/reference/UIButton_Class/UIButton/UIButton.html#//apple_ref/occ/instm/UIButton/setImage:forState :

If you are showing ans as title label of button, then you have to use setBackgroundImage:forState:

Edit
instead of

 [cell.ansBtn2 setImage:[UIImage imageNamed:@"option_red.png"]  forState:UIControlStateSelected];

you should use

 [cell.ansBtn2 setBackgroundImage:[UIImage imageNamed:@"option_red.png"]  forState:UIControlStateSelected];

cause you also have to show your ans as title label of that button.

Answer 2

Add target methods in your UIbutton. Define it -(IBAction)btnClick:(id)sender. Then create button from sender object in the this method so whenever we click on button, we will get the sender object and change it background image using setBackgroundImage method of button. This may help you.