滾動UITableview會更改UIButton，UITableview滾動問題的圖像

Question

我正在做的是，我有一個UITableview ，我添加了UIButton作為自定義視圖。 我給每個按鈕添加標簽，並在動作方法中收到標簽 。 當我按下按鈕時，它會更改所選和未選擇按鈕的圖像，但是當我滾動它時，它將進入正常狀態。

這是我在索引方法行的單元格

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
}
followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];
NSLog(@"row--%d",indexPath.row);
followingButton.tag=indexPath.row;
NSLog(@"followingButton.tag--%d",followingButton.tag);
[self configureCellFollowing:cell forIndexPath:indexPath];
return cell;
}

==================

//Here is the action method

-(void)followingButtonpressed:(id)sender
{
    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;
    if([btnPly isSelected])
    {
        [btnPly setSelected:NO];
        [btnPly setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [btnPly setSelected:YES];
        [btnPly setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

Answer 1

注意：此代碼為每行數據創建單元格（不重用單元格）

您只需按描述進行更改，可能對您有所幫助

NSString *CellIdentifier = [NSString stringWithFormat:@"S%1dR%1d",indexPath.section,indexPath.row];

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

可能會解決你的問題:)

Answer 2

您的按鈕“重置”的原因是因為tableView：cellForRowAtIndexPath被多次調用（每當一個單元格即將可見時）。

每次調用此按鈕時，您都會重新初始化按鈕並將圖像重置為following12.png（默認狀態）。 這就是滾動按鈕時出現重置的原因。

您不能依賴單元本身來保留狀態，因為單元格每次都會重置。 您需要將狀態移動到其他位置（例如在數組實例變量中）。 然后，當您必須在tableView：cellForRowAtIndexPath中配置新單元格時，可以將其初始化為正確的狀態（基於數組）。

因此，創建一個名為myStateArray（或其他）的NSMutableArray實例變量來存儲您的按鈕狀態，然后您的cellForRowAtIndexPath看起來應該更像：

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
}
followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];

// -- Fetch the state from your array
BOOL buttonPressed = [[self.myStateArray objectAtIndex:indexPath.row] boolValue];

// -- Initialize the button state correctly
[followingButton setSelected:buttonPressed];
if (buttonPressed) {
    [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
} else {
    [followingButton setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
}



followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];
NSLog(@"row--%d",indexPath.row);
followingButton.tag=indexPath.row;
NSLog(@"followingButton.tag--%d",followingButton.tag);
[self configureCellFollowing:cell forIndexPath:indexPath];
return cell;
}

然后按下按鈕確保保存狀態：

-(void)followingButtonpressed:(id)sender
{
    // -- Save the state
    [self.myStateArray insertObject:[NSNumber numberWithBool:[btnPly isSelected]] atIndex:[sender tag]];

    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;
    if([btnPly isSelected])
    {
        [btnPly setSelected:NO];
        [btnPly setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [btnPly setSelected:YES];
        [btnPly setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

Answer 3

據我所知，每當UITableView請求單元格時，您都會創建UIButton。 在這兩種情況下，如果您創建一個新單元格或使用出列單元格。 然后，每次在已創建的按鈕上創建並添加一個按鈕。 if您的cellForRowAtIndexPath方法應該如此， if按鈕創建移動到單元格創建

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell4";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
        followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
        [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
        followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
        [cell.contentView addSubview:followingButton];
    }
    NSLog(@"row--%d",indexPath.row);
    followingButton.tag=indexPath.row;
    NSLog(@"followingButton.tag--%d",followingButton.tag);
    [self configureCellFollowing:cell forIndexPath:indexPath];
    return cell;
}

但這不會成為您問題的競爭解決方案。 您可能知道UITableView使用“可重用”單元來減少系統內存使用量。 它只使用當前需要顯示的細胞數量。 因此，在具有100個單元格的表格中，它實際上將創建大約10個。並且它們都不會存儲所有按下/未按下按鈕的正確狀態。 要實現正確的行為，您必須拒絕使用標記並使用某些模型邏輯。 最簡單的方法 - NSMutableArray，您將存儲按鈕狀態。 在followingButtonpressed:方法中，您將正確的對象設置為YES / NO，在cellForRowAtIndexPath您將讀取此值。 檢查下面的代碼

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell4";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
        followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
        [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
        followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
        [cell.contentView addSubview:followingButton];

        BOOL isSelected = [[statesArray objectAtIndex:btnPly.tag] boolValue];
        [self setState:isSelected forButton:followingButton];
    }
    NSLog(@"row--%d",indexPath.row);
    followingButton.tag=indexPath.row;
    NSLog(@"followingButton.tag--%d",followingButton.tag);
    [self configureCellFollowing:cell forIndexPath:indexPath];
    return cell;
}

-(void)followingButtonpressed:(id)sender
{
    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;

    BOOL isSelected = [[statesArray objectAtIndex:btnPly.tag] boolValue];
    [statesArray replaceObjectAtIndex:btnPly.tag withObject:[NSNumber numberWithBool:!isSelected]];

    if(isSelected)
    {
        [self setState:NO forButton:btnPly];
    }
    else
    {
        [self setState:YES forButton:btnPly];
    }
}

- (void) setState:(BOOL)state forButton:(UIButton *)button
{
    if(state)
    {
        [button setSelected:NO];
        [button setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [button setSelected:YES];
        [button setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

statesArray在哪里

NSMutableArray *statesArray = [NSMutableArray new];

你必須在課堂上的某個地方創建並初始化它。 statesArray的對象計數必須與tableView的單元格數相同。

Answer 4

這是因為每次滾動時都會調用此代碼

[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];

所以現在檢查

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];

followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];

[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];

followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];

[self configureCellFollowing:cell forIndexPath:indexPath];
}
return cell;
}