以编程方式更改视图以使其向左或向右对齐-Changingaviewprogrammaticallytoalignleftorright

1  

What you explain makes little sense to me, but if it is happening only with the first row, then I would try forcing the layout to redraw by doing:

你的解释对我来说没有什么意义，但是如果它只发生在第一行，那么我将尝试通过以下操作来迫使布局重新绘制:

cell.setNeedsLayout() cell.layoutIfNeeded()

cell.layoutIfNeeded cell.setNeedsLayout()()

from the cellForRowAtIndexPath

从cellForRowAtIndexPath

BTW, I think a better approach would be to register 2 different cells, and create them both in IB. This approach will keep your code shorter and will allow you to modify not only the trailing/leading but also colors, fonts or whatever you need. You give them 2 different IDs, but keep the same implementation class, and you just deque the one you need on your cellForRowAtIndexPath.

顺便说一句，我认为更好的方法是注册两个不同的单元格，并在IB中创建它们。这种方法将使您的代码更短，不仅允许您修改尾随/引导，还可以修改颜色、字体或任何您需要的东西。您给它们两个不同的id，但是保持相同的实现类，并且您只需要在cellForRowAtIndexPath上做一个您需要的。

Keeping a different cell per style is the standard way to do these things with IB.

每个样式都保留一个不同的单元格是处理IB的标准方法。

1  

removeConstraint: is deprecated, in favor of using the active property instead (or NSLayoutConstraint's deactivateConstraints:). While removeConstraint: still usually works, combining that with setting your constraints' active property makes this worse. Either use all activate and deactivate (preferred) or use add and remove.

removeConstraint:已弃用，改为使用活动属性(或NSLayoutConstraint的反激活约束:)。虽然removeConstraint:仍然正常工作，但是结合设置约束的活动属性会使情况变得更糟。要么使用所有激活和停用(首选)，要么使用添加和删除。

So instead of cell.removeConstraint:, use this:

而不是细胞。removeConstraint:用这个:

cell.bubbleViewTrailing.active = false

One thing I may note is that your leading and trailing is reversed. Leading is on the left and trailing is on the right, except for right-to-left localization.

有一件事我可能会注意到，你的领先和落后是颠倒的。前导在左边，尾在右边，除了从右到左定位。

0  

Here is the Custom ChatMessageCell that I have implemented for you in which I have applied programmatically constrains using the KVConstraintExtensionsMaster library to apply constraints that I have implemented.

下面是我为您实现的自定义ChatMessageCell，其中我使用kvconstraintextensmaster库以编程方式约束应用我实现的约束。

I have update the leading & trailing constraints Constant value instead of activate/deactivate constraint or remove/add constraint.

我更新了引导和跟踪约束常量值，而不是激活/停用约束或删除/添加约束。

I hope this may help you.

我希望这能对你有所帮助。

Put below code in ChatMessageCell.h header file

在ChatMessageCell中输入以下代码。h头文件

typedef NS_ENUM(NSUInteger, Type) {
    TypeSender,
    TypeReceiver,
};

@interface ChatMessageCell : UITableViewCell

@property (assign, nonatomic) Type cellType;
@property (strong, nonatomic) UIView *msgBackgroundView;
@property (strong, nonatomic) UILabel *messageLabel;

@end

Put below code in ChatMessageCell.m file

在ChatMessageCell中输入以下代码。m文件

#import "ChatMessageCell.h"
#import "KVConstraintExtensionsMaster.h"

@implementation ChatMessageCell

- (void)awakeFromNib {
    [super awakeFromNib];
    // Initialization code
}

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {
        [self createAndConfigureViewHierarchy];
    }    
    return self;
}

- (void)createAndConfigureViewHierarchy
{
    _msgBackgroundView = [UIView prepareNewViewForAutoLayout];
    [self.contentView addSubview:_msgBackgroundView];

    _msgBackgroundView.backgroundColor = [UIColor clearColor];
    [_msgBackgroundView.layer setCornerRadius:6.0];

    _labelMessage = [UILabel prepareNewViewForAutoLayout];
    [_labelMessage setLineBreakMode:NSLineBreakByTruncatingTail];
    [_labelMessage setNumberOfLines:0];
    [_labelMessage setTextAlignment:NSTextAlignmentLeft];
    [_labelMessage setTextColor:[UIColor whiteColor]];
    self.labelMessage.backgroundColor = [UIColor clearColor];

    [_msgBackgroundView addSubview:_labelMessage];

    [self applyConstraints];
}

-(void)applyConstraints
{
    // now applying the constraints by using KVConstraintExtensionsMaster library
    CGFloat padding = 8.0;

    // adding Top and Bottom contraints of _msgBackgroundView
    [_msgBackgroundView applyTopAndBottomPinConstraintToSuperviewWithPadding:padding];

    // adding leading and trailing contraints of _msgBackgroundView
    [_msgBackgroundView applyLeadingAndTrailingPinConstraintToSuperviewWithPadding:padding];

    // adding Top and Bottom contraints of _msgBackgroundView
    [_labelMessage applyTopAndBottomPinConstraintToSuperviewWithPadding:padding];

    // adding leading and trailing contraints of _msgBackgroundView
    [_labelMessage applyLeadingAndTrailingPinConstraintToSuperviewWithPadding:padding];

}

-(void)setCellType:(Type)cellType
{
    switch (cellType) {
        case TypeSender:
        {
            [_msgBackgroundView setBackgroundColor:[UIColor redColor]];
            [_labelMessage setTextAlignment:NSTextAlignmentRight];

            // this method will change the Leading Pin Constraint Constant value by 100.0
            [_msgBackgroundView applyLeadingPinConstraintToSuperviewWithPadding:100.0];

            // this method will increase the Leading Pin Constraint Constant value with proper ratio only iPad
            [_msgBackgroundView updateAppliedConstraintConstantValueForIpadByAttribute:NSLayoutAttributeLeading];
            break;
        }

        case TypeReceiver:
        {
            [_msgBackgroundView setBackgroundColor:[UIColor redColor]];
            [_labelMessage setTextAlignment:NSTextAlignmentLeft];

            // this method will change the Trailing Pin Constraint Constant value by 100.0
            [_msgBackgroundView applyTrailingPinConstraintToSuperviewWithPadding:100.0];

            // this method will increase the Leading Pin Constraint Constant value with proper ratio only iPad
            [_msgBackgroundView updateAppliedConstraintConstantValueForIpadByAttribute:NSLayoutAttributeTrailing];
            break;
        }
    }

    [self.contentView setNeedsLayout];
    [self.contentView updateModifyConstraints];
}

-(void)prepareForReuse
{
    // this method will change the Leading And Trailing Pin Constraints Constant value by 8.0
    [_msgBackgroundView applyLeadingAndTrailingPinConstraintToSuperviewWithPadding:8.0];
    [super prepareForReuse];
}

@end

Put the below code in the viewDidLoad method ofyour ViewController is:

在视图控制器的viewDidLoad方法中放入以下代码是:

[self.tableView registerClass:ChatMessageCell.class forCellReuseIdentifier:@"KVChatMessageCell"];
self.tableView.rowHeight = UITableViewAutomaticDimension;
/* any estimated height but must be more than 2 */
self.tableView.estimatedRowHeight = 44.0;

Now implement UITableView DataSource in your ViewController

现在在视图控制器中实现UITableView数据源

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection: (NSInteger)section{
    return messages.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath: (NSIndexPath *)indexPath{
    static NSString *cellIdentifier = @"KVChatMessageCell";

    ChatMessageCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];

    [cell.labelMessage setText:messages[indexPath.row]];
    cell.selectiOnStyle= UITableViewCellSelectionStyleNone;

    if (indexPath.row%2 == 0) {
       // here all even cell are the sender type
        [cell setCellType:TypeSender];
    }
    else {
       // here all odd cell are the Receiver type
        [cell setCellType:TypeReceiver];
    }

    return cell;
}