In my app, I would like to resize the tableview's height when it's in edit mode vs when it's not (in order to make room for editing controls below the table view)
How should this be done?
I found that manipulating the "bounds" property can result in some unexpected behavior when you have a floating table inside another view. Sometimes the table expands upward when increasing the height, even though the origin is still 0,0.
The "frame" property might be more effective:
CGRect tvframe = [tableView frame];
[tableView setFrame:CGRectMake(tvframe.origin.x,
tvframe.origin.y,
tvframe.size.width,
tvframe.size.height + 20)];
You need to set the bounds of the tableview:
CGRect tvbounds = [tableView bounds];
[tableView setBounds:CGRectMake(tvbounds.origin.x,
tvbounds.origin.y,
tvbounds.size.width,
tvbounds.size.height + 20)];
You can implement the table view delegate's tableView:willBeginEditingRowAtIndexPath: and tableView:didEndEditingRowAtIndexPath: to figure out when a given row (and thus the table) goes into and out of editing mode, respectively.
From there, you can just tweak the value of the frame.size.height property of the table view (optionally inside a UIView animations block) as appropriate. It may also be helpful to check the editing property of the table view as a whole inside the delegate methods, in case you receive multiple calls to either delegate method before receiving any calls to their complementary methods.
More info:
UITableView: editing property
UITableViewDelegate: tableView:willBeginEditingRowAtIndexPath: method (didEndEditing is also in this document)
Related
I have an iPhone app in which I'm using a UITableView to format a set of text responses, one per row. I've set up the cell in the storyboard to have a label inside it, and set up a constraint saying that the label should be 10 points from the edge of the cell. I then set up a custom subclass of UITableViewCell, set the cell in the storyboard to be of that class, and connected the outlet.
However, when I load the table, I see the text in the cell moving slightly to the right under some circumstances: when I select the cell, or when I load additional cells into the table. In fact, in the latter case, sometimes everything gets shifted to the right, even cells which were already there!
What the heck is going on here? The only changes I'm making in tableView:cellForRowAtIndexPath: are to the text in the label, and I'm always setting it. And I've unset "Indent While Editing" on the cell in the storyboard.
Answering some of the questions: I'm setting the view up using the storyboard. Xcode isn't reporting any ambiguity with the constraints. Also, here are the screenshots, before and after:
My guess is that the constraints for the label are ambiguous. Ambiguity can make UI components jump around for inexplicable reasons. You probably need to set more constraints for the label to define its position on both axes.
Or, maybe all you need to do is set the label to the "size that fits content" (intrinsic content size) under the Editor menu in IB.
Did you add a new label to the UITableViewCell, or are you working with the textLabel that already exists in it? If you added a new one, consider removing it and using the cell's existing textLabel property instead. If that's not an option for some reason, double-check that the label you've added is in the contentView of the cell, and that all the constraints are relative to the parent view, not to the cell itself.
Also, for debugging, you could set the cell's contentView background color to red (cell.contentView.backgroundColor = [UIColor redColor];) - this might give you a better sense of what's moving, the label or the whole view.
This is just a guess without seeing your code. I had a similar problem once, when the app reused an existing cell, the dimensions of the label were not correct. So, I had to remove the old label in my cellForRowAtIndexPath method, before adding a new label. Here's how I removed the old one:
UIView *oldLabel = [cell viewWithTag:3];
if (oldLabel != nil)
{
[oldLabel removeFromSuperview];
}
Then I added a new label like this:
[cell.contentView addSubview:newLabelOrWhatever];
It might be worth checking to see that your string content doesn't have a space prefixed on it. Also, you could verify the actual position of the label by setting the background color.
I had a similar issue when the label would move when the cell was selected. It was a custom cell that I was loading from a custom Nib.
In the Nib I had not set the backgroundView of the UITableViewCell (superclass) to any view. Once I set it (I set it to the ContentView) the issue stopped.
My auto-layout constrains seems fine and had no issues, so I'm assuming it was the above that fixed it.
If you have a custom subclass of UITableViewCell, try implementing layoutSubviews. Let me try from the top of my head:
static CGFloat const kLeftMargin = 10.0f;
- (void) layoutSubviews
{
[super layoutSubviews];
/* Prepare for processing */
CGSize cellSize = self.bounds.size;
/* Change the textLabel frame */
{
/* Compute the new label frame */
CGSize labelSize = self.textLabel.bounds.size;
CGFloat xCoor = kLeftMargin;
CGFloat yCoor = roundf((cellSize.height - labelSize.height) / 2.0f);
CGRect labelFrame = CGRectMake(xCoor, yCoor,
labelSize.width, labelSize.height);
/* Set the new label frame */
self.textLabel.frame = labelFrame;
}
}
Now, this isn't what is usually recommended (since a lot of people use Storyboards and NIBs), but from experience, if you want some correct layouting done, implement layoutSubviews.
When a user adds an item to my list, I want to scroll to the new row, highlight it, and select it (which will push a new controller). The key part is waiting for the scroll animation to complete before pushing the new controller.
In this answer, I learned how to use the animation delegate to wait until the scroll is complete.
However, if the insertion row is already on scree, the table view will not scroll and the method will not fire.
How can I wait to push the new controller until the end of the scroll, and deal with the case where no scroll will be initiated - and how might I tell the difference between each case?
The easiest way to check whether a given row is visible in your table view is something like this:
if (!CGRectContainsRect([self.tableView bounds], [self.tableView rectForRowAtIndexPath:indexPath])
{
// the row is partially outside the table view’s boundaries and needs to be scrolled for full visibility
}
else
{
// the row is within the boundaries and does not need to be scrolled
}
Try creating a method to see if scrolling is needed. If no scrolling is needed, call the push right away, otherwise wait for the delegate call and push.
- (BOOL)isSrollingingNeededForIndexPath:(NSIndexPath *)indexPath {
NSArray *visibleIndices = [self.tableView indexPathsForVisibleRows];
for (NSIndexPath *visibleIndexPath in visibleIndices)
if ([indexPath compare:visibleIndexPath] == NSOrderedSame)
return NO;
return YES;
}
Edit: Good point. Since indexPathsForVisibleRows is used for data rendering.
You could do essentially the same thing with indexPathsForRowsInRect where you use the content.offset.y and the tableview.frame.size.height to determine your "visible rect".
Then to account for partially visible rows at the top and bottom you could add rowHeight-1 to the top of the rect and subtract rowHeight - 1 from the bottom of the rect. Code shouldn't be too gnarly if you have static height rows. If you have varying height rows it would still work, but it would be a bit more involved.
All said though, it seems like a lot of code for something which you'd think would have a simple answer.
I have a potentially very long scrolling log of messages within a UITableView The user would be able to navigate the table by scrolling.
What I'm trying to do is add new content at the top of the table. If the top of the table is visible, the new row would push the rest of the content down. But if the first row of the table is not visible, the table would silently add another row on top without scrolling.
I'm doing this to prevent the table scrolling to the top from interrupting the user browsing data. If I ask the table to simply scroll to the new insertion point, the user's position within the table would be lost, frustrating the user.
One of the ways I can try to implement this is by inserting data into an NSMutableArray at index 0. Would this work? An extra question: how expensive is inserting data at the beginning of an NSMutableArray. I would expect that such operation is optimized, but would like to make sure. What am I missing with this implementation?
Thank you!
How to insert without bumping the view:
Use the tableView's (UIScrollView) contentOffset values to find where the user is currently scrolled to.
Add the new row at the top, with animated:NO
Update the tableView's contentOffset to be where the user was at plus whatever the height of your row is.
How to avoid causing issues doing this while the user is dragging:
Keep track of when the user is dragging, and if you want to insert rows during a drag / motion, add them to a queue that is executed after the user releases.
CGSize beforeContentSize = self.tableView.contentSize;
[self.tableView reloadData];
CGSize afterContentSize = self.tableView.contentSize;
CGPoint afterContentOffset = self.tableView.contentOffset;
CGPoint newContentOffset = CGPointMake(afterContentOffset.x, afterContentOffset.y + afterContentSize.height - beforeContentSize.height);
self.tableView.contentOffset = newContentOffset;
Just posted an answer with code snippets here
Keep uitableview static when inserting rows at the top
Basically:
Save the scroll offset where you would have called beginUpdate:.
In place of calls to InsertCell you add the cell's height to the saved offset.
Where you would have called endUpdate:, call reloadData, then scroll by the saved offset with NO animation.
I have a tableView with the custom cell (see image below.)
Taking a three row table as an example, if a user changes segment controller in row 0 to "Yes," can I automatically change the segment controllers in rows 1 & 2 to "No?"
I am using the following to detect a segment change:
- (void)seg_changed:(id) sender {
cell=(switchCell*) [[sender superview] superview];
UITableView *table=(UITableView*) [cell superview];
NSIndexPath *path=[table indexPathForCell:cell];
NSLog(#"been pressed %d si %d",path.section, path.row);
}
Much appreciated.
In this method you call just tell those other segment controllers to set their values to "NO". The hard part is figuring out where those two other controls are. You have to do the hard work of tracking them.
If your design ensures there are always two more cell with segmented controls you can just access the correct cells by incrementing the path.row value.
This change can tell your data model that a value has changed, the model object then updates the associated values, and notifies the cells displaying those other values.
You can add an array to this cell class that keeps track of what other cells should be modified with this change.
Edit: (to respond to a comment) To change the setting displayed on the segmented control just set the property selectedSegmentIndex of the UISegmentedControl to the appropriate value. "Yes" should be 0, and "No" should be 1.
For performance reasons, I draw the strings for my UITableViewCell in a custom view that overrides its drawRect method to draw strings directly in the view rectangle using NSString:drawInRect. This is similar to Apple's TableViewSuite Example 5-CustomTableViewCell.
However, when I invoke setEditing on the cell to bring up the delete button, the view ends up with a squeezed appearance after the animation completes. To demonstrate this, invoke setEditing:YES on the CustomTableViewCell example mentioned above and observe the distortion. Is there any way around this or should I just revert back to using UILabels for my text?
I had a similar problem with a UIView inside a UITableViewCell. I solved it by changing the UIView's contentMode to UIViewContentModeLeft. (I wrote it up here, with screenshots.)
I had this problem too, and in my case I fixed it by handling the 2 states in my drawRect method, one while editting, the other while not. In other words I accounted for the size of the delete button, and got my UI to repaint the cell differently. I'm not sure if it's the most efficient way to go, but here is the code that I used to force a repaint:
-(void)_refreshTableAndCells{
//refresh the table
[myCustomTableView reloadData];
//refresh all the visible cells
for (UITableViewCell *cell in myCustomTableView.visibleCells){
LocationCellView *locationCell = [cell.contentView.subviews objectAtIndex:0];
[locationCell setNeedsDisplay];
}
}
I'm an Objective-C n00b though, so I'd be more than happy for someone to suggest a better way than this.
I usually just modify the x and width values (or whatever else) of whatever I want to be different when editing or not. UITableView automatically calls layoutSubviews when you begin editing, so you don't have to loop through your cells and do it yourself.
- (void)layoutSubviews {
[super layoutSubviews];
CGFloat editingPadding = 5.0;
self.textLabel = CGRectMake((self.editing ? self.textLabel.frame.origin.x + editingPadding : self.textLabel.frame.origin.x), self.textLabel.origin.y, (self.editing ? self.textLabel.frame.size.width - editingPadding : self.textLabel.frame.size.width), self.textLabel.frame.size.height);
}
Try setting the contentMode of your own custom view (which resides inside the cell's contentView) to UIViewContentModeLeft. The "squeezing" is due to the fact that the default contentMode is UIViewContentModeScaleToFill.