Question

我有一个基于视图的NSTableView，有多行（例如20条），每次当我向下滚动滚动条时，我都希望它滚动到下一行。

例如，现在选择第5行，然后向下滚动将选择第6行。但是现在，滚动视图可以停在第5行和第6行之间的中间。

所以我的问题是，当单元格高度为50时，有什么方法可以设置“滚动步长”，然后每次向上/向下滚动50。

NotificationCenter.default.addObserver(self,
                             selector: #selector(scollDidEnd(_:)),
                             name: NSScrollView.didLiveScrollNotification,
                             object: tableView.enclosingScrollView)

@objc func scollDidEnd(_ notification : Notification){


}

Answer 1

这是我的Objective-C解决方案。目标行滚动到visibleRect高度的2/3，这对我的特定应用程序来说是一个折衷。调整2/3数学以适应您的需求。

#pragma mark -
#pragma mark NSTableView category
@implementation NSTableView (VNSTableViewCategory)

-(NSInteger)visibleRow
{
   NSRect theRect = [self visibleRect];
   NSRange theRange = [self rowsInRect:theRect];
   if ( theRange.length == 0 )
      return -1;
   else if ( NSLocationInRange( [self editedRow], theRange ) )
      return [self editedRow];        
   else if ( NSLocationInRange( [self clickedRow], theRange ) )
      return [self clickedRow];      
   else if ( NSLocationInRange( [self selectedRow], theRange ) )
      return [self selectedRow];
   else
      return theRange.location + (theRange.length/2);
}

-(NSRange)visibleRows
{
   NSRect theRect = [self visibleRect];
   NSRange theRange = [self rowsInRect:theRect];
   return theRange;
}

-(void)scrollRowToVisibleTwoThirds:(NSInteger)row
{
   NSRect theVisRect = [self visibleRect];
   NSUInteger numRows = [self numberOfRows];   
   NSRange visibleRows = [self rowsInRect:theVisRect];
   //NSUInteger lastVisibleRow = NSMaxRange(visibleRows);
   if ( NSLocationInRange( row, visibleRows ) )
   {
      if ( row - visibleRows.location < (visibleRows.length * 2 / 3) )
      {
         // may need to scroll up
         if ( visibleRows.location == 0 )
         {
            // top row at least partially visible.  Only scroll if near top
            if ( row == 0 || row == 1 )
                [self scrollRowToVisible:0];
            return;
         }
         else if ((row - visibleRows.location) > 2 )
            return;
      }
   }

   NSRect theRowRect = [self rectOfRow:row];

   NSPoint thePoint  = theRowRect.origin;
   thePoint.y -= theVisRect.size.height / 4; // scroll to 25% from top

   if (thePoint.y < 0 )
      thePoint.y = 0;

   NSRect theLastRowRect = [self rectOfRow:numRows-1];
   if ( thePoint.y + theVisRect.size.height > NSMaxY(theLastRowRect) )
      [self scrollRowToVisible:numRows-1];
   else
   {
      [self scrollPoint:thePoint]; // seems to be the 'preferred' method of doing this

      // kpk note: these other approaches cause redraw artifacts in many situations:
//      NSClipView *clipView = [[self enclosingScrollView] contentView];
//      [clipView scrollToPoint:[clipView constrainScrollPoint:thePoint]];
//      [[self enclosingScrollView] reflectScrolledClipView:clipView];
//      [self scrollRowToVisible:row];

//      [[[self enclosingScrollView] contentView] scrollToPoint:thePoint];
//      [[self enclosingScrollView] reflectScrolledClipView:[[self enclosingScrollView] contentView]];       
   }

}
@end

如何使scrollview的上移或下移步长等于NSTableView中表格单元的高度？

1 个答案: