我知道关于更改交替行颜色还有其他问题。这很容易，这不是我想做的。
我想在基于视图的 NSTableView 中绘制自定义的交替颜色行，这些行看起来像 iTunes 11 中的那些（行的顶部和底部有轻微的边框，如此截图所示）：
我知道我可以继承 NSTableRowView 并在那里进行自定义绘图。但是，这不是一个可接受的答案，因为自定义行将仅用于表中有数据的行。换句话说，如果表格只有 5 行，那 5 行将使用我的自定义 NSTableRowView 类，但表格其余部分（为空）中剩余的“行”将使用标准的交替颜色。在这种情况下，前 5 行将显示挡板，其余的不会。不好。
那么，我如何破解 NSTableView 来为填充行和空行绘制这些样式的交替行？
正如您所说，那个“小边框”实际上可以很容易地通过我们的一点作弊来完成。因为，如果你仔细观察，每个单元格的顶部都是比深色交替行略浅的蓝色，每个单元格的底部都是深灰色，你可以继承 NSTableView，然后重写- (void)drawRow:(NSInteger)row clipRect:(NSRect)clipRect：
- (void)drawRow:(NSInteger)row clipRect:(NSRect)clipRect
{
//Use the drawing code from http://stackoverflow.com/a/5101923/945847, but change the colors to
//look like iTunes's alternating rows.
NSRect cellBounds = [self rectOfRow:row];
NSColor *color = (row % 2) ? [NSColor colorWithCalibratedWhite:0.975 alpha:1.000] : [NSColor colorWithCalibratedRed:0.932 green:0.946 blue:0.960 alpha:1.000];
[color setFill];
NSRectFill(cellBounds);
/* Slightly dark gray color */
[[NSColor colorWithCalibratedWhite:0.912 alpha:1.000] set];
/* Get the current graphics context */
CGContextRef currentContext = [[NSGraphicsContext currentContext]graphicsPort];
/*Draw a one pixel line of the slightly lighter blue color */
CGContextSetLineWidth(currentContext,1.0f);
/* Start the line at the top of our cell*/
CGContextMoveToPoint(currentContext,0.0f, NSMaxY(cellBounds));
/* End the line at the edge of our tableview, for multi-columns, this will actually be overkill*/
CGContextAddLineToPoint(currentContext,NSMaxX(cellBounds), NSMaxY(cellBounds));
/* Use the context's current color to draw the line */
CGContextStrokePath(currentContext);
/* Slightly lighter blue color */
[[NSColor colorWithCalibratedRed:0.961 green:0.970 blue:0.985 alpha:1.000] set];
CGContextSetLineWidth(currentContext,1.0f);
CGContextMoveToPoint(currentContext,0.0f,1.0f);
CGContextAddLineToPoint(currentContext,NSMaxX(self.bounds), 1.0f);
CGContextStrokePath(currentContext);
[super drawRow:row clipRect:clipRect];
}
当在一个快速的小表格视图中完成时，它看起来像这样：
但是tableview的顶部和底部怎么办呢？毕竟，它们要么是丑陋的白色，要么是默认的交替行颜色。好吧，正如 Apple 所揭示的（在一个名为“有趣的是，基于 View Based NSTableView, Basic To Advanced ”的演讲中），您可以覆盖-(void)drawBackgroundInClipRect:(NSRect)clipRect并做一些数学运算来绘制 tableview 的背景，就像额外的行一样。一个快速的实现看起来像这样：
-(void)drawBackgroundInClipRect:(NSRect)clipRect
{
// The super class implementation obviously does something more
// than just drawing the striped background, because
// if you leave this out it looks funny
[super drawBackgroundInClipRect:clipRect];
CGFloat yStart = 0;
NSInteger rowIndex = -1;
if (clipRect.origin.y < 0) {
while (yStart > NSMinY(clipRect)) {
CGFloat yRowTop = yStart - self.rowHeight;
NSRect rowFrame = NSMakeRect(0, yRowTop, clipRect.size.width, self.rowHeight);
NSUInteger colorIndex = rowIndex % self.colors.count;
NSColor *color = [self.colors objectAtIndex:colorIndex];
[color set];
NSRectFill(rowFrame);
/* Slightly dark gray color */
[[NSColor colorWithCalibratedWhite:0.912 alpha:1.000] set];
/* Get the current graphics context */
CGContextRef currentContext = [[NSGraphicsContext currentContext]graphicsPort];
/*Draw a one pixel line of the slightly lighter blue color */
CGContextSetLineWidth(currentContext,1.0f);
/* Start the line at the top of our cell*/
CGContextMoveToPoint(currentContext,0.0f, yRowTop + self.rowHeight - 1);
/* End the line at the edge of our tableview, for multi-columns, this will actually be overkill*/
CGContextAddLineToPoint(currentContext,NSMaxX(clipRect), yRowTop + self.rowHeight - 1);
/* Use the context's current color to draw the line */
CGContextStrokePath(currentContext);
/* Slightly lighter blue color */
[[NSColor colorWithCalibratedRed:0.961 green:0.970 blue:0.985 alpha:1.000] set];
CGContextSetLineWidth(currentContext,1.0f);
CGContextMoveToPoint(currentContext,0.0f,yRowTop);
CGContextAddLineToPoint(currentContext,NSMaxX(clipRect), yRowTop);
CGContextStrokePath(currentContext);
yStart -= self.rowHeight;
rowIndex--;
}
}
}
但是，这会使 tableview 的底部留下同样丑陋的空白白色！因此，我们还必须覆盖-(void)drawGridInClipRect:(NSRect)clipRect. 另一个快速实现如下所示：
-(void)drawGridInClipRect:(NSRect)clipRect {
[super drawGridInClipRect:clipRect];
NSUInteger numberOfRows = self.numberOfRows;
CGFloat yStart = 0;
if (numberOfRows > 0) {
yStart = NSMaxY([self rectOfRow:numberOfRows - 1]);
}
NSInteger rowIndex = numberOfRows + 1;
while (yStart < NSMaxY(clipRect)) {
CGFloat yRowTop = yStart - self.rowHeight;
NSRect rowFrame = NSMakeRect(0, yRowTop, clipRect.size.width, self.rowHeight);
NSUInteger colorIndex = rowIndex % self.colors.count;
NSColor *color = [self.colors objectAtIndex:colorIndex];
[color set];
NSRectFill(rowFrame);
/* Slightly dark gray color */
[[NSColor colorWithCalibratedWhite:0.912 alpha:1.000] set];
/* Get the current graphics context */
CGContextRef currentContext = [[NSGraphicsContext currentContext]graphicsPort];
/*Draw a one pixel line of the slightly lighter blue color */
CGContextSetLineWidth(currentContext,1.0f);
/* Start the line at the top of our cell*/
CGContextMoveToPoint(currentContext,0.0f, yRowTop - self.rowHeight);
/* End the line at the edge of our tableview, for multi-columns, this will actually be overkill*/
CGContextAddLineToPoint(currentContext,NSMaxX(clipRect), yRowTop - self.rowHeight);
/* Use the context's current color to draw the line */
CGContextStrokePath(currentContext);
/* Slightly lighter blue color */
[[NSColor colorWithCalibratedRed:0.961 green:0.970 blue:0.985 alpha:1.000] set];
CGContextSetLineWidth(currentContext,1.0f);
CGContextMoveToPoint(currentContext,0.0f,yRowTop);
CGContextAddLineToPoint(currentContext,NSMaxX(self.bounds), yRowTop);
CGContextStrokePath(currentContext);
yStart += self.rowHeight;
rowIndex++;
}
}
当一切都说完了，我们在我们的剪辑视图的顶部和底部得到了漂亮的小假表视图单元格行，看起来有点像这样：
完整的子类可以在这里找到。
您可以使用
- (void)setUsesAlternatingRowBackgroundColors:(BOOL)useAlternatingRowColors
用useAlternatingRowColorsYES 指定背景的标准交替行颜色，用 NO 指定纯色。
我发现您可以在@CodaFi 解决方案drawBackgroundInClipRect的缺失子句中画出顶部和底部。else
所以这是 Swift 中的一种方法，假设您可以访问backgroundColorand alternateBackgroundColor：
override func drawBackground(inClipRect clipRect: NSRect) {
// I didn't find leaving this out changed appearance at all unlike
// CodaFi stated.
super.drawBackground(inClipRect: clipRect)
guard usesAlternatingRowBackgroundColors else { return }
drawTopAlternatingBackground(inClipRect: clipRect)
drawBottomAlternatingBackground(inClipRect: clipRect)
}
fileprivate func drawTopAlternatingBackground(inClipRect clipRect: NSRect) {
guard clipRect.origin.y < 0 else { return }
let backgroundColor = self.backgroundColor
let alternateColor = self.alternateBackgroundColor
let rectHeight = rowHeight + intercellSpacing.height
let minY = NSMinY(clipRect)
var row = 0
while true {
if row % 2 == 0 {
backgroundColor.setFill()
} else {
alternateColor.setFill()
}
let rowRect = NSRect(
x: 0,
y: (rectHeight * CGFloat(row) - rectHeight),
width: NSMaxX(clipRect),
height: rectHeight)
NSRectFill(rowRect)
drawBezel(inRect: rowRect)
if rowRect.origin.y < minY { break }
row -= 1
}
}
fileprivate func drawBottomAlternatingBackground(inClipRect clipRect: NSRect) {
let backgroundColor = self.backgroundColor
let alternateColor = self.alternateBackgroundColor
let rectHeight = rowHeight + intercellSpacing.height
let maxY = NSMaxY(clipRect)
var row = rows(in: clipRect).location
while true {
if row % 2 == 1 {
backgroundColor.setFill()
} else {
alternateColor.setFill()
}
let rowRect = NSRect(
x: 0,
y: (rectHeight * CGFloat(row)),
width: NSMaxX(clipRect),
height: rectHeight)
NSRectFill(rowRect)
drawBezel(inRect: rowRect)
if rowRect.origin.y > maxY { break }
row += 1
}
}
func drawBezel(inRect rect: NSRect) {
let topLine = NSRect(x: 0, y: NSMaxY(rect) - 1, width: NSWidth(rect), height: 1)
NSColor(calibratedWhite: 0.912, alpha: 1).set()
NSRectFill(topLine)
let bottomLine = NSRect(x: 0, y: NSMinY(rect) , width: NSWidth(rect), height: 1)
NSColor(calibratedRed:0.961, green:0.970, blue:0.985, alpha:1).set()
NSRectFill(bottomLine)
}
如果您不绘制NSTableRowView子类：
override func drawRow(_ row: Int, clipRect: NSRect) {
let rowRect = rect(ofRow: row)
let color = row % 2 == 0 ? self.backgroundColor : self.alternateBackgroundColor
color.setFill()
NSRectFill(rowRect)
drawBezel(inRect: rowRect)
}