我一直试图通过几种方式将渐变放到我的表格视图单元格背景中，似乎没有任何方法。我一直试图用quarz核心图形绘制它，将背景插座放在IB上的不同视图中，将imageview放在背面用代码。似乎没有人以某种方式出现在背面，我没有得到什么错。如果需要，我可以详细说明，谢谢！
答案 0 :(得分：2)
我在this question中找到了一些代码并对其进行了调整以适用于我的应用程序。它适用于普通表和分组表。
//
// UAGradientCellBackgroundLayer.h
//
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
@class UAGradientCellBackgroundView;
@interface UAGradientCellBackgroundLayer : CAGradientLayer {
CGFloat *colorComponents;
BOOL _override;
}
@property(nonatomic,assign) BOOL override;
- (void)setColorComponents:(CGFloat *)components;
@end
//
// UAGradientCellBackgroundLayer.m
//
#import "UAGradientCellBackgroundLayer.h"
#import "UAGradientCellBackgroundView.h"
#define TABLE_CELL_BACKGROUND {1, 1, 1, 1, 204/255.0, 204/255.0, 204/255.0, 1} // #FFFFFF and #DDDDDD
@implementation UAGradientCellBackgroundLayer
@synthesize override = _override;
///////////////////////////////////////////////////////////////////////////////////////////////////
- (id)init {
if ((self = [super init])) {
colorComponents = NSZoneMalloc(NSDefaultMallocZone(), 8*sizeof(CGFloat));
CGFloat c[8] = TABLE_CELL_BACKGROUND;
for (int i = 0; i < 8; i++) {
colorComponents[i] = c[i];
}
// self.cornerRadius = 10;
// self.backgroundColor = [UIColor clearColor].CGColor;
}
return self;
}
- (void) dealloc {
NSZoneFree(NSDefaultMallocZone(), colorComponents);
[super dealloc];
}
- (void)display {
if (_override) {
self.colors =
[NSArray arrayWithObjects:
(id)[UIColor colorWithRed:colorComponents[0] green:colorComponents[1] blue:colorComponents[2] alpha:colorComponents[3]].CGColor,
(id)[UIColor colorWithRed:colorComponents[4] green:colorComponents[5] blue:colorComponents[6] alpha:colorComponents[7]].CGColor,
nil];
} else {
self.colors =
[NSArray arrayWithObjects:
(id)[UIColor clearColor].CGColor,
(id)[UIColor clearColor].CGColor,
nil];
}
[super display];
}
- (void)setColorComponents:(CGFloat *)components {
for (int i = 0; i < 8; i++) {
colorComponents[i] = components[i];
}
}
@end
//
// UAGradientCellBackgroundView.h
//
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
typedef enum {
UAGradientCellBackgroundViewPositionMiddle = 0,
UAGradientCellBackgroundViewPositionTop,
UAGradientCellBackgroundViewPositionBottom,
UAGradientCellBackgroundViewPositionSingle,
UAGradientCellBackgroundViewPositionPlain
} UAGradientCellBackgroundViewPosition;
@interface UAGradientCellBackgroundView : UIView {
UAGradientCellBackgroundViewPosition position;
CGFloat colors[8];
}
@property(nonatomic, assign) UAGradientCellBackgroundViewPosition position;
- (void)setColors:(CGFloat[8])comps;
@end
//
// UAGradientCellBackgroundView.m
//
#import "UAGradientCellBackgroundView.h"
#import "UAGradientCellBackgroundLayer.h"
#import <QuartzCore/QuartzCore.h>
#define kDefaultMargin 10
#define TABLE_CELL_BACKGROUND {1, 1, 1, 1, 204/255.0, 204/255.0, 204/255.0, 1} // #FFFFFF and #DDDDDD
static void addRoundedRectToPath(CGContextRef context, CGRect rect,
float ovalWidth,float ovalHeight);
@implementation UAGradientCellBackgroundView
@synthesize position;
//////////////////////////////////////////////////////////////////////
// PLAIN CELL
//
// layerClass
//
// returns a CAGradientLayer class as the default layer class for this view
//
+ (Class)layerClass {
return [UAGradientCellBackgroundLayer class];
}
//////////////////////////////////////////////////////////////////////
- (void)updateLayer {
UAGradientCellBackgroundLayer* layer = (UAGradientCellBackgroundLayer*)self.layer;
// This is dramatically faster than calling drawRect.
[layer setColorComponents:colors];
layer.override = (self.position == UAGradientCellBackgroundViewPositionPlain);
[layer setNeedsDisplay];
}
////////////////////////////////////////////////////////////////////
// GROUPED CELL
- (void)setColors:(CGFloat[8])comps {
for (int i = 0; i < 8; i++) {
colors[i] = comps[i];
}
}
- (BOOL)isOpaque {
return YES;
}
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self != nil) {
CGFloat comps[8] = TABLE_CELL_BACKGROUND;
[self setColors:comps];
}
return self;
}
- (void)debugView:(UIView *)view {
NSLog(@"%@ - %@", view.backgroundColor, [[view class] description]);
for (UIView* child in view.subviews) {
[self debugView:child];
}
}
-(void)drawRect:(CGRect)aRect {
[super drawRect:aRect];
// Drawing code
if (position == UAGradientCellBackgroundViewPositionPlain) {
return;
}
CGContextRef c = UIGraphicsGetCurrentContext();
// TODO - Dirty, Dirty hack to fix the background black corners on pop issue. doesnt handle rotation.
// CGContextSetFillColorWithColor(c, [UAColor offsetPinstripesColor].CGColor);
// CGContextFillRect(c, aRect);
int lineWidth = 1;
CGRect rect = [self bounds];
rect.size.width -= lineWidth;
rect.size.height -= lineWidth;
rect.origin.x += lineWidth / 2.0;
rect.origin.y += lineWidth / 2.0;
CGFloat minx = CGRectGetMinX(rect), midx = CGRectGetMidX(rect), maxx = CGRectGetMaxX(rect);
CGFloat miny = CGRectGetMinY(rect), midy = CGRectGetMidY(rect), maxy = CGRectGetMaxY(rect);
miny -= 1;
CGFloat locations[2] = { 0.0, 1.0 };
CGColorSpaceRef myColorspace = CGColorSpaceCreateDeviceRGB();
CGGradientRef myGradient = nil;
CGContextSetStrokeColorWithColor(c, [UIColor darkGrayColor].CGColor);
CGContextSetLineWidth(c, lineWidth);
CGContextSetAllowsAntialiasing(c, YES);
CGContextSetShouldAntialias(c, YES);
if (position == UAGradientCellBackgroundViewPositionTop) {
miny += 1;
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, minx, maxy);
CGPathAddArcToPoint(path, NULL, minx, miny, midx, miny, kDefaultMargin);
CGPathAddArcToPoint(path, NULL, maxx, miny, maxx, maxy, kDefaultMargin);
CGPathAddLineToPoint(path, NULL, maxx, maxy);
CGPathAddLineToPoint(path, NULL, minx, maxy);
CGPathCloseSubpath(path);
// Fill and stroke the path
CGContextSaveGState(c);
CGContextAddPath(c, path);
CGContextClip(c);
myGradient = CGGradientCreateWithColorComponents(myColorspace, colors, locations, 2);
CGContextDrawLinearGradient(c, myGradient, CGPointMake(minx,miny), CGPointMake(minx,maxy), 0);
CGContextAddPath(c, path);
CGPathRelease(path);
CGContextStrokePath(c);
CGContextRestoreGState(c);
} else if (position == UAGradientCellBackgroundViewPositionBottom) {
//maxy -= 1; // -1 for the shadow
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, minx, miny);
CGPathAddArcToPoint(path, NULL, minx, maxy, midx, maxy, kDefaultMargin);
CGPathAddArcToPoint(path, NULL, maxx, maxy, maxx, miny, kDefaultMargin);
CGPathAddLineToPoint(path, NULL, maxx, miny);
CGPathAddLineToPoint(path, NULL, minx, miny);
CGPathCloseSubpath(path);
// Fill and stroke the path
CGContextSaveGState(c);
CGContextAddPath(c, path);
CGContextClip(c);
myGradient = CGGradientCreateWithColorComponents(myColorspace, colors, locations, 2);
CGContextDrawLinearGradient(c, myGradient, CGPointMake(minx,miny), CGPointMake(minx,maxy), 0);
CGContextAddPath(c, path);
CGPathRelease(path);
CGContextStrokePath(c);
CGContextRestoreGState(c);
} else if (position == UAGradientCellBackgroundViewPositionMiddle) {
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, minx, miny);
CGPathAddLineToPoint(path, NULL, maxx, miny);
CGPathAddLineToPoint(path, NULL, maxx, maxy);
CGPathAddLineToPoint(path, NULL, minx, maxy);
CGPathAddLineToPoint(path, NULL, minx, miny);
CGPathCloseSubpath(path);
// Fill and stroke the path
CGContextSaveGState(c);
CGContextAddPath(c, path);
CGContextClip(c);
myGradient = CGGradientCreateWithColorComponents(myColorspace, colors, locations, 2);
CGContextDrawLinearGradient(c, myGradient, CGPointMake(minx,miny), CGPointMake(minx,maxy), 0);
CGContextAddPath(c, path);
CGPathRelease(path);
CGContextStrokePath(c);
CGContextRestoreGState(c);
} else if (position == UAGradientCellBackgroundViewPositionSingle) {
miny += 1;
//maxy -= 1; // -1 for the shadow
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, minx, midy);
CGPathAddArcToPoint(path, NULL, minx, miny, midx, miny, kDefaultMargin);
CGPathAddArcToPoint(path, NULL, maxx, miny, maxx, midy, kDefaultMargin);
CGPathAddArcToPoint(path, NULL, maxx, maxy, midx, maxy, kDefaultMargin);
CGPathAddArcToPoint(path, NULL, minx, maxy, minx, midy, kDefaultMargin);
CGPathCloseSubpath(path);
// Shadow
// CGContextAddPath(c, path);
// CGContextSaveGState(c);
// CGContextSetShadow(c, CGSizeMake(0, -1), 1);
// CGContextFillPath(c);
// Fill and stroke the path
CGContextSaveGState(c);
CGContextAddPath(c, path);
CGContextClip(c);
myGradient = CGGradientCreateWithColorComponents(myColorspace, colors, locations, 2);
CGContextDrawLinearGradient(c, myGradient, CGPointMake(minx,miny), CGPointMake(minx,maxy), 0);
CGContextAddPath(c, path);
CGPathRelease(path);
CGContextStrokePath(c);
CGContextRestoreGState(c);
}
CGColorSpaceRelease(myColorspace);
CGGradientRelease(myGradient);
return;
}
- (void)setPosition:(UAGradientCellBackgroundViewPosition)newPosition {
if (position != newPosition) {
position = newPosition;
[self updateLayer];
}
}
@end
static void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth,float ovalHeight) {
float fw, fh;
if (ovalWidth == 0 || ovalHeight == 0) {// 1
CGContextAddRect(context, rect);
return;
}
CGContextSaveGState(context);// 2
CGContextTranslateCTM (context, CGRectGetMinX(rect),// 3
CGRectGetMinY(rect));
CGContextScaleCTM (context, ovalWidth, ovalHeight);// 4
fw = CGRectGetWidth (rect) / ovalWidth;// 5
fh = CGRectGetHeight (rect) / ovalHeight;// 6
CGContextMoveToPoint(context, fw, fh/2); // 7
CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);// 8
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);// 9
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);// 10
CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1); // 11
CGContextClosePath(context);// 12
CGContextRestoreGState(context);// 13
}
用法样本（普通表）：
#import "UAGradientCellBackgroundView.h"
CGFloat COLORS[8] = { 0.0/255, 0.0/255, 255.0/255, 1.0, 0.0/255, 0.0/255, 0.0/255, 1.0 }
...
- (UITableViewCell *)tableView:(UITableView *)table cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *cellID = @"CellID";
// create cell
UITableViewCell *cell = (UITableViewCell *)[table dequeueReusableCellWithIdentifier:cellID];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID] autorelease];
UAGradientCellBackgroundView *bgView = [[[UAGradientCellBackgroundView alloc] initWithFrame:CGRectZero] autorelease];
[bgView setBackgroundColor:[UIColor clearColor]];
[bgView setColors:COLORS];
[bgView setPosition:UAGradientCellBackgroundViewPositionPlain];
cell.selectedBackgroundView = bgView;
cell.textLabel.backgroundColor = [UIColor clearColor];
cell.imageView.image = [UIImage imageNamed:@"cellimg.png"];
}
cell.textLabel.text = @"Text";
return cell;
}