如何在缩放ipad时在图形计算器中显示小数位

Question

我正在研究iPad的计算器。当用户键入一个函数，例如x ^ 2然后按下一个按钮时，它应该打开一个带有该函数图形的屏幕。当用户缩放时，坐标应相应地改变。目前它工作，但在最大缩放比例，它只显示整数值1,2,3 ...要求是，在继续缩放时，它应显示小数位，如0.1,0.2 ...至少一个小数位。在UIView drawRect方法中的方法

[AxesDrawer drawAxesInRect:self.bounds originAtPoint:midpoint scale:self.scale*self.contentScaleFactor];

调用

，在绘制轴之后调用

[self drawHashMarksInRect:bounds originAtPoint:axisOrigin scale:pointsPerUnit];

绘制标签的方法：

#define ANCHOR_CENTER 0
#define ANCHOR_TOP 1
#define ANCHOR_LEFT 2
#define ANCHOR_BOTTOM 3
#define ANCHOR_RIGHT 4
#define HASH_MARK_FONT_SIZE 20.0
#define HORIZONTAL_TEXT_MARGIN 6
#define VERTICAL_TEXT_MARGIN 3
#define HASH_MARK_SIZE 3
#define MIN_PIXELS_PER_HASHMARK 25
+ (void)drawHashMarksInRect:(CGRect)bounds originAtPoint:(CGPoint)axisOrigin scale:  
(CGFloat)pointsPerUnit
{
if (!pointsPerUnit) return;
if (((axisOrigin.x < bounds.origin.x) || (axisOrigin.x > bounds.origin.x+bounds.size.width)) &&
((axisOrigin.y < bounds.origin.y) || (axisOrigin.y > bounds.origin.y+bounds.size.height))) {
return;
}
int unitsPerHashmark = MIN_PIXELS_PER_HASHMARK * 2 / pointsPerUnit;
//NSLog(@"unitsperhashmark %d",unitsPerHashmark);
if (!unitsPerHashmark)
{
unitsPerHashmark = 1;
}
CGFloat pixelsPerHashmark = pointsPerUnit * unitsPerHashmark;
BOOL boundsContainsOrigin = CGRectContainsPoint(bounds, axisOrigin);
if (boundsContainsOrigin)
{
if ((axisOrigin.x - pixelsPerHashmark < bounds.origin.x) &&
(axisOrigin.x + pixelsPerHashmark > bounds.origin.x + bounds.size.width) &&
(axisOrigin.y - pixelsPerHashmark < bounds.origin.y) &&
(axisOrigin.y + pixelsPerHashmark > bounds.origin.y + bounds.size.height)) {
return;
}
}
else
{
if ((axisOrigin.y >= bounds.origin.y) &&
(axisOrigin.y <= bounds.origin.y+bounds.size.height) &&
(bounds.size.width <= pixelsPerHashmark)) {
return;
}
if ((axisOrigin.x >= bounds.origin.x) &&
(axisOrigin.x <= bounds.origin.x+bounds.size.width) &&
(bounds.size.height <= pixelsPerHashmark)) {
return;
}
}   
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 5);
CGContextBeginPath(context);
int started = NO;
int stillGoing = YES;
NSLog(@"unitsperhashmark 2 %d",unitsPerHashmark);
for (int offset = unitsPerHashmark; !started || stillGoing; offset += unitsPerHashmark)
{
NSString *positiveLabel = nil;
NSString *negativeLabel = nil;
BOOL drew = NO;
CGFloat scaledOffset = floor(offset * pointsPerUnit);
CGPoint hashMarkPoint;
hashMarkPoint.x = axisOrigin.x+scaledOffset;
hashMarkPoint.y = axisOrigin.y;   
if (CGRectContainsPoint(bounds, hashMarkPoint)) {
CGContextMoveToPoint(context, hashMarkPoint.x, hashMarkPoint.y-HASH_MARK_SIZE);
CGContextAddLineToPoint(context, hashMarkPoint.x, hashMarkPoint.y+HASH_MARK_SIZE);
if (!positiveLabel) positiveLabel = [NSString stringWithFormat:@"%d", offset];
//NSLog(@"positivelabel %@",positiveLabel);
[self drawString:positiveLabel atPoint:hashMarkPoint withAnchor:ANCHOR_TOP];
drew = YES;
}
hashMarkPoint.x = axisOrigin.x-scaledOffset;
if (CGRectContainsPoint(bounds, hashMarkPoint)) {
CGContextMoveToPoint(context, hashMarkPoint.x, hashMarkPoint.y-HASH_MARK_SIZE);
CGContextAddLineToPoint(context, hashMarkPoint.x, hashMarkPoint.y+HASH_MARK_SIZE);
if (boundsContainsOrigin) negativeLabel = positiveLabel;
if (!negativeLabel) negativeLabel = [NSString stringWithFormat:@"%d", (boundsContainsOrigin ? 
offset : -offset)];
[self drawString:negativeLabel atPoint:hashMarkPoint withAnchor:ANCHOR_TOP];
drew = YES;
}
hashMarkPoint.x = axisOrigin.x;
hashMarkPoint.y = axisOrigin.y-scaledOffset;
if (CGRectContainsPoint(bounds, hashMarkPoint)) {
CGContextMoveToPoint(context, hashMarkPoint.x-HASH_MARK_SIZE, hashMarkPoint.y);
CGContextAddLineToPoint(context, hashMarkPoint.x+HASH_MARK_SIZE, hashMarkPoint.y);
if (!positiveLabel) {
if (boundsContainsOrigin) positiveLabel = negativeLabel;
if (!positiveLabel) positiveLabel = [NSString stringWithFormat:@"%d", offset];
}
[self drawString:positiveLabel atPoint:hashMarkPoint withAnchor:ANCHOR_LEFT];
drew = YES;
}
hashMarkPoint.y = axisOrigin.y+scaledOffset;
if (CGRectContainsPoint(bounds, hashMarkPoint)) {
CGContextMoveToPoint(context, hashMarkPoint.x-HASH_MARK_SIZE, hashMarkPoint.y);
CGContextAddLineToPoint(context, hashMarkPoint.x+HASH_MARK_SIZE, hashMarkPoint.y);
if (!negativeLabel) {
if (boundsContainsOrigin) negativeLabel = positiveLabel;
if (!negativeLabel) negativeLabel = [NSString stringWithFormat:@"%d", (boundsContainsOrigin ?  
offset : -offset)];
}
[self drawString:negativeLabel atPoint:hashMarkPoint withAnchor:ANCHOR_LEFT];
drew = YES;
}
positiveLabel = nil;
negativeLabel = nil;     
if (drew) started = YES;
stillGoing = drew;
}   
CGContextStrokePath(context);
}

我真的很感激任何帮助。提前谢谢。

祝你好运

Answer 1

好的。我假设
positiveLabel = [NSString stringWithFormat：@“％d”，offset]; positiveLabel负责绘制字符串，格式为％d（十进制） 将其更改为％f（浮动），因此显示的值将处于浮点状态。

Answer 2

我更新了方法，以便用作计算井号的步骤的偏移量变量根据缩放而变化。当较少的散列标记为1时，如果用户继续缩放，则散列标记具有步骤0.2，并且如果他继续缩放，则它们具有步骤0.1。为此我使用了两个不同的循环，一个用于int hashmarks，一个用于float hash     +（void）drawHashMarksInRect：（CGRect）bounds originAtPoint：（CGPoint）axisOrigin scale：
    （CGFloat的）pointsPerUnit     {     if（！pointsPerUnit）返回;     if（（（axisOrigin.x＆lt; bounds.origin.x）||（axisOrigin.x＆gt; bounds.origin.x + bounds.size.width））＆amp;＆amp;     （（axisOrigin.y＆lt; bounds.origin.y）||（axisOrigin.y＆gt; bounds.origin.y + bounds.size.height）））{     返回;     }     int unitsPerHashmark = MIN_PIXELS_PER_HASHMARK * 2 / pointsPerUnit;     if（！unitsPerHashmark）     {     unitsPerHashmark = 1;     }     CGFloat pixelsPerHashmark = pointsPerUnit * unitsPerHashmark;     BOOL boundsContainsOrigin = CGRectContainsPoint（bounds，axisOrigin）;     if（boundsContainsOrigin）     {     if（（axisOrigin.x - pixelsPerHashmark＆lt; bounds.origin.x）＆amp;＆amp;     （axisOrigin.x + pixelsPerHashmark＆gt; bounds.origin.x + bounds.size.width）＆amp;＆amp;     （axisOrigin.y - pixelsPerHashmark＆lt; bounds.origin.y）＆amp;＆amp;     （axisOrigin.y + pixelsPerHashmark＆gt; bounds.origin.y + bounds.size.height））{     返回;     }     }     其他     {     if（（axisOrigin.y＆gt; = bounds.origin.y）＆amp;＆amp;     （axisOrigin.y＆lt; = bounds.origin.y + bounds.size.height）＆amp;＆amp;     （bounds.size.width＆lt; = pixelsPerHashmark））{     返回;     }     if（（axisOrigin.x＆gt; = bounds.origin.x）＆amp;＆amp;     （axisOrigin.x＆lt; = bounds.origin.x + bounds.size.width）＆amp;＆amp;     （bounds.size.height＆lt; = pixelsPerHashmark））{     返回;     }     }     CGContextRef context = UIGraphicsGetCurrentContext（）;     CGContextSetLineWidth（context，5）;     CGContextBeginPath（上下文）;     int started = NO;     int stillGoing = YES;     float decimalUnits;     if（（unitsPerHashmark == 1）＆amp;＆amp;（pointsPerUnit＆gt; 86））     {     if（pointsPerUnit＆gt; 490）{     decimalUnits = 0.1;     } else if（pointsPerUnit＆gt; 420）{     decimalUnits = 0.2;     }其他     {     decimalUnits = 0.5;     }     for（float offsetFloat = decimalUnits;！started || stillGoing; offsetFloat + = decimalUnits）     {     NSString * positiveLabel = nil;     NSString * negativeLabel = nil;     BOOL画了= NO;     CGFloat scaledOffset = floor（offsetFloat * pointsPerUnit）;     CGPoint hashMarkPoint;     hashMarkPoint.x = axisOrigin.x + scaledOffset;     hashMarkPoint.y = axisOrigin.y;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x，hashMarkPoint.y-HASH_MARK_SIZE）;     CGContextAddLineToPoint（context，hashMarkPoint.x，hashMarkPoint.y + HASH_MARK_SIZE）;     if（！positiveLabel）     {     positiveLabel = [NSString stringWithFormat：@＆＃34;％0.01f＆＃34;，offsetFloat];     if（[[positiveLabel substringFromIndex：1] compare：@＆＃34; .0＆＃34;] == NSOrderedSame）{     positiveLabel = [positiveLabel substringToIndex：1];     }     }     [self drawString：positiveLabel atPoint：hashMarkPoint withAnchor：ANCHOR_TOP];     画了=是;     }     hashMarkPoint.x = axisOrigin.x-scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x，hashMarkPoint.y-HASH_MARK_SIZE）;     CGContextAddLineToPoint（context，hashMarkPoint.x，hashMarkPoint.y + HASH_MARK_SIZE）;     if（boundsContainsOrigin）negativeLabel = [NSString stringWithFormat：@＆＃34; - ％@＆＃34;，positiveLabel];     if（！negativeLabel）negativeLabel = [NSString stringWithFormat：@＆＃34;％0.01f＆＃34;，（boundsContainsOrigin     ？ offsetFloat：-offsetFloat）];     if（[[negativeLabel substringFromIndex：1] compare：@＆＃34; .0＆＃34;] == NSOrderedSame）{     negativeLabel = [negativeLabel substringToIndex：1];     }     [self drawString：negativeLabel atPoint：hashMarkPoint withAnchor：ANCHOR_TOP];     画了=是;     }     hashMarkPoint.x = axisOrigin.x;     hashMarkPoint.y = axisOrigin.y-scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x-HASH_MARK_SIZE，hashMarkPoint.y）;     CGContextAddLineToPoint（context，hashMarkPoint.x + HASH_MARK_SIZE，hashMarkPoint.y）;     if（！positiveLabel）{     if（boundsContainsOrigin）     {     if（[negativeLabel characterAtIndex：0] ==＆＃39; - ＆＃39;）{     positiveLabel = [negativeLabel substringFromIndex：1];     }其他     {     positiveLabel = negativeLabel;     }     }     if（！positiveLabel）positiveLabel = [NSString stringWithFormat：@＆＃34;％0.01f＆＃34;，offsetFloat];     if（[[positiveLabel substringFromIndex：1] compare：@＆＃34; .0＆＃34;] == NSOrderedSame）{     positiveLabel = [positiveLabel substringToIndex：1];     }     }     [self drawString：positiveLabel atPoint：hashMarkPoint withAnchor：ANCHOR_LEFT];     画了=是;     }     hashMarkPoint.y = axisOrigin.y + scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x-HASH_MARK_SIZE，hashMarkPoint.y）;     CGContextAddLineToPoint（context，hashMarkPoint.x + HASH_MARK_SIZE，hashMarkPoint.y）;     if（！negativeLabel）{     if（boundsContainsOrigin）negativeLabel = [NSString stringWithFormat：@＆＃34; - ％@＆＃34;，positiveLabel];     if（！negativeLabel）negativeLabel = [NSString stringWithFormat：@＆＃34;％0.01f＆＃34;，（boundsContainsOrigin
    ？ offsetFloat：-offsetFloat）];     if（[[negativeLabel substringFromIndex：1] compare：@＆＃34; .0＆＃34;] == NSOrderedSame）{     negativeLabel = [negativeLabel substringToIndex：1];     }     }     [self drawString：negativeLabel atPoint：hashMarkPoint withAnchor：ANCHOR_LEFT];     画了=是;     }     positiveLabel = nil;     negativeLabel = nil;     if（画）开始= YES;     stillGoing = drew;     }     }     其他     {     for（int offset = unitsPerHashmark;！started || stillGoing; offset + = unitsPerHashmark）     {     NSString * positiveLabel = nil;     NSString * negativeLabel = nil;     BOOL画了= NO;     CGFloat scaledOffset = floor（offset * pointsPerUnit）;     CGPoint hashMarkPoint;     hashMarkPoint.x = axisOrigin.x + scaledOffset;     hashMarkPoint.y = axisOrigin.y;
    if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x，hashMarkPoint.y-HASH_MARK_SIZE）;     CGContextAddLineToPoint（context，hashMarkPoint.x，hashMarkPoint.y + HASH_MARK_SIZE）;     if（！positiveLabel）positiveLabel = [NSString stringWithFormat：@＆＃34;％d＆＃34;，offset];     [self drawString：positiveLabel atPoint：hashMarkPoint withAnchor：ANCHOR_TOP];     画了=是;     }     hashMarkPoint.x = axisOrigin.x-scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x，hashMarkPoint.y-HASH_MARK_SIZE）;     CGContextAddLineToPoint（context，hashMarkPoint.x，hashMarkPoint.y + HASH_MARK_SIZE）;     if（boundsContainsOrigin）negativeLabel = [NSString stringWithFormat：@＆＃34; - ％@＆＃34;，positiveLabel];     if（！negativeLabel）negativeLabel = [NSString stringWithFormat：@＆＃34;％d＆＃34;，（boundsContainsOrigin？     offset：-offset）];     [self drawString：negativeLabel atPoint：hashMarkPoint withAnchor：ANCHOR_TOP];     画了=是;     }     hashMarkPoint.x = axisOrigin.x;     hashMarkPoint.y = axisOrigin.y-scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x-HASH_MARK_SIZE，hashMarkPoint.y）;     CGContextAddLineToPoint（context，hashMarkPoint.x + HASH_MARK_SIZE，hashMarkPoint.y）;     if（！positiveLabel）{     if（boundsContainsOrigin）     {     if（[negativeLabel characterAtIndex：0] ==＆＃39; - ＆＃39;）{     positiveLabel = [negativeLabel substringFromIndex：1];     }其他     {     positiveLabel = negativeLabel;     }
    }     if（！positiveLabel）positiveLabel = [NSString stringWithFormat：@＆＃34;％d＆＃34;，offset];     }     [self drawString：positiveLabel atPoint：hashMarkPoint withAnchor：ANCHOR_LEFT];     画了=是;     }     hashMarkPoint.y = axisOrigin.y + scaledOffset;     if（CGRectContainsPoint（bounds，hashMarkPoint））{     CGContextMoveToPoint（context，hashMarkPoint.x-HASH_MARK_SIZE，hashMarkPoint.y）;     CGContextAddLineToPoint（context，hashMarkPoint.x + HASH_MARK_SIZE，hashMarkPoint.y）;     if（！negativeLabel）{     if（boundsContainsOrigin）negativeLabel = [NSString stringWithFormat：@＆＃34; - ％@＆＃34;，positiveLabel];     if（！negativeLabel）negativeLabel = [NSString stringWithFormat：@＆＃34; - ％d＆＃34;，（boundsContainsOrigin？     offset：-offset）];     }     [self drawString：negativeLabel atPoint：hashMarkPoint withAnchor：ANCHOR_LEFT];     画了=是;     }     positiveLabel = nil;     negativeLabel = nil;     if（画）开始= YES;     stillGoing = drew;     }     }
    CGContextStrokePath（上下文）;     }