從百度上搜索了一下layoutSubviews的用處,以下是搜索的結果,當然,筆者是會一一驗證的.
1、 init初始化不會觸發layoutSubviews
2、 addSubview會觸發layoutSubviews
3、 設置view的Frame會觸發layoutSubviews，當然前提是frame的值設置前後發生了變化
4、 滾動一個UIScrollView會觸發layoutSubviews
5、 旋轉Screen會觸發父UIView上的layoutSubviews事件
6、 改變一個UIView大小的時候也會觸發父UIView上的layoutSubviews事件
在開始驗證之前,先看看layoutSubviews到底是啥來着:)
Lays out subviews.
The default implementation of this method does nothing on iOS 5.1 and earlier. Otherwise, the default implementation uses any constraints you have set to determine the size and position of any subviews.
在iOS5.1或之前的版本中,這個方法什麼也沒幹.這個方法的默認實現是 用參數來設定subviews的尺寸和位置的 .
Subclasses can override this method as needed to perform more precise layout of their subviews. You should override this method only if the autoresizing and constraint-based behaviors of the subviews do not offer the behavior you want. You can use your implementation to set the frame rectangles of your subviews directly.
如果你需要更加精確的佈局,可以在子類裏面重寫這個方法.僅僅在以下情況下:自動佈局達不到你想要效果時你纔有必要重寫這個方法.你可以直接設置subviews的尺寸.
You should not call this method directly. If you want to force a layout update, call the setNeedsLayout method instead to do so prior to the next drawing update. If you want to update the layout of your views immediately, call the layoutIfNeeded method.
你不能直接調用這個方法.如果你需要強制layout刷新,調用setNeedsLayout來代替.如果你想要立即刷新你的view,調用layoutIfNeeded
大概總結以下就是:
你不要直接調用方法layoutSubviews,如果想要刷新,請調用 setNeedsLayout 或者 layoutIfNeeded
好了,開始驗證:)
現在提供繼承至UIView的類如下:
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> TestView.h</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> LayoutSubviews</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> Copyright (c) 2014年 Y.X. All rights reserved.</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span>
</span>
<span style="color: rgb(0, 0, 255);">#<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">import</span></span> <UIKit/UIKit.h>
<span style="color: rgb(0, 0, 255);">@interface</span><span style="color: rgb(0, 0, 0);"> TestView : UIView
</span><span style="color: rgb(0, 0, 255);">@end</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> TestView.m</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> LayoutSubviews</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> Copyright (c) 2014年 Y.X. All rights reserved.</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span>
</span>
<span style="color: rgb(0, 0, 255);">#<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">import</span></span> <span style="color: rgb(128, 0, 0);"><span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">TestView.h</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span>
<span style="color: rgb(0, 0, 255);">@implementation</span><span style="color: rgb(0, 0, 0);"> TestView
</span>- (<span style="color: rgb(0, 0, 255);">id</span><span style="color: rgb(0, 0, 0);">)initWithFrame:(CGRect)frame
{
<span class="indent"> </span>self </span>=<span style="color: rgb(0, 0, 0);"> [<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">super</span> initWithFrame:frame];
<span class="indent"> </span></span><span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">if</span></span><span style="color: rgb(0, 0, 0);"> (self)
<span class="indent"> </span>{
<span class="indent"> </span><span class="indent"> </span>NSLog(</span><span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">initWithFrame:%@</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span><span style="color: rgb(0, 0, 0);"> ,NSStringFromCGRect(frame));
<span class="indent"> </span>}
<span class="indent"> </span></span><span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">return</span></span><span style="color: rgb(0, 0, 0);"> self;
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)layoutSubviews
{
<span class="indent"> </span>NSLog(</span><span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">layoutSubviews %@</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);">, self</span><span style="color: rgb(0, 0, 0);">);
<span class="indent"> </span>[<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">super</span> layoutSubviews];
}
</span><span style="color: rgb(0, 0, 255);">@end</span>測試代碼:
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> RootViewController.m</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> LayoutSubviews</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span>
<span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> Copyright (c) 2014年 Y.X. All rights reserved.</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span>
</span>
<span style="color: rgb(0, 0, 255);">#<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">import</span></span> <span style="color: rgb(128, 0, 0);"><span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">RootViewController.h</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span>
<span style="color: rgb(0, 0, 255);">#<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">import</span></span> <span style="color: rgb(128, 0, 0);"><span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">TestView.h</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span>
<span style="color: rgb(0, 0, 255);">@interface</span><span style="color: rgb(0, 0, 0);"> RootViewController ()
<span class="annotation">@property</span> (nonatomic, strong) NSTimer </span>*<span style="color: rgb(0, 0, 0);">timer;
<span class="annotation">@property</span> (nonatomic, strong) TestView </span>*<span style="color: rgb(0, 0, 0);">largeView;
<span class="annotation">@property</span> (nonatomic, strong) TestView </span>*<span style="color: rgb(0, 0, 0);">smallView;
</span><span style="color: rgb(0, 0, 255);">@end</span>
<span style="color: rgb(0, 0, 255);">@implementation</span><span style="color: rgb(0, 0, 0);"> RootViewController
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)viewDidLoad
{
<span class="indent"> </span>[<span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">super</span> viewDidLoad];
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> 1、init初始化不會觸發layoutSubviews [正確的]</span></span><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> 2、addSubview會觸發layoutSubviews [不完全正確,當frame爲0時是不會觸發的]</span></span><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> 3、設置view的Frame會觸發layoutSubviews，當然前提是frame的值設置前後發生了變化 [正確]</span></span><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span>
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> [self test_1];</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> [self test_2];</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> [self test_3];</span></span><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span>
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> 4、滾動一個UIScrollView會觸發layoutSubviews[錯誤,不用滾動就會觸發]</span></span><span style="color: rgb(0, 128, 0);">
</span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> [self test_4];</span></span><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span>
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">//</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);"> 5、改變一個UIView大小的時候也會觸發父UIView上的layoutSubviews事件</span></span><span style="color: rgb(0, 128, 0);"></span>
<span style="color: rgb(0, 0, 0);"><span class="indent"> </span>[self test_5];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)test_1
{
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">/*</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span> 解釋:
<span class="indent"> </span>
<span class="indent"> </span> 走了initWithFrame:方法,但是又有frame值爲{{0, 0}, {0, 0}},並不需要繪製任何的東西,
<span class="indent"> </span> 所以即使添加了test,也沒必要繪製它,同時也驗證了addSubview會觸發layoutSubviews是錯
<span class="indent"> </span> 誤的,只有當被添加的view有着尺寸的時候纔會觸發layoutSubviews
<span class="indent"> </span> </span><span style="color: rgb(0, 128, 0);">*/</span></span><span style="color: rgb(0, 128, 0);"></span><span style="color: rgb(0, 0, 0);">
<span class="indent"> </span>
<span class="indent"> </span>TestView </span>*test = [TestView <span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">new</span></span><span style="color: rgb(0, 0, 0);">];
<span class="indent"> </span>[self.view addSubview:test];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)test_2
{
<span class="indent"> </span>TestView </span>*test = [TestView <span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">new</span></span><span style="color: rgb(0, 0, 0);">];
<span class="indent"> </span>test.frame </span>= CGRectMake(<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span><span style="color: rgb(0, 0, 0);">);
<span class="indent"> </span>[self.view addSubview:test];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)test_3
{
<span class="indent"> </span></span><span style="color: rgb(0, 128, 0);"><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;">/*</span></span><span class="comment" style="color: rgb(153, 153, 136); font-style: italic;"><span style="color: rgb(0, 128, 0);">
<span class="indent"> </span> 解釋:
<span class="indent"> </span>
<span class="indent"> </span> layoutSubviews這個方法自身無法調用,是被父類添加的時候才執行的方法
<span class="indent"> </span> </span><span style="color: rgb(0, 128, 0);">*/</span></span><span style="color: rgb(0, 128, 0);"></span><span style="color: rgb(0, 0, 0);">
<span class="indent"> </span>
<span class="indent"> </span>TestView </span>*test = [TestView <span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">new</span></span><span style="color: rgb(0, 0, 0);">];
<span class="indent"> </span>test.frame </span>= CGRectMake(<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">50</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">50</span></span><span style="color: rgb(0, 0, 0);">);
<span class="indent"> </span>UIView </span>*showView = [[UIView alloc] initWithFrame:CGRectMake(<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">50</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">50</span></span><span style="color: rgb(0, 0, 0);">)];
<span class="indent"> </span>[test addSubview:showView];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)test_4
{
<span class="indent"> </span>CGRect rect </span>=<span style="color: rgb(0, 0, 0);"> self.view.bounds;
<span class="indent"> </span>CGFloat height </span>=<span style="color: rgb(0, 0, 0);"> rect.size.height;
<span class="indent"> </span>CGFloat width </span>=<span style="color: rgb(0, 0, 0);"> rect.size.width;
<span class="indent"> </span>
<span class="indent"> </span>UIScrollView </span>*rootScroll =<span style="color: rgb(0, 0, 0);"> [[UIScrollView alloc] initWithFrame:self.view.bounds];
<span class="indent"> </span>NSArray </span>*data = @[<span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">""</span></span>, <span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">""</span></span>, <span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">""</span></span>, <span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">""</span></span><span style="color: rgb(0, 0, 0);">];
<span class="indent"> </span>[data enumerateObjectsUsingBlock:</span>^(<span style="color: rgb(0, 0, 255);">id</span> obj, NSUInteger idx, BOOL *<span style="color: rgb(0, 0, 0);">stop) {
<span class="indent"> </span><span class="indent"> </span>TestView </span>*tmp = [[TestView alloc] initWithFrame:CGRectMake(width*idx, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span><span style="color: rgb(0, 0, 0);">,
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> width, height)];
<span class="indent"> </span><span class="indent"> </span>[rootScroll addSubview:tmp];
<span class="indent"> </span>}];
<span class="indent"> </span>rootScroll.contentSize </span>= CGSizeMake(width *<span style="color: rgb(0, 0, 0);"> data.count, height);
<span class="indent"> </span>[self.view addSubview:rootScroll];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span><span style="color: rgb(0, 0, 0);">)test_5
{
<span class="indent"> </span>_timer </span>= [NSTimer scheduledTimerWithTimeInterval:<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">1</span></span><span class="number" style="color: rgb(0, 153, 153);"><span style="color: rgb(0, 0, 0);">.</span></span><span style="color: rgb(0, 0, 0);">f
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> target:self
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span>selector:<span class="annotation">@selector</span>(timerEvent:)
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span>userInfo:nil
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> repeats:YES];
<span class="indent"> </span>_largeView </span>=<span style="color: rgb(0, 0, 0);"> [[TestView alloc] initWithFrame:self.view.bounds];
<span class="indent"> </span>[self.view addSubview:_largeView];
<span class="indent"> </span>
<span class="indent"> </span>_smallView </span>= [[TestView alloc] initWithFrame:CGRectMake(<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">0</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span>, <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span><span style="color: rgb(0, 0, 0);">)];
<span class="indent"> </span>[_largeView addSubview:_smallView];
}
</span>- (<span style="color: rgb(0, 0, 255);"><span class="keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span></span>)timerEvent:(<span style="color: rgb(0, 0, 255);">id</span><span style="color: rgb(0, 0, 0);">)sender
{
<span class="indent"> </span>_smallView.frame </span>= CGRectMake(arc4random()%<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span> + <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">20</span></span><span style="color: rgb(0, 0, 0);">,
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> arc4random()</span>%<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span> + <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">20</span></span><span style="color: rgb(0, 0, 0);">,
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> arc4random()</span>%<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span> + <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">20</span></span><span style="color: rgb(0, 0, 0);">,
<span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span><span class="indent"> </span> arc4random()</span>%<span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">100</span></span> + <span style="color: rgb(128, 0, 128);"><span class="number" style="color: rgb(0, 153, 153);">20</span></span><span style="color: rgb(0, 0, 0);">);
<span class="indent"> </span>NSLog(</span><span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">_smallView %@</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span><span style="color: rgb(0, 0, 0);">, _smallView);
<span class="indent"> </span>NSLog(</span><span style="color: rgb(128, 0, 0);">@<span class="string" style="color: rgb(221, 17, 68);">"</span></span><span class="string" style="color: rgb(221, 17, 68);"><span style="color: rgb(128, 0, 0);">_smallView %@</span><span style="color: rgb(128, 0, 0);">"</span></span><span style="color: rgb(128, 0, 0);"></span><span style="color: rgb(0, 0, 0);">, _largeView);
}
</span><span style="color: rgb(0, 0, 255);">@end</span>測試後的結論是這樣子的:
1. 一個view是不能夠自己調用layoutSubviews,如果要調用,需要調用 setNeedsLayout或者 layoutIfNeeded
2. 如果view的frame值爲0,即使被添加了耶不會調用layoutSubviews
3. 如果一個view的frame值改變了,那麼它的父類的layoutSubviews也會被執行
layoutSubviews對subviews重新佈局
layoutSubviews方法調用先於drawRect
setNeedsLayout在receiver標上一個需要被重新佈局的標記，在系統runloop的下一個週期自動調用layoutSubviews
layoutIfNeeded方法如其名，UIKit會判斷該receiver是否需要layout.根據Apple官方文檔,layoutIfNeeded方法應該是這樣的
layoutIfNeeded遍歷的不是superview鏈，應該是subviews鏈
drawRect是對receiver的重繪，能獲得context
setNeedDisplay在receiver標上一個需要被重新繪圖的標記，在下一個draw週期自動重繪，iphone device的刷新頻率是60hz，也就是1/60秒後重繪