我們首先來看看Core Animation類的繼承關系圖

687474703a2f2f696d672e6d792e6373646e2e6e65742f75706c6f6164732f3230313530372f32332f313433373631373536325f333139302e706e67.png

Class
CABasicAnimation
An object that provides basic, single-keyframe animation capabilities for a layer property.
//為圖層屬性提供基本的單關鍵幀動畫功能的對象。介紹了這個類的作用
//關鍵詞：basic, single-keyframe animation（單關鍵幀，你可以理解成CABasicAnimation是CAKeyframeAnimation的特殊化） 

Overview(概述)
You create an instance of CABasicAnimation using the inherited animationWithKeyPath: method, specifying the key path of the property to be animated in the render tree.
//你可以使用繼承的animationWithKeyPath：方法創建CABasicAnimation的實例，指定要在渲染樹中進行動畫處理的屬性的鍵路徑。

For example, you can animate a layer's scalar (i.e. containing a single value) properties such as its opacity. Listing 1 fades in a layer by animating its opacity from 0 to 1.
//如列表1中，你可以為涂層屬性（不透明度）設置動畫，使其不透明度從0到1淡化

Listing 1 
Creating an animation to animate opacity
let animation = CABasicAnimation(keyPath: "opacity") 
animation.fromValue = 0 
animation.toValue = 1
Non-scalar properties, such as backgroundColor, can also be animated. Core Animation will interpolate between the fromValue color and the toValue color. The animation created in Listing 2 fades a layer's background color from red to blue.
//非標量屬性，如backgroundColor，也可以是動畫。 核心動畫將在fromValue顏色和toValue顏色之間進行插值。 清單2中創建的動畫會將圖層的背景顏色從紅色漸變為藍色

Listing 2 
Creating an animation to animate background color.
let animation = CABasicAnimation(keyPath: "backgroundColor")
animation.fromValue = NSColor.red.cgColor
animation.toValue = NSColor.blue.cgColor
If you want to animate the individual(個人) components（組件、元件） of a non-scalar property with different values, you pass the values to toValue and fromValue as arrays. The animation created in Listing 3 moves a layer from (0, 0) to (100, 100).
//如果要為具有不同值的非標量屬性的各個組件設置動畫，請將值傳遞到toValue和fromValue作為數組。 清單3中創建的動畫將一個圖層從（0,0）移動到（100，100）。

Listing 3 
Creating an animation to animate position
let animation = CABasicAnimation(keyPath: "position")
animation.fromValue = [0, 0]
animation.toValue = [100, 100]
The keyPath can access the individual components of a property. For example, the Listing 4 stretches a layer by animating its transform object's x from 1 to 2.
//keyPath可以訪問屬性的各個組件。 例如，清單4通過將其變換對象的x從1動畫化為2來展開圖層。

Listing 4 
Creating an animation to animate scale
let animation = CABasicAnimation(keyPath: "transform.scale.x")
animation.fromValue = 1
animation.toValue = 2

Setting Interpolation Values(設置插值)
The fromValue, byValue and toValue properties define the values being interpolated between. All are optional, and no more than two should be non-nil. The object type should match the type of the property being animated.
//fromValue，byValue和toValue屬性定義在之間插入的值。 所有都是可選的，不超過兩個應該是非零。 對象類型應與要動畫的屬性的類型匹配
//注意：不超過兩個是非零，byValue是一個相對值，例如，如果指定了`fromValue`等于2，`toValue`等于4，`byValue`等于3，那么Core Animation就不知道結果到底是4（`toValue`）還是5（`fromValue + byValue`）了
The interpolation values are used as follows:
//內插值使用如下
Both fromValue and toValue are non-nil. Interpolates between fromValue and toValue.
//fromValue和toValue都是非零。 插值(也就是動畫執行)從fromValue到toValue
fromValue and byValue are non-nil. Interpolates between fromValue and (fromValue + byValue).
//fromValue和byValue是非零。 插值(也就是動畫執行)從fromValue到fromValue ＋ byValue。
byValue and toValue are non-nil. Interpolates between (toValue - byValue) and toValue.
//byValue和toValue是非零。 插值(也就是動畫執行)從toValue - byValue到toValue
fromValue is non-nil. Interpolates between fromValue and the current presentation value of the property.
//fromValue是非零,fromValue->當前
toValue is non-nil. Interpolates between the current value of keyPath in the target layer’s presentation layer and toValue.
//toValue是非零,當前->toValue
byValue is non-nil. Interpolates between the current value of keyPath in the target layer’s presentation layer and that value plus byValue.
//byValue是非零,當前值->當前值 + byValue
All properties are nil. Interpolates between the previous value of keyPath in the target layer’s presentation layer and the current value of keyPath in the target layer’s presentation layer.
//super與當前的對比，沒意義
Symbols

Interpolation values
fromValue
Defines the value the receiver uses to start interpolation.
//定義接收器用于開始插值的值。
toValue
Defines the value the receiver uses to end interpolation.
//定義接收器用于結束插值的值
byValue
Defines the value the receiver uses to perform relative interpolation.
//定義接收器用于執行相對插值的值

示例

從蘋果官方API我們可以了解到CABasicAnimation（基礎動畫）算是CAKeyframeAnimation（關鍵幀動畫）的特殊化，CABaseAnimation只能從一個數值（fromValue）變換成另一個數值（toValue),而CAKeyframeAnimation則會使用一個NSArray保存一組關鍵幀.

使用CABasicAnimation可操控的幾種屬性

• opacity （透明度）
• backgroundColor （背景色）
• position （位置）
• transform.scale.x(多種)

1 opacity

 CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"opacity"];
 anima.fromValue = [NSNumber numberWithFloat:1.0f];
 anima.toValue = [NSNumber numberWithFloat:0.2f];
 anima.duration = 1.0f;
 [_demoView.layer addAnimation:anima forKey:@"opacityAniamtion"];

2 backgroundColor

CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"backgroundColor"];
anima.toValue =(id) [UIColor greenColor].CGColor;
anima.duration = 1.0f;
[_demoView.layer addAnimation:anima forKey:@"backgroundAnimation"];

3 position

CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"position"];
anima.fromValue = [NSValue valueWithCGPoint:CGPointMake(0, SCREEN_HEIGHT/2-75)];
anima.toValue = [NSValue valueWithCGPoint:CGPointMake(SCREEN_WIDTH, SCREEN_HEIGHT/2-75)];
anima.duration = 3.0f;
//如果fillMode=kCAFillModeForwards和removedOnComletion=NO，那么在動畫執行完畢后，圖層會保持顯示動畫執行后的狀態。但在實質上，圖層的屬性值還是動畫執行前的初始值，并沒有真正被改變。
//anima.fillMode = kCAFillModeForwards;
//anima.removedOnCompletion = NO;
anima.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
[_demoView.layer addAnimation:anima forKey:@"positionAnimation"];

4 transform

//縮放
CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"transform.scale"];//同上
anima.toValue = [NSNumber numberWithFloat:2.0f];
anima.duration = 3.0f;
[_demoView.layer addAnimation:anima forKey:@"scaleAnimation"];

//旋轉
CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];//繞著z軸為矢量，進行旋轉(@"transform.rotation.z"==@@"transform.rotation")
anima.toValue = [NSNumber numberWithFloat:M_PI];
anima.duration = 1.0f;
[_demoView.layer addAnimation:anima forKey:@"rotateAnimation"];