Lottie主要類圖:
Lottie對外通過控件LottieAnimationView暴露接口,控制動畫。
LottieAnimationView繼承自ImageView,通過當前時間繪製canvas顯示到界面上。這裏有兩個關鍵類:LottieComposition 負責解析json描述文件,把json內容轉成Java數據對象;LottieDrawable負責繪製,把LottieComposition轉成的數據對象繪製成drawable顯示到View上。順序如下:
json文件解析
LottieComposition負責解析json文件,建立數據到java對象的映射關係。
解析json外部結
LottieComposition封裝整個動畫的信息,包括動畫大小,動畫時長,幀率,用到的圖片,字體,圖層等等。
json外部結構
{
"v": "5.1.13", // bodymovin 版本
"fr": 30, // 幀率
"ip": 0, // 起始關鍵幀
"op": 20, // 結束關鍵幀
"w": 150, // 視圖寬
"h": 130, // 視圖高
"nm": "鵝頭收起動畫", // 名稱
"ddd": 0, // 3d
"assets": [], // 資源集合
"layers": [], // 圖層集合
"masker": [] // 蒙層集合
}
上圖爲一個動畫json文件,上面給出了各個參數的含義。其中ip表示其實關鍵幀,一般爲0,op表示動畫的結束關鍵幀,fr表示幀率,所以動畫時間等於:(op-ip)/fr
。w和h分別表示視圖的寬和高。
由於assets、layers、masker裏面的數據可能很大,所以上面用空數組代替。其中layers是一個圖層集合,它裏面數據一般很大,裏面包含了當前動畫的所有圖層數據,assets是一個資源集合,它裏面包含了當前動畫使用的資源圖層數據。masks則表示蒙層集合,裏面包含了所有的蒙層數據。
在lottie-android中,處理以上這些數據的代碼如下所示(刪除了一些相關性不強的代碼,完整的代碼請看lottie-android源碼):
public static LottieComposition parse(JsonReader reader) throws IOException {
float scale = Utils.dpScale();
float startFrame = 0f;
float endFrame = 0f;
float frameRate = 0f;
final LongSparseArray<Layer> layerMap = new LongSparseArray<>();
final List<Layer> layers = new ArrayList<>();
int width = 0;
int height = 0;
Map<String, List<Layer>> precomps = new HashMap<>();
Map<String, LottieImageAsset> images = new HashMap<>();
Map<String, Font> fonts = new HashMap<>();
List<Marker> markers = new ArrayList<>();
SparseArrayCompat<FontCharacter> characters = new SparseArrayCompat<>();
LottieComposition composition = new LottieComposition();
reader.beginObject();
while (reader.hasNext()) {
switch (reader.nextName()) {
case "w":
width = reader.nextInt();
break;
case "h":
height = reader.nextInt();
break;
case "ip":
startFrame = (float) reader.nextDouble();
break;
case "op":
endFrame = (float) reader.nextDouble() - 0.01f;
break;
case "fr":
frameRate = (float) reader.nextDouble();
break;
case "v":
String version = reader.nextString();
String[] versions = version.split("\\.");
int majorVersion = Integer.parseInt(versions[0]);
int minorVersion = Integer.parseInt(versions[1]);
int patchVersion = Integer.parseInt(versions[2]);
if (!Utils.isAtLeastVersion(majorVersion, minorVersion, patchVersion,
4, 4, 0)) {
composition.addWarning("Lottie only supports bodymovin >= 4.4.0");
}
break;
case "layers":
parseLayers(reader, composition, layers, layerMap);
break;
case "assets":
parseAssets(reader, composition, precomps, images);
break;
case "fonts":
parseFonts(reader, fonts); //解析字體
break;
case "chars":
parseChars(reader, composition, characters); //解析字符
break;
case "markers": //解析蒙層
parseMarkers(reader, composition, markers);
break;
default:
reader.skipValue();
}
}
reader.endObject();
int scaledWidth = (int) (width * scale);
int scaledHeight = (int) (height * scale);
Rect bounds = new Rect(0, 0, scaledWidth, scaledHeight);
composition.init(bounds, startFrame, endFrame, frameRate, layers, layerMap, precomps,
images, characters, fonts, markers);
return composition;
}
圖層元素 layer
動畫是由一個一個的圖層組合起來,並在圖層上進行偏移、縮放等操作來實現動畫的。圖層的解析是lottie的主要功能模塊。 一個layer圖層的數據格式一般如下:
{
"ddd": 0, // 是否爲3d
"ind": 1, // layer的ID,唯一
"ty": 0, // 圖層類型
"nm": "鵝頭收起", // 圖層名稱
"refId": "comp_0", // 引用的資源,圖片/預合成層
"sr": 1,
"ks": {}, // 變換。對應AE中的變換設置
layer: [], // 該圖層包含的子圖層
shaps: [], // 形狀圖層
"ao": 0,
"w": 1334,
"h": 750,
"ip": 0, // 該圖層開始關鍵幀
"op": 60, // 該圖層結束關鍵幀
"st": 0, // 該圖層
"bm": 0
}
上面是一個layer圖層的object的格式。
其中說明一下nm屬性,該屬性是在AE中對該圖層的命名,通過在SVG中修改該命名,可以設置對應的svg的class和id。如果命名爲'#svgId',生成的對應的svg元素的id則爲'svgId';如果命名爲'.svg-class',則生成的對應的svg元素的class爲'svg-class'。
ty表示類型,例如:
- 2: image,圖片
- 0: comp,合成圖層
- 1: solid;
- 3: null;
- 4: shape,形狀圖層
- 5: text,文字
lottie-android中對layers圖層數據相應的處理有:
public static Layer parse(JsonReader reader, LottieComposition composition) throws IOException {
// This should always be set by After Effects. However, if somebody wants to minify
// and optimize their json, the name isn't critical for most cases so it can be removed.
String layerName = "UNSET";
Layer.LayerType layerType = null;
String refId = null;
long layerId = 0;
int solidWidth = 0;
int solidHeight = 0;
int solidColor = 0;
int preCompWidth = 0;
int preCompHeight = 0;
long parentId = -1;
float timeStretch = 1f;
float startFrame = 0f;
float inFrame = 0f;
float outFrame = 0f;
String cl = null;
boolean hidden = false;
Layer.MatteType matteType = Layer.MatteType.NONE;
AnimatableTransform transform = null;
AnimatableTextFrame text = null;
AnimatableTextProperties textProperties = null;
AnimatableFloatValue timeRemapping = null;
List<Mask> masks = new ArrayList<>();
List<ContentModel> shapes = new ArrayList<>();
reader.beginObject();
while (reader.hasNext()) {
switch (reader.nextName()) {
case "nm":
layerName = reader.nextString();
break;
case "ind":
layerId = reader.nextInt();
break;
case "refId":
refId = reader.nextString();
break;
case "ty":
int layerTypeInt = reader.nextInt();
if (layerTypeInt < Layer.LayerType.UNKNOWN.ordinal()) {
layerType = Layer.LayerType.values()[layerTypeInt];
} else {
layerType = Layer.LayerType.UNKNOWN;
}
break;
case "parent":
parentId = reader.nextInt();
break;
case "sw":
solidWidth = (int) (reader.nextInt() * Utils.dpScale());
break;
case "sh":
solidHeight = (int) (reader.nextInt() * Utils.dpScale());
break;
case "sc":
solidColor = Color.parseColor(reader.nextString());
break;
case "ks": //ks變換
transform = AnimatableTransformParser.parse(reader, composition);
break;
case "tt":
matteType = Layer.MatteType.values()[reader.nextInt()];
composition.incrementMatteOrMaskCount(1);
break;
case "masksProperties":
reader.beginArray();
while (reader.hasNext()) {
masks.add(MaskParser.parse(reader, composition));
}
composition.incrementMatteOrMaskCount(masks.size());
reader.endArray();
break;
case "shapes":
reader.beginArray();
while (reader.hasNext()) {
ContentModel shape = ContentModelParser.parse(reader, composition);
if (shape != null) {
shapes.add(shape);
}
}
reader.endArray();
break;
case "t":
reader.beginObject();
while (reader.hasNext()) {
switch (reader.nextName()) {
case "d":
text = AnimatableValueParser.parseDocumentData(reader, composition);
break;
case "a":
reader.beginArray();
if (reader.hasNext()) {
textProperties = AnimatableTextPropertiesParser.parse(reader, composition);
}
while (reader.hasNext()) {
reader.skipValue();
}
reader.endArray();
break;
default:
reader.skipValue();
}
}
reader.endObject();
break;
case "ef":
reader.beginArray();
List<String> effectNames = new ArrayList<>();
while (reader.hasNext()) {
reader.beginObject();
while (reader.hasNext()) {
switch (reader.nextName()) {
case "nm":
effectNames.add(reader.nextString());
break;
default:
reader.skipValue();
}
}
reader.endObject();
}
reader.endArray();
composition.addWarning("Lottie doesn't support layer effects. If you are using them for " +
" fills, strokes, trim paths etc. then try adding them directly as contents " +
" in your shape. Found: " + effectNames);
break;
case "sr":
timeStretch = (float) reader.nextDouble();
break;
case "st":
startFrame = (float) reader.nextDouble();
break;
case "w":
preCompWidth = (int) (reader.nextInt() * Utils.dpScale());
break;
case "h":
preCompHeight = (int) (reader.nextInt() * Utils.dpScale());
break;
case "ip":
inFrame = (float) reader.nextDouble();
break;
case "op":
outFrame = (float) reader.nextDouble();
break;
case "tm":
timeRemapping = AnimatableValueParser.parseFloat(reader, composition, false);
break;
case "cl":
cl = reader.nextString();
break;
case "hd":
hidden = reader.nextBoolean();
break;
default:
reader.skipValue();
}
}
reader.endObject();
// Bodymovin pre-scales the in frame and out frame by the time stretch. However, that will
// cause the stretch to be double counted since the in out animation gets treated the same
// as all other animations and will have stretch applied to it again.
inFrame /= timeStretch;
outFrame /= timeStretch;
List<Keyframe<Float>> inOutKeyframes = new ArrayList<>();
// Before the in frame
if (inFrame > 0) {
Keyframe<Float> preKeyframe = new Keyframe<>(composition, 0f, 0f, null, 0f, inFrame);
inOutKeyframes.add(preKeyframe);
}
// The + 1 is because the animation should be visible on the out frame itself.
outFrame = (outFrame > 0 ? outFrame : composition.getEndFrame());
Keyframe<Float> visibleKeyframe =
new Keyframe<>(composition, 1f, 1f, null, inFrame, outFrame);
inOutKeyframes.add(visibleKeyframe);
Keyframe<Float> outKeyframe = new Keyframe<>(
composition, 0f, 0f, null, outFrame, Float.MAX_VALUE);
inOutKeyframes.add(outKeyframe);
if (layerName.endsWith(".ai") || "ai".equals(cl)) {
composition.addWarning("Convert your Illustrator layers to shape layers.");
}
return new Layer(shapes, composition, layerName, layerId, layerType, parentId, refId,
masks, transform, solidWidth, solidHeight, solidColor, timeStretch, startFrame,
preCompWidth, preCompHeight, text, textProperties, inOutKeyframes, matteType,
timeRemapping, hidden);
}
}
ks變換
ks對應AE中圖層的變換屬性,可以通過設置錨點、位置、旋轉、縮放、透明度等來控制圖層,並設置這些屬性的變換曲線,來實現動畫。下面是一個ks屬性值:
"ks": { // 變換。對應AE中的變換設置
"o": { // 透明度
"a": 0,
"k": 100,
"ix": 11
},
"r": { // 旋轉
"a": 0,
"k": 0,
"ix": 10
},
"p": { // 位置
"a": 0,
"k": [-167, 358.125, 0],
"ix": 2
},
"a": { // 錨點
"a": 0,
"k": [667, 375, 0],
"ix": 1
},
"s": { // 縮放
"a": 0,
"k": [100, 100, 100],
"ix": 6
}
}
lottie-android會把ks處理成transform的屬性,用於對元素進行變換操作。transform包含了translate(平移)、scale(縮放)、rotate(旋轉)、skew(傾斜)等幾種。lottie-android中處理ks(變換)的相關代碼爲:
public static AnimatableTransform parse(
JsonReader reader, LottieComposition composition) throws IOException {
AnimatablePathValue anchorPoint = null;
AnimatableValue<PointF, PointF> position = null;
AnimatableScaleValue scale = null;
AnimatableFloatValue rotation = null;
AnimatableIntegerValue opacity = null;
AnimatableFloatValue startOpacity = null;
AnimatableFloatValue endOpacity = null;
AnimatableFloatValue skew = null;
AnimatableFloatValue skewAngle = null;
boolean isObject = reader.peek() == JsonToken.BEGIN_OBJECT;
if (isObject) {
reader.beginObject();
}
while (reader.hasNext()) {
switch (reader.nextName()) {
case "a":
reader.beginObject();
while (reader.hasNext()) {
if (reader.nextName().equals("k")) {
anchorPoint = AnimatablePathValueParser.parse(reader, composition);
} else {
reader.skipValue();
}
}
reader.endObject();
break;
case "p":
position =
AnimatablePathValueParser.parseSplitPath(reader, composition);
break;
case "s":
scale = AnimatableValueParser.parseScale(reader, composition);
break;
case "rz":
composition.addWarning("Lottie doesn't support 3D layers.");
case "r":
/**
* Sometimes split path rotation gets exported like:
* "rz": {
* "a": 1,
* "k": [
* {}
* ]
* },
* which doesn't parse to a real keyframe.
*/
rotation = AnimatableValueParser.parseFloat(reader, composition, false);
if (rotation.getKeyframes().isEmpty()) {
rotation.getKeyframes().add(new Keyframe(composition, 0f, 0f, null, 0f, composition.getEndFrame()));
} else if (rotation.getKeyframes().get(0).startValue == null) {
rotation.getKeyframes().set(0, new Keyframe(composition, 0f, 0f, null, 0f, composition.getEndFrame()));
}
break;
case "o":
opacity = AnimatableValueParser.parseInteger(reader, composition);
break;
case "so":
startOpacity = AnimatableValueParser.parseFloat(reader, composition, false);
break;
case "eo":
endOpacity = AnimatableValueParser.parseFloat(reader, composition, false);
break;
case "sk":
skew = AnimatableValueParser.parseFloat(reader, composition, false);
break;
case "sa":
skewAngle = AnimatableValueParser.parseFloat(reader, composition, false);
break;
default:
reader.skipValue();
}
}
if (isObject) {
reader.endObject();
}
if (isAnchorPointIdentity(anchorPoint)) {
anchorPoint = null;
}
if (isPositionIdentity(position)) {
position = null;
}
if (isRotationIdentity(rotation)) {
rotation = null;
}
if (isScaleIdentity(scale)) {
scale = null;
}
if (isSkewIdentity(skew)) {
skew = null;
}
if (isSkewAngleIdentity(skewAngle)) {
skewAngle = null;
}
return new AnimatableTransform(anchorPoint, position, scale, rotation, opacity, startOpacity, endOpacity, skew, skewAngle);
}
shape
shape參數的值,對應AE中圖層的內容中的形狀設置的內容,其主要用於繪製圖形。下面一個shape的json爲例:
"shapes": [{
"ty": "gr", // 類型。混合圖層
"it": [{ // 各圖層json
"ind": 0,
"ty": "sh", // 類型,sh表示圖形路徑
"ix": 1,
"ks": {
"a": 0,
"k": {
"i": [ // 內切線點集合
[0, 0],
[0, 0]
],
"o": [ // 外切線點集合
[0, 0],
[0, 0]
],
"v": [ // 頂點座標集合
[182, -321.75],
[206.25, -321.75]
],
"c": false // 貝塞爾路徑閉合
},
"ix": 2
},
"nm": "路徑 1",
"mn": "ADBE Vector Shape - Group",
"hd": false
},{
"ty": "st", // 類型。圖形描邊
"c": { // 線的顏色
"a": 0,
"k": [0, 0, 0, 1],
"ix": 3
},
"o": { // 線的不透明度
"a": 0,
"k": 100,
"ix": 4
},
"w": { // 線的寬度
"a": 0,
"k": 3,
"ix": 5
},
"lc": 2, // 線段的頭尾樣式
"lj": 1, // 線段的連接樣式
"ml": 4, // 尖角限制
"nm": "描邊 1",
"mn": "ADBE Vector Graphic - Stroke",
"hd": false
}]
}]
上面是一個shape形狀的json示例,可以看出不同的shape類型,參數也不同。shape對應的是AE中的圖層的內容的設置。shape中的ty字段表示shape的類型,ty有以下幾種:
- gr: 圖形合併
- st: 圖形描邊
- fl: 圖形填充
- tr: 圖形變換
- sh: 圖形路徑
- el: 橢圓路徑
- rc: 矩形路徑
- tm: 剪裁路徑
lottie-android中處理shape的相關代碼爲:
static ContentModel parse(JsonReader reader, LottieComposition composition)
throws IOException {
String type = null;
reader.beginObject();
// Unfortunately, for an ellipse, d is before "ty" which means that it will get parsed
// before we are in the ellipse parser.
// "d" is 2 for normal and 3 for reversed.
int d = 2;
typeLoop:
while (reader.hasNext()) {
switch (reader.nextName()) {
case "ty":
type = reader.nextString();
break typeLoop;
case "d":
d = reader.nextInt();
break;
default:
reader.skipValue();
}
}
if (type == null) {
return null;
}
ContentModel model = null;
switch (type) {
case "gr":
model = ShapeGroupParser.parse(reader, composition);
break;
case "st":
model = ShapeStrokeParser.parse(reader, composition);
break;
case "gs":
model = GradientStrokeParser.parse(reader, composition);
break;
case "fl":
model = ShapeFillParser.parse(reader, composition);
break;
case "gf":
model = GradientFillParser.parse(reader, composition);
break;
case "tr":
model = AnimatableTransformParser.parse(reader, composition);
break;
case "sh":
model = ShapePathParser.parse(reader, composition);
break;
case "el":
model = CircleShapeParser.parse(reader, composition, d);
break;
case "rc":
model = RectangleShapeParser.parse(reader, composition);
break;
case "tm":
model = ShapeTrimPathParser.parse(reader, composition);
break;
case "sr":
model = PolystarShapeParser.parse(reader, composition);
break;
case "mm":
model = MergePathsParser.parse(reader);
composition.addWarning("Animation contains merge paths. Merge paths are only " +
"supported on KitKat+ and must be manually enabled by calling " +
"enableMergePathsForKitKatAndAbove().");
break;
case "rp":
model = RepeaterParser.parse(reader, composition);
break;
default:
Log.w(L.TAG, "Unknown shape type " + type);
}
while (reader.hasNext()) {
reader.skipValue();
}
reader.endObject();
return model;
}