getSceneIndicesForInterpolationInputRange.js
1.57 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
/* @flow */
import type {
NavigationSceneRendererProps,
NavigationScene,
SceneIndicesForInterpolationInputRange,
} from '../TypeDefinition';
function getSceneIndicesForInterpolationInputRange(
props: NavigationSceneRendererProps
): SceneIndicesForInterpolationInputRange | null {
const { scene, scenes } = props;
const index = scene.index;
const lastSceneIndexInScenes = scenes.length - 1;
const isBack = !scenes[lastSceneIndexInScenes].isActive;
if (isBack) {
const currentSceneIndexInScenes = scenes.findIndex(
(item: NavigationScene) => item === scene
);
const targetSceneIndexInScenes = scenes.findIndex(
(item: NavigationScene) => item.isActive
);
const targetSceneIndex = scenes[targetSceneIndexInScenes].index;
const lastSceneIndex = scenes[lastSceneIndexInScenes].index;
if (
index !== targetSceneIndex &&
currentSceneIndexInScenes === lastSceneIndexInScenes
) {
return {
first: Math.min(targetSceneIndex, index - 1),
last: index + 1,
};
} else if (
index === targetSceneIndex &&
currentSceneIndexInScenes === targetSceneIndexInScenes
) {
return {
first: index - 1,
last: Math.max(lastSceneIndex, index + 1),
};
} else if (
index === targetSceneIndex ||
currentSceneIndexInScenes > targetSceneIndexInScenes
) {
return null;
} else {
return { first: index - 1, last: index + 1 };
}
} else {
return { first: index - 1, last: index + 1 };
}
}
export default getSceneIndicesForInterpolationInputRange;