react native 为我们调用本地的图片资源提供了一个api接口CameraRoll.

CameraRoll 
CameraRoll provides access to the local camera roll / gallery. Before using this you must link the RCTCameraRoll library. You can refer to Linking for help.

CameraRoll主要的作用在于我们可以利用他来展示我们的本地的图片，来做一个图片墙，你也可以将网络上的图片保存进你的本机

CameraRoll主要为我们提供了三个方法：如下：
static saveImageWithTag(tag)
static saveToCameraRoll(tag,type?)

*Saves the photo or video to the camera roll / gallery.
On Android,the tag must be a local image or video URI,such as “file:///sdcard/img.png”.
On iOS,the tag can be any image URI (including local,remote asset-library and base64 data URIs) or a local video file URI (remote or data URIs are not supported for saving video at this time).
If the tag has a file extension of .mov or .mp4,it will be inferred as a video. Otherwise it will be treated as a photo. To override the automatic choice,you can pass an optional type parameter that must be one of ‘photo’ or ‘video’.
Returns a Promise which will resolve with the new URI.*

static getPhotos(params)
Returns a Promise with photo identifier objects from the local camera roll of the device matching shape defined by getPhotosReturnChecker.

@param {object} params See getPhotosParamChecker.

Returns a Promise which when resolved will be of shape getPhotosReturnChecker.

前两个方法是用来保存图片的，具体用法我也没有用过，这边就不多做解释
getPhotos(params)这个方法用来获取图片，可以配合image来使用。
里面用个参数params：分别可以填入
first：数字类型，想要逆序显示的照片
after：字符串类型，一个匹配前一次调用getPhotos的page_info{end_cursor}的信息指针
groupTypes：字符串类型，指定特定的组别来过滤结果。可能是Album，All和Event等值。完整的groupTypes可在源码看到
groupName：字符串类型，在改组指定一个过滤器，例如Recent Photos或一个相册名称
assetType：值为all。photos或videos的其中一个，为资源类型指定一个过渡期
mimeTypes：字符串数组类型，基于MiMe类型进行过滤

源码展示：

componentDidMount(){
        CameraRoll.getPhotos({first: 5}).done(
            (data) =>{
                 console.log(data);
                    this.setState({
                    photoSource: {uri: data.edges[3].node.image.uri}
                    })
                },(error) => {
                console.warn(error);
            }
        );
    }

对了还要记住加权限

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />