react native 自定义下拉刷新——桥接MJRefresh

0、React Native 中的下拉刷新、上拉更多一直是一个很让人头疼的问题,RN中的API只能使用默认的UIRefreshControl,定制和体验上都很差,下面我通过修改系统组件的方法桥接一个原生中常用的三方库 MJRefresh ,至于上拉更多我一般使用react-native-giftedListView,可以和我这个桥接完美结合。https://github.com/XHTeng/react-native-gifted-listview

注意:该方法的缺点是每次更新react-native 组件都需要重新修改添加一次,还没有找到好的办法能够保存修改(除非不更新RN)

1、在React 项目中引入MJRefresh包,注意,MJRefresj.bundle 要引入到自己项目中,不要放在React项目中,不然资源无法加载。
目录结构
2、RCTScrollView.h 添加以下代码,并引入#import "MJRefresh.h"
@property(nonatomic, copy) RCTDirectEventBlock onRefreshData;
@property(nonatomic, assign) BOOL isOnPullToRefresh;
@property (assign, nonatomic) BOOL currentRefreshingState;
@property(nonatomic, assign) BOOL enablePullToRefresh;
- (void)startPullToRefresh;
- (void)stopPullToRefresh;

注意,要添加在RCTScrollView的下面,不要加在了RCTEventDispatcher里面!


RCTScrollView

RCTEventDispatcher
3、RCTScrollView.m 的RCTScrollView中添加以下代码,同样注意添加的位置,可以在这里修改为你需要的下拉样式
RCTScrollView
- (void)setEnablePullToRefresh:(BOOL)enablePullToRefresh
{
  _enablePullToRefresh = enablePullToRefresh;
  if (enablePullToRefresh) {
    if (_scrollView.mj_header == nil) {
      MJRefreshNormalHeader *header = [MJRefreshNormalHeader headerWithRefreshingTarget:self refreshingAction:@selector(refreshData)];
      header.lastUpdatedTimeLabel.hidden = YES;
      header.stateLabel.hidden = YES;
      
      _scrollView.mj_header = header;
      self.currentRefreshingState = NO;
    }
  }
}

- (void)setIsOnPullToRefresh:(BOOL)isOnPullToRefresh
{
  if (_currentRefreshingState != isOnPullToRefresh) {
    _currentRefreshingState = isOnPullToRefresh;
    if (isOnPullToRefresh) {
      [_scrollView.mj_header beginRefreshing];
      
    } else {
      [_scrollView.mj_header endRefreshing];
    }
  }
}

-(void)refreshData
{
  _currentRefreshingState = _scrollView.mj_header.isRefreshing;
  if (_onRefreshData) {
    _onRefreshData(nil);
  }
}

- (void)startPullToRefresh
{
  self.isOnPullToRefresh = YES;
  [_scrollView.header beginRefreshing];
  
}

- (void)stopPullToRefresh
{
  self.isOnPullToRefresh = NO;
  [_scrollView.header endRefreshing];
  
}
4、修改RCTCustomScrollView的- (void)dockClosestSectionHeader方法实现,(RCTCustomScrollView位于RCTScrollView.m)

找个下面这一段代码:

if (_rctRefreshControl != nil && _rctRefreshControl.refreshing) {
    scrollTop -= _rctRefreshControl.frame.size.height;
  }

在后面添加如下代码:

if (self.header != nil && self.header.isRefreshing) {
    scrollTop -= self.header.frame.size.height;
}
5、在RCTScrollViewManager.m中增加如下代码,方便ScrollView.js中调用
RCT_EXPORT_VIEW_PROPERTY(onRefreshData, RCTDirectEventBlock)
RCT_EXPORT_VIEW_PROPERTY(isOnPullToRefresh, BOOL)
RCT_EXPORT_VIEW_PROPERTY(enablePullToRefresh, BOOL)

RCT_EXPORT_METHOD(stopPullToRefresh:(nonnull NSNumber *)reactTag)
{
    [self.bridge.uiManager addUIBlock:
     ^(__unused RCTUIManager *uiManager, NSDictionary<NSNumber *, RCTScrollView *> *viewRegistry) {
         
         RCTScrollView *view = viewRegistry[reactTag];
         if (!view || ![view isKindOfClass:[RCTScrollView class]]) {
             RCTLogError(@"Cannot find RCTScrollView with tag #%@", reactTag);
             return;
         }
         
         [view stopPullToRefresh];
     }];
}

RCT_EXPORT_METHOD(startPullToRefresh:(nonnull NSNumber *)reactTag)
{
    [self.bridge.uiManager addUIBlock:
     ^(__unused RCTUIManager *uiManager, NSDictionary<NSNumber *, RCTScrollView *> *viewRegistry) {
         
         RCTScrollView *view = viewRegistry[reactTag];
         if (!view || ![view isKindOfClass:[RCTScrollView class]]) {
             RCTLogError(@"Cannot find RCTScrollView with tag #%@", reactTag);
             return;
         }
         
         [view startPullToRefresh];
     }];
}
6、修改React Native自带的ScrollView.js(位于./node_modules/react-native/Libraries/Components/ScrollView/ScrollView.js),桥接上面添加的属性、方法对应的props和函数

增加props:

enablePullToRefresh: PropTypes.bool,
isOnPullToRefresh: PropTypes.bool,
onRefreshData: PropTypes.func,

增加函数:

startPullToRefresh: function() {
  RCTScrollViewManager.startPullToRefresh(
      ReactNative.findNodeHandle(this)
  );
},

stopPullToRefresh: function() {
  RCTScrollViewManager.stopPullToRefresh(
      ReactNative.findNodeHandle(this)
  );
},
7、完成,在ListView或ScrollView中添加以下三个属性即可
isOnPullToRefresh={this.state.isRefreshing} // 控制刷新状态,true 开始刷新,false 停止刷新
onRefreshData={() => {  this._onRefresh();}} // 刷新回调的方法
enablePullToRefresh={true} // 是否打开下拉刷新

一般会加上系统判断,Android不需要增加修改这三个属性

推荐阅读更多精彩内容