RxJava从Observable更新数据
[英]RxJava update data from Observable
问题描述
I have 2 listview's. 
我有2个listview。 It contains text items. 它包含文本项。 I want to drag text item from left list and drop to right list. 我想将文本项从左侧列表拖放到右侧列表。 Whith This I have no problem. 惠特这我没问题。 Also, I have an Observable, which emmits KalturaVideo objects. 另外，我还有一个Observable，它发出KalturaVideo对象。 Here is code how I getting this observable: This function get's id of already added in right listview, and excludes object from result, if object id equals to some id from targetList: 这是我如何可观察到的代码：此函数获取已经在正确的listview中添加的ID，并且如果对象ID等于targetList中的某个ID，则从结果中排除对象：
private Observable<KalturaVideo> getSourceListObservalbe(String kalturaPlaylistId){
Observable<String[]> targetIdList = Observable.just(targetList)
.map((List<KalturaVideo> kalturaVideos) -> {
if(kalturaVideos == null || kalturaVideos.isEmpty()){
return new String[]{""};
}
String[] result = new String[kalturaVideos.size()];
int index = 0;
for (KalturaVideo item : kalturaVideos) {
result[index] = item.getId();
}
return result;
});
return Observable.combineLatest(
targetIdList,
KalturaVideoRetriver.getVideoList(BuildPlaylistStep2Activity.this, kalturaPlaylistId),
(String[] idListOfTarget, KalturaVideo kalturaVideo) -> {
for (String item :idListOfTarget){
if(item.equals(kalturaVideo.getId())){
return null;
}
}
return kalturaVideo;
})
.doOnError(throwable -> {
int i =0;
i++;
throwable.printStackTrace();
})
.filter(kalturaVideo -> {
return kalturaVideo != null;
});
}
Here is a code of video retriver: 这是视频检索的代码：
public class KalturaVideoRetriver {
public static final String KALTURA_NEW_PLAYLIST_ID = "NEW_PLAYLIST";
public static Observable<KalturaVideo> getVideoList(Context context, String kalturaPlaylistId){
return Observable.create(new Observable.OnSubscribe<KalturaVideo>() {
@Override
public void call(Subscriber<? super KalturaVideo> subscriber) {
getKalturaPlaylistContentObservable(kalturaPlaylistId, context)
.flatMap(new Func1<String[], Observable<?>>() {
@Override
public Observable<?> call(String[] videoIdList) {
return getKalturaVideoListObservable(context, videoIdList)
.doOnNext(kalturaVideo -> {
subscriber.onNext(kalturaVideo);
})
.doOnCompleted(() -> subscriber.onCompleted());
}
})
.subscribe();
}
});
}
private static Observable<KalturaVideo> getKalturaVideoListObservable(Context context, String[] kalturaVideoIdArray){
return Observable.create(new Observable.OnSubscribe<KalturaVideo>() {
@Override
public void call(Subscriber<? super KalturaVideo> subscriber) {
Cursor query;
List<KalturaVideo> result = new ArrayList<>();
if(kalturaVideoIdArray == null || kalturaVideoIdArray.length == 0) {
query = context.getContentResolver().query(KalturaVideoColumns.CONTENT_URI, null, null, null, null);
}else {
KalturaVideoSelection where = new KalturaVideoSelection();
where.kalturaIdLike(kalturaVideoIdArray);
query = context.getContentResolver().query(
KalturaVideoColumns.CONTENT_URI,
null,
where.sel(),
where.args(),
null);
}
if(!query.moveToFirst()){
query.close();
subscriber.onCompleted();
}
KalturaVideoCursor cursor = new KalturaVideoCursor(query);
do{
KalturaVideo video = new KalturaVideo();
video.setId(cursor.getKalturaId());
video.setName(cursor.getName());
video.setDescription(cursor.getDescription());
video.setCategories(cursor.getCategories());
video.setCategoriesIds(cursor.getCategoriesIds());
video.setDownloadUrl(cursor.getDownloadUrl());
video.setThumbnailUrl(cursor.getThumbnailUrl());
video.setDataUrl(cursor.getDataUrl());
video.setDuration(cursor.getDuration());
subscriber.onNext(video);
}while (cursor.moveToNext());
query.close();
subscriber.onCompleted();
}
});
}
private static Observable<String[]> getKalturaPlaylistContentObservable(String kalturaPlaylistId, Context context){
return Observable.create(new Observable.OnSubscribe<String[]>() {
@Override
public void call(Subscriber<? super String[]> subscriber) {
if(kalturaPlaylistId.equals(KALTURA_NEW_PLAYLIST_ID)){
subscriber.onNext(new String[]{});
subscriber.onCompleted();
return;
}
KalturaPlaylistContentSelection where = new KalturaPlaylistContentSelection();
where.playlistId(kalturaPlaylistId);
Cursor query = context.getContentResolver().query(
KalturaPlaylistContentColumns.CONTENT_URI,
null,
where.sel(),
where.args(),
null
);
if(!query.moveToFirst()){
subscriber.onNext(new String[]{});
query.close();
subscriber.onCompleted();
return;
}
KalturaPlaylistContentCursor cursor = new KalturaPlaylistContentCursor(query);
String[] result = new String[query.getCount()];
int index = 0;
do{
result[index] = cursor.getKalturaVideoId();
index++;
}while (query.moveToNext());
query.close();
subscriber.onNext(result);
subscriber.onCompleted();
}
});
}
}
first of all, in retriver, I gettting video id's by playlist id. 首先，在检索中，我通过播放列表ID来获取视频ID。 If PlaylistId is empty - I get all videos id's, which stored in my db. 如果PlaylistId为空-我将获取所有视频ID，并将其存储在数据库中。 After this I getting all videos from db by id's, which i get at previous step. 在此之后，我通过ID获得了来自db的所有视频，这是在上一步获得的。
Here is function, which helps me to get all videos and display it: 这是功能，可帮助我获取所有视频并显示它：
private Observable<KalturaVideo> fillLists(){
return getSourceListObservalbe(KalturaVideoRetriver.KALTURA_NEW_PLAYLIST_ID)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doOnError(throwable -> {
Log.e("TAG", throwable.getCause().toString());
})
.doOnNext(kalturaVideo -> {
sourceList.add(kalturaVideo);
})
.doOnCompleted(() -> {
viewHolder.sourceListView.setAdapter(new BuildPlaylistContentAdapter(
BuildPlaylistStep2Activity.this,
-1,
sourceList));
viewHolder.sourceListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
KalturaVideo video = (KalturaVideo) view.getTag();
ClipData data = ClipData.newPlainText("kalturaVideoId", video.getId());
View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
view.startDrag(data, shadowBuilder, view, 0);
view.setVisibility(View.INVISIBLE);
return false;
}
});
viewHolder.targetListView.setAdapter(new BuildPlaylistContentAdapter(
BuildPlaylistStep2Activity.this,
-1,
targetList
));
});
}
And here is how I sibscribe on it: 这是我的预定方式：
subscription = fillLists().subscribe();
Here is, how I trying to update 2 lists after drag and drop: 这是拖放后如何尝试更新2个列表的方法：
targetList.add(video);
sourceList.clear();
fillLists().subscribe();
where video - is video related to view, which was dropped to new list. 视频-与观看相关的视频，已删除到新列表中。
So, when I dropped view to another list first time, it works fine. 因此，当我第一次将视图放到另一个列表时，它可以正常工作。 But when I drop second time, I get this stacktrace in my doOnError method: 但是当我第二次掉线时，在我的doOnError方法中得到了这个堆栈跟踪 ：
04-20 18:46:02.072 8015-8083/com.mediamanagment.app W/System.err﹕ java.lang.NullPointerException 04-20 18:46:02.072
8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.activity.BuildPlaylistStep2Activity.lambda$getSourceListObservalbe$3(BuildPlaylistStep2Activity.java:106) 04-20 18:46:02.072 8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.activity.BuildPlaylistStep2Activity.access$lambda$1(BuildPlaylistStep2Activity.java) 04-20 18:46:02.072 8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.activity.BuildPlaylistStep2Activity$$Lambda$2.call(Unknown Source) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.functions.Functions$3.call(Functions.java:76) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorCombineLatest$Collector.next(OperatorCombineLatest.java:157) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorCombineLatest$SourceSubscriber.onNext(OperatorCombineLatest.java:218) 04-20 18:46:02.080 8015-8083/com.mediamanagm
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.080
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:153) 04-20 18:46:02.080
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.080
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable.unsafeSubscribe(Observable.java:6110) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorMerge$1.onNext(OperatorMerge.java:66) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorMerge$1.onNext(OperatorMerge.java:43) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorMap$1.onNext(OperatorMap.java:54) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.retrivers.KalturaVideoRetriver$3.call(KalturaVideoRetriver.java:93) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.retrivers.KalturaVideoRetriver$3.call(KalturaVideoRetriver.java:89) 04-20 18:46:02.080 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:153) 04-20 18:46:02.080
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.080
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:153) 04-20 18:46:02.088
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.088
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable.subscribe(Observable.java:6177) 04-20 18:46:02.088
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable.subscribe(Observable.java:5842) 04-20 18:46:02.088
8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.retrivers.KalturaVideoRetriver$1.call(KalturaVideoRetriver.java:41) 04-20 18:46:02.088 8015-8083/com.mediamanagment.app W/System.err﹕ at com.mediamanagment.app.retrivers.KalturaVideoRetriver$1.call(KalturaVideoRetriver.java:27) 04-20 18:46:02.088 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable.unsafeSubscribe(Observable.java:6110) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorCombineLatest.call(OperatorCombineLatest.java:87) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorCombineLatest.call(OperatorCombineLatest.java:40) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:153) 04-20 18:46:02.095
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.095
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:153) 04-20 18:46:02.095
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable$2.call(Observable.java:149) 04-20 18:46:02.095
8015-8083/com.mediamanagment.app W/System.err﹕ at rx.Observable.unsafeSubscribe(Observable.java:6110) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:60) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at rx.schedulers.NewThreadScheduler$NewThreadWorker$ScheduledAction.run(NewThreadScheduler.java:141) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:390) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at java.util.concurrent.FutureTask.run(FutureTask.java:234) 04-20 18:46:02.095 8015-8083/com.mediamanagment.app W/System.err﹕ at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:153) 04-20 18:46:02.103 8015-8083/com.mediamanagment.app W/System.err﹕ at java.util.concurrent.ScheduledThreadPoolExecutor$Sched
And nothing videos was returned 没有任何视频返回
1 个解决方案
解决方案1
2 已采纳 2015-04-20 22:24:38
you've got an NullPointerException in this code 您在此代码中有一个NullPointerException
Log.e("TAG", throwable.getCause().toString());
I think that your exception doesn't have a cause, so the toString call throw a NPE (NullPointerException) 我认为您的异常没有原因，因此toString调用会引发NPE（NullPointerException）
Replace your code with 将您的代码替换为
Log.e("TAG", throwable.getCause());
It should fix this issue 它应该解决这个问题
BUT your code is very complex, and some parts can be writen in a different way. 但是您的代码非常复杂，并且某些部分可以用不同的方式编写。 Some other a buggy. 其他一些越野车。
For example : 例如 ：
Bug 窃听器
.doOnError(throwable -> {
int i =0;
i++;
throwable.printStackTrace();
})
i will always be equal to 0 (or 1 after i++ ). i将始终等于0（或i++之后为1）。 Is it voluntary ? 是自愿的吗？
Bad code 错误的代码
public static Observable<KalturaVideo> getVideoList(Context context, String kalturaPlaylistId){
return Observable.create(new Observable.OnSubscribe<KalturaVideo>() {
@Override
public void call(Subscriber<? super KalturaVideo> subscriber) {
getKalturaPlaylistContentObservable(kalturaPlaylistId, context)
.flatMap(new Func1<String[], Observable<?>>() {
@Override
public Observable<?> call(String[] videoIdList) {
return getKalturaVideoListObservable(context, videoIdList)
.doOnNext(kalturaVideo -> {
subscriber.onNext(kalturaVideo);
})
.doOnCompleted(() -> subscriber.onCompleted());
}
})
.subscribe();
}
});
}
Don't use an Observable in a Observable. 不要在Observable 中使用Observable。 Just transform the first one 只需转换第一个
public static Observable<KalturaVideo> getVideoList(Context context, String kalturaPlaylistId){
return getKalturaPlaylistContentObservable(kalturaPlaylistId, context).flatMap((String[] videoIdList) -> getKalturaVideoListObservable(context, videoIdList));
}
Complex code 复杂代码
Observable<String[]> targetIdList = Observable.just(targetList)
.map((List<KalturaVideo> kalturaVideos) -> {
if(kalturaVideos == null || kalturaVideos.isEmpty()){
return new String[]{""};
}
String[] result = new String[kalturaVideos.size()];
int index = 0;
for (KalturaVideo item : kalturaVideos) {
result[index] = item.getId();
}
return result;
});
You try to rewrite code that Rx can natively already do. 您尝试重写Rx本身已经可以执行的代码。
Observable<String[]> targetIdList = Observable.just(targetList)
.flatMapIterable(videos -> videos)
.map(video -> video.getId())
.toList()
.map(l -> l.toArray(new String[]));
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