我正在使用西班牙语新闻应用程序，请参见此处：
该应用程序的问题在于，每当任何用户单击喜欢，播放音频或翻译按钮时，recyclerView都会跳至顶部。
数据是从Firebase实时数据库中按片段提取的。请帮忙。
@覆盖 公共视图onCreateView（LayoutInflater充气机，ViewGroup容器， 捆绑保存的InstanceState）{ //扩充此片段的布局 mView = inflater.inflate（R.layout.fragment_feed，container，false）;
MobileAds.initialize(mView.getContext(), "XXXXXXXXX");
mRewardedVideoAd = MobileAds.getRewardedVideoAdInstance(mView.getContext());
mRewardedVideoAd.setRewardedVideoAdListener(this);
loadRewardedVideoAd();
mAuth = FirebaseAuth.getInstance();
feedRecycler = mView.findViewById(R.id.recycler_feed);
feedRecycler.setLayoutManager(new LinearLayoutManager(getContext()));
RecyclerView.Adapter adapter = new FeedAdapter(mView.getContext(),mRecyclerViewItems);
feedRecycler.setAdapter(adapter);
userImage = mView.findViewById(R.id.feed_img);
username = mView.findViewById(R.id.feed_name);
usercomment = mView.findViewById(R.id.feed_edittext);
subMitComment = mView.findViewById(R.id.feed_submit);
mUSerCmt = FirebaseDatabase.getInstance().getReference().child("feeds");
mScoreRef = FirebaseDatabase.getInstance().getReference().child("scores");
if(mAuth.getCurrentUser().getPhotoUrl()!= null) {
Picasso.get().load(mAuth.getCurrentUser().getPhotoUrl().toString()).into(userImage);
username.setText(mAuth.getCurrentUser().getDisplayName());
} else {
startActivity(new Intent(mView.getContext(),UserProfile.class));
}
subMitComment.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String usercmt = usercomment.getText().toString();
if(!usercmt.equals("")){
writeNewPost(usercmt,mAuth.getUid(),mAuth.getCurrentUser().getDisplayName(),mAuth.getCurrentUser().getPhotoUrl().toString());
Toast.makeText(mView.getContext(),"Comment updated!",Toast.LENGTH_SHORT).show();
}
usercomment.setText("");
}
});
mUSerCmt.orderByChild("timestamp").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
mRecyclerViewItems.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
Model_Feed epiModel = dataSnapshot1.getValue(Model_Feed.class);
mRecyclerViewItems.add(epiModel);
}
FeedAdapter = new FeedAdapter(mView.getContext(), mRecyclerViewItems);
feedRecycler.setAdapter(FeedAdapter);
FeedAdapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
return mView;
}
private void writeNewPost(String sen, String uid, String name, String img) {
// Create new post at /user-posts/$userid/$postid and at
// /posts/$postid simultaneously
String key = mUSerCmt.push().getKey();
long time = System.currentTimeMillis() * (-1);
Model_Feed post = new Model_Feed(sen,time,uid, name, img,key);
Map<String, Object> postValues = post.toMap();
Map<String, Object> childUpdates = new HashMap<>();
childUpdates.put(key, postValues);
mUSerCmt.updateChildren(childUpdates);
}
public class FeedAdapter extends RecyclerView.Adapter<FeedAdapter.FeedViewHolder>{
private Context context;
private List<Object> mRecyclerViewItems;
public FeedAdapter(Context context, List<Object> mRecyclerViewItems) {
this.context = context;
this.mRecyclerViewItems = mRecyclerViewItems;
}
@NonNull
@Override
public FeedViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(R.layout.rec_words,viewGroup,false);
return new FeedViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull final FeedViewHolder feedViewHolder, int i) {
final Model_Feed modelFeed = (Model_Feed) mRecyclerViewItems.get(i);
Picasso.get().load(modelFeed.getImg()).into(feedViewHolder.circleImageView);
feedViewHolder.nameWord.setText(modelFeed.getName());
feedViewHolder.statusword.setText(modelFeed.getSen());
feedViewHolder.fireword.setText(String.valueOf(modelFeed.fires.size()));
feedViewHolder.playword.setText(String.valueOf(modelFeed.plays.size()));
if(modelFeed.fires.containsKey(mAuth.getUid())){
feedViewHolder.fireimage.setImageDrawable(getResources().getDrawable(R.drawable.fire));
}
if(modelFeed.plays.containsKey(mAuth.getUid())){
feedViewHolder.playimage.setImageDrawable(getResources().getDrawable(R.drawable.play_button));
}
feedViewHolder.fireLinear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
feedViewHolder.fireimage.setImageDrawable(getResources().getDrawable(R.drawable.fire));
onFireClicked(mUSerCmt.child(modelFeed.getKey()),modelFeed.getUid());
}
});
feedViewHolder.playLinear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
feedViewHolder.playimage.setImageDrawable(getResources().getDrawable(R.drawable.play_button));
sen_sound = modelFeed.getSen();
mScoreRef.child(mAuth.getUid()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
final Model_Score modelScore = dataSnapshot.getValue(Model_Score.class);
long scoreCheck = modelScore.getScore();
if (scoreCheck < 1 ){
AlertDialog.Builder builder;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
builder = new AlertDialog.Builder(context, android.R.style.Theme_Material_Dialog_Alert);
} else {
builder = new AlertDialog.Builder(context);
}
builder.setTitle("Insufficient Coins")
.setMessage("You've insufficient coins in your wallet to listen this audio, Watch a reward video complete and get 50 coins.")
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
long score = modelScore.getScore() + 5;
Model_Score modelScore1 = new Model_Score(score, modelScore.getReput(), mAuth.getUid());
mScoreRef.child(mAuth.getUid()).setValue(modelScore1);
}
scorez = modelScore.getScore();
reputz = modelScore.getReput();
})
.setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(mView.getContext(),"Our Apologies for inconvenience",Toast.LENGTH_SHORT).show();
}
})
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
}else {
long score = modelScore.getScore() - 10;
Model_Score modelScore1 = new Model_Score(score, modelScore.getReput(), mAuth.getUid());
mScoreRef.child(mAuth.getUid()).setValue(modelScore1);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
});
}
@Override
public int getItemCount() {
return mRecyclerViewItems.size();
}
public class FeedViewHolder extends RecyclerView.ViewHolder{
CircleImageView circleImageView;
TextView nameWord, statusword,fireword,playword;
LinearLayout fireLinear, playLinear;
ImageView fireimage, playimage;
public FeedViewHolder(@NonNull View itemView) {
super(itemView);
circleImageView = itemView.findViewById(R.id.word_image);
nameWord = itemView.findViewById(R.id.word_name);
statusword = itemView.findViewById(R.id.word_status);
fireword = itemView.findViewById(R.id.word_text_fire);
playword = itemView.findViewById(R.id.word_text_play);
fireLinear = itemView.findViewById(R.id.word_fire_linear);
playLinear = itemView.findViewById(R.id.word_play_linear);
fireimage = itemView.findViewById(R.id.word_img_fire);
playimage = itemView.findViewById(R.id.word_img_play);
}
}
}
void sendReward(long scores, long reputs){
long score = scores + 50;
Model_Score modelScore1 = new Model_Score(score, reputs, mAuth.getUid());
mScoreRef.child(mAuth.getUid()).setValue(modelScore1);
}
void showToast(String msg){
Toast.makeText(mView.getContext(),msg,Toast.LENGTH_SHORT).show();
}
private void onFireClicked(DatabaseReference postRef, final String cr_uid) {
postRef.runTransaction(new Transaction.Handler() {
@Override
public Transaction.Result doTransaction(MutableData mutableData) {
Model_Feed p = mutableData.getValue(Model_Feed.class);
if (p == null) {
return Transaction.success(mutableData);
}
if (p.fires.containsKey(mAuth.getUid())) {
// Unstar the post and remove self from stars
p.firecount = p.firecount - 1;
p.fires.remove(mAuth.getUid());
} else {
// Star the post and add self to stars
p.firecount = p.firecount + 1;
p.fires.put(mAuth.getUid(), true);
mScoreRef.child(cr_uid).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Model_Score modelScore = dataSnapshot.getValue(Model_Score.class);
long reput = modelScore.getReput();
Model_Score modelScore1 = new Model_Score(modelScore.getScore(), reput + 10, cr_uid);
mScoreRef.child(cr_uid).setValue(modelScore1);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
// Set value and report transaction success
mutableData.setValue(p);
return Transaction.success(mutableData);
}
@Override
public void onComplete(DatabaseError databaseError, boolean b,
DataSnapshot dataSnapshot) {
// Transaction completed
//Log.d(TAG, "postTransaction:onComplete:" + databaseError);
}
});
}
private void onPlayClicked(DatabaseReference postRef) {
postRef.runTransaction(new Transaction.Handler() {
@Override
public Transaction.Result doTransaction(MutableData mutableData) {
Model_Feed p = mutableData.getValue(Model_Feed.class);
if (p == null) {
return Transaction.success(mutableData);
}
if (p.plays.containsKey(mAuth.getUid())) {
// Unstar the post and remove self from stars
p.playcount = p.playcount + 1;
p.plays.put(mAuth.getUid() + p.playcount,true);
new readSen().execute();
} else {
// Star the post and add self to stars
p.playcount = p.playcount + 1;
p.plays.put(mAuth.getUid(), true);
}
// Set value and report transaction success
mutableData.setValue(p);
return Transaction.success(mutableData);
}
@Override
public void onComplete(DatabaseError databaseError, boolean b,
DataSnapshot dataSnapshot) {
// Transaction completed
//Log.d(TAG, "postTransaction:onComplete:" + databaseError);
}
});
}
答案 0 :(得分：0)
可能的原因是因为更新帖子会触发ValueEventListener中的回调，该回调用于填充此行中的RecyclerView
mUSerCmt.orderByChild("timestamp").addValueEventListener( ... )
由于视图已被完全清除并重新加载，因此自然看起来就好像它已滚动到顶部一样。可以采用多种方法来避免这种情况，确切的选择将取决于应用程序的更新需求。我能想到的一些是：
最好的选择，尽管在编码上有些棘手，但还是使用DiffUtil来进行原位更新（带有动画），而不会清除整个列表。您应该能够找到一些有关如何在线使用该类的简单教程。
使用addListenerForSingleValueEvent，以便对子项的更新不会触发列表的清除。这可能是一个错误的选择，因为您的应用程序显示的新闻可能会经常更改。但是，如果用户经常切换屏幕（例如，阅读新闻文章），则刷新将发生足够的时间，并且使其不那么引人注意。在提取文章时分页还可以确保最新的批次是最新的，而较旧的批次可能具有未同步的更改。
第一个选项是我推荐的选项，但是第二个选项更易于编码，可用于解决问题，同时获得一些时间来正确实现DiffUtil。
答案 1 :(得分：0)
无论何时设置新适配器，RecyclerView都会删除并分离旧适配器。相反，您可以尝试仅更新当前适配器上的数据，一个简单的方法是在适配器上创建一个公共方法来重新分配数据：
public class FeedAdapter extends RecyclerView.Adapter<FeedAdapter.FeedViewHolder> {
// ...
public void setItems(List<Object> items) {
mRecyclerViewItems = items;
}
// ...
}
然后在onDataChange回调中更新适配器：
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
mRecyclerViewItems.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
Model_Feed epiModel = dataSnapshot1.getValue(Model_Feed.class);
mRecyclerViewItems.add(epiModel);
}
if (FeedAdapter != null) {
FeedAdapter.setItems(mRecyclerViewItems);
FeedAdapter. notifyDataSetChanged();
} else {
FeedAdapter = new FeedAdapter(mView.getContext(), mRecyclerViewItems);
feedRecycler.setAdapter(FeedAdapter);
}
}