我试图在recyclerview中的滚动顶部添加一些日期。 它是有效的，除了滚动之外，它会在添加一些新数据时弄乱一切。
我看到了这个主题：
但他们都没有解决我的问题。
也许有人可以帮我解决这个问题......
我使用排球获得一些数据，如下：
try {
//Getting json
json = array.getJSONObject(i);
//Adding data to the object
PostObj.setImageUrl(json.getString(Config.TAG_PPIC));
...
} catch (JSONException e) {
e.printStackTrace();
}
//Adding object to the list
listLf.add(0, PostObj); //0, postobj
}
//Notifying the adapter that data has been added or changed
//adapter.notifyDataSetChanged(); the scroll will jump to position 0
adapter.notifyItemRangeChanged(0, adapter.getItemCount()); // still not working
}
我尝试添加adapter.notifyItemRangeChanged(0, adapter.getItemCount());，但仍然是相同的。
我也尝试过：
// Save state
private Parcelable recyclerViewState;
recyclerViewState = recyclerView.getLayoutManager().onSaveInstanceState();
// Restore state
recyclerView.getLayoutManager().onRestoreInstanceState(recyclerViewState);
它也不起作用。也许我把它放在错误的地方或某事......
我想要一些建议我做错了什么以及如何获取新数据，通知适配器而不会弄乱滚动位置？
编辑---------------------------------- 全班：
public class Comments extends BaseActivity {
private List<LfGetSet> listLf;
//Creating Views
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapter;
//Volley Request Queue
private RequestQueue requestQueue;
private String requestCount = "0";
private String lastrequestCount = "0";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ViewGroup content = (ViewGroup) findViewById(R.id.content_frame);
getLayoutInflater().inflate(R.layout.activity_comments, content, true);
//Initializing Views
recyclerView = (RecyclerView) findViewById(R.id.recyclerViewLf);
recyclerView.setHasFixedSize(true);
//layoutManager = new LinearLayoutManager(this);
final LinearLayoutManager layoutManager = new LinearLayoutManager(this);
layoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(layoutManager);
//Initializing our list
listLf = new ArrayList<>();
requestQueue = Volley.newRequestQueue(this);
//Calling method to get data to fetch data
getData();
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (isLastItemDisplaying(recyclerView)) {
getData();
}
}
});
//initializing our adapter
adapter = new LfAdapter(listLf, this);
//Adding adapter to recyclerview
recyclerView.setAdapter(adapter);
}
private JsonArrayRequest getDataFromServer(String requestCount) {
...
return jsonArrayRequest;
}
//This method will get data from the web api
private void getData() {
//Adding the method to the queue by calling the method getDataFromServer
requestQueue.add(getDataFromServer(requestCount));
lastrequestCount = requestCount;
//Incrementing the request counter
requestCount++;
}
//This method will parse json data
private void parseData(JSONArray array) {
for (int i = 0; i < array.length(); i++) {
//Creating the object
LfGetSet PostObj = new LfGetSet();
JSONObject json = null;
try {
//Getting json
json = array.getJSONObject(i);
//Adding data to the object
PostObj.setImageUrl(json.getString(Config.TAG_PPIC));
...
} catch (JSONException e) {
e.printStackTrace();
}
//Adding object to the list
listLf.add(0, PostObj); //0, postobj
}
//Notifying the adapter that data has been added or changed
adapter.notifyDataSetChanged();
}
//This method would check that the recyclerview scroll has reached the bottom or not
private boolean isLastItemDisplaying(RecyclerView recyclerView) {
if (recyclerView.getAdapter().getItemCount() != 0) {
int lastVisibleItemPosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstVisibleItemPosition();
if (lastVisibleItemPosition != RecyclerView.NO_POSITION
&& lastVisibleItemPosition == 1
&& lastrequestCount != requestCount
&& requestCount != "0")
return true;
}
return false;
}
}
答案 0 :(得分：1)
您可以尝试这种方法，按照正常情况将新项目添加到列表中，然后更新阵列中的数据并将新项目放在顶部。
// Add a new item the usual way so it goes at the bottom
int x = 0;
// Create a new Data list. New item goes 1st
// Create a Loop
myList.remove(x); // Remove item from the array at position
MyList myList = new MyList();
myList.add(x, theData); // Add data to array at position
// Now that new data has been inserted to the Array at position X update the List item at that same Position. I usually do this in the Background.
Handler handler = new Handler();
final int finalX = x;
final Runnable r = new Runnable() {
public void run() {
adapter.notifyItemChanged(finalX); // Notify Adapter that the Items data has changed and Update
}
};
handler.post(r);
x++;
从数据库读取更新数据然后使用该新数据动态更新列表项的代码。但在您的情况下，您需要添加1个新项目并使用数组中位置0和列表上的新项目数据更新List。旧物品的位置移动了1。
public void updateStocks() {
System.out.println("Updating");
int rec = db.getRecordsCount() - 1;
List<Records> record = db.getAllRecords();
int x = 0;
for (Records cn : record) {
stocksList.remove(x);
Livestocks stocks = new Livestocks();
stocks.setID(cn.getID());
stocks.setName(cn.getName());
stocks.setTicker(cn.getTicker());
stocks.setPrice(cn.getPrice());
stocks.setOpen(cn.getOpen());
stocks.setChange(cn.getChange());
stocks.setPchange(cn.getPchange());
stocks.setDhigh(cn.getDhigh());
stocks.setDlow(cn.getDlow());
stocks.setYhigh(cn.getYhigh());
stocks.setYlow(cn.getYlow());
stocks.setVol(cn.getVol());
stocks.setShares(cn.getShares());
stocks.setIown(cn.getIown());
stocks.setMcap(cn.getMcap());
stocks.setStatus(cn.getStatus());
stocks.setExchange(cn.getExchange());
stocksList.add(x, stocks);
Handler handler = new Handler();
final int finalX = x;
final Runnable r = new Runnable() {
public void run() {
adapter.notifyItemChanged(finalX);
}
};
handler.post(r);
x++;
if (rec == x) {
//do nothing
}
}
}