我正在尝试在我的应用中实现刷卡刷新。触发刷卡到刷新时，首先从JSON获取所有数据，然后将其存储在数据库中。存储数据后，所有新数据都将添加到recyclerview的顶部。我阅读了一些文章，但却设法找到了在列表顶部添加单个项目的信息。但对于我的应用程序，可以显示多个项目，我该怎么办？
这是我的数据库表的代码，其中第一个新帖子被提取，最后一个帖子ID显示在recyclerview中：
@Override
public ArrayList<Post> getAllNewPost(int T) {
SQLiteDatabase db = this.getReadableDatabase();
ArrayList<Post> postList = null;
try {
postList = new ArrayList<Post>();
String QUERY = "SELECT * FROM " + TABLE_NAME + " INNER JOIN "+TABLE_FOLLOWER+
" ON post_table.user_id = follower.user_id WHERE follower.follow = '1' AND post_table.post_id > "+T+" ORDER BY "+POST_ID+" DESC";
Cursor cursor = db.rawQuery(QUERY, null);
if (!cursor.isLast()) {
while (cursor.moveToNext()) {
Post post = new Post();
post.setPost_id(cursor.getString(0));
Log.d("post_id",cursor.getString(0));
post.setUser_id(cursor.getString(1));
post.setUser_name(cursor.getString(2));
post.setImg_link(cursor.getString(3));
post.setPost_title(cursor.getString(4));
post.setPost_cat(cursor.getString(6));
post.setPost_time(cursor.getString(8));
postList.add(post);
}
}
db.close();
} catch (Exception e) {
Log.e("error", e + "");
}
return postList;
}
这是recyclerview的数组适配器：
public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {
Context context;
ArrayList<Post> listData = new ArrayList<>();
String rpostid,ruserid,rname,rcat,rdate,rtittle,urlThumnail;
private VolleySingleton volleySingleton;
ImageLoader imageLoader = VolleySingleton.getsInstance().getImageLoad();
public PostAdapter(ArrayList<Post> postList) {
this.listData=postList;
}
public PostAdapter(Context context){
this.context = context;
}
@Override
public PostAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
View v = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.post_item, viewGroup, false);
return new posts(v);
}
public class posts extends ViewHolder {
TextView tvTittle,tvPostId,tvUseId,tvName,tvCat,tvDate;
ImageView row_img;
public posts(View v) {
super(v);
tvTittle = (TextView) v.findViewById(R.id.row_cmnt);
tvPostId = (TextView) v.findViewById(R.id.row_postid);
tvUseId = (TextView) v.findViewById(R.id.row_userid);
tvName = (TextView) v.findViewById(R.id.row_name);
tvCat = (TextView) v.findViewById(R.id.row_cat);
tvDate = (TextView) v.findViewById(R.id.row_date);
row_img = (ImageView) v.findViewById(R.id.row_img);
v.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent;
TextView text = (TextView) v.findViewById(R.id.row_postid);
String lst_txt = text.getText().toString().trim();
intent = new Intent(v.getContext(), PostView.class);
intent.putExtra("post_id", lst_txt);
v.getContext().startActivity(intent);
}
});
}
}
@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {
final posts holder = (posts) viewHolder;
Post post = listData.get(position);
rpostid = post.getPost_id();
ruserid = post.getUser_id();
rname = post.getUser_name();
rcat = post.getPost_cat();
rdate = post.getPost_time();
rtittle = post.getPost_title();
holder.tvPostId.setText(rpostid);
holder.tvUseId.setText(ruserid);
holder.tvName.setText(rname);
holder.tvCat.setText(rcat);
holder.tvDate.setText(rdate);
holder.tvTittle.setText(rtittle);
urlThumnail = post.getImg_link();
Log.d("qwerty","link of image lru: "+ urlThumnail);
if (urlThumnail != null){
imageLoader.get(urlThumnail, new ImageLoader.ImageListener() {
@Override
public void onResponse(ImageLoader.ImageContainer response, boolean isImmediate) {
holder.row_img.setImageBitmap(response.getBitmap());
Log.d("qwerty","post attached 2");
}
@Override
public void onErrorResponse(VolleyError error) {
Log.d("qwerty","post attached 3");
}
});
}
}
@Override
public int getItemCount() {
return (null != listData ? listData.size() : 0);
}
}
以下是从数据库中提取所有新帖子的代码：
private ArrayList<Post> parseJSONResponse(JSONObject response) {
if (response == null || response.length() == 0) {
} else {
try {
JSONArray jsonArray = response.getJSONArray("post");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObjectPOST = jsonArray.getJSONObject(i);
String post_id = jsonObjectPOST.getString(Key_post_id);
String user_id = jsonObjectPOST.getString(Key_user_id);
String user_name = jsonObjectPOST.getString(Key_user_name);
String img_link = jsonObjectPOST.getString(Key_img_link);
String post_title = jsonObjectPOST.getString(Key_post_title);
String post_desc = jsonObjectPOST.getString(Key_post_desc);
String post_exp_date = jsonObjectPOST.getString(Key_post_exp);
String post_cat = jsonObjectPOST.getString(Key_post_cat);
String post_time = jsonObjectPOST.getString(Key_post_time);
Log.d("response",post_id+" "+user_id+" "+user_name+" "+img_link);
Post postitem = new Post();
postitem.setPost_id(post_id);
postitem.setUser_id(user_id);
postitem.setUser_name(user_name);
postitem.setImg_link(img_link);
postitem.setPost_title(post_title);
postitem.setDesc(post_desc);
postitem.setEXP(post_exp_date);
postitem.setPost_cat(post_cat);
postitem.setPost_time(post_time);
if(jsonObjectPOST.has(Key_post_id) &&
jsonObjectPOST.has(Key_user_id) &&
jsonObjectPOST.has(Key_user_name) &&
jsonObjectPOST.has(Key_img_link) &&
jsonObjectPOST.has(Key_post_title) &&
jsonObjectPOST.has(Key_post_desc) &&
jsonObjectPOST.has(Key_post_exp) &&
jsonObjectPOST.has(Key_post_cat) &&
jsonObjectPOST.has(Key_post_time)){
if(!jsonObjectPOST.isNull(Key_post_id) &&
!jsonObjectPOST.isNull(Key_user_id) &&
!jsonObjectPOST.isNull(Key_user_name) &&
!jsonObjectPOST.isNull(Key_img_link) &&
!jsonObjectPOST.isNull(Key_post_title) &&
!jsonObjectPOST.isNull(Key_post_desc) &&
!jsonObjectPOST.isNull(Key_post_exp) &&
!jsonObjectPOST.isNull(Key_post_cat) &&
!jsonObjectPOST.isNull(Key_post_time)){
handler.addPost(postitem);
new CountDownTimer(2000, 1000) {
public void onTick(long millisUntilFinished) {}
public void onFinish() {
postList = handler.getAllPost();
t = Integer.parseInt(postList.get(1).getPost_id().toString().trim());
Log.d("Check", "postid: "+t);
Hpbar.setVisibility(View.INVISIBLE);
Log.d("jsonCount", String.valueOf(postList));
String AdapterData = String.valueOf(postList);
if(AdapterData.equals("[]")){
Htvnopostfound.setVisibility(View.VISIBLE);
}else{
adapter = new PostAdapter(postList);
listView.setAdapter(adapter);
}
}
}.start();
}else{
}
}else{
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
return postList;
}
private ArrayList<Post> swipeJSONResponse(JSONObject response) {
if (response == null || response.length() == 0) {
} else {
try {
JSONArray jsonArray = response.getJSONArray("post");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObjectPOST = jsonArray.getJSONObject(i);
String post_id = jsonObjectPOST.getString(Key_post_id);
String user_id = jsonObjectPOST.getString(Key_user_id);
String user_name = jsonObjectPOST.getString(Key_user_name);
String img_link = jsonObjectPOST.getString(Key_img_link);
String post_title = jsonObjectPOST.getString(Key_post_title);
String post_desc = jsonObjectPOST.getString(Key_post_desc);
String post_exp_date = jsonObjectPOST.getString(Key_post_exp);
String post_cat = jsonObjectPOST.getString(Key_post_cat);
String post_time = jsonObjectPOST.getString(Key_post_time);
Post postitem = new Post();
postitem.setPost_id(post_id);
postitem.setUser_id(user_id);
postitem.setUser_name(user_name);
postitem.setImg_link(img_link);
postitem.setPost_title(post_title);
postitem.setDesc(post_desc);
postitem.setEXP(post_exp_date);
postitem.setPost_cat(post_cat);
postitem.setPost_time(post_time);
if(jsonObjectPOST.has(Key_post_id) &&
jsonObjectPOST.has(Key_user_id) &&
jsonObjectPOST.has(Key_user_name) &&
jsonObjectPOST.has(Key_img_link) &&
jsonObjectPOST.has(Key_post_title) &&
jsonObjectPOST.has(Key_post_desc) &&
jsonObjectPOST.has(Key_post_exp) &&
jsonObjectPOST.has(Key_post_cat) &&
jsonObjectPOST.has(Key_post_time)){
if(!jsonObjectPOST.isNull(Key_post_id) &&
!jsonObjectPOST.isNull(Key_user_id) &&
!jsonObjectPOST.isNull(Key_user_name) &&
!jsonObjectPOST.isNull(Key_img_link) &&
!jsonObjectPOST.isNull(Key_post_title) &&
!jsonObjectPOST.isNull(Key_post_desc) &&
!jsonObjectPOST.isNull(Key_post_exp) &&
!jsonObjectPOST.isNull(Key_post_cat) &&
!jsonObjectPOST.isNull(Key_post_time)){
handler.addPost(postitem);
new CountDownTimer(2000, 1000) {
public void onTick(long millisUntilFinished) {}
public void onFinish() {
postList = handler.getAllNewPost(t);
adapter.notifyItemInserted(1);
Log.d("check","post_id "+t+" hello");
/*adapter = new PostAdapter(postList);
listView.setAdapter(adapter);
Log.d("check","post_id "+t+" hello 2");*/
Log.d("check","post_id "+t+" hello 2");
Hpbar.setVisibility(View.INVISIBLE);
swipeRefreshLayout.setRefreshing(false);
}
}.start();
}else{
}
}else{
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
return postList;
}
在启动时使用parseJSONResponse并使用swipeToRefresh swipeJSONResponse。在parseJSONResponse中，最后显示的帖子的ID存储在int t中，然后将此int t传递给swipeJSONResponse以获取新帖子。
但刷新后，新数据不会显示在列表中。那么，请告诉我该怎么做。我已经阅读了一些使用add的文章，如下：
listview.add(0, item);
但我不知道如何同时使用多行数据来实现它。提前谢谢。
答案 0 :(得分：1)
更新listView中数据的正确方法应该是：
1）在适配器中创建更新数据方法。在你的情况下可能是这样的：
public updateData(ArrayList<Post> postList) {
this.listData=postList;
notifyDataSetChanged();
}
或者，如果您只想在顶部添加数据：
public addNewDataOnTop(ArrayList<Post> postList) {
this.listData.addAll(0,postList);
notifyDataSetChanged();
}
2）当您要添加新数据时，请不要创建新适配器，只需更新数据
在开头创建listView时，设置空适配器：
adapter = new PostAdapter(new ArrayList());
listView.setAdapter(adapter);
收到新数据后，只需更新适配器：
adapter.addNewDataOnTop(postList);
我希望它有所帮助
答案 1 :(得分：0)
我会使用以下方法在顶部插入每个项目：
mArrayList.add(0, item1);
notifyItemInserted(0);
mArrayList.add(0, item2);
notifyItemInserted(0);
对所有项目执行以下操作。