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我正在從服務器接收新項目數據並將其設置爲我的RecyclerView的適配器。當我第一次啓動異步任務來獲取數據時，獲取的數據從頂部顯示。但是當我再次啓動異步任務來獲取新數據時，新數據會附加在（不可見的）舊數據下面，儘管我在開始服務器請求之前設置了adapter = null。RecyclerView：新加載的項目不會添加到頂部
一般方法：
1）啓動活性及的AsyncTask從服務器獲取數據：asynctask.execute();
2）調用mRecyclerView.setAdapter(mAdapter);和mAdapter.notifyDataSetChanged();和數據將被從頂部被顯示在
3）initate的AsyncTask再次：第一組mAdapter = null;並加載另一個數據
問題在3）：現在新裝DA ta不會從頂部顯示，而是低於1）中的數據，但由於mAdapter = null;而不可見。這就像RecyclerView沒有「刪除」1）中顯示的舊數據的空間。
這很奇怪，有人有任何想法爲什麼會出現這種行爲？
代碼：
一）我的適配器：
public class Adapter_New extends RecyclerView.Adapter<Adapter_New.CustomViewHolder> {
private List<Data_B> feedItemList;
private Context mContext;
private int lastPosition = -1, b_height;
int width, height, targetHeight;
private ViewHolderState viewHolderState = ViewHolderState.getInstance();
public Adapter_New(Context context, List<Data_B> feedItemList) {
this.feedItemList = feedItemList;
this.mContext = context;
}
@Override
public CustomViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
DisplayMetrics metrics = mContext.getResources().getDisplayMetrics();
int calc_width= metrics.widthPixels;
int calc_height=metrics.heightPixels;
int dens=metrics.densityDpi;
double wi=(double)calc_width/(double)dens;
double hi=(double)calc_height/(double)dens;
double x = Math.pow(wi,2);
double y = Math.pow(hi,2);
double screenInches = Math.sqrt(x + y);
if (screenInches >= 7.0){
width = metrics.widthPixels/3;
height = metrics.heightPixels/4;
}else{
width = metrics.widthPixels/2;
height = metrics.heightPixels/4;
}
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.list_item_grid, null);
CustomViewHolder viewHolder = new CustomViewHolder(view);
return viewHolder;
}
@Override
public void onViewDetachedFromWindow(CustomViewHolder holder) {
super.onViewDetachedFromWindow(holder);
((CustomViewHolder) holder).clearAnimation();
((CustomViewHolder) holder).cleanup();
}
@Override
public void onBindViewHolder(final CustomViewHolder customViewHolder, int i) {
Data_Borrow data = feedItemList.get(i);
final Target target = new Target() {
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {
}
@Override
public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
b_height = bitmap.getHeight();
customViewHolder.frame.getLayoutParams().height = b_height; //setting height dynamically
customViewHolder.imageView.getLayoutParams().height = b_height; //setting height dynamically
customViewHolder.imageView.setImageBitmap(bitmap);
}
@Override
public void onBitmapFailed(Drawable errorDrawable) {
}
};
customViewHolder.imageView.setTag(target);
Picasso.with(mContext)
.load(data.getImageUrl())
.resize(width, height)
.into(target);
// Animation apply
setAnimation(customViewHolder.rel_container, i);
}
//Animation
private void setAnimation(View viewToAnimate, int position) {
// If the bound view wasn't previously displayed on screen, it's animated
if (position > lastPosition) {
Animation animation = AnimationUtils.loadAnimation(mContext, R.anim.slide_in_up);
viewToAnimate.startAnimation(animation);
lastPosition = position;
}
}
@Override
public int getItemCount() {
return (null != feedItemList ? feedItemList.size() : 0);
}
public void add_new(List<Data_Borrow> datas) {
//feedItemList.clear();
feedItemList.addAll(datas);
notifyDataSetChanged();
}
public void clear() {
feedItemList.clear();
notifyDataSetChanged();
}
public class CustomViewHolder extends RecyclerView.ViewHolder {
protected ImageView imageView;
protected RelativeLayout rel_container;
protected FrameLayout frame;
protected CardView card_view;
public CustomViewHolder(View view) {
super(view);
this.imageView = (ImageView) view.findViewById(R.id.thumbnail);
this.title = (TextView) view.findViewById(R.id.title);
this.rel_container = (RelativeLayout) view.findViewById(R.id.rel_grid_item);
this.frame = (FrameLayout) view.findViewById(R.id.frame_current);
this.frame.getLayoutParams().width = width; //setting width dynamically
this.card_view = (CardView) view.findViewById(R.id.card_view);
}
public void cleanup() {
Picasso.with(mContext)
.cancelRequest(imageView);
}
public void clearAnimation() {
rel_container.clearAnimation();
}
}
}
B）我的活動：
public class MyActivity extends AppCompatActivity implements FetchDataListener, SearchView.OnQueryTextListener, AdapterView.OnItemSelectedListener {
private List<Data_B> feedsList = null;
private RecyclerView mRecyclerView;
private Adapter_New mAdapter;
StaggeredGridLayoutManager StaggeredGridLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
StaggeredGridLayoutManager = new StaggeredGridLayoutManager(3, 1);
StaggeredGridLayoutManager.setGapStrategy(StaggeredGridLayoutManager.GAP_HANDLING_NONE);
mRecyclerView.setAdapter(new Data_Borrow_Adapter_New(this, feedsList)); // first add empty adapter
mRecyclerView.setLayoutManager(StaggeredGridLayoutManager);
initView(); //start initView when activity starts
//******* WHEN I CLICK TO GET NEW FILTERED DATA, then new data is not shown from top on ****//
btn_start_filtered_asynctask = (Button) findViewById(R.id.btn_filter);
btn_start_filtered_asynctask.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
initViewFilterd();
}
});
}
private void initView() {
String url = "http://xxx/xx.php";
String show_from = "0";
FetchDataTask_ALL task = new FetchDataTask_ALL(this);
task.execute(url, show_from);
loading = true;
}
private void initViewFilterd() {
String url = "http://xxx/xx.php";
String show_from = "0";
String result_category_pos = "2";
FetchDataTask_Filtered task = new FetchDataTask_Filtered(this);
task.execute(url, result_category_pos, show_from);
mAdapter = null; //setting adapter null
loading = true;
}
@Override
public void onFetchComplete(List<Data_B> data) {
if (mAdapter == null)
{
mAdapter = new Adapter_New(getApplicationContext(), data);
mRecyclerView.setAdapter(mAdapter);
mAdapter.notifyDataSetChanged();
} else {
mAdapter.add_new(data);
}
searchItem.collapseActionView();
loading = false;
mRecyclerView.setVisibility(View.VISIBLE);
}
}
您可以加入相關的代碼，而不是模糊的描述？ – tynn
好的我收錄了我的活動和我的適配器。請參閱更新的問題。 – Sin
爲什麼你在'add_new'中註釋'feedItemList.clear（）'？ – tynn