我有带200多个标签的ViewPager。每个选项卡都包括recyclerview以及可通过Retrofit2动态加载数据的视图。每执行一次onTabSelected()
操作,数据就会加载。
但是由于加载了Viewpager position-1 (if any), position, position+1 (if any)
,我得到了2-3个具有相同数据的标签。
问题是-如何仅加载当前选择的一个片段而没有相邻位置?
我以为BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
中的FragmentPagerAdapter
可以通过简单地将其传递给构造函数来解决我的问题:
public Adapter_programmes(FragmentManager fm, Context context) {
super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
mContext = context;
fragment_some = new Fragment_Some();
}
但是什么都没有改变。
UPD:我想我在这里找到了解决方法:ViewPager offscreen page limit
但是我听不懂:使用占位符图像加载网格,并且在更改页面之前不要加载真实图像。
** UPD2:**setOffscreenPageLimit(1)无法解决我的问题。
我的代码:
片段:
public static Fragment_some newInstance(int page) {
Bundle args = new Bundle();
args.putInt(ARG_PAGE, page);
Fragment_some fragment = new Fragment_some();
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mPage = getArguments().getInt(ARG_PAGE);
}
arrayNames.clear();
arrayTimes.clear();
}
@Override
public void onAttach(@NonNull Context context) {
super.onAttach(context);
mContext=context;
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
Log.d(TAG, "");
//creating fragment
rootView = inflater.inflate(R.layout.content_list, container, false);
loadProgrammes(CID); //doing retrofit query for data, using argument which I've got from onTabSelected by SharedPreferences
//data loaded succecfully
Handler handler = new Handler();
handler.postDelayed(() -> {
adapterItem = new Adapter_programme_item(mContext, arrayTimes, arrayNames);
RecyclerView RV = rootView.findViewById(R.id.recycler_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(mContext);
RV.setLayoutManager(layoutManager);
RV.setAdapter(adapterItem);
}, 3000); //3 seconds waiting
return rootView;
}
FragmentPagerAdapter:
public Adapter_programmes(FragmentManager fm, Context context) {
super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
mContext = context;
fragment_some = new Fragment_some();
}
@Override public int getCount() {
return PAGE_COUNT;
}
@Override public Fragment getItem(int position) {
return fragment_some.newInstance(position + 1);
}
@Override public CharSequence getPageTitle(int position) {
return tabTitles[position];
}
public void updateTitleData(String[] titles) {
...
notifyDataSetChanged();
}
MainActivity:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter = new Adapter_programmes(getSupportFragmentManager(), MainActivity.this);
ViewPager viewPager = findViewById(R.id.viewpager);
viewPager.setAdapter(adapter);
TabLayout tabLayout = findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
loaderFromURL(); //getting tab titles via retrofit
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
@Override
public void onTabSelected(TabLayout.Tab tab) {
Log.d(TAG, "onTabSelected");
String mCID = listm3u.get(tab.getPosition()).getItemCID();
AppPreferences.setCurrentCID(MainActivity.this, mCID);
String iconURL = listm3u.get(tab.getPosition()).getItemIcon();
ImageView IVChanelLogo = findViewById(R.id.IVChanelLogo);
Picasso.with(MainActivity.this).load(iconURL).into(IVChanelLogo);
}
});
}
因为您正在将片段的onCreateView
中的recyclerview填充为BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
,所以不会产生任何影响。
BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
而不是使当前片段+/- OffscreenPageLimit(默认为1)进入“恢复”状态,它仅使当前片段进入“恢复”状态,而使其他任何片段进入“开始”状态生命周期。
由于“开始”已超过onCreateView
,因此您的回收站视图的填充时间过早。
解决方案在Fragment的onCreateView
中创建没有数据的recyclerview适配器,找到recyclerView,设置其layoutmanger和适配器,等等。>>
然后在Fragment的onResume
方法中,获取recyclerView的数据,并使用此新数据更新recyclerview适配器,然后通知RecyclerView它的数据已更改。
然后您可以删除onTabSelected
内容
没有足够的示例代码来提供有效的示例,但下面的示例片段显示了textview2
的当前时间与“开始”时设置的textview1
相比,“恢复”时当前时间的更新。 “状态(您将在Viewpager中设置BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
的情况下创建此片段的3个副本)
package com.test.viewpager;
import android.content.Context;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Locale;
public class TextFragment extends Fragment {
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private int mParam1;
private View view;
public TextFragment() {
// Required empty public constructor
}
public static TextFragment newInstance(int param1) {
TextFragment fragment = new TextFragment();
Bundle args = new Bundle();
args.putInt(ARG_PARAM1, param1);
fragment.setArguments(args);
Log.d("Frag", "newInstance");
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getInt(ARG_PARAM1);
}
Log.d("Frag", "onCreate");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
Log.d("Frag", "onCreateView:" + mParam1);
view = inflater.inflate(R.layout.fragment_text, container, false);
return view;
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
Log.d("Frag", "onViewCreated:" + mParam1);
Bundle args = getArguments();
TextView textView1 = view.findViewById(R.id.textview1);
DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH-mm-ss.sss", Locale.US);
String dt = df.format(Calendar.getInstance().getTime());
textView1.setText(dt);
}
public void updateView(){
Log.d("Frag", "updateView");
TextView textView2 = view.findViewById(R.id.textview2);
DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH-mm-ss.sss", Locale.US);
String dt = df.format(Calendar.getInstance().getTime());
textView2.setText(dt);
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.d("Frag", "onAttach:" + mParam1);
}
@Override
public void onDetach() {
super.onDetach();
Log.d("Frag", "onDetach:" + mParam1);
}
@Override
public void onResume() {
super.onResume();
Log.d("Frag", "onResume:" + mParam1);
updateView();
}
@Override
public void onPause() {
super.onPause();
Log.d("Frag", "onPause:" + mParam1);
}
}