我有一个包含4个项目的SwitchTabActivty。就我而言，我使用第二项来通过回收站视图从Web获取一些数据。问题是，当我按下第四个项目（它包含一个开始活动的按钮）并返回到我的第二个标签时，我的再循环视图再次与相同的数据相乘。
Switchtabactivity：
public class SwitchTabActivity extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
private boolean pressToExit = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_switch_tab);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.weather_tab);
tabLayout.getTabAt(1).setIcon(R.drawable.events);
tabLayout.getTabAt(2).setIcon(R.drawable.details_tab);
tabLayout.getTabAt(3).setIcon(R.drawable.settings_tab);
setColorTab(tabLayout);
}
private void setColorTab(TabLayout tab) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
tab.setTabTextColors(getResources().getColorStateList(R.color.tab_colors, null));
} else {
tab.setTabTextColors(getResources().getColorStateList(R.color.tab_colors));
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
}
@Override
public void onBackPressed() {
if (!pressToExit) {
Toast.makeText(this, "Press back again to exit.", Toast.LENGTH_SHORT).show();
pressToExit = true;
} else {
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
}
@Override
public void onResume() {
super.onResume();
pressToExit = false;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_switch_tab, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return WeatherFragment.newInstance(position);
case 1:
return EventFragment.newInstance(position);
case 2:
return OwnEventFragment.newInstance(position);
case 3:
return SettingsFragment.newInstance(position);
}
return null;
}
@Override
public int getCount() {
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Weather";
case 1:
return "Events";
case 2:
return "My Events";
case 3:
return "Settings";
}
return null;
}
}
EventFragment：
public class EventFragment extends Fragment implements EventResponse {
private String latitude, longitude;
private static final String ARG_SECTION_NUMBER = "section_number";
private RecyclerView eventList;
private EventAdapter adapter;
private TextView ifNullEvents;
private final ArrayList<EventData> eventsData = new ArrayList<>();
private UserDataBase db;
private List<String> latLonList;
private ProgressBar progressBar;
public EventFragment() {
}
public static EventFragment newInstance(int sectionNumber) {
EventFragment fragment = new EventFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.event_fragment, container, false);
initView(rootView);
db = new UserDataBase(getContext());
checkLocationChanged();
latLonList = db.getLatLon();
latitude = latLonList.get(0);
longitude = latLonList.get(1);
String EVENT_BRITE_URL_PARSE = "MY_URL";
String EVENT_BRITE_TOKEN = "MY_TOKEN";
new EventBriteApi(this, getContext()).execute(EVENT_BRITE_URL_PARSE + EVENT_BRITE_TOKEN);
setupRecyclerView();
setLocationMessage();
return rootView;
}
private void initView(View view) {
eventList = (RecyclerView) view.findViewById(R.id.event_recycler_view);
ifNullEvents = (TextView) view.findViewById(R.id.text_null_location);
progressBar = (ProgressBar) view.findViewById(R.id.progress_bar_event);
}
private void checkLocationChanged() {
if (WePrefs.isLocationChanged) {
eventsData.clear();
ifNullEvents.setText(getResources().getString(R.string.waiting_for_data));
ifNullEvents.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.VISIBLE);
WePrefs.setIsLocationChanged(false);
} else {
progressBar.setVisibility(View.GONE);
ifNullEvents.setVisibility(View.GONE);
}
if (WePrefs.isNullEventLocation) {
ifNullEvents.setText(getResources().getString(R.string.no_events_found));
ifNullEvents.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.INVISIBLE);
WePrefs.setIsNullEventLocation(false);
}
}
private void setupRecyclerView() {
eventList.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
eventList.setLayoutManager(linearLayoutManager);
adapter = new EventAdapter(getActivity(), eventsData);
adapter.setHasStableIds(true);
eventList.setAdapter(adapter);
}
@Override
public void onResume() {
checkLocationChanged();
setLocationMessage();
super.onResume();
}
private void setLocationMessage() {
if (eventsData.isEmpty()) {
ifNullEvents.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.VISIBLE);
} else {
ifNullEvents.setVisibility(View.GONE);
progressBar.setVisibility(View.GONE);
}
progressBar.setVisibility(View.GONE);
}
@Override
public void getArray(ArrayList<EventData> data) {
eventsData.clear();
eventsData.addAll(new ArrayList<>(new LinkedHashSet<>(data)));
}
}
适配器：
ublic class EventAdapter extends RecyclerView.Adapter<EventAdapter.EventHolder> {
ArrayList<EventData> data;
Context context;
public EventAdapter(Context context, ArrayList<EventData> events) {
this.context = context;
data = events;
}
@Override
public EventHolder onCreateViewHolder(ViewGroup parent, int viewType) {
RelativeLayout layout = (RelativeLayout) LayoutInflater.from(parent.getContext()).inflate(R.layout.single_event_view, parent, false);
return new EventAdapter.EventHolder(layout);
}
@Override
public void onBindViewHolder(EventHolder holder, int position) {
holder.eventName.setText(data.get(position).getEventName());
if (data.get(position).getEventImageUrl() != null) {
Picasso.with(context).load(data.get(position).getEventImageUrl()).into(holder.eventPic);
} else {
holder.eventPic.setImageDrawable(ContextCompat.getDrawable(context, R.drawable.no_image));
}
}
@Override
public int getItemCount() {
return data.size();
}
public class EventHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
TextView eventName;
ImageView eventPic;
RelativeLayout layout;
public EventHolder(View itemView) {
super(itemView);
eventName = (TextView) itemView.findViewById(R.id.event_name);
eventPic = (ImageView) itemView.findViewById(R.id.event_image);
layout = (RelativeLayout) itemView.findViewById(R.id.event_layout);
layout.setOnClickListener(this);
}
@Override
public void onClick(View view) {
//context.startActivity(new Intent(context, WebViewActivity.class));
}
}
}
这些是我用于此类事情的一些java类。
无论如何，另一个问题是，当我更改位置（接收我的事件）时，我必须转到另一个选项卡，然后返回查看我的事件列表（我认为它需要重新创建视图）所以，因为我打电话给Resume，但它没有帮助。