我有一个片段，它从一个活动中调用，在其中一个标签中显示。我希望每次单击片段的选项卡按钮时都会刷新片段数据 这是我的片段 -
public class ChatFragment extends Fragment {
private String TAG = MainActivity.class.getSimpleName();
private ArrayList<ChatRoom> chatRoomArrayList;
private ChatRoomsAdapter mAdapter;
private RecyclerView recyclerView;
View convertedView;
private String selfUserId;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
convertedView = inflater.inflate(R.layout.content_main, null, false);
return convertedView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//setListAdapter(adapter);
//getListView().setOnItemClickListener(this);
//registerForContextMenu(getListView());
recyclerView = (RecyclerView) convertedView.findViewById(R.id.recycler_view);
selfUserId = MyApplication.getInstance().getPrefManager().getUser().getId();
chatRoomArrayList = new ArrayList<>();
mAdapter = new ChatRoomsAdapter(getContext(), chatRoomArrayList);
final LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);
recyclerView.addItemDecoration(new SimpleDividerItemDecoration(
getContext().getApplicationContext()
));
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(mAdapter);
recyclerView.addOnItemTouchListener(new ChatRoomsAdapter.RecyclerTouchListener(getContext().getApplicationContext(),
recyclerView, new ChatRoomsAdapter.ClickListener() {
@Override
public void onClick(View view, int position) {
// when chat is clicked, launch full chat thread activity
ChatRoom userChatRoom = chatRoomArrayList.get(position);
Intent intent = new Intent(getContext(), ChatRoomActivity.class);
intent.putExtra("user_id", userChatRoom.getId());
intent.putExtra("name", userChatRoom.getName());
startActivity(intent);
}
@Override
public void onLongClick(View view, int position) {
}
}));
fetchChats();
}
private void fetchChats() {
String endPoint = EndPoints.CHAT_ROOMS.replace("_ID_", selfUserId);
Log.e(TAG, "endPoint: " + endPoint);
StringRequest strReq = new StringRequest(Request.Method.GET,
endPoint, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.e(TAG, "response: " + response);
try {
JSONObject obj = new JSONObject(response);
// check for error flag
if (obj.getBoolean("error") == false) {
JSONArray chatRoomsArray = obj.getJSONArray("chat_rooms");
for (int i = 0; i < chatRoomsArray.length(); i++) {
JSONObject chatRoomsObj = (JSONObject) chatRoomsArray.get(i);
ChatRoom cr = new ChatRoom();
cr.setId(chatRoomsObj.getString("user_id"));
cr.setName(chatRoomsObj.getString("name"));
cr.setLastMessage("");
cr.setUnreadCount(0);
cr.setTimestamp(chatRoomsObj.getString("created_at"));
chatRoomArrayList.add(cr);
}
} else {
// error in fetching chat rooms
Toast.makeText(getContext().getApplicationContext(), "" + obj.getJSONObject("error").getString("message"), Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
Log.e(TAG, "json parsing error: " + e.getMessage());
Toast.makeText(getContext().getApplicationContext(), "Json parse error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
mAdapter.notifyDataSetChanged();
// subscribing to all chat room topics
//subscribeToAllTopics();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
NetworkResponse networkResponse = error.networkResponse;
Log.e(TAG, "Volley error: " + error.getMessage() + ", code: " + networkResponse);
Toast.makeText(getContext().getApplicationContext(), "Volley error: " + error.getMessage(), Toast.LENGTH_SHORT).show();
}
});
//Adding request to request queue
MyApplication.getInstance().addToRequestQueue(strReq);
}
}
每当我打开选项卡以显示此片段时，我希望调用fetchChats（）以使用新更新的Chats刷新片段中的视图。我怎么能这样做？
错误日志 -
FATAL EXCEPTION: main
Process: com.wipro.chat, PID: 19283
java.lang.NullPointerException: replacement == null
at java.lang.String.replace(String.java:972)
at com.wipro.chat.tabs.ChatFragment.fetchChats(ChatFragment.java:112)
at com.wipro.chat.tabs.ChatFragment.setUserVisibleHint(ChatFragment.java:107)
at android.support.v4.app.FragmentPagerAdapter.setPrimaryItem(FragmentPagerAdapter.java:130)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1175)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:668)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:735)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18788)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
at android.view.View.measure(View.java:18788)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
答案 0 :(得分：1)
覆盖片段中的onResume()方法，然后只需拨打fetchChats()中的onResume()。
您也可以在片段的onStart()方法中执行此操作。
如果在您的情况下没有调用这些方法，请将fetchChats()从私有更改为公共。然后保留对您的片段的引用。向选中时调用的选项卡添加一个监听器，并在选择所需选项卡时调用fragment.fetchChats()。
答案 1 :(得分：0)
覆盖片段中的方法
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
//do your work here
}
}