我仍在尝试为我的应用程序找到正确的设计，以防止在我的应用程序的tab host中以两个单独的片段调用适配器列表视图。
我到目前为止访问listviews的适配器时，只能在null为空时访问该值，我假设因为片段尚未完全设置且适配器没有＆＃虽然我不确定，但是已经创造了。如何在调用pubnub访问它之前确保适配器已设置？
我找到的唯一答案是使用处理程序来延迟事件，直到片段设置完毕，但这对我没有用。适配器仍为空。
片段1：
public class GroupChatFragment extends Fragment{
public ArrayAdapter<String> adapter;
private Context context;
public GroupChatFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_group_chat, container, false);
ListView chatListView = (ListView) rootView.findViewById(R.id.chatList);
adapter = new ArrayAdapter<>(context, android.R.layout.simple_list_item_1);
chatListView.setAdapter(adapter);
return rootView;
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context;
}
@Override
public void onDetach() {
super.onDetach();
}
}
片段2：
public class GroupTasksFragment extends Fragment {
public ArrayAdapter<String> adapter;
private Context context;
public GroupTasksFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_group_tasks, container, false);
ListView taskListView = (ListView) rootView.findViewById(R.id.tasksList);
adapter = new ArrayAdapter<>(context, android.R.layout.simple_list_item_1);
taskListView.setAdapter(adapter);
return rootView;
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context;
}
@Override
public void onDetach() {
super.onDetach();
}
}
引用片段的类（为了清楚起见，已经注释了访问适配器的行）：
public class GroupContentActivity extends AppCompatActivity {
private GroupChatFragment chatFrag;
private GroupTasksFragment taskFrag;
private PubNub connection;
private String groupName;
private String nickName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_group_content);
FragmentTabHost tabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);
tabHost.setup(this, getSupportFragmentManager(), android.R.id.tabcontent);
tabHost.addTab(tabHost.newTabSpec("tasks").setIndicator("Tasks"),
GroupTasksFragment.class, null);
tabHost.addTab(tabHost.newTabSpec("chat")
.setIndicator("Chat"), GroupChatFragment.class, null);
groupName = getIntent().getStringExtra("groupName");
nickName = getIntent().getStringExtra("nickName");
PNConfiguration config = new PNConfiguration();
config.setPublishKey("pub-c-d8414fbe-6925-4511-9bda-8fa682138fb1");
config.setSubscribeKey("sub-c-50acdc56-c1a3-11e6-b07a-0619f8945a4f");
connection = new PubNub(config);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
chatFrag = (GroupChatFragment) getSupportFragmentManager().findFragmentByTag("chat");
taskFrag = (GroupTasksFragment) getSupportFragmentManager().findFragmentByTag("tasks");
connection.history()
.channel(groupName)
.count(50)
.async(new PNCallback<PNHistoryResult>() {
@Override
public void onResponse(PNHistoryResult result, PNStatus status) {
for (PNHistoryItemResult item : result.getMessages()) {
String[] sForm = item.getEntry().getAsString().split(">>>>");
String m = "";
if (sForm.length > 2) {
for (int x = 1; x < sForm.length; x++) {
m += sForm[x];
}
} else {
m = sForm[1];
}
switch (sForm[0]) {
case "chat":
//chatFrag.adapter.add(m);
break;
case "addTask":
if (taskFrag.adapter.getPosition(m) < 0) {
//taskFrag.adapter.add(m);
}
break;
case "deleteTask":
if (taskFrag.adapter.getPosition(m) >= 0) {
//taskFrag.adapter.remove(m);
}
break;
case "groupCreated":
//taskFrag.adapter.clear();
//chatFrag.adapter.clear();
break;
}
}
}
});
connection.addListener(new SubscribeCallback() {
@Override
public void status(PubNub pubnub, PNStatus status) {
if (status.getCategory() == PNStatusCategory.PNUnexpectedDisconnectCategory) {
Toast.makeText(getApplicationContext(), "You were disconnected!", Toast.LENGTH_SHORT).show();
} else if (status.getCategory() == PNStatusCategory.PNConnectedCategory) {
if (status.getCategory() == PNStatusCategory.PNConnectedCategory) {
pubnub.publish().channel(groupName).message("chat>>>><ADMIN> User '" + nickName + "' Connected").async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult result, PNStatus status) {
}
});
}
} else if (status.getCategory() == PNStatusCategory.PNReconnectedCategory) {
Toast.makeText(getApplicationContext(), "You were reconnected!", Toast.LENGTH_SHORT).show();
}
}
@Override
public void message(PubNub pubnub, PNMessageResult message) {
String[] sForm = message.getMessage().getAsString().split(">>>>");
String m = "";
if (sForm.length > 2) {
for (int x = 1; x < sForm.length; x++) {
m += sForm[x];
}
} else {
m = sForm[1];
}
switch (sForm[0]) {
case "chat":
//chatFrag.adapter.add(m);
break;
case "addTask":
//taskFrag.adapter.add(m);
connection.publish().channel(groupName).message("chat>>>><ADMIN> Task '" + m + "' added.").async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult pnPublishResult, PNStatus pnStatus) {
}
});
break;
case "deleteTask":
//taskFrag.adapter.remove(m);
connection.publish().channel(groupName).message("chat>>>><ADMIN> Task '" + m + "' deleted.").async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult pnPublishResult, PNStatus pnStatus) {
}
});
break;
}
}
@Override
public void presence(PubNub pubnub, PNPresenceEventResult presence) {
}
});
connection.subscribe().channels(java.util.Collections.singletonList(groupName)).execute();
}
}, 100);
}
public void goHome(View v) {
Intent i = new Intent(getApplicationContext(), MainActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(i);
}
public void sendMessage(View v) {
String message = ((EditText) findViewById(R.id.messageToSend)).getText().toString();
connection.publish().channel(groupName).message("chat>>>><" + nickName + "> " + message).async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult pnPublishResult, PNStatus pnStatus) {
}
});
}
public void deleteTask(View v) {
final EditText input = new EditText(getApplicationContext());
input.setTextColor(Color.BLACK);
LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.MATCH_PARENT);
input.setLayoutParams(lp);
new AlertDialog.Builder(this)
.setTitle("Delete Task")
.setMessage("What task would you like to delete?")
.setView(input)
.setPositiveButton(R.string.OK, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (taskFrag.adapter.getPosition(input.getText().toString()) < 0) {
connection.publish().channel(groupName).message("deleteTask>>>>" + input.getText().toString()).async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult pnPublishResult, PNStatus pnStatus) {
}
});
dialog.cancel();
} else {
Toast.makeText(getApplicationContext(), "This task doesn't exist", Toast.LENGTH_SHORT).show();
dialog.cancel();
}
}
})
.setNegativeButton(R.string.CANCEL, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
})
.show();
}
public void addTask(View v) {
final EditText input = new EditText(getApplicationContext());
input.setTextColor(Color.BLACK);
LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.MATCH_PARENT);
input.setLayoutParams(lp);
new AlertDialog.Builder(this)
.setTitle("Create New Task")
.setView(input)
.setMessage("What task would you like to create?")
.setPositiveButton(R.string.OK, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (taskFrag.adapter.getPosition(input.getText().toString()) >= 0) {
connection.publish().channel(groupName).message("addTask>>>>" + input.getText().toString()).async(new PNCallback<PNPublishResult>() {
@Override
public void onResponse(PNPublishResult pnPublishResult, PNStatus pnStatus) {
}
});
dialog.cancel();
} else {
Toast.makeText(getApplicationContext(), "This task already exists", Toast.LENGTH_SHORT).show();
dialog.cancel();
}
}
})
.setNegativeButton(R.string.CANCEL, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
})
.show();
}
}
我也考虑过使用静态变量等，但我不知道如何使用静态变量作为设置状态，仍然在方法中使用代码，因为方法和变量必须是静态的，PubNub调用不可能。
我也不能公开变量并做类似的事情，因为没有实例可以传递给片段，因为它们的设置方式。
有没有办法用片段到活动通信接口来做这件事呢？
编辑：从片段的第一个答案添加了代码，仍然导致空的适配器。
答案 0 :(得分：1)
您的代码存在两个问题：
当您使用其他视图初始化子视图时，您将向Fragment返回另一个视图：
View rootView = inflater.inflate(R.layout.fragment_group_tasks, container, false);
是您应该返回的视图，而不是：
return inflater.inflate(R.layout.fragment_group_chat, container, false);
这样做：
return rootView;
您没有使用已在Fragment类中重写的onAttach()方法。这样做：
private Context context;
并在您的onAttach方法中
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context; //when fragment is created, context will be initialised.
}
现在，使用您的适配器，而不是传递getContext()，传递初始化的context：
String[] items = {"item1", "item2"}
adapter = new ArrayAdapter<>(context, android.R.layout.simple_list_item_1, items);
chatListView.setAdapter(adapter);