Java 方法 getApplicationContext() 未定义 - 片段问题
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时间：2020-08-11 00:06:37 来源:igfitidea点击:
The method getApplicationContext() is undefined - fragment issues
提问by John
I am getting the following errors: The method getApplicationContext() is undefined The method findViewById(int) is undefined for the type Fragment1
我收到以下错误： getApplicationContext() 方法未定义 方法 findViewById(int) 未定义为 Fragment1 类型
These errors seem to be eliminated when my class is extended to an Activity as oppose to a fragment, but it is important that this activity remains as a fragment, so I am not too sure how to work this out.
当我的类扩展到与片段相反的活动时，这些错误似乎被消除了，但重要的是该活动仍然是一个片段，所以我不太确定如何解决这个问题。
Any help would be greatly appreciated. Thanks in advance.
任何帮助将不胜感激。提前致谢。
Below is the code
下面是代码
public class Fragment1 extends Fragment {
private String currentUserId;
private ArrayAdapter<String> namesArrayAdapter;
private ArrayList<String> names;
private ListView usersListView;
private Button logoutButton;
String userGender = ParseUser.getCurrentUser().getString("Gender");
String activityName = ParseUser.getCurrentUser().getString("ActivityName");
Number maxDistance = ParseUser.getCurrentUser().getNumber("Maximum_Distance");
String userLookingGender = ParseUser.getCurrentUser().getString("Looking_Gender");
Number minimumAge = ParseUser.getCurrentUser().getNumber("Minimum_Age");
Number maximumAge = ParseUser.getCurrentUser().getNumber("Maximum_Age");
Number userage = ParseUser.getCurrentUser().getNumber("Age");
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
if (container == null){
return null;
}
return (LinearLayout)inflater.inflate(R.layout.fragment1_layout,
container,false);
logoutButton = (Button) findViewById(R.id.logoutButton);
logoutButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
ParseUser.logOut();
Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
startActivity(intent);
}
});
setConversationsList();
}
private void setConversationsList() {
currentUserId = ParseUser.getCurrentUser().getObjectId();
names = new ArrayList<String>();
// String userActivitySelectionName = null;
ParseQuery<ParseUser> query = ParseUser.getQuery();
// query.whereEqualTo("ActivityName",userActivitySelectionName);
query.whereNotEqualTo("objectId", ParseUser.getCurrentUser().getObjectId());
// users with Gender = currentUser.Looking_Gender
query.whereEqualTo("Gender", userLookingGender);
// users with Looking_Gender = currentUser.Gender
query.whereEqualTo("Looking_Gender", userGender);
query.setLimit(1);
query.whereEqualTo("ActivityName", activityName);
query.whereGreaterThanOrEqualTo("Minimum_Age", minimumAge).whereGreaterThanOrEqualTo("Age", userage);
query.whereLessThanOrEqualTo("Maximum_Age", maximumAge).whereLessThanOrEqualTo("Age", userage);
// query.whereWithinKilometers("Maximum_Distance", point, maxDistance)
query.findInBackground(new FindCallback<ParseUser>() {
public void done(List<ParseUser> userList, ParseException e) {
if (e == null) {
for (int i=0; i<userList.size(); i++) {
names.add(userList.get(i).get("Name").toString());
names.add(userList.get(i).get("Headline").toString());
names.add(userList.get(i).get("Age").toString());
// names.add(userList.get(i).getParseObject("ProfilePicture").;
}
usersListView = (ListView)findViewById(R.id.usersListView);
namesArrayAdapter =
new ArrayAdapter<String>(getApplicationContext(),
R.layout.user_list_item, names);
usersListView.setAdapter(namesArrayAdapter);
usersListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> a, View v, int i, long l) {
openConversation(names, i);
}
});
} else {
Toast.makeText(getApplicationContext(),
"Error loading user list",
Toast.LENGTH_LONG).show();
}
}
});
}
public void openConversation(ArrayList<String> names, int pos) {
ParseQuery<ParseUser> query = ParseUser.getQuery();
query.whereEqualTo("Name", names.get(pos));
query.findInBackground(new FindCallback<ParseUser>() {
public void done(List<ParseUser> user, ParseException e) {
if (e == null) {
Intent intent = new Intent(getApplicationContext(), MessagingActivity.class);
intent.putExtra("RECIPIENT_ID", user.get(0).getObjectId());
startActivity(intent);
} else {
Toast.makeText(getApplicationContext(),
"Error finding that user",
Toast.LENGTH_SHORT).show();
}
}
});
}
}
Update Unreachable code error for setConversationList
更新 setConversationList 的无法访问代码错误
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
if (container == null){
return null;
}
return (LinearLayout)inflater.inflate(R.layout.fragment1_layout,
container,false);
setConversationsList();
}
private void setConversationsList() {
currentUserId = ParseUser.getCurrentUser().getObjectId();
names = new ArrayList<String>();
// String userActivitySelectionName = null;
ParseQuery<ParseUser> query = ParseUser.getQuery();
Update
更新
Upon launching the activity, I received the following message:
启动活动后，我收到以下消息：
08-15 14:52:16.365: E/AndroidRuntime(3332): FATAL EXCEPTION: main
08-15 14:52:16.365: E/AndroidRuntime(3332): Process: com.dooba.beta, PID: 3332
08-15 14:52:16.365: E/AndroidRuntime(3332): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dooba.beta/com.dooba.beta.usermatch}: java.lang.NullPointerException
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread.access0(ActivityThread.java:135)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.os.Handler.dispatchMessage(Handler.java:102)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.os.Looper.loop(Looper.java:136)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-15 14:52:16.365: E/AndroidRuntime(3332): at java.lang.reflect.Method.invokeNative(Native Method)
08-15 14:52:16.365: E/AndroidRuntime(3332): at java.lang.reflect.Method.invoke(Method.java:515)
08-15 14:52:16.365: E/AndroidRuntime(3332): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-15 14:52:16.365: E/AndroidRuntime(3332): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-15 14:52:16.365: E/AndroidRuntime(3332): at dalvik.system.NativeStart.main(Native Method)
08-15 14:52:16.365: E/AndroidRuntime(3332): Caused by: java.lang.NullPointerException
08-15 14:52:16.365: E/AndroidRuntime(3332): at com.dooba.beta.usermatch.initialisePaging(usermatch.java:32)
08-15 14:52:16.365: E/AndroidRuntime(3332): at com.dooba.beta.usermatch.onCreate(usermatch.java:20)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.Activity.performCreate(Activity.java:5231)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-15 14:52:16.365: E/AndroidRuntime(3332): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
08-15 14:52:16.365: E/AndroidRuntime(3332): ... 11 more
Below is the activity page that calls for the fragment
下面是调用片段的活动页面
import java.util.List;
import java.util.Vector;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;
public class usermatch extends FragmentActivity {
private PageAdapter mPagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.viewpager_layout);
initialisePaging();
}
private void initialisePaging() {
// TODO Auto-generated method stub
List<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this, Fragment1.class.getName()));
fragments.add(Fragment.instantiate(this, Fragment2.class.getName()));
fragments.add(Fragment.instantiate(this, Fragment3.class.getName()));
mPagerAdapter = new PageAdapter(this.getSupportFragmentManager(), fragments);
ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
pager.setAdapter(mPagerAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.mood, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Update 2Below is the message I receive in logcat
更新 2下面是我在 logcat 中收到的消息
08-15 17:42:28.863: E/AndroidRuntime(4974): FATAL EXCEPTION: main
08-15 17:42:28.863: E/AndroidRuntime(4974): Process: com.dooba.beta, PID: 4974
08-15 17:42:28.863: E/AndroidRuntime(4974): java.lang.NullPointerException
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.dooba.beta.Fragment1.done(Fragment1.java:108)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.parse.FindCallback.internalDone(FindCallback.java:45)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.parse.FindCallback.internalDone(FindCallback.java:1)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.parse.Parse.run(Parse.java:888)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Handler.handleCallback(Handler.java:733)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Handler.dispatchMessage(Handler.java:95)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Looper.loop(Looper.java:136)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-15 17:42:28.863: E/AndroidRuntime(4974): at java.lang.reflect.Method.invokeNative(Native Method)
08-15 17:42:28.863: E/AndroidRuntime(4974): at java.lang.reflect.Method.invoke(Method.java:515)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-15 17:42:28.863: E/AndroidRuntime(4974): at dalvik.system.NativeStart.main(Native Method)
采纳答案by Eran
You can get the activity that contains the fragment with getActivity().
您可以使用 获取包含片段的活动getActivity()。
Therefore getActivity().getApplicationContext()would work.
因此getActivity().getApplicationContext()会起作用。
getActivity().findViewById(int)would also work.
getActivity().findViewById(int)也会工作。
Make sure, though, you don't use getActivity()prior to onActivityCreated(), since it would return null prior to that.
但是，请确保不要使用getActivity()before onActivityCreated()，因为它会在此之前返回 null。
回答by Chefes
Change
改变
Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
to
到
Intent intent = new Intent(getActivity(), LoginActivity.class);
回答by btinsae
you can access context from onAttach() like below example
您可以从 onAttach() 访问上下文，如下例所示
@Override
public void onAttach(@NonNull Context context) {
super.onAttach(context);
}
