Java 使用片段-NullPointerException
我在包含各种片段的活动上收到了一个空指针异常错误。在该活动中,用户列表将通过基于性别、最低年龄等各种标准的解析填充到当前用户 下面是启动应用程序时意外收到的logcat消息Java 使用片段-NullPointerException,java,android,android-activity,android-fragments,parse-platform,Java,Android,Android Activity,Android Fragments,Parse Platform,我在包含各种片段的活动上收到了一个空指针异常错误。在该活动中,用户列表将通过基于性别、最低年龄等各种标准的解析填充到当前用户 下面是启动应用程序时意外收到的logcat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
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$1.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$6$1.run(Parse.java:888)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Handler.handleCallback(Handler.java:733)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Handler.dispatchMessage(Handler.java:95)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.os.Looper.loop(Looper.java:136)
08-15 17:42:28.863: E/AndroidRuntime(4974): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-15 17:42:28.863: E/AndroidRuntime(4974): at java.lang.reflect.Method.invokeNative(Native Method)
08-15 17:42:28.863: E/AndroidRuntime(4974): at java.lang.reflect.Method.invoke(Method.java:515)
08-15 17:42:28.863: E/AndroidRuntime(4974): at com.android.internal.os.ZygoteInit$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)
下面是保存发生错误的片段的活动代码
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);
}
}
第108行
usersListView.setAdapter(namesArrayAdapter);
更新的活动代码
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 void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setConversationsList();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment1_layout, container, false);
return view;
}
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)getActivity().findViewById(R.id.usersListView);
namesArrayAdapter =
new ArrayAdapter<String>(getActivity().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(getActivity().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(getActivity().getApplicationContext(), MessagingActivity.class);
intent.putExtra("RECIPIENT_ID", user.get(0).getObjectId());
startActivity(intent);
} else {
Toast.makeText(getActivity().getApplicationContext(),
"Error finding that user",
Toast.LENGTH_SHORT).show();
}
}
});
}
}
公共类Fragment1扩展了Fragment{
私有字符串currentUserId;
私有ArrayAdapter名称ArrayAdapter;
私有数组列表名称;
私有列表视图用户列表视图;
私人按钮注销按钮;
字符串userGender=ParseUser.getCurrentUser().getString(“性别”);
String activityName=ParseUser.getCurrentUser().getString(“activityName”);
Number maxDistance=ParseUser.getCurrentUser().getNumber(“最大_距离”);
String userLookingGender=ParseUser.getCurrentUser().getString(“Looking_-Gender”);
Number minimumAge=ParseUser.getCurrentUser().getNumber(“最小年龄”);
Number maximumAge=ParseUser.getCurrentUser().getNumber(“最大年龄”);
Number userage=ParseUser.getCurrentUser().getNumber(“年龄”);
@凌驾
已创建ActivityState上的公共无效(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
setConversationsList();
}
@凌驾
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态){
视图=充气机。充气(右布局。碎片1_布局,容器,假);
返回视图;
}
私有void setConversationsList(){
currentUserId=ParseUser.getCurrentUser().getObjectId();
名称=新的ArrayList();
//字符串userActivitySelectionName=null;
ParseQuery=ParseUser.getQuery();
//query.whereEqualTo(“ActivityName”,userActivitySelectionName);
query.whereNotEqualTo(“objectId”,ParseUser.getCurrentUser().getObjectId());
//性别=currentUser.Looking\u性别的用户
查询:whereEqualTo(“性别”,userLookingGender);
//具有Looking_Gender=currentUser.Gender的用户
查询:whereEqualTo(“寻找性别”,用户性别);
查询设置限制(1);
查询。whereEqualTo(“活动名称”,活动名称);
查询。whereGreaterThanOrEqualTo(“最小年龄”,minimumAge)。whereGreaterThanOrEqualTo(“年龄”,userage);
查询。whereLessThanOrEqualTo(“最大年龄”,最大年龄)。whereLessThanOrEqualTo(“年龄”,用户年龄);
//查询。Wherethinkilometer(“最大距离”、点、最大距离)
findInBackground(新的FindCallback(){
public void done(List userList,parsee异常){
如果(e==null){
对于(int i=0;i,再次调用getActivity()
之前的onActivityCreated()
,因此getActivity()
返回null
onCreateView()
在调用onActivityCreated()
之前,当活动的onCreate()方法返回时,调用onActivityCreated()
。
这意味着当调用onCreateView()
时,片段的getActivitiy()
方法将返回null
在
onCreateView()
中调用setConversationsList()
,该列表在多个位置访问getActivity()
。因此NullPointerException再次调用getActivity()
之前的onActivityCreated()
,因此getActivity()
返回null
onCreateView()
在调用onActivityCreated()
之前,当活动的onCreate()方法返回时,调用onActivityCreated()
。
这意味着当调用onCreateView()
时,片段的getActivitiy()
方法将返回null
在
onCreateView()
中调用setConversationsList()
哪个访问getActivity()
在多个位置。因此,NullPointerException
在迭代之前,您可能需要检查List userList
是否为空。在迭代之前,您可能需要检查List userList
是否为空。如果在setConversationsList()中找到的视图
来自片段的布局(R.layout.fragment1\u布局
),则必须首先充气布局:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment1_layout, container, false);
setConversationsList();
return view;
}
请注意,在创建活动之前使用
getActivity
是完全正常的,因为它已经可用,因为onAttach
。但是,如果您要查找的视图属于活动的布局,那么您应该在创建活动的视图中找到它们,如果您在setCon>中找到视图,则应该在onActivityCreated
中找到它们versationsList()
来自片段的布局(R.layout.fragment1\u layout
),则必须首先对布局进行充气:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment1_layout, container, false);
setConversationsList();
return view;
}
请注意,在
onActivityCreated
之前使用getActivity
是完全正常的,因为它已经在onAttach
中可用。但是,如果您要查找的视图属于活动的布局,那么您应该在onActivityCreated
中找到它们,fragment1.java的第108行是什么?是什么在fragment1.java的第108行?谢谢你的回复。我试图移动东西,但我不确定应该在哪里调用它以避免遇到其他错误。@user3907211你能将setConversationsList()
移动到onActivityCreated()吗
?@user3907211为什么不尝试将onActivityCreated
添加到您的片段中?感谢您的回复。我已将onActivityCreated添加到片段中,但不幸的是,这导致了另一个nullpointer异常代码。我已在我的初始帖子中更新了更新后的代码,如果您能仔细查看,这将非常有用有帮助。@user3907211是usersListView
null?谢谢你的回复
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment1_layout, container, false);
setConversationsList();
return view;
}