尝试从片段加载新活动时遇到了空指针异常 - 它实际上告诉我发生了意外错误。以下是log cat消息：
08-21 11:57:14.801: E/AndroidRuntime(1245): FATAL EXCEPTION: main
08-21 11:57:14.801: E/AndroidRuntime(1245): Process: com.dooba.beta, PID: 1245
08-21 11:57:14.801: E/AndroidRuntime(1245): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dooba.beta/com.dooba.beta.matchOptionActivity}: java.lang.NullPointerException
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread.access$800(ActivityThread.java:135)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.os.Handler.dispatchMessage(Handler.java:102)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.os.Looper.loop(Looper.java:136)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-21 11:57:14.801: E/AndroidRuntime(1245): at java.lang.reflect.Method.invokeNative(Native Method)
08-21 11:57:14.801: E/AndroidRuntime(1245): at java.lang.reflect.Method.invoke(Method.java:515)
08-21 11:57:14.801: E/AndroidRuntime(1245): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-21 11:57:14.801: E/AndroidRuntime(1245): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-21 11:57:14.801: E/AndroidRuntime(1245): at dalvik.system.NativeStart.main(Native Method)
08-21 11:57:14.801: E/AndroidRuntime(1245): Caused by: java.lang.NullPointerException
08-21 11:57:14.801: E/AndroidRuntime(1245): at com.dooba.beta.matchOptionActivity.onCreate(matchOptionActivity.java:29)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.Activity.performCreate(Activity.java:5231)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-21 11:57:14.801: E/AndroidRuntime(1245): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
08-21 11:57:14.801: E/AndroidRuntime(1245): ... 11 more
下面是片段活动代码（调用新意图活动的地方）
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);
Button newPage = (Button)view.findViewById(R.id.btnMatchConfirm);
newPage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(getActivity(), matchOptionActivity.class);
startActivity(intent);
}
});
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("Age", minimumAge);
// query.whereLessThanOrEqualTo("Age", maximumAge);
query.orderByDescending("Name");
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).get("ActivityName").toString());
// names.add(userList.get(i).getParseObject("ProfilePicture").;
}
usersListView = (ListView)getActivity().findViewById(R.id.userlistview1);
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();
}
}
});
}
}
下面是matchOption活动的代码（按钮点击时调用的活动）
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.matchoption);
final ImageView idrinks = (ImageView) this.findViewById(R.id.icasual);
idrinks.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
matchOptionActivity.this.startActivity(new Intent(matchOptionActivity.this, MessagingActivity.class));
}
});
}
}
此外，我正在使用Parse来填充我的用户列表，我想知道如果列表为空，我将如何隐藏确认按钮。
提前致谢。
更新 下面是片段XML文件
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/blue_bac3"
android:orientation="vertical" >
<ListView
android:id="@+id/userlistview1"
android:layout_width="match_parent"
android:layout_height="400dp"
android:textColor="#ffffff"
android:divider="@null"
>
</ListView>
<Button
android:id="@+id/btnMatchConfirm"
android:layout_width="100dp"
android:layout_height="50dp"
android:background="@drawable/gray_bac"
android:layout_below="@+id/userlistview1"
android:layout_centerHorizontal="true"
android:layout_marginTop="13dp"
android:text="Confirm" />
</RelativeLayout>
答案 0 :(得分：1)
我没有声誉添加评论...你还可以提供matchoption xml进行进一步分析或检查onClick（）方法。看起来像那边的一些问题
引起：java.lang.NullPointerException 08-21 11：57：14.801：E / AndroidRuntime（1245）：at com.dooba.beta.matchOptionActivity.onCreate（matchOptionActivity.java:29）
答案 1 :(得分：0)
我猜您需要更改代码
来自
idrinks.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
matchOptionActivity.this.startActivity(new Intent(matchOptionActivity.this, MessagingActivity.class));
}
});
到此
idrinks.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(this,MessagingActivity.class);
i.startActivity(new Intent(matchOptionActivity.this, MessagingActivity.class));
}
});