java - 空指针异常 - 从 fragment 加载新 Activity

Question

当我尝试从 fragment 加载新 Activity 时遇到了空指针异常 - 它本质上告诉我发生了意外错误。以下是日志猫消息:

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fragment Activity代码(调用新intent Activity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 Activity 的代码(单击按钮时调用的 Activity )

   @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 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 fragment 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>

Answer 1

我没有权限添加评论...您能否提供 matchoption xml 以供进一步分析或检查 onClick() 方法。看起来那里有些问题

引起:java.lang.NullPointerException08-21 11:57:14.801: E/AndroidRuntime(1245): 在 com.dooba.beta.matchOptionActivity.onCreate(matchOptionActivity.java:29)