小贝子编程

对null对象执行FrameLayout.getId()



我有方法loadFragment((；我在其中加载DashboardFragment，它有一个框架布局小部件。但在loadFragment((中，我得到了一个空指针异常，我不知道为什么。我已经附加了loadFragment((。请帮帮我。谢谢！

错误为：

java.lang.NullPointerException：尝试在null对象引用上调用虚拟方法"int android.widget.FrameLayout.getId(("。网址：com.qdocs.smartschool.frages.StudentDashboardFragment.loadFragment(StudentDashboard Fragment.java:241(

loadFragment(new DashboardCalender());
private void loadFragment(Fragment fragment) {
// load fragment
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.replace(calenderFrame.getId(), fragment);
transaction.addToBackStack(null);
transaction.commit();
}

studentDashboardFragment类

package com.qdocs.smartschool.fragments;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.widget.CardView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.qdocs.smartschool.R;
import com.qdocs.smartschool.students.StudentAttendance;
import com.qdocs.smartschool.students.StudentHomework;
import com.qdocs.smartschool.students.StudentTasks;
import com.qdocs.smartschool.utils.Constants;
import com.qdocs.smartschool.utils.Utility;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
public class StudentDashboardFragment extends Fragment {
RelativeLayout attendanceLayout, homeworkLayout, pendingTaskLayout;
TextView attendanceValue, homeworkValue, pendingTaskValue;
CardView attendanceCard, homeworkCard, pendingTaskCard;
FrameLayout calenderFrame;
public Map<String, String> headers = new HashMap<String, String>();
public Map<String, String> params = new Hashtable<String, String>();
public StudentDashboardFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
loadData();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View mainView = inflater.inflate(R.layout.student_dashboard_fragment, container, false);
attendanceLayout = mainView.findViewById(R.id.student_dashboard_fragment_attendanceView);
homeworkLayout = mainView.findViewById(R.id.student_dashboard_fragment_homeworkView);
pendingTaskLayout = mainView.findViewById(R.id.student_dashboard_fragment_pendingTaskView);
attendanceCard = mainView.findViewById(R.id.student_dashboard_fragment_attendanceCard);
homeworkCard = mainView.findViewById(R.id.student_dashboard_fragment_homeworkCard);
pendingTaskCard = mainView.findViewById(R.id.student_dashboard_fragment_pendingTaskCard);
attendanceValue = mainView.findViewById(R.id.student_dashboard_fragment_attendance_value);
homeworkValue = mainView.findViewById(R.id.student_dashboard_fragment_homework_value);
pendingTaskValue = mainView.findViewById(R.id.student_dashboard_fragment_pendingTask_value);
calenderFrame = mainView.findViewById(R.id.dashboardViewPager);
loadData();
attendanceLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent asd = new Intent(getActivity().getApplicationContext(), StudentAttendance.class);
getActivity().startActivity(asd);
}
});
homeworkLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent asd = new Intent(getActivity().getApplicationContext(), StudentHomework.class);
getActivity().startActivity(asd);
}
});
pendingTaskLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent asd = new Intent(getActivity().getApplicationContext(), StudentTasks.class);
getActivity().startActivity(asd);
}
});
Log.e("STATUS", "onCreateView");
return mainView;
}
private void loadData() {
//decorate();
loadFragment(new DashboardCalender());
params.put("student_id", Utility.getSharedPreferences(getActivity().getApplicationContext(), Constants.studentId));
params.put("date_from", getDateOfMonth(new Date(), "first"));
params.put("date_to", getDateOfMonth(new Date(), "last"));
JSONObject obj=new JSONObject(params);
Log.e("params ", obj.toString());
getDataFromApi(obj.toString());
try {
JSONArray modulesArray = new JSONArray(Utility.getSharedPreferences(getActivity().getApplicationContext(), Constants.modulesArray));
if(modulesArray.length() != 0) {
ArrayList<String> moduleCodeList = new ArrayList<String>();
ArrayList<String> moduleStatusList = new ArrayList<String>();
for (int i = 0; i<modulesArray.length(); i++) {
if(modulesArray.getJSONObject(i).getString("short_code").equals("student_attendance")
&& modulesArray.getJSONObject(i).getString("is_active").equals("0") ) {
attendanceCard.setVisibility(View.GONE);
} if(modulesArray.getJSONObject(i).getString("short_code").equals("homework")
&& modulesArray.getJSONObject(i).getString("is_active").equals("0") ) {
homeworkCard.setVisibility(View.GONE);
} if(modulesArray.getJSONObject(i).getString("short_code").equals("calendar_to_do_list")
&& modulesArray.getJSONObject(i).getString("is_active").equals("0") ) {
pendingTaskCard.setVisibility(View.GONE);
calenderFrame.setVisibility(View.GONE);
}
}
}
} catch (JSONException e) {
Log.d("Error", e.toString());
}
}
private void getDataFromApi (String bodyParams) {
Log.e("RESULT PARAMS", bodyParams);
final ProgressDialog pd = new ProgressDialog(getActivity());
pd.setMessage("Loading");
pd.setCancelable(false);
pd.show();
final String requestBody = bodyParams;
String url = Utility.getSharedPreferences(getActivity().getApplicationContext(), "apiUrl") + Constants.getDashboardUrl;
StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
@Override
public void onResponse(String result) {
if (result != null) {
pd.dismiss();
try {
Log.e("Result", result);
JSONObject object = new JSONObject(result);
//TODO success
String success = "1"; //object.getString("success");
if (success.equals("1")) {
if(object.getString("attendence_type").equals("0")){
attendanceValue.setText(object.getString("student_attendence_percentage") + "%");
}else{
attendanceCard.setVisibility(View.GONE);
}
homeworkValue.setText(object.getString("student_homework_incomplete"));
pendingTaskValue.setText(object.getString("student_incomplete_task"));
String classid = object.getString("class_id");
Utility.setSharedPreference(getActivity().getApplicationContext(), Constants.classId, classid);
Utility.setSharedPreference(getActivity().getApplicationContext(), Constants.sectionId, object.getString("section_id"));

} else {
Toast.makeText(getActivity().getApplicationContext(), object.getString("errorMsg"), Toast.LENGTH_SHORT).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
pd.dismiss();
Toast.makeText(getActivity().getApplicationContext(), R.string.noInternetMsg, Toast.LENGTH_SHORT).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError volleyError) {
pd.dismiss();
Log.e("Volley Error", volleyError.toString());
Toast.makeText(getActivity(), R.string.slowInternetMsg, Toast.LENGTH_LONG).show();
}
}) {
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
headers.put("Client-Service", Constants.clientService);
headers.put("Auth-Key", Constants.authKey);
headers.put("Content-Type", Constants.contentType);
headers.put("User-ID", Utility.getSharedPreferences(getActivity().getApplicationContext(), "userId"));
headers.put("Authorization", Utility.getSharedPreferences(getActivity().getApplicationContext(), "accessToken"));
return headers;
}
@Override
public String getBodyContentType() {
return "application/json; charset=utf-8";
}
@Override
public byte[] getBody() throws AuthFailureError {
try {
return requestBody == null ? null : requestBody.getBytes("utf-8");
} catch (UnsupportedEncodingException uee) {
VolleyLog.wtf("Unsupported Encoding while trying to get the bytes of %s using %s", requestBody, "utf-8");
return null;
}
}
};
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());//Creating a Request Queue
requestQueue.add(stringRequest);//Adding request to the queue
}
private void decorate() {
attendanceLayout.setBackgroundColor(Color.parseColor(Constants.defaultSecondaryColour));
homeworkLayout.setBackgroundColor(Color.parseColor(Constants.defaultSecondaryColour));
pendingTaskLayout.setBackgroundColor(Color.parseColor(Constants.defaultSecondaryColour));
}
private void loadFragment(Fragment fragment) {
// load fragment
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
//        transaction.replace(calenderFrame.getId(), fragment);
transaction.addToBackStack(null);
transaction.commit();
}
public static String getDateOfMonth(Date date, String index){
Calendar cal = Calendar.getInstance();
cal.setTime(date);
if(index.equals("first")) {
cal.set(Calendar.DAY_OF_MONTH, cal.getActualMinimum(Calendar.DAY_OF_MONTH));
} else {
cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
}
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd");
return dateFormatter.format(cal.getTime());
}
}

包含xml的viewpager

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.v7.widget.CardView
android:id="@+id/student_dashboard_fragment_attendanceCard"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="@style/CustomCardView"
>
<RelativeLayout
android:id="@+id/student_dashboard_fragment_attendanceView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:paddingStart="10dp"
>
<ImageView
android:id="@+id/student_dashboard_fragment_attendanceView_icon"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_alignParentStart="true"
android:src="@drawable/ic_dashboard_attendance"
android:layout_centerVertical="true"
android:layout_marginStart="10dp"
/>
<RelativeLayout
android:id="@+id/student_dashboard_fragment_attendance"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="35dp"
android:layout_marginEnd="60dp"
android:layout_marginTop="10dp"
>
<TextView
android:id="@+id/student_dashboard_fragment_attendance_head"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="17sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:textColor="@color/textHeading"
android:text="@string/attendance"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="12sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:text="@string/thisMonth"
android:textColor="@color/textHeading"
android:layout_below="@+id/student_dashboard_fragment_attendance_head"
/>
</RelativeLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_centerVertical="true"
android:layout_marginEnd="5dp"
>
<TextView
android:id="@+id/student_dashboard_fragment_attendance_value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="22sp"
android:gravity="center"
android:textColor="@color/textHeading"
/>
</RelativeLayout>
</RelativeLayout>
</android.support.v7.widget.CardView>
<android.support.v7.widget.CardView
android:id="@+id/student_dashboard_fragment_homeworkCard"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="@style/CustomCardView"
>
<RelativeLayout
android:id="@+id/student_dashboard_fragment_homeworkView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:paddingStart="10dp"
>
<ImageView
android:id="@+id/student_dashboard_fragment_homeworkView_icon"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_alignParentStart="true"
android:src="@drawable/ic_dashboard_homework"
android:layout_centerVertical="true"
android:layout_marginStart="10dp"
/>
<RelativeLayout
android:id="@+id/student_dashboard_fragment_homework"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="35dp"
android:layout_marginEnd="60dp"
android:layout_marginTop="10dp"
>
<TextView
android:id="@+id/student_dashboard_fragment_homework_head"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="17sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:textColor="@color/textHeading"
android:text="@string/homework"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="12sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:text="@string/incomplete"
android:textColor="@color/textHeading"
android:layout_below="@+id/student_dashboard_fragment_homework_head"
/>
</RelativeLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_centerVertical="true"
android:layout_marginEnd="5dp"
>
<TextView
android:id="@+id/student_dashboard_fragment_homework_value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="22sp"
android:gravity="center"
android:textColor="@color/textHeading"
/>
</RelativeLayout>
</RelativeLayout>
</android.support.v7.widget.CardView>
<android.support.v7.widget.CardView
android:id="@+id/student_dashboard_fragment_pendingTaskCard"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="@style/CustomCardView"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<RelativeLayout
android:id="@+id/student_dashboard_fragment_pendingTaskView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:paddingStart="10dp"
>
<ImageView
android:id="@+id/student_dashboard_fragment_pendingTaskView_icon"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_alignParentStart="true"
android:src="@drawable/ic_dashboard_pandingtask"
android:layout_centerVertical="true"
android:layout_marginStart="10dp"
/>
<RelativeLayout
android:id="@+id/student_dashboard_fragment_pendingTask"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="35dp"
android:layout_marginEnd="60dp"
android:layout_marginTop="10dp">
<TextView
android:id="@+id/student_dashboard_fragment_pendingTask_head"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="17sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:textColor="@color/textHeading"
android:text="@string/pendingTask" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="12sp"
android:gravity="start|center"
android:paddingStart="5dp"
android:paddingEnd="5dp"
android:text="@string/today"
android:textColor="@color/textHeading"
android:layout_below="@+id/student_dashboard_fragment_pendingTask_head" />
</RelativeLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_centerVertical="true"
android:layout_marginEnd="5dp">
<TextView
android:id="@+id/student_dashboard_fragment_pendingTask_value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="22sp"
android:gravity="center"
android:textColor="@color/textHeading"
/>
</RelativeLayout>
</RelativeLayout>
<FrameLayout
android:id="@+id/dashboardViewPager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/textHeading"
/>
</LinearLayout>

</android.support.v7.widget.CardView>
</LinearLayout>
</android.support.v4.widget.NestedScrollView>


</LinearLayout>

这个错误很容易解释。calenderFrame为空，意味着您从未初始化过它。

我找到了答案。在片段的onCreate((中，我的代码在初始化calendarFrame之前调用了loadFragment((方法。

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