nullpointerexception

问题 I am trying to implement swipe to delete in RecyclerView. Everything seems to be working fine except drawing a delete icon below the item that's being swiped. This is how I am doing it: ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) { @Override public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) { return false; } @Override public void

问题 I have a configuration class for MongoDB collections as example: @Configuration public class MongoDBConfiguration{ @Bean public MongoCollection<Document> collection() { MongoClient mongoClient = MongoClients.create(mongoURI); MongoDatabase database = mongoClient.getDatabase(mongoDatabase); return database.getCollection(mongoCollection); } } Then I have another class that where I want to use that collection. In this class I get NullPointerException. @Component public class ExampleClass {

问题 I am using Android Studio for my Android projects. I faced an issue when builds crash with strange stacktrace, like this: Error:Execution failed for task ':app:compileDevDebugJavaWithJavac'. java.lang.RuntimeException: failure, see logs for details. cannot generate view binders java.lang.NullPointerException at android.databinding.tool.reflection.ModelMethod.isBoxingConversion(ModelMethod.java:155) at android.databinding.tool.store.SetterStore.isBetterParameter(SetterStore.java:946) at

问题 This question already has answers here : java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' [duplicate] (1 answer) java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference [duplicate] (2 answers) Closed last month . I have a bug in my app and I don't know how to resolve it. When I try to run my app, it just says, unfortunately app has stopped and in the logcat it says this: java

问题 I 'm building a JSP web application using Eclipse IDE. The web application loads without issue on tomcat server ver 7. We got a new requirement to read from xls and xlsx file. So we have used Apache POI library (4.1.2) to implement this as follows: I have taken out other codes as they are not relevant for this post FileInputStream file = new FileInputStream(new File(args[0])); //Create Workbook instance holding reference to .xlsx file XSSFWorkbook workbook = new XSSFWorkbook(file); //<- This

问题 I made a JavaFX Application, and its GUI has these four following things: A TextField , called name (takes in the username) A PasswordField , called password (takes in the password) A ToggleGroup , called gender (there's a method related to this ToggleGroup (male,female,other)) A TextField , called locationField (takes in the location name) There is a sign up button at the bottom that takes all the data and saves it into the MySQL database Here's the method related to the ToggleGroup public

问题 I made a JavaFX Application, and its GUI has these four following things: A TextField , called name (takes in the username) A PasswordField , called password (takes in the password) A ToggleGroup , called gender (there's a method related to this ToggleGroup (male,female,other)) A TextField , called locationField (takes in the location name) There is a sign up button at the bottom that takes all the data and saves it into the MySQL database Here's the method related to the ToggleGroup public

问题 Suppose I have 4 fragments that I put in mainActivity, I want to create different actionbar different in each frgament. When I press fragment 1 then the actionBar appears fragment 1, when I press the two fragment that appears actoinbar belonging to fragment 2 01-02 20:12:33.700 15035-15035/src.go_letskerja E/AndroidRuntime: FATAL EXCEPTION: main Process: src.go_letskerja, PID: 15035 java.lang.NullPointerException at src.go_letskerja.Fragment.OtherFragment.onCreateView(OtherFragment.java:26)

问题 In my program I have a class called Hive which contains Honey, Pollen, royalJelly and an arraylist of several types of bees. Some of the bee types have an eat method which is pretty much identical between them with the difference being in what they eat or the quantity they eat. Each bee has an anotherDay method which calls the eat method on the bee and in thehive's anotherDay method it loops through the arraylist calling each bees anotherDay. My Queen bees eat runs perfectly however, when I

问题 Android Studio 3.6 in app/build.gradle: android { viewBinding.enabled = true Here my xml: <?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent"> <androidx.constraintlayout.widget.ConstraintLayout android:id="@+id/bluetoothBottonMainContainer" android:layout_width="0dp" android