Android studio java lang nullpointerexception

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Gradle sync failed: java.lang.NullPointerException when syncing in Android Studio #656

Gradle sync failed: java.lang.NullPointerException when syncing in Android Studio #656

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Steps to reproduce:

• add @sentry/react-native to package.json
• npm i
• npx jetify (for AndroidX support)
• generate sentry.properties for android and add credentials
• add next code to settings.gradle
  include ‘:@sentry/react-native’ project(‘:@sentry/react-native’).projectDir = new File(rootProject.projectDir, ‘../node_modules/@sentry/react-native/android’)

Actual result:

Expected result:

If I implement full linking process, result is the same. It breaks after adding those lines and never changes further

The text was updated successfully, but these errors were encountered:

I am not entirely sure this has to do with our SDK, starting a clean react-native init project doesn’t have this error, therefore, it most likely has something to do with your project setup.
Can you provide a minimal repro case for this since I suppose you cannot share you project to debug it?!

@HazAT Thank you for taking the time to troubleshoot this with me.

I was able to reproduce this issue by making the following changes after running react-native init in order to recreate our project’s configuration:

1. In package.json , set the react version to 16.8.3 and react-native to 0.59.9
2. On the command line, run yarn add @sentry/react-native
3. Open the Android project in Android Studio
4. Open settings.gradle and replace the lines below rootProject.name with the following:

include ':@sentry/react-native' project(':@sentry/react-native').projectDir = new File(rootProject.projectDir, '../node_modules/@sentry/react-native/android') 

1. Open File -> Project Structure in Android Studio
2. Set Gradle Plugin Version to 3.3.1 and Gradle Version to 4.10.3
3. Click File -> Sync Project with Gradle Files

@bhollander-root Thanks for the repro.
Why are you replacing these lines in the first place in settings.gradle ?
For a react-native init app the content looks something like this:

rootProject.name = 'RN061' apply from: file("../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesSettingsGradle(settings) include ':app' 

Our docs might be completly out of sync here.

@HazAT Thanks for updating the docs, but I’m not sure I understand the fix. If I do not define the project in settings.gradle and do not include the project in the dependencies in build.gradle , it appears that the Java code cannot reference the Sentry library.

Is it possible for you to upgrade to a new react-native version?
TBH I can’t really tell you where exactly the issue is, your repo case by just downgrading the dependencies in package.json after a clean react-native init doesn’t work because it creates a completely different project structure. Can you create a repo somewhere with the broken project which I can just run and see the same error?

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Null pointer exception in android studio

Whenever one is working with the android studio to develop android applications, errors and exceptions are common things that every developer must be ready to deal with. The biggest challenge when it comes to errors and exceptions is not knowing how to handle them or identifying where they are occurring at.

There are different kinds of errors and exceptions that are prone to happen when developing android applications, some of these errors we have highlighted how to solve them in these previous articles.

In this article, we shall discuss in detail what null pointer exception in android is, how to handle null pointer exception in android, how to avoid null pointer exception in android, and also how to fix null pointer exception in android.

What is a null pointer exception in android?

A null pointer exception is regarded as a type of error that returns null whenever an object or instance is called. When the result is null, the exception occurs and the thread stops executing and what happens next is that the app crashes.

When does null pointer exception occur in android?

From the definition of a null pointer exception, it is clear that is known as null since the instance referenced is null or the result generated is null.

• When calling a method of a null object
• Sending a null value when a real value is required
• Trying to access or modifying a null value

How to avoid null pointer exception in android?

From the above listing of what causes null pointer exception in android, you can easily avoid it easily.

First of all, you will need to have a clear understanding of android data types, methods, and objects to ensure that every time you are handling each instance everything is in the correct format.

Also ensure that you are using the correct data types and you have defined and instantiated each data type as they are supposed to, for example, understand how to use global variables and local variables.

In a case where you try to use a local variable outside the defined method or class, you will get the exception.

Ensure that the value you are sending to a method or object is not null and also check the response of a particular action either using logcat or toast to check whether it’s a null result or not.

How to handle null pointer exception in android?

If a null result occurs at any time due to some reasons which may not be predictable, you can handle it and avoid your app from crashing.

The most common and used way to handle null pointer exception is the use of a try-catch block. This assists in a way that, when the exception occurs in the try block, it will jump that section and move to the catch block where the exception is handled or displayed.

The catch block syntax in java language is used as follows;

try // block of code to execute

>catch (Exception e)// handling exception

>

The usage of a try-catch block is demonstrated in the example below

How to fix null pointer exception in android

To fix null pointer exception starts at the stage of first identifying what is causing the exception.

Next step of fixing the exception is by handling the exception using the try-catch block and displaying a toast or using logcat to view the line where the exception is occurring.

Finally is ensuring that at no stage you are submitting a null value or trying to access a null value.

An example demonstrating how null pointer occurs in android

Am creating a sample android app with a text view and a button, am going to use the button defined to update or change the text of the text view.

The XML code for design is as follows;

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

android:layout_marginTop="150dp"

android:layout_marginLeft="50dp"

tools:context=".MainActivity">

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Hello World!"

android:id="@+id/textView1"

android:textSize="30sp"

android:textColor="#000000"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintLeft_toLeftOf="parent"

app:layout_constraintRight_toRightOf="parent"

app:layout_constraintTop_toTopOf="parent"/>

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="submit"

android:id="@+id/button1"

android:textSize="20sp"

android:layout_marginTop="50dp"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintLeft_toLeftOf="parent"

app:layout_constraintRight_toRightOf="parent"

app:layout_constraintTop_toTopOf="parent"/>

The current text for the defined text view with id textView1 is Hello World, but once we click the button submit, we want to change the text to This is an updated text.

In the java code, we have initialized two text views textview1 and textview2 where textview1 is the one to reference the one to change the text.

The exception will occur since we are trying to update a text in a text view that is not defined and that will result to a null pointer exception as shown in the java code below

package com.example.null_p;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity TextView textview1,textview2;

Button button1;

@Override

protected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

textview1=findViewById(R.id.textView1);

button1=findViewById(R.id.button1);

button1.setOnClickListener(new View.OnClickListener() @Override

public void onClick(View view) try textview2.setText("This is an updated text");

>catch (Exception e) Toast.makeText(MainActivity.this,"An exception occured"+e,Toast.LENGTH_LONG).show();

>

>

>);

>

>

To ensure that the application will not crash and give an error shown below

FATAL EXCEPTION: main

Process: com.example.null_p, PID: 4029

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

We use the try-catch block as shown in the code above such that instead of the app crashing when you click the button, we handle the exception and display it as a toast message.

Conclusion

From the above discussion, we have defined what is a null pointer exception, why and when it occurs in android, how to handle and prevent the null pointer exception, and also how to fix the exception.

Given the example we have shown and the image of the error when the exception has occurred, you can now be able to identify it and easily fix it.

That’s it for this discussion, thank you for following.

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