android.opengl.GLSurfaceView$GLThread.surfaceCreated()' on a null object reference

Question

Im trying to use GLSurface to display a custom view.

My xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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"
    tools:context="net.letsense.matrixtest.MainActivity">


    <android.opengl.GLSurfaceView
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:id="@+id/my_surface_view"
        />

</android.support.constraint.ConstraintLayout>

My Main

package net.letsense.matrixtest;

import android.app.Activity;
import android.opengl.GLSurfaceView;
import android.os.Bundle;

/**
 * Created by borislegovic on 03/11/2017.
 */

public class Main extends Activity {
    private int mPositionHandle;
    private int mColorHandle;


    private GLSurfaceView mGLView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Create a GLSurfaceView instance and set it
        // as the ContentView for this Activity.
      //  mGLView = new MyGLSurfaceView(this);
        // mGLView = findViewById(R.id.my_surface_view);
       //mGLView.setEGLContextClientVersion(2);
       // mGLView = new MyGLSurfaceView(this);
     //   setContentView(mGLView);
    }

    @Override
    protected void onPause() {
        // The following call pauses the rendering thread.
        // If your OpenGL application is memory intensive,
        // you should consider de-allocating objects that
        // consume significant memory here.
        super.onPause();
      //  mGLView.onPause();
    }

    @Override
    protected void onResume() {
        // The following call resumes a paused rendering thread.
        // If you de-allocated graphic objects for onPause()
        // this is a good place to re-allocate them.
        super.onResume();
       // mGLView.onResume();
    }

}

The strange thing is i dont do anything with surfaceView object and it still gives me this crash :

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.opengl.GLSurfaceView$GLThread.surfaceCreated()' on a null object reference at android.opengl.GLSurfaceView.surfaceCreated(GLSurfaceView.java:524)

Answer 1

Your GLSurfaceView is not initialized, you need to initialize it.

First create class MyGLRenderer:

class MyGLRenderer implements GLSurfaceView.Renderer {
    public void onSurfaceCreated(GL10 gl, EGLConfig config)
    {
       gl.glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
    }

    public void onSurfaceChanged(GL10 gl, int w, int h) {
        gl.glViewport(0, 0, w, h);
    }

    public void onDrawFrame(GL10 gl) {
        gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
    }
} 

And then add this to your OnCreate method:

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

           mGLView = (GLSurfaceView) this.findViewById(R.id.my_surface_view);
           mGLView.setRenderer(new MyGLRenderer());

    }

You can read more about OpenGL ES here.