Android 9 Development Cookbook - Third Edition

How to do it...

As stated previously, we will continue, not from the previous recipe, but from the Applying the projection and camera view while drawing recipe. Open MainActivity.java and follow these steps:

1. Add the following global variables to the MainActivity class:

private float mCenterX=0; 
private float mCenterY=0; 

2. Add the following code to the GLRendered class:

private float[] mRotationMatrix = new float[16];public volatile float mAngle;public void setAngle(float angle) {    mAngle = angle;}

3. In the same class, modify the onDrawFrame() method by replacing the existing mTriangle.draw(mMVPMatrix); statement with the following code:

float[] tempMatrix = new float[16];Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0, -1.0f);Matrix. ...