Use GlsurfaceView to perform operation methods and understanding of events

// Activity for rendering 3D object openGL ES 1.0
 public class GL_ExampleActivity extends Activity
 {
 private GLSurfaceView surface;

 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);

 surface = new GL_ExampleSurfaceView(this);
 setContentView(surface);
 }

 @Override
 protected void onPause()
 {
 // TODO Auto-generated method stub
super.onPause();
 surface.onPause();
 }

 @Override
 protected void onResume()
 {
 / / TODO Auto-generated method stub
 super.onResume();
 surface.onResume();
 }
 }

 class GL_ExampleSurfaceView extends GLSurfaceView< br /> {
 private static final String TAG = "Touch";

 Matrix matrix_new = new Matrix();
 Matrix last_matrix = new Matrix();
 
 static final int NONE = 0;
 static final int DRAG = 1;
 static final int ZOOM = 2;
 int mode = NONE;

 PointF start = new PointF();
 PointF mid = new PointF();
 float oldDist = 1f;


 private final float SCALE_FACTOR = 180.0f / 320 ;
 private GLRenderer renderer;
 private float previous_x;
 private float previous_y;

 public GL_ExampleSurf aceView(Context context)
 {
 super(context);

 renderer = new GLRenderer();
 setRenderer(renderer);

 setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
 }

 @Override
 public boolean onTouchEvent(MotionEvent e)
 {
 // handler for drag and zoom events
 switch (e.getAction() & MotionEvent.ACTION_MASK)
 {
 case MotionEvent.ACTION_DOWN:
 last_matrix.set(matrix_new);
 start.set( e.getX(), e.getY());
 Log.d(TAG, "mode=DRAG");
 mode = DRAG;
 //requestRender();
 break;
 case MotionEvent.ACTION_POINTER_DOWN:
 oldDist = finger_distance(e);
 Log.d(TAG, "oldDist=" + oldDist);
 if (oldDist> 10f)
 {
 last_matrix.set(matrix_new);
 finger_distance_midpoint(mid, e);
 mode = ZOOM;
 Log.d(TAG , "mode=ZOOM");
 }
 //requestRender();
 break;
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_POINTER_UP:
 mode = NONE;
 Log.d(TAG, "mode=NONE");
 //requestRender();
 break;
 case MotionEvent.ACTION_MOVE:
 if (mode == DRAG)
 {
 matrix_new.set(last_matrix);
 matrix_new.postTranslate(e.getX()-start.x, e.getY()-start. y);
 }
 else if (m ode == ZOOM)
 {
 float newDist = finger_distance(e);
 Log.d(TAG, "newDist=" + newDist);
 if (newDist> 10f) 
 {
 matrix_new.set(last_matrix);
 float scale = newDist / oldDist;
 matrix_new.postScale(scale, scale, mid.x, mid.y);
 }
 }
 //requestRender();
 break;
 }
 //view.setImageMatrix(matrix_new);

 

 // handler for rotation event, y and x axis
 float x = e.getX();
 float y = e.getY();
< br /> switch (e.getAction())
 {
 case MotionEvent.ACTION_MOVE:

 float dx = x-previous_x; 
 float dy = y-previous_y;

 if (y> getHeight() / 2)
 {
 dx = dx * -1 ;
} 

 if (x  {
 dy = dy * -1 ;
 }
 renderer.angle_x += dx * SCALE_FACTOR;
 renderer.angle_y += dy * SCALE_FACTOR;
 requestRender();
 }
 previous_x = x;
 previous_y = y;
 return true ;
 }


 private float finger_distance(MotionEvent e)
 {
 float x = e.getX(0)-e.getX(1) ;
 float y = e.getY(0)-e.getY(1);
 return FloatMath.sqrt(x * x + y * y);
 }
< br /> private void finger_distance_midpoint(PointF point, MotionEvent e)
 {
 float x = e.getX(0) + e.getX(1);< br /> float y = e.getY(0) + e.getY(1);
 point.set(x / 2, y / 2);
 }

 }

I use standard vertices, colors And the point buffer shows a 3D object.

I can..

>Use touch events to rotate the object
>Use GL10 to render the object using openGL ES 1.0< br>>Everything is great

Now I want to be able to zoom in and out with two fingers for a “pinch in” action. I found some good tutorials and sample codes, but it is mainly used for ImageViews . I am still a semi-newbie to Android, and I don’t fully understand how to make this zoom function applicable to GLSurfaceView.

Below is the code I currently write for the Activity class. The first touch handler I passed as The zoom event found in the tutorial designed by ImageView (I use it because I think it will be a simple conversion). The second handler is for the rotation event and it works fine.

Thank you in advance , I hope this article can help others solve the same problem.
If any edits or additions are needed, I will be on standby at any time.

// Activity for rendering 3D object openGL ES 1.0
 public class GL_Exampl eActivity extends Activity
 {
 private GLSurfaceView surface;

 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate( savedInstanceState);

 surface = new GL_ExampleSurfaceView(this);
 setContentView(surface);
 }

 @Override
 protected void onPause ()
 {
 // TODO Auto-generated method stub
 super.onPause();
 surface.onPause();
 }

 @Override
 protected void onResume()
 {
 // TODO Auto-generated method stub
 super.onResume();
 surface.onResume(); 
 }
 }

 class GL_ExampleSurfaceView extends GLSurfaceView
 {
 private static final String TAG = "Touch";

 Matrix matrix_new = new Matrix();
 Matrix last_matrix = new Matrix();
 
 static final int NONE = 0;
 static final int DRAG = 1;
 static final int ZOOM = 2;
 int mode = NONE;

 PointF start = new PointF();
 PointF mid = new PointF();
 float oldDist = 1f;


 private final float SCALE_FACTOR = 180.0f / 320 ;
 private GLRenderer renderer;
 private float previous_x;
 private float previous_y;

 public GL_ExampleSurfaceView(Context context)
 {
 super( context);

 renderer = new GLRenderer();
 setRenderer(renderer);

 setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
 }

 @Override
 public boolean onTouchEvent(MotionEvent e)
 {
 // handler for drag and zoom events
 switch (e.getAction() & MotionEvent.ACTION_MASK )
 {
 case MotionEvent.ACTI ON_DOWN:
 last_matrix.set(matrix_new);
 start.set(e.getX(), e.getY());
 Log.d(TAG, "mode=DRAG") ;
 mode = DRAG;
 //requestRender();
 break;
 case MotionEvent.ACTION_POINTER_DOWN:
 oldDist = finger_distance(e);
 Log .d(TAG, "oldDist=" + oldDist);
 if (oldDist> 10f)
 {
 last_matrix.set(matrix_new);
 finger_distance_midpoint(mid, e); 
 mode = ZOOM;
 Log.d(TAG, "mode=ZOOM");
 }
 //requestRender();
 break;
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_POINTER_UP:
 mode = NONE;
 Log.d(TAG, "mode=NONE");
 //requestRender();
 break;
 case MotionEvent.ACTION_MOVE:
 if (mode == DRAG)
 {
 matrix_new.set(last_matrix);
 matrix_new.postTranslate(e.getX()-start.x, e.getY()-start.y) ;
 }
 else if (mode == ZOOM)
 {
 float newDist = finger_distance(e);
 Log.d(TAG, "newDist=" + newDist);
 if (newDist> 10f)
 {
 matrix_new.set(last_matrix);
 float scale = newDist / oldDist;
 matrix_new.postScale(scale, scale, mid.x, mid.y);
 }
 }
 //requestRender();
 break;
 }
 //view.setImageMatrix(matrix_new);



 // handler for rotation event, y and x axis
 float x = e.getX();
 float y = e.getY();

 switch (e. getAction())
 {
 case MotionEvent.ACTION_MOVE:

 float dx = x-previous_x;
 float dy = y-previous_y;

 if (y> getHeight() / 2)
 {
 dx = dx * -1 ;
 }

 if (x  {
 dy = dy * -1 ;
 }
 renderer.angle_x += dx * SCALE_FACTOR;
 renderer.angle_y += dy * SCALE_FACTOR;
 requestRender();
 }
 previous_x = x;
 previous_y = y;
 return true;
 }


 private float finger_distance(MotionEvent e)
 {
 float x = e.getX(0)-e.getX(1);
 float y = e.getY(0)-e.getY(1);
 return FloatMath.sqrt(x * x + y * y);
 }

 private void finger_distance_midpoint(PointF point, MotionEvent e)
 {
 float x = e.getX(0) + e.getX(1);
 float y = e.getY(0) + e.getY(1);
 point.set(x / 2, y / 2);
} 

 }

Thanks again…

There are two obvious ways to solve this problem. If you Just want to increase the size of a single object, you can use glScalef when drawing objects. Using scalef is easy and relatively simple, but it does not fully meet your requirements.

Another solution is Apply a scaling factor to the projection matrix to produce the desired effect. To achieve this, just multiply the left, right, top, and bottom distances of the projection matrix by such a ratio before drawing.

gl.glFrustumf(width/2*zoom, width/2*zoom, height/2*zoom, height/2*zoom, 1, -1);
(Note that if you use an orthogonal matrix, you will use glOrthof instead)

If you are interested, you can find more information about the projection matrix here