Posted by Sushant on July 6, 2012, filed in: Android Beginner Tutorials, Android Development
This example shows how you can create touch and rotate effect on an object.
Algorithm:
1.) Create a new project by File-> New -> Android Project name it TouchRotateExample.
2.) Create and write following into src/cube.java file:
package com.example.TouchRotateExample;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import javax.microedition.khronos.opengles.GL10;
class Cube
{
public Cube()
{
int one = 0×10000;
int vertices[] = {
-one, -one, -one,
one, -one, -one,
one, one, -one,
-one, one, -one,
-one, -one, one,
one, -one, one,
one, one, one,
-one, one, one,
};
int colors[] = {
0, 0, 0, one,
one, 0, 0, one,
one, one, 0, one,
0, one, 0, one,
0, 0, one, one,
one, 0, one, one,
one, one, one, one,
0, one, one, one,
};
byte indices[] = {
0, 4, 5, 0, 5, 1,
1, 5, 6, 1, 6, 2,
2, 6, 7, 2, 7, 3,
3, 7, 4, 3, 4, 0,
4, 7, 6, 4, 6, 5,
3, 0, 1, 3, 1, 2
};
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length*4);
vbb.order(ByteOrder.nativeOrder());
mVertexBuffer = vbb.asIntBuffer();
mVertexBuffer.put(vertices);
mVertexBuffer.position(0);
ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length*4);
cbb.order(ByteOrder.nativeOrder());
mColorBuffer = cbb.asIntBuffer();
mColorBuffer.put(colors);
mColorBuffer.position(0);
mIndexBuffer = ByteBuffer.allocateDirect(indices.length);
mIndexBuffer.put(indices);
mIndexBuffer.position(0);
}
public void draw(GL10 gl)
{
gl.glFrontFace(GL10.GL_CW);
gl.glVertexPointer(3, GL10.GL_FIXED, 0, mVertexBuffer);
gl.glColorPointer(4, GL10.GL_FIXED, 0, mColorBuffer);
gl.glDrawElements(GL10.GL_TRIANGLES, 36, GL10.GL_UNSIGNED_BYTE, mIndexBuffer);
}
private IntBuffer mVertexBuffer;
private IntBuffer mColorBuffer;
private ByteBuffer mIndexBuffer;
}
3.) Run for output.
Steps:
1.) Create a project named TouchRotateExample and set the information as stated in the image.
Build Target: Android 4.0
Application Name: TouchRotateExample
Package Name: com. example. TouchRotateExample
Activity Name: TouchRotateExample
Min SDK Version: 14
2.) Open TouchRotateExample.java file and write following code there:
package com.example.TouchRotateExample;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
import android.app.Activity;
import android.content.Context;
import android.opengl.GLSurfaceView;
import android.os.Bundle;
import android.view.MotionEvent;
public class TouchRotateExample extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mGLSurfaceView = new TouchSurfaceView(this);
setContentView(mGLSurfaceView);
mGLSurfaceView.requestFocus();
mGLSurfaceView.setFocusableInTouchMode(true);
}
@Override
protected void onResume() {
super.onResume();
mGLSurfaceView.onResume();
}
@Override
protected void onPause() {
super.onPause();
mGLSurfaceView.onPause();
}
private GLSurfaceView mGLSurfaceView;
}
class TouchSurfaceView extends GLSurfaceView {
public TouchSurfaceView(Context context) {
super(context);
mRenderer = new CubeRenderer();
setRenderer(mRenderer);
setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
}
@Override public boolean onTrackballEvent(MotionEvent e) {
mRenderer.mAngleX += e.getX() * TRACKBALL_SCALE_FACTOR;
mRenderer.mAngleY += e.getY() * TRACKBALL_SCALE_FACTOR;
requestRender();
return true;
}
@Override public boolean onTouchEvent(MotionEvent e) {
float x = e.getX();
float y = e.getY();
switch (e.getAction()) {
case MotionEvent.ACTION_MOVE:
float dx = x - mPreviousX;
float dy = y - mPreviousY;
mRenderer.mAngleX += dx * TOUCH_SCALE_FACTOR;
mRenderer.mAngleY += dy * TOUCH_SCALE_FACTOR;
requestRender();
}
mPreviousX = x;
mPreviousY = y;
return true;
}
private class CubeRenderer implements GLSurfaceView.Renderer {
public CubeRenderer() {
mCube = new Cube();
}
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
gl.glTranslatef(0, 0, -3.0f);
gl.glRotatef(mAngleX, 0, 1, 0);
gl.glRotatef(mAngleY, 1, 0, 0);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
mCube.draw(gl);
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
float ratio = (float) width / height;
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10);
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glDisable(GL10.GL_DITHER);
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT,
GL10.GL_FASTEST);
gl.glClearColor(0,0,0,0);
gl.glEnable(GL10.GL_CULL_FACE);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glEnable(GL10.GL_DEPTH_TEST);
}
private Cube mCube;
public float mAngleX;
public float mAngleY;
}
private final float TOUCH_SCALE_FACTOR = 180.0f / 320;
private final float TRACKBALL_SCALE_FACTOR = 36.0f;
private CubeRenderer mRenderer;
private float mPreviousX;
private float mPreviousY;
}
3.) Compile and build the project.
Output
jebaranjan 
Perfect! Very useful lesson. Thanks.