Cómo responder a eventos táctiles
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Hacer que los objetos se muevan de acuerdo con un programa preestablecido como el triángulo que rota es útil para
captar algo de atención, pero ¿y si quieres que los usuarios interactúen con tus gráficos de OpenGL ES?
La clave para que tu aplicación de OpenGL ES sea interactiva táctil es expandir tu implementación de
GLSurfaceView
para anular el
onTouchEvent()
para escuchar eventos táctiles.
En esta lección, se muestra cómo escuchar eventos táctiles para permitir que los usuarios roten un objeto de OpenGL ES.
Cómo configurar un objeto de escucha táctil
Para que tu aplicación OpenGL ES responda a eventos táctiles, debes implementar el
onTouchEvent()
en tu
Clase GLSurfaceView
. En la siguiente implementación de ejemplo, se muestra cómo escuchar
MotionEvent.ACTION_MOVE
y traducirlos al
un ángulo de rotación de una forma.
Kotlin
private const val TOUCH_SCALE_FACTOR: Float = 180.0f / 320f
...
private var previousX: Float = 0f
private var previousY: Float = 0f
override fun onTouchEvent(e: MotionEvent): Boolean {
// MotionEvent reports input details from the touch screen
// and other input controls. In this case, you are only
// interested in events where the touch position changed.
val x: Float = e.x
val y: Float = e.y
when (e.action) {
MotionEvent.ACTION_MOVE -> {
var dx: Float = x - previousX
var dy: Float = y - previousY
// reverse direction of rotation above the mid-line
if (y > height / 2) {
dx *= -1
}
// reverse direction of rotation to left of the mid-line
if (x < width / 2) {
dy *= -1
}
renderer.angle += (dx + dy) * TOUCH_SCALE_FACTOR
requestRender()
}
}
previousX = x
previousY = y
return true
}
Java
private final float TOUCH_SCALE_FACTOR = 180.0f / 320;
private float previousX;
private float previousY;
@Override
public boolean onTouchEvent(MotionEvent e) {
// MotionEvent reports input details from the touch screen
// and other input controls. In this case, you are only
// interested in events where the touch position changed.
float x = e.getX();
float y = e.getY();
switch (e.getAction()) {
case MotionEvent.ACTION_MOVE:
float dx = x - previousX;
float dy = y - previousY;
// reverse direction of rotation above the mid-line
if (y > getHeight() / 2) {
dx = dx * -1 ;
}
// reverse direction of rotation to left of the mid-line
if (x < getWidth() / 2) {
dy = dy * -1 ;
}
renderer.setAngle(
renderer.getAngle() +
((dx + dy) * TOUCH_SCALE_FACTOR));
requestRender();
}
previousX = x;
previousY = y;
return true;
}
Ten en cuenta que, después de calcular el ángulo de rotación, este método llama
requestRender()
para indicarle
representativo de que es el momento
de renderizar el fotograma. Este enfoque es el más eficiente en este ejemplo
porque no es necesario volver a dibujar el marco, a menos que haya un cambio en la rotación. Sin embargo,
no tiene ningún impacto en la eficiencia, a menos que también solicites que el renderizador solo vuelva a dibujar cuando
los datos cambian con setRenderMode()
así que asegúrate de que esta línea no esté comentada en el procesador:
Kotlin
class MyGlSurfaceView(context: Context) : GLSurfaceView(context) {
init {
// Render the view only when there is a change in the drawing data
renderMode = GLSurfaceView.RENDERMODE_WHEN_DIRTY
}
}
Java
public MyGLSurfaceView(Context context) {
...
// Render the view only when there is a change in the drawing data
setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
}
Expón el ángulo de rotación
El código de ejemplo anterior requiere que expongas el ángulo de rotación a través del renderizador. Para ello, haz lo siguiente:
agregando un miembro público. Dado que el código del procesador se ejecuta en un subproceso independiente del usuario principal
de la aplicación, debes declarar esta variable pública como volatile
.
Aquí está el código para declarar la variable y exponer el par captador y establecedor:
Kotlin
class MyGLRenderer4 : GLSurfaceView.Renderer {
@Volatile
var angle: Float = 0f
}
Java
public class MyGLRenderer implements GLSurfaceView.Renderer {
...
public volatile float mAngle;
public float getAngle() {
return mAngle;
}
public void setAngle(float angle) {
mAngle = angle;
}
}
Cómo aplicar rotación
Para aplicar la rotación generada por la entrada táctil, comenta el código que genera un ángulo y
Agrega una variable que contenga el ángulo generado por la entrada táctil:
Kotlin
override fun onDrawFrame(gl: GL10) {
...
val scratch = FloatArray(16)
// Create a rotation for the triangle
// long time = SystemClock.uptimeMillis() % 4000L;
// float angle = 0.090f * ((int) time);
Matrix.setRotateM(rotationMatrix, 0, angle, 0f, 0f, -1.0f)
// Combine the rotation matrix with the projection and camera view
// Note that the mvpMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
Matrix.multiplyMM(scratch, 0, mvpMatrix, 0, rotationMatrix, 0)
// Draw triangle
triangle.draw(scratch)
}
Java
public void onDrawFrame(GL10 gl) {
...
float[] scratch = new float[16];
// Create a rotation for the triangle
// long time = SystemClock.uptimeMillis() % 4000L;
// float angle = 0.090f * ((int) time);
Matrix.setRotateM(rotationMatrix, 0, mAngle, 0, 0, -1.0f);
// Combine the rotation matrix with the projection and camera view
// Note that the vPMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
Matrix.multiplyMM(scratch, 0, vPMatrix, 0, rotationMatrix, 0);
// Draw triangle
mTriangle.draw(scratch);
}
Cuando hayas completado los pasos descritos anteriormente, ejecuta el programa y arrastra el dedo sobre el
pantalla para rotar el triángulo:
Figura 1: Triángulo rotado con entrada táctil (el círculo muestra el tacto
ubicación).
El contenido y las muestras de código que aparecen en esta página están sujetas a las licencias que se describen en la Licencia de Contenido. Java y OpenJDK son marcas registradas de Oracle o sus afiliados.
Última actualización: 2025-07-27 (UTC)
[[["Fácil de comprender","easyToUnderstand","thumb-up"],["Resolvió mi problema","solvedMyProblem","thumb-up"],["Otro","otherUp","thumb-up"]],[["Falta la información que necesito","missingTheInformationINeed","thumb-down"],["Muy complicado o demasiados pasos","tooComplicatedTooManySteps","thumb-down"],["Desactualizado","outOfDate","thumb-down"],["Problema de traducción","translationIssue","thumb-down"],["Problema con las muestras o los códigos","samplesCodeIssue","thumb-down"],["Otro","otherDown","thumb-down"]],["Última actualización: 2025-07-27 (UTC)"],[],[],null,["# Respond to touch events\n\nMaking objects move according to a preset program like the rotating triangle is useful for\ngetting some attention, but what if you want to have users interact with your OpenGL ES graphics?\nThe key to making your OpenGL ES application touch interactive is expanding your implementation of\n[GLSurfaceView](/reference/android/opengl/GLSurfaceView) to override the\n[onTouchEvent()](/reference/android/view/View#onTouchEvent(android.view.MotionEvent)) to listen for touch events.\n\nThis lesson shows you how to listen for touch events to let users rotate an OpenGL ES object.\n\nSetup a touch listener\n----------------------\n\nIn order to make your OpenGL ES application respond to touch events, you must implement the\n[onTouchEvent()](/reference/android/view/View#onTouchEvent(android.view.MotionEvent)) method in your\n[GLSurfaceView](/reference/android/opengl/GLSurfaceView) class. The example implementation below shows how to listen for\n[MotionEvent.ACTION_MOVE](/reference/android/view/MotionEvent#ACTION_MOVE) events and translate them to\nan angle of rotation for a shape. \n\n### Kotlin\n\n```kotlin\nprivate const val TOUCH_SCALE_FACTOR: Float = 180.0f / 320f\n...\nprivate var previousX: Float = 0f\nprivate var previousY: Float = 0f\n\noverride fun onTouchEvent(e: MotionEvent): Boolean {\n // MotionEvent reports input details from the touch screen\n // and other input controls. In this case, you are only\n // interested in events where the touch position changed.\n\n val x: Float = e.x\n val y: Float = e.y\n\n when (e.action) {\n MotionEvent.ACTION_MOVE -\u003e {\n\n var dx: Float = x - previousX\n var dy: Float = y - previousY\n\n // reverse direction of rotation above the mid-line\n if (y \u003e height / 2) {\n dx *= -1\n }\n\n // reverse direction of rotation to left of the mid-line\n if (x \u003c width / 2) {\n dy *= -1\n }\n\n renderer.angle += (dx + dy) * TOUCH_SCALE_FACTOR\n requestRender()\n }\n }\n\n previousX = x\n previousY = y\n return true\n}\n```\n\n### Java\n\n```java\nprivate final float TOUCH_SCALE_FACTOR = 180.0f / 320;\nprivate float previousX;\nprivate float previousY;\n\n@Override\npublic boolean onTouchEvent(MotionEvent e) {\n // MotionEvent reports input details from the touch screen\n // and other input controls. In this case, you are only\n // interested in events where the touch position changed.\n\n float x = e.getX();\n float y = e.getY();\n\n switch (e.getAction()) {\n case MotionEvent.ACTION_MOVE:\n\n float dx = x - previousX;\n float dy = y - previousY;\n\n // reverse direction of rotation above the mid-line\n if (y \u003e getHeight() / 2) {\n dx = dx * -1 ;\n }\n\n // reverse direction of rotation to left of the mid-line\n if (x \u003c getWidth() / 2) {\n dy = dy * -1 ;\n }\n\n renderer.setAngle(\n renderer.getAngle() +\n ((dx + dy) * TOUCH_SCALE_FACTOR));\n requestRender();\n }\n\n previousX = x;\n previousY = y;\n return true;\n}\n```\n\nNotice that after calculating the rotation angle, this method calls\n[requestRender()](/reference/android/opengl/GLSurfaceView#requestRender()) to tell the\nrenderer that it is time to render the frame. This approach is the most efficient in this example\nbecause the frame does not need to be redrawn unless there is a change in the rotation. However, it\ndoes not have any impact on efficiency unless you also request that the renderer only redraw when\nthe data changes using the [setRenderMode()](/reference/android/opengl/GLSurfaceView#setRenderMode(int))\nmethod, so make sure this line is uncommented in the renderer: \n\n### Kotlin\n\n```kotlin\nclass MyGlSurfaceView(context: Context) : GLSurfaceView(context) {\n\n init {\n // Render the view only when there is a change in the drawing data\n renderMode = GLSurfaceView.RENDERMODE_WHEN_DIRTY\n }\n}\n```\n\n### Java\n\n```java\npublic MyGLSurfaceView(Context context) {\n ...\n // Render the view only when there is a change in the drawing data\n setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);\n}\n```\n\nExpose the rotation angle\n-------------------------\n\nThe example code above requires that you expose the rotation angle through your renderer by\nadding a public member. Since the renderer code is running on a separate thread from the main user\ninterface thread of your application, you must declare this public variable as `volatile`.\nHere is the code to declare the variable and expose the getter and setter pair: \n\n### Kotlin\n\n```kotlin\nclass MyGLRenderer4 : GLSurfaceView.Renderer {\n\n @Volatile\n var angle: Float = 0f\n}\n```\n\n### Java\n\n```java\npublic class MyGLRenderer implements GLSurfaceView.Renderer {\n ...\n\n public volatile float mAngle;\n\n public float getAngle() {\n return mAngle;\n }\n\n public void setAngle(float angle) {\n mAngle = angle;\n }\n}\n```\n\nApply rotation\n--------------\n\nTo apply the rotation generated by touch input, comment out the code that generates an angle and\nadd a variable that contains the touch input generated angle: \n\n### Kotlin\n\n```kotlin\noverride fun onDrawFrame(gl: GL10) {\n ...\n val scratch = FloatArray(16)\n\n // Create a rotation for the triangle\n // long time = SystemClock.uptimeMillis() % 4000L;\n // float angle = 0.090f * ((int) time);\n Matrix.setRotateM(rotationMatrix, 0, angle, 0f, 0f, -1.0f)\n\n // Combine the rotation matrix with the projection and camera view\n // Note that the mvpMatrix factor *must be first* in order\n // for the matrix multiplication product to be correct.\n Matrix.multiplyMM(scratch, 0, mvpMatrix, 0, rotationMatrix, 0)\n\n // Draw triangle\n triangle.draw(scratch)\n}\n```\n\n### Java\n\n```java\npublic void onDrawFrame(GL10 gl) {\n ...\n float[] scratch = new float[16];\n\n // Create a rotation for the triangle\n // long time = SystemClock.uptimeMillis() % 4000L;\n // float angle = 0.090f * ((int) time);\n Matrix.setRotateM(rotationMatrix, 0, mAngle, 0, 0, -1.0f);\n\n // Combine the rotation matrix with the projection and camera view\n // Note that the vPMatrix factor *must be first* in order\n // for the matrix multiplication product to be correct.\n Matrix.multiplyMM(scratch, 0, vPMatrix, 0, rotationMatrix, 0);\n\n // Draw triangle\n mTriangle.draw(scratch);\n}\n```\n\nWhen you have completed the steps described above, run the program and drag your finger over the\nscreen to rotate the triangle:\n\n\n**Figure 1.** Triangle being rotated with touch input (circle shows touch\nlocation)."]]