【Android OpenGL ES】阅读hello-gl2代码（二）Java代码

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.android.gl2jni">
    <application
            android:label="@string/gl2jni_activity">
        <activity android:name="GL2JNIActivity"
                android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
                android:launchMode="singleTask"
                android:configChanges="orientation|keyboardHidden">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
    <uses-feature android:glEsVersion="0x00020000"/>
    <uses-sdk android:minSdkVersion="5"/>
</manifest>

首先，我们看<activity />标签，定义了GL2JNIActivity

android:theme="@android:style/Theme.NoTitleBar.Fullscreen" 定义该Activity的主题，全屏无标题栏。

android:launchMode="singleTask"  定义该Activity运行模式为“singleTask”。

android:configChanges="orientation|keyboardHidden"

默认情况下，Android每次屏幕旋转都会重新创建Activity，该属性将不会重新创建Activity，而只是调用onConfigurationChange(Configuration config)。

然后，我们看<users-feature android:glEsVersion="0x00020000">，定义使用的OpenGL ES版本为2.0。

 

GL2JNIActivity.java

package com.android.gl2jni;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.WindowManager;

import java.io.File;


public class GL2JNIActivity extends Activity {

    GL2JNIView mView;

    @Override protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mView = new GL2JNIView(getApplication());
    setContentView(mView);
    }

    @Override protected void onPause() {
        super.onPause();
        mView.onPause();
    }

    @Override protected void onResume() {
        super.onResume();
        mView.onResume();
    }
}

mView = new GL2JNIView(getApplication());

setContentView(mView);

新建一个GL2JNIView对象，并设置该GL2JNIView为Activity的Content View显示。

@Override protected void onPause() {
    super.onPause();
    mView.onPause();
}

@Override protected void onResume() {
    super.onResume();
    mView.onResume();
}

GL2JNIView为GLSurfaceView子类：

A GLSurfaceView must be notified when the activity is paused and resumed. GLSurfaceView clients are required to call onPause() when the activity pauses and onResume() when the activity resumes. These calls allow GLSurfaceView to pause and resume the rendering thread, and also allow GLSurfaceView to release and recreate the OpenGL display.

 

GL2JNIView.java

package com.android.gl2jni;

import android.content.Context;
import android.graphics.PixelFormat;
import android.opengl.GLSurfaceView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;

import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLContext;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.opengles.GL10;

/**
 * A simple GLSurfaceView sub-class that demonstrate how to perform
 * OpenGL ES 2.0 rendering into a GL Surface. Note the following important
 * details:
 *
 * - The class must use a custom context factory to enable 2.0 rendering.
 *   See ContextFactory class definition below.
 *
 * - The class must use a custom EGLConfigChooser to be able to select
 *   an EGLConfig that supports 2.0. This is done by providing a config
 *   specification to eglChooseConfig() that has the attribute
 *   EGL10.ELG_RENDERABLE_TYPE containing the EGL_OPENGL_ES2_BIT flag
 *   set. See ConfigChooser class definition below.
 *
 * - The class must select the surface's format, then choose an EGLConfig
 *   that matches it exactly (with regards to red/green/blue/alpha channels
 *   bit depths). Failure to do so would result in an EGL_BAD_MATCH error.
 */
class GL2JNIView extends GLSurfaceView {
    private static String TAG = "GL2JNIView";
    private static final boolean DEBUG = false;

    public GL2JNIView(Context context) {
        super(context);
        init(false, 0, 0);
    }

    public GL2JNIView(Context context, boolean translucent, int depth, int stencil) {
        super(context);
        init(translucent, depth, stencil);
    }

    private void init(boolean translucent, int depth, int stencil) {

        /* By default, GLSurfaceView() creates a RGB_565 opaque surface.
         * If we want a translucent one, we should change the surface's
         * format here, using PixelFormat.TRANSLUCENT for GL Surfaces
         * is interpreted as any 32-bit surface with alpha by SurfaceFlinger.
         */
        if (translucent) {
            this.getHolder().setFormat(PixelFormat.TRANSLUCENT);
        }

        /* Setup the context factory for 2.0 rendering.
         * See ContextFactory class definition below
         */
        setEGLContextFactory(new ContextFactory());

        /* We need to choose an EGLConfig that matches the format of
         * our surface exactly. This is going to be done in our
         * custom config chooser. See ConfigChooser class definition
         * below.
         */
        setEGLConfigChooser( translucent ?
                             new ConfigChooser(8, 8, 8, 8, depth, stencil) :
                             new ConfigChooser(5, 6, 5, 0, depth, stencil) );

        /* Set the renderer responsible for frame rendering */
        setRenderer(new Renderer());
    }

    private static class ContextFactory implements GLSurfaceView.EGLContextFactory {
        private static int EGL_CONTEXT_CLIENT_VERSION = 0x3098;
        public EGLContext createContext(EGL10 egl, EGLDisplay display, EGLConfig eglConfig) {
            Log.w(TAG, "creating OpenGL ES 2.0 context");
            checkEglError("Before eglCreateContext", egl);
            int[] attrib_list = {EGL_CONTEXT_CLIENT_VERSION, 2, EGL10.EGL_NONE };
            EGLContext context = egl.eglCreateContext(display, eglConfig, EGL10.EGL_NO_CONTEXT, attrib_list);
            checkEglError("After eglCreateContext", egl);
            return context;
        }

        public void destroyContext(EGL10 egl, EGLDisplay display, EGLContext context) {
            egl.eglDestroyContext(display, context);
        }
    }

    private static void checkEglError(String prompt, EGL10 egl) {
        int error;
        while ((error = egl.eglGetError()) != EGL10.EGL_SUCCESS) {
            Log.e(TAG, String.format("%s: EGL error: 0x%x", prompt, error));
        }
    }

    private static class ConfigChooser implements GLSurfaceView.EGLConfigChooser {

        public ConfigChooser(int r, int g, int b, int a, int depth, int stencil) {
            mRedSize = r;
            mGreenSize = g;
            mBlueSize = b;
            mAlphaSize = a;
            mDepthSize = depth;
            mStencilSize = stencil;
        }

        /* This EGL config specification is used to specify 2.0 rendering.
         * We use a minimum size of 4 bits for red/green/blue, but will
         * perform actual matching in chooseConfig() below.
         */
        private static int EGL_OPENGL_ES2_BIT = 4;
        private static int[] s_configAttribs2 =
        {
            EGL10.EGL_RED_SIZE, 4,
            EGL10.EGL_GREEN_SIZE, 4,
            EGL10.EGL_BLUE_SIZE, 4,
            EGL10.EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
            EGL10.EGL_NONE
        };

        public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display) {

            /* Get the number of minimally matching EGL configurations
             */
            int[] num_config = new int[1];
            egl.eglChooseConfig(display, s_configAttribs2, null, 0, num_config);

            int numConfigs = num_config[0];

            if (numConfigs <= 0) {
                throw new IllegalArgumentException("No configs match configSpec");
            }

            /* Allocate then read the array of minimally matching EGL configs
             */
            EGLConfig[] configs = new EGLConfig[numConfigs];
            egl.eglChooseConfig(display, s_configAttribs2, configs, numConfigs, num_config);

            if (DEBUG) {
                 printConfigs(egl, display, configs);
            }
            /* Now return the "best" one
             */
            return chooseConfig(egl, display, configs);
        }

        public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display,
                EGLConfig[] configs) {
            for(EGLConfig config : configs) {
                int d = findConfigAttrib(egl, display, config,
                        EGL10.EGL_DEPTH_SIZE, 0);
                int s = findConfigAttrib(egl, display, config,
                        EGL10.EGL_STENCIL_SIZE, 0);

                // We need at least mDepthSize and mStencilSize bits
                if (d < mDepthSize || s < mStencilSize)
                    continue;

                // We want an *exact* match for red/green/blue/alpha
                int r = findConfigAttrib(egl, display, config,
                        EGL10.EGL_RED_SIZE, 0);
                int g = findConfigAttrib(egl, display, config,
                            EGL10.EGL_GREEN_SIZE, 0);
                int b = findConfigAttrib(egl, display, config,
                            EGL10.EGL_BLUE_SIZE, 0);
                int a = findConfigAttrib(egl, display, config,
                        EGL10.EGL_ALPHA_SIZE, 0);

                if (r == mRedSize && g == mGreenSize && b == mBlueSize && a == mAlphaSize)
                    return config;
            }
            return null;
        }

        private int findConfigAttrib(EGL10 egl, EGLDisplay display,
                EGLConfig config, int attribute, int defaultValue) {

            if (egl.eglGetConfigAttrib(display, config, attribute, mValue)) {
                return mValue[0];
            }
            return defaultValue;
        }

        private void printConfigs(EGL10 egl, EGLDisplay display,
            EGLConfig[] configs) {
            int numConfigs = configs.length;
            Log.w(TAG, String.format("%d configurations", numConfigs));
            for (int i = 0; i < numConfigs; i++) {
                Log.w(TAG, String.format("Configuration %d:\n", i));
                printConfig(egl, display, configs[i]);
            }
        }

        private void printConfig(EGL10 egl, EGLDisplay display,
                EGLConfig config) {
            int[] attributes = {
                    EGL10.EGL_BUFFER_SIZE,
                    EGL10.EGL_ALPHA_SIZE,
                    EGL10.EGL_BLUE_SIZE,
                    EGL10.EGL_GREEN_SIZE,
                    EGL10.EGL_RED_SIZE,
                    EGL10.EGL_DEPTH_SIZE,
                    EGL10.EGL_STENCIL_SIZE,
                    EGL10.EGL_CONFIG_CAVEAT,
                    EGL10.EGL_CONFIG_ID,
                    EGL10.EGL_LEVEL,
                    EGL10.EGL_MAX_PBUFFER_HEIGHT,
                    EGL10.EGL_MAX_PBUFFER_PIXELS,
                    EGL10.EGL_MAX_PBUFFER_WIDTH,
                    EGL10.EGL_NATIVE_RENDERABLE,
                    EGL10.EGL_NATIVE_VISUAL_ID,
                    EGL10.EGL_NATIVE_VISUAL_TYPE,
                    0x3030, // EGL10.EGL_PRESERVED_RESOURCES,
                    EGL10.EGL_SAMPLES,
                    EGL10.EGL_SAMPLE_BUFFERS,
                    EGL10.EGL_SURFACE_TYPE,
                    EGL10.EGL_TRANSPARENT_TYPE,
                    EGL10.EGL_TRANSPARENT_RED_VALUE,
                    EGL10.EGL_TRANSPARENT_GREEN_VALUE,
                    EGL10.EGL_TRANSPARENT_BLUE_VALUE,
                    0x3039, // EGL10.EGL_BIND_TO_TEXTURE_RGB,
                    0x303A, // EGL10.EGL_BIND_TO_TEXTURE_RGBA,
                    0x303B, // EGL10.EGL_MIN_SWAP_INTERVAL,
                    0x303C, // EGL10.EGL_MAX_SWAP_INTERVAL,
                    EGL10.EGL_LUMINANCE_SIZE,
                    EGL10.EGL_ALPHA_MASK_SIZE,
                    EGL10.EGL_COLOR_BUFFER_TYPE,
                    EGL10.EGL_RENDERABLE_TYPE,
                    0x3042 // EGL10.EGL_CONFORMANT
            };
            String[] names = {
                    "EGL_BUFFER_SIZE",
                    "EGL_ALPHA_SIZE",
                    "EGL_BLUE_SIZE",
                    "EGL_GREEN_SIZE",
                    "EGL_RED_SIZE",
                    "EGL_DEPTH_SIZE",
                    "EGL_STENCIL_SIZE",
                    "EGL_CONFIG_CAVEAT",
                    "EGL_CONFIG_ID",
                    "EGL_LEVEL",
                    "EGL_MAX_PBUFFER_HEIGHT",
                    "EGL_MAX_PBUFFER_PIXELS",
                    "EGL_MAX_PBUFFER_WIDTH",
                    "EGL_NATIVE_RENDERABLE",
                    "EGL_NATIVE_VISUAL_ID",
                    "EGL_NATIVE_VISUAL_TYPE",
                    "EGL_PRESERVED_RESOURCES",
                    "EGL_SAMPLES",
                    "EGL_SAMPLE_BUFFERS",
                    "EGL_SURFACE_TYPE",
                    "EGL_TRANSPARENT_TYPE",
                    "EGL_TRANSPARENT_RED_VALUE",
                    "EGL_TRANSPARENT_GREEN_VALUE",
                    "EGL_TRANSPARENT_BLUE_VALUE",
                    "EGL_BIND_TO_TEXTURE_RGB",
                    "EGL_BIND_TO_TEXTURE_RGBA",
                    "EGL_MIN_SWAP_INTERVAL",
                    "EGL_MAX_SWAP_INTERVAL",
                    "EGL_LUMINANCE_SIZE",
                    "EGL_ALPHA_MASK_SIZE",
                    "EGL_COLOR_BUFFER_TYPE",
                    "EGL_RENDERABLE_TYPE",
                    "EGL_CONFORMANT"
            };
            int[] value = new int[1];
            for (int i = 0; i < attributes.length; i++) {
                int attribute = attributes[i];
                String name = names[i];
                if ( egl.eglGetConfigAttrib(display, config, attribute, value)) {
                    Log.w(TAG, String.format("  %s: %d\n", name, value[0]));
                } else {
                    // Log.w(TAG, String.format("  %s: failed\n", name));
                    while (egl.eglGetError() != EGL10.EGL_SUCCESS);
                }
            }
        }

        // Subclasses can adjust these values:
        protected int mRedSize;
        protected int mGreenSize;
        protected int mBlueSize;
        protected int mAlphaSize;
        protected int mDepthSize;
        protected int mStencilSize;
        private int[] mValue = new int[1];
    }

    private static class Renderer implements GLSurfaceView.Renderer {
        public void onDrawFrame(GL10 gl) {
            GL2JNILib.step();
        }

        public void onSurfaceChanged(GL10 gl, int width, int height) {
            GL2JNILib.init(width, height);
        }

        public void onSurfaceCreated(GL10 gl, EGLConfig config) {
            // Do nothing.
        }
    }
}

重载构造方法：

public GL2JNIView(Context context)

public GL2JNIView(Context context, boolean translucent, int depth, int stencil)

 

构造方法调用

private void init(boolean translucent, int depth, int stencil)

进行初始化工作：

if (translucent) {
    this.getHolder().setFormat(PixelFormat.TRANSLUCENT);
}

By default GLSurfaceView will create a PixelFormat.RGB_565 format surface. If a translucent surface is required, call getHolder().setFormat(PixelFormat.TRANSLUCENT). The exact format of a TRANSLUCENT surface is device dependent, but it will be a 32-bit-per-pixel surface with 8 bits per component.

 

setEGLContextFactory(new ContextFactory());

文档：public void setEGLContextFactory (GLSurfaceView.EGLContextFactory factory)

 

setEGLConfigChooser( translucent ?
    new ConfigChooser(8, 8, 8, 8, depth, stencil) :
    new ConfigChooser(5, 6, 5, 0, depth, stencil) ); 

文档：public void setEGLConfigChooser (GLSurfaceView.EGLConfigChooser configChooser)

 

setRenderer(new Renderer());

文档：public void setRenderer (GLSurfaceView.Renderer renderer)

 

私有内部类Renderer定义如下：

private static class Renderer implements GLSurfaceView.Renderer {
    public void onDrawFrame(GL10 gl) {
        GL2JNILib.step();
    }

    public void onSurfaceChanged(GL10 gl, int width, int height) {
        GL2JNILib.init(width, height);
    }

    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        // Do nothing.
    }
}

文档：GLSurfaceView.Renderer

当surface改变尺寸，调用GL2JNILib.init(width, height);

当画当前帧的时候，调用GL2JNILib.step();

 

GL2JNILib.java

package com.android.gl2jni;

// Wrapper for native library

public class GL2JNILib {

     static {
         System.loadLibrary("gl2jni");
     }

    /**
     * @param width the current view width
     * @param height the current view height
     */
     public static native void init(int width, int height);
     public static native void step();
}

static {
    System.loadLibrary("gl2jni");
}

加载静态库gl2jni

public static native void init(int width, int height);
public static native void step();

声明public static native方法，通过JNI调用C/C++的native方法。