刚开始学习AndEngine，将源码整理好，跑了一次，大体上看了一下Demo，非常不错！今天就正式开始学习了！
网上大部分帖子都说，要使用AndEngine,首先需要一个Activity继承BaseGameActivity。而然，最新代码里面，又对BaseGameActivity进行了一层封装---SimpleBaseGameActivity。源码如下：
public abstract class SimpleBaseGameActivity extends BaseGameActivity {
// ===========================================================
// Constants
// ===========================================================
// ===========================================================
// Fields
// ===========================================================
// ===========================================================
// Constructors
// ===========================================================
// ===========================================================
// Getter & Setter
// ===========================================================
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
protected abstract void onCreateResources();
protected abstract Scene onCreateScene();
@Override
public final void onCreateResources(final OnCreateResourcesCallback pOnCreateResourcesCallback) throws Exception {
this.onCreateResources();
pOnCreateResourcesCallback.onCreateResourcesFinished();
}
@Override
public final void onCreateScene(final OnCreateSceneCallback pOnCreateSceneCallback) throws Exception {
final Scene scene = this.onCreateScene();
pOnCreateSceneCallback.onCreateSceneFinished(scene);
}
@Override
public final void onPopulateScene(final Scene pScene, final OnPopulateSceneCallback pOnPopulateSceneCallback) throws Exception {
pOnPopulateSceneCallback.onPopulateSceneFinished();
}
// ===========================================================
// Methods
// ===========================================================
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
}
其类继承关系如图：
那么我们就一次来看看。首先看其超类BaseActivity：
public abstract class BaseActivity extends Activity {
// ===========================================================
// Constants
// ===========================================================
// ===========================================================
// Fields
// ===========================================================
// ===========================================================
// Constructors
// ===========================================================
// ===========================================================
// Getter & Setter
// ===========================================================
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
// ===========================================================
// Methods
// ===========================================================
public void toastOnUIThread(final CharSequence pText) {
this.toastOnUIThread(pText, Toast.LENGTH_LONG);
}
public void toastOnUIThread(final CharSequence pText, final int pDuration) {
if(Looper.getMainLooper().getThread() == Thread.currentThread()) {
Toast.makeText(BaseActivity.this, pText, pDuration).show();
} else {
this.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(BaseActivity.this, pText, pDuration).show();
}
});
}
}
/**
* Performs a task in the background, showing a {@link ProgressDialog},
* while the {@link Callable} is being processed.
*
* @param <T>
* @param pTitleResourceID
* @param pMessageResourceID
* @param pErrorMessageResourceID
* @param pCallable
* @param pCallback
*/
protected <T> void doAsync(final int pTitleResourceID, final int pMessageResourceID, final Callable<T> pCallable, final Callback<T> pCallback) {
this.doAsync(pTitleResourceID, pMessageResourceID, pCallable, pCallback, null);
}
/**
* Performs a task in the background, showing a indeterminate {@link ProgressDialog},
* while the {@link Callable} is being processed.
*
* @param <T>
* @param pTitleResourceID
* @param pMessageResourceID
* @param pErrorMessageResourceID
* @param pCallable
* @param pCallback
* @param pExceptionCallback
*/
protected <T> void doAsync(final int pTitleResourceID, final int pMessageResourceID, final Callable<T> pCallable, final Callback<T> pCallback, final Callback<Exception> pExceptionCallback) {
ActivityUtils.doAsync(this, pTitleResourceID, pMessageResourceID, pCallable, pCallback, pExceptionCallback);
}
/**
* Performs a task in the background, showing a {@link ProgressDialog} with an ProgressBar,
* while the {@link AsyncCallable} is being processed.
*
* @param <T>
* @param pTitleResourceID
* @param pMessageResourceID
* @param pErrorMessageResourceID
* @param pAsyncCallable
* @param pCallback
*/
protected <T> void doProgressAsync(final int pTitleResourceID, final int pIconResourceID, final ProgressCallable<T> pCallable, final Callback<T> pCallback) {
this.doProgressAsync(pTitleResourceID, pIconResourceID, pCallable, pCallback, null);
}
/**
* Performs a task in the background, showing a {@link ProgressDialog} with a ProgressBar,
* while the {@link AsyncCallable} is being processed.
*
* @param <T>
* @param pTitleResourceID
* @param pMessageResourceID
* @param pErrorMessageResourceID
* @param pAsyncCallable
* @param pCallback
* @param pExceptionCallback
*/
protected <T> void doProgressAsync(final int pTitleResourceID, final int pIconResourceID, final ProgressCallable<T> pCallable, final Callback<T> pCallback, final Callback<Exception> pExceptionCallback) {
ActivityUtils.doProgressAsync(this, pTitleResourceID, pIconResourceID, pCallable, pCallback, pExceptionCallback);
}
/**
* Performs a task in the background, showing an indeterminate {@link ProgressDialog},
* while the {@link AsyncCallable} is being processed.
*
* @param <T>
* @param pTitleResourceID
* @param pMessageResourceID
* @param pErrorMessageResourceID
* @param pAsyncCallable
* @param pCallback
* @param pExceptionCallback
*/
protected <T> void doAsync(final int pTitleResourceID, final int pMessageResourceID, final AsyncCallable<T> pAsyncCallable, final Callback<T> pCallback, final Callback<Exception> pExceptionCallback) {
ActivityUtils.doAsync(this, pTitleResourceID, pMessageResourceID, pAsyncCallable, pCallback, pExceptionCallback);
}
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
}
看到代码，其实里面的东西是比较少的，大致归纳起来就俩个方面：一个封装的Toast（主要是让toast永远都在UI线程中）！再者就是几个doAsync()方法（主要就是封装好了一个异步任务），其具体实现在ActivityUtils中：
public static <T> void doAsync(final Context pContext, final CharSequence pTitle, final CharSequence pMessage, final Callable<T> pCallable, final Callback<T> pCallback, final Callback<Exception> pExceptionCallback, final boolean pCancelable) {
new AsyncTask<Void, Void, T>() {
private ProgressDialog mPD;
private Exception mException = null;
@Override
public void onPreExecute() {
this.mPD = ProgressDialog.show(pContext, pTitle, pMessage, true, pCancelable);
if(pCancelable) {
this.mPD.setOnCancelListener(new OnCancelListener() {
@Override
public void onCancel(final DialogInterface pDialogInterface) {
pExceptionCallback.onCallback(new CancelledException());
pDialogInterface.dismiss();
}
});
}
super.onPreExecute();
}
@Override
public T doInBackground(final Void... params) {
try {
return pCallable.call();
} catch (final Exception e) {
this.mException = e;
}
return null;
}
@Override
public void onPostExecute(final T result) {
try {
this.mPD.dismiss();
} catch (final Exception e) {
Debug.e("Error", e);
}
if(this.isCancelled()) {
this.mException = new CancelledException();
}
if(this.mException == null) {
pCallback.onCallback(result);
} else {
if(pExceptionCallback == null) {
Debug.e("Error", this.mException);
} else {
pExceptionCallback.onCallback(this.mException);
}
}
super.onPostExecute(result);
}
}.execute((Void[]) null);
}
接着，我们看下其子类BaseGameActivity，由于代码较多，就不贴了。
@Override
protected void onCreate(final Bundle pSavedInstanceState) {
if(BuildConfig.DEBUG) {
Debug.d(this.getClass().getSimpleName() + ".onCreate" + " @(Thread: '" + Thread.currentThread().getName() + "')");
}
super.onCreate(pSavedInstanceState);
this.mGamePaused = true;
this.mEngine = this.onCreateEngine(this.onCreateEngineOptions()
);this.mEngine.startUpdateThread();this.applyEngineOptions();this.onSetContentView();}
这里面很清楚看到调用几个方法，我们依次来看看！
this.mEngine = this.onCreateEngine(this.onCreateEngineOptions());
嘿嘿，mEngine看到就高兴了！这个就是AndEngine中的engine对象了，而且，当activity运行起来的时候，就会尝试去构造一个AndEngine对象，其实现方式在：
@Override
public Engine onCreateEngine(final EngineOptions pEngineOptions) {
return new Engine(pEngineOptions);
}
可以看到，其实就只构造了一个Engine，但是，我们不能忽略的是其参数中EngineOptions pEngineOptions，那我们来看看这个参数是如何来的？
this.onCreateEngineOptions()
是这样来的，那么这个this指的是什么呢？----IGameInterface！
但是在BaseGameActivity中是没有实现这个借口的，那意思就是说，他的子类就必须实现这个方法了，所以导致其子类SimpleBaseGameActivity中就必须实现这个方法！而且，程序最开始加载的就是这个方法。
然后就是开启引擎的线程了，这个以后再研究。
紧接着就是，applyEngineOptions（），我们来看看其实现方式：
private void applyEngineOptions() {
final EngineOptions engineOptions = this.mEngine.getEngineOptions();
if(engineOptions.isFullscreen()) {
ActivityUtils.requestFullscreen(this);
}
if(engineOptions.getAudioOptions().needsMusic() || engineOptions.getAudioOptions().needsSound()) {
this.setVolumeControlStream(AudioManager.STREAM_MUSIC);
}
switch(engineOptions.getScreenOrientation()) {
case LANDSCAPE_FIXED:
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
break;
case LANDSCAPE_SENSOR:
if(SystemUtils.SDK_VERSION_GINGERBREAD_OR_LATER) {
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE);
} else {
Debug.w(ScreenOrientation.class.getSimpleName() + "." + ScreenOrientation.LANDSCAPE_SENSOR + " is not supported on this device. Falling back to " + ScreenOrientation.class.getSimpleName() + "." + ScreenOrientation.LANDSCAPE_FIXED);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}
break;
case PORTRAIT_FIXED:
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
break;
case PORTRAIT_SENSOR:
if(SystemUtils.SDK_VERSION_GINGERBREAD_OR_LATER) {
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT);
} else {
Debug.w(ScreenOrientation.class.getSimpleName() + "." + ScreenOrientation.PORTRAIT_SENSOR + " is not supported on this device. Falling back to " + ScreenOrientation.class.getSimpleName() + "." + ScreenOrientation.PORTRAIT_FIXED);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}
break;
}
}
这个主要干的就是，应用引擎的配置，如是否全屏、是否开启声音、图像布局方式等。
再来就是，this.onSetContentView();我们看看其实现：
protected void onSetContentView() {
this.mRenderSurfaceView = new RenderSurfaceView(this);
this.mRenderSurfaceView.setRenderer(this.mEngine, this);
this.setContentView(this.mRenderSurfaceView, BaseGameActivity.createSurfaceViewLayoutParams());
}
虽然，从这来看其实就是设置显示的视图。看起来很简单，但是我们要注意：
this.mRenderSurfaceView = new RenderSurfaceView(this);
this.mRenderSurfaceView.setRenderer(this.mEngine, this);
这俩行代码，这俩行真是太重要了，整个引擎的渲染、运行都是由这俩行开始的，我们来具体看下。
this.mRenderSurfaceView = new RenderSurfaceView(this);
构造一个RenderSurfaceView对象。可以看到RenderSurfaceView其实又是对OpenGL GLSurfaceView的一层封装。重点来了，我们看
this.mRenderSurfaceView.setRenderer(this.mEngine, this);
其实现是：
public void setRenderer(final Engine pEngine, final IRendererListener pRendererListener) {
if(this.mConfigChooser == null) {
final boolean multiSampling = pEngine.getEngineOptions().getRenderOptions().isMultiSampling();
this.mConfigChooser = new ConfigChooser(multiSampling);
}
this.setEGLConfigChooser(this.mConfigChooser);
this.setOnTouchListener(pEngine);
this.mEngineRenderer = new EngineRenderer(pEngine, this.mConfigChooser, pRendererListener);
this.setRenderer(this.mEngineRenderer);
}
嘿嘿，这里面的this，原来是IRendererListener这个，源代码如下：
public interface IRendererListener {
// ===========================================================
// Constants
// ===========================================================
public void onSurfaceCreated(final GLState pGlState);
public void onSurfaceChanged(final GLState pGlState, final int pWidth, final int pHeight);
// ===========================================================
// Methods
// ===========================================================
}
看名字就应该能猜出个大致意思了，待会，我们在BaseGameActivity中是如何实现这个接口的。现在还是继续看setRender里面的东西，
this.mEngineRenderer = new EngineRenderer(pEngine, this.mConfigChooser, pRendererListener);
this.setRenderer(this.mEngineRenderer);
这个，构造了EngineRender，我们跟进去看下：
public class EngineRenderer implements GLSurfaceView.Renderer {
// ===========================================================
// Constants
// ===========================================================
// ===========================================================
// Fields
// ===========================================================
final Engine mEngine;
final ConfigChooser mConfigChooser;
final boolean mMultiSampling;
final IRendererListener mRendererListener;
final GLState mGLState;
// ===========================================================
// Constructors
// ===========================================================
public EngineRenderer(final Engine pEngine, final ConfigChooser pConfigChooser, final IRendererListener pRendererListener) {
this.mEngine = pEngine;
this.mConfigChooser = pConfigChooser;
this.mRendererListener = pRendererListener;
this.mGLState = new GLState();
this.mMultiSampling = this.mEngine.getEngineOptions().getRenderOptions().isMultiSampling();
}
// ===========================================================
// Getter & Setter
// ===========================================================
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
@Override
public void onSurfaceCreated(final GL10 pGL, final EGLConfig pEGLConfig) {
synchronized(GLState.class) {
final RenderOptions renderOptions = this.mEngine.getEngineOptions().getRenderOptions();
this.mGLState.reset(renderOptions, this.mConfigChooser, pEGLConfig);
// TODO Check if available and make available through EngineOptions-RenderOptions
// GLES20.glEnable(GLES20.GL_POLYGON_SMOOTH);
// GLES20.glHint(GLES20.GL_POLYGON_SMOOTH_HINT, GLES20.GL_NICEST);
// GLES20.glEnable(GLES20.GL_LINE_SMOOTH);
// GLES20.glHint(GLES20.GL_LINE_SMOOTH_HINT, GLES20.GL_NICEST);
// GLES20.glEnable(GLES20.GL_POINT_SMOOTH);
// GLES20.glHint(GLES20.GL_POINT_SMOOTH_HINT, GLES20.GL_NICEST);
this.mGLState.disableDepthTest();
this.mGLState.enableBlend();
this.mGLState.setDitherEnabled(renderOptions.isDithering());
/* Enabling culling doesn't really make sense, because triangles are never drawn 'backwards' on purpose. */
// this.mGLState.enableCulling();
// GLES20.glFrontFace(GLES20.GL_CCW);
// GLES20.glCullFace(GLES20.GL_BACK);
if(this.mRendererListener != null) {
this.mRendererListener.onSurfaceCreated(this.mGLState);
}
}
}
@Override
public void onSurfaceChanged(final GL10 pGL, final int pWidth, final int pHeight) {
this.mEngine.setSurfaceSize(pWidth, pHeight);
GLES20.glViewport(0, 0, pWidth, pHeight);
this.mGLState.loadProjectionGLMatrixIdentity();
if(this.mRendererListener != null) {
this.mRendererListener.onSurfaceChanged(this.mGLState, pWidth, pHeight);
}
}
@Override
public void onDrawFrame(final GL10 pGL) {
synchronized(GLState.class) {
if (this.mMultiSampling && this.mConfigChooser.isCoverageMultiSampling()) {
final int GL_COVERAGE_BUFFER_BIT_NV = 0x8000;
GLES20.glClear(GL_COVERAGE_BUFFER_BIT_NV);
}
try {
this.mEngine.onDrawFrame(this.mGLState);
} catch (final InterruptedException e) {
Debug.e("GLThread interrupted!", e);
}
}
}
// ===========================================================
// Methods
// ===========================================================
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
}
我们看到，它里面是回调了IRendererListener的俩个方法的，至于，如何回调，回调机制如何，那就和OpenGL相关了，不讨论！
看到这里面，我们大致知道了，当oncreate的时候，会去创建引擎，然后，引擎创建render，然后等render创建之后，又回调到BaseGameActivity中！现在，我们回到BaseGameActivity中，看看其回调的实现：
@Override
public synchronized void onSurfaceCreated(final GLState pGLState) {
if(BuildConfig.DEBUG) {
Debug.d(this.getClass().getSimpleName() + ".onSurfaceCreated" + " @(Thread: '" + Thread.currentThread().getName() + "')");
}
if(this.mGameCreated) {
this.onReloadResources();
if(this.mGamePaused && this.mGameCreated) {
this.onResumeGame();
}
} else {
if(this.mCreateGameCalled) {
this.mOnReloadResourcesScheduled = true;
} else {
this.mCreateGameCalled = true;
this.onCreateGame();
}
}
}
@Override
public synchronized void onSurfaceChanged(final GLState pGLState, final int pWidth, final int pHeight) {
if(BuildConfig.DEBUG) {
Debug.d(this.getClass().getSimpleName() + ".onSurfaceChanged(Width=" + pWidth + ", Height=" + pHeight + ")" + " @(Thread: '" + Thread.currentThread().getName() + "')");
}
}
我们，具体看
public synchronized void onSurfaceCreated(final GLState pGLState)
它首先会调用onCreateGame()，其实现代码就省略了，我们可以看到里面就执行了一句：
this.onCreateResources(onCreateResourcesCallback);
而这个onCreateResources也是IGameInterface中的一个方法，其具体实现就是：
@Override
public final void onCreateResources(final OnCreateResourcesCallback pOnCreateResourcesCallback) throws Exception {
this.onCreateResources();
pOnCreateResourcesCallback.onCreateResourcesFinished();
}
其中：
protected abstract void onCreateResources();
那么，其子类就必须实现这个方法，这个方法就是load我们游戏中可能会用到的资源，当资源load完成之后，就回调到BaseGameActivity中的onCreateGame()去，根据源码将执行：
final OnCreateResourcesCallback onCreateResourcesCallback = new OnCreateResourcesCallback() {
@Override
public void onCreateResourcesFinished() {
try {
if(BuildConfig.DEBUG) {
Debug.d(BaseGameActivity.this.getClass().getSimpleName() + ".onCreateScene" + " @(Thread: '" + Thread.currentThread().getName() + "')");
}
BaseGameActivity.this.onCreateScene(onCreateSceneCallback);
} catch(final Throwable pThrowable) {
Debug.e(BaseGameActivity.this.getClass().getSimpleName() + ".onCreateScene failed." + " @(Thread: '" + Thread.currentThread().getName() + "')", pThrowable);
}
}
};
同样，onCreateScene也是IGameInterface中的一个方法，其实现同样也是在BaseGameActivity的子类，SimpleBaseGameActivity中实现的：
@Override
public final void onCreateScene(final OnCreateSceneCallback pOnCreateSceneCallback) throws Exception {
final Scene scene = this.onCreateScene();
pOnCreateSceneCallback.onCreateSceneFinished(scene);
}
而，onCreateScene也是抽象方法，需在其子类中实现！通过分享到这，我们就可以大致得到AndEngine的大致流程了：
onCreateEngineOptions() ------onCreateResources()--------onCreateScene()
当onCreateScene()执行完毕之后，又会想上面那样回调，然后执行onPopulateScene（），然后回调执行onGameCreated();这样整个游戏框架就跑起来了！
其他的就不具体说了，感觉有点多，说不清了！但是有点需要注意的是：
BaseGameActivity中，防着Activity的生命周期，写了游戏的生命周期，onGameCreated()类似的，根据网上找的前辈的经验，尽量使用AndEngine的声明为好！
支持，完毕，有点乱！
总体来说，我们使用AndEngine的时候，只需要继承SimpleBaseGameActivity并实现onCreateEngineOptions() ------onCreateResources()--------onCreateScene()就可以了，其执行顺序为onCreateEngineOptions() ------onCreateResources()--------onCreateScene()！