读 Beginning Android Games 2nd Edition (二十二) 封装OpenGL之GLGame类

 GLGame类使用了大部分此书前面写过的AndroidGame类的代码，并增加了渲染和UI线程间的同步

package com.badlogic.androidgames.framework.impl;

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.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;
import android.os.PowerManager;
import android.os.PowerManager.WakeLock;
import android.view.Window;
import android.view.WindowManager;

import com.badlogic.androidgames.framework.Audio;
import com.badlogic.androidgames.framework.FileIO;
import com.badlogic.androidgames.framework.Game;
import com.badlogic.androidgames.framework.Graphics;
import com.badlogic.androidgames.framework.Input;
import com.badlogic.androidgames.framework.Screen;

public abstract class GLGame extends Activity implements Game, Renderer {
	//定义一个枚举,跟踪GLGame实例状态
    enum GLGameState {
        Initialized,
        Running,
        Paused,
        Finished,
        Idle
    }
    
    GLSurfaceView glView;    
    GLGraphics glGraphics;
    Audio audio;
    Input input;
    FileIO fileIO;
    Screen screen;
    //初始化游戏状态
    GLGameState state = GLGameState.Initialized;
    Object stateChanged = new Object();
    long startTime = System.nanoTime();
    //WakeLock可避免手机进入暗屏状态
    WakeLock wakeLock;

    @Override 
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //设置无标题界面
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        //设置全屏
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                             WindowManager.LayoutParams.FLAG_FULLSCREEN);
        glView = new GLSurfaceView(this);
        glView.setRenderer(this);
        setContentView(glView);
        //实例化文件,音频,输入对象
        glGraphics = new GLGraphics(glView);
        fileIO = new AndroidFileIO(this);
        audio = new AndroidAudio(this);
        input = new AndroidInput(this, glView, 1, 1);
        //电源管理器
        PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "GLGame");        
    }
    
    @Override
    public void onResume() {
        super.onResume();
        //开始让GLSurfaceView渲染线程工作
        glView.onResume();
        wakeLock.acquire();
    }
    
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {        
        glGraphics.setGL(gl);
        
        synchronized(stateChanged) {
        	//如果游戏刚开始,设置游戏状态并跳到开始画面
            if(state == GLGameState.Initialized)
                screen = getStartScreen();
            //设置游戏状态为运行阶段
            state = GLGameState.Running;
            screen.resume();
            //记录游戏的开始时间
            startTime = System.nanoTime();
        }        
    }

    public void onSurfaceChanged(GL10 gl, int width, int height) {        
    }

    //这个方法中检查游戏状态和实现相应的反应
    public void onDrawFrame(GL10 gl) {                
        GLGameState state = null;
        
        synchronized(stateChanged) {
            state = this.state;
        }
        
        //如果游戏在进行中,那么告诉当前屏幕更新delta时间,并把它显示出来
        if(state == GLGameState.Running) {
            float deltaTime = (System.nanoTime()-startTime) / 1000000000.0f;
            startTime = System.nanoTime();
            
            screen.update(deltaTime);
            screen.present(deltaTime);
        }
        
        if(state == GLGameState.Paused) {
            screen.pause();            
            synchronized(stateChanged) {
                this.state = GLGameState.Idle;
                stateChanged.notifyAll();
            }
        }
        
        if(state == GLGameState.Finished) {
            screen.pause();
            screen.dispose();
            synchronized(stateChanged) {
                this.state = GLGameState.Idle;
                stateChanged.notifyAll();
            }            
        }
    }

    @Override 
    public void onPause() {        
        synchronized(stateChanged) {
            if(isFinishing())            
                state = GLGameState.Finished;
            else
                state = GLGameState.Paused;
            while(true) {
                try {
                    stateChanged.wait();
                    break;
                } catch(InterruptedException e) { 
                }
            }
        }
        wakeLock.release();
        glView.onPause();  
        super.onPause();
    }  

    public GLGraphics getGLGraphics() {
        return glGraphics;
    }  

    public Input getInput() {
        return input;
    }

    public FileIO getFileIO() {
        return fileIO;
    }

    public Graphics getGraphics() {
        throw new IllegalStateException("We are using OpenGL!");
    }

    public Audio getAudio() {
        return audio;
    }

    //设置当前屏幕
    public void setScreen(Screen newScreen) {
        if (newScreen == null)
            throw new IllegalArgumentException("Screen must not be null");

        this.screen.pause();
        this.screen.dispose();
        newScreen.resume();
        newScreen.update(0);
        this.screen = newScreen;
    }

    public Screen getCurrentScreen() {
        return screen;
    }
}