《Beginning Android Games》 学习笔记二

简要分析一下代码：

两个线程:

1.主线程(Main Looper)

   处理Activity的生命周期(onCreate,onResume,onPause)和获取用户的输入(Sensor,TouchEvent)

2.GLSurfaceView线程

   Renderer接口中注册的回调方法，显示界面，处理用户的输入

两个线程需要同步GameState对象和相应的用户输入的内存池

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 {
    enum GLGameState {
        Initialized,
        Running,
        Paused,
        Finished,
        Idle
    }

    GLSurfaceView glView;
    GLGraphics glGraphics;
    Audio audio;
    Input input;
    FileIO fileIO;
    Screen screen;
    GLGameState state = GLGameState.Initialized;
    Object stateChanged = new Object();//同步对象锁
    long startTime = System.nanoTime();
    WakeLock wakeLock;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                             WindowManager.LayoutParams.FLAG_FULLSCREEN);
        glView = new GLSurfaceView(this);
        glView.setRenderer(this);//设置GLSurfaceView对应的回调接口
        setContentView(glView);

        glGraphics = new GLGraphics(glView);
        fileIO = new AndroidFileIO(getAssets());
        audio = new AndroidAudio(this);
        input = new AndroidInput(this, glView, 1, 1);
        PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "GLGame");
    }

    public void onResume() {
        super.onResume();
        glView.onResume();//启动GLSurfaceView线程
        wakeLock.acquire();
    }

     //启动GLSurfaceView线程时调用
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        glGraphics.setGL(gl);

        synchronized(stateChanged) {
            if(state == GLGameState.Initialized)
                screen = getStartScreen();
            state = GLGameState.Running;
            screen.resume();
            startTime = System.nanoTime();
        }
    }


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

     //GLSurfaceView线程中as often as possible的被调用
    public void onDrawFrame(GL10 gl) {
        GLGameState state = null;

        synchronized(stateChanged) {
            state = this.state;
        }

        if(state == GLGameState.Running) {
            float deltaTime = (System.nanoTime()-startTime) / 1000000000.0f;
            startTime = System.nanoTime();

            screen.update(deltaTime);//处理用户的事件
            screen.present(deltaTime);//显示当前的屏幕
        }

        if(state == GLGameState.Paused) {
            screen.pause(); //设定相应的screen的状态为Paused，为了在以后处在Running状态的时候进行显示
            synchronized(stateChanged) {
                this.state = GLGameState.Idle;
                stateChanged.notifyAll();//通知主线程状态已经设定完毕
            }
        }

        if(state == GLGameState.Finished) {
            screen.pause();
            screen.dispose();
            synchronized(stateChanged) {
                this.state = GLGameState.Idle;
                stateChanged.notifyAll();
            }
        }
    }


    public void onPause() {
        synchronized(stateChanged) {
            if(isFinishing())
                state = GLGameState.Finished;
            else
                state = GLGameState.Paused;
            while(true) {
                try {
                    stateChanged.wait();//本线程(Main Looper)等待，直到GLSurfaceView线程完成界面的状态设定
                    break;
                } catch(InterruptedException e) {
                }
            }
        }
        wakeLock.release();
        glView.onPause(); //停止GLSurfaceView线程
        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;
    }

     //设置一个Screen为当前的要显示的，GLSurfaceView将根据这个进行事件处理和显示
    public void setScreen(Screen screen) {
        if (screen == null)
            throw new IllegalArgumentException("Screen must not be null");
        this.screen.pause();
        this.screen.dispose();
        screen.resume();
        screen.update(0);
        this.screen = screen;
    }


    public Screen getCurrentScreen() {
        return screen;
    }
}