二:虚拟游戏摇杆

andengine中绘制虚拟游戏摇杆非常简单，只需要实现AnalogOnScreenControl模拟摇杆类，在设置一些属性即可。先看效果图：

左边的摇杆是控制精灵上下左右移动，右边的摇杆空值精灵的旋转。代码结构跟andengine学习系列二一样，其中很多注释在系列二中有说明，在该章内便不多复述。

onLoadEngine()方法：

@Override
    public Engine onLoadEngine() {
        this.mCamera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
        final Engine engine = new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), this.mCamera));

        try {       //因为有两个摇杆，需要两个手指同时进行，所以这里要注册多点触控
            if(MultiTouch.isSupported(this)) {
                engine.setTouchController(new MultiTouchController());
                if(MultiTouch.isSupportedDistinct(this)) {
                    Toast.makeText(this, "MultiTouch detected --> Both controls will work properly!", Toast.LENGTH_LONG).show();
                } else {
                    this.mPlaceOnScreenControlsAtDifferentVerticalLocations = true;
                    Toast.makeText(this, "MultiTouch detected, but your device has problems distinguishing between fingers.\n\nControls are placed at different vertical locations.", Toast.LENGTH_LONG).show();
                }
            } else {
                Toast.makeText(this, "Sorry your device does NOT support MultiTouch!\n\n(Falling back to SingleTouch.)\n\nControls are placed at different vertical locations.", Toast.LENGTH_LONG).show();
            }
        } catch (final MultiTouchException e) {
            Toast.makeText(this, "Sorry your Android Version does NOT support MultiTouch!\n\n(Falling back to SingleTouch.)\n\nControls are placed at different vertical locations.", Toast.LENGTH_LONG).show();
        }

        return engine;
    }

 

onLoadResources()方法：

public void onLoadResources() {

        this.mTexture = new Texture(32, 32, TextureOptions.BILINEAR_PREMULTIPLYALPHA);
        this.mFaceTextureRegion = TextureRegionFactory.createFromAsset(this.mTexture, this, "face_box.png", 0, 0);

        this.mOnScreenControlTexture = new Texture(256, 128, TextureOptions.BILINEAR_PREMULTIPLYALPHA);
        this.mOnScreenControlBaseTextureRegion = TextureRegionFactory.createFromAsset(this.mOnScreenControlTexture, this, "onscreen_control_base.png", 0, 0);   //这里是加载摇杆的地盘的纹理图片
        this.mOnScreenControlKnobTextureRegion = TextureRegionFactory.createFromAsset(this.mOnScreenControlTexture, this, "onscreen_control_knob.png", 128, 0); //这里是加载摇杆的纹理图片

        this.mEngine.getTextureManager().loadTextures(this.mTexture, this.mOnScreenControlTexture);
    }

onLoadScene()方法,关键的业务逻辑便在该方法中：

public Scene onLoadScene() {
        this.mEngine.registerUpdateHandler(new FPSLogger());

        final Scene scene = new Scene(1);
        scene.setBackground(new ColorBackground(0.09804f, 0.6274f, 0.8784f));

        final int centerX = (CAMERA_WIDTH - this.mFaceTextureRegion.getWidth()) / 2;
        final int centerY = (CAMERA_HEIGHT - this.mFaceTextureRegion.getHeight()) / 2;
        final Sprite face = new Sprite(centerX, centerY, this.mFaceTextureRegion);

        scene.getTopLayer().addEntity(face);

//-------------------------------------------以下为左摇杆的实现----------------------------------------------------------------------                                                                final int x1 = 0;                                                   //y坐标为屏幕的高度减去摇杆底盘的高度，注意屏幕在前面已经被强制横屏
        final int y1 = CAMERA_HEIGHT - this.mOnScreenControlBaseTextureRegion.getHeight();                                                                              //AnalogOnScreenControl构造方法中：第一第二参数是该摇杆的坐标，第三个参数为上面定义camera，第四第五个参数为摇杆底盘和摇杆的纹理区域，第六个参数为pTimeBetweenUpdates界面的更新
        final AnalogOnScreenControl velocityOnScreenControl = new AnalogOnScreenControl(x1, y1, this.mCamera, this.mOnScreenControlBaseTextureRegion, this.mOnScreenControlKnobTextureRegion, 0.1f, new IAnalogOnScreenControlListener() {                                          //备注1
            @Override
            public void onControlChange(final BaseOnScreenControl pBaseOnScreenControl, final float pValueX, final float pValueY) {
                Log.i("test","x1:"+x1+",y1:"+y1+",pValueX:"+pValueX+",pValueY:"+pValueY);
                face.setVelocity(pValueX * 100, pValueY * 100); //备注2
            }

            @Override
            public void onControlClick(final AnalogOnScreenControl pAnalogOnScreenControl) {    //备注3
                /* Nothing. */
            }
        });
        velocityOnScreenControl.getControlBase().setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);                                          //备注4
        velocityOnScreenControl.getControlBase().setAlpha(0.5f);

        scene.setChildScene(velocityOnScreenControl);
//-------------------------------------------------------end 坐摇杆的实现------------------------------------------------------------//-------------------------------------------------------以下为右摇杆的实现----------------------------------------------------------

        final int y2 = (this.mPlaceOnScreenControlsAtDifferentVerticalLocations) ? 0 : y1;
        final int x2 = CAMERA_WIDTH - this.mOnScreenControlBaseTextureRegion.getWidth();
        final AnalogOnScreenControl rotationOnScreenControl = new AnalogOnScreenControl(x2, y2, this.mCamera, this.mOnScreenControlBaseTextureRegion, this.mOnScreenControlKnobTextureRegion, 0.1f, new IAnalogOnScreenControlListener() {
            @Override
            public void onControlChange(final BaseOnScreenControl pBaseOnScreenControl, final float pValueX, final float pValueY) {
                Log.i("test","x2:"+x2+",y2:"+y2+",pValueX:"+pValueX+",pValueY:"+pValueY);
                if(pValueX == x1 && pValueY == x1) {
                    face.setRotation(x1);
                } else {
                    face.setRotation(MathUtils.radToDeg((float)Math.atan2(pValueX, -pValueY)));
                                //备注5
                }
            }

            @Override
            public void onControlClick(final AnalogOnScreenControl pAnalogOnScreenControl) {
                /* Nothing. */
            }
        });
        rotationOnScreenControl.getControlBase().setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
        rotationOnScreenControl.getControlBase().setAlpha(0.5f);

        velocityOnScreenControl.setChildScene(rotationOnScreenControl);     //备注6

        return scene;
    }                                                       //---------------------------------------------end 右摇杆的实现-------