Gallery3d 代码分析之渲染流程
RenderView

gallery3d 的渲染从 RenderView 开始。RenderView 从 GLSurfaceView 继承而来，采用了通知型绘制模式，即通过调用 requestRender 通知 RenderView 重绘屏幕。

RenderView 将所有需要绘制的对象都保存一个 Lists中，Lists 包含了5个ArrayList，其定义如下所示：

        public final ArrayList<Layer> updateList = new ArrayList<Layer>();        public final ArrayList<Layer> opaqueList = new ArrayList<Layer>();        public final ArrayList<Layer> blendedList = new ArrayList<Layer>();        public final ArrayList<Layer> hitTestList = new ArrayList<Layer>();        public final ArrayList<Layer> systemList = new ArrayList<Layer>();

RenderView 的 onDrawFrame 接口完成每一帧的绘制操作，绘制时遍历 lists 里每个 list 的每一个成员并调用其 renderXXX 函数。主要代码如下所示：

    ...    final Lists lists = sLists;    final ArrayList<Layer> updateList = lists.updateList;    boolean isDirty = false;    for (int i = 0, size = updateList.size(); i != size; ++i) {        boolean retVal = updateList.get(i).update(this, mFrameInterval);        isDirty |= retVal;    }    if (isDirty) {        requestRender();    }    // Clear the depth buffer.    gl.glClear(GL11.GL_DEPTH_BUFFER_BIT);    gl.glEnable(GL11.GL_SCISSOR_TEST);    gl.glScissor(0, 0, getWidth(), getHeight());    // Run the opaque pass.    gl.glDisable(GL11.GL_BLEND);    final ArrayList<Layer> opaqueList = lists.opaqueList;    for (int i = opaqueList.size() - 1; i >= 0; --i) {        final Layer layer = opaqueList.get(i);        if (!layer.mHidden) {            layer.renderOpaque(this, gl);        }    }    // Run the blended pass.    gl.glEnable(GL11.GL_BLEND);    final ArrayList<Layer> blendedList = lists.blendedList;    for (int i = 0, size = blendedList.size(); i != size; ++i) {        final Layer layer = blendedList.get(i);        if (!layer.mHidden) {            layer.renderBlended(this, gl);        }    }    gl.glDisable(GL11.GL_BLEND);

lists 的各个 list 里包含的各个 layer 如下所示：

lists  |------------------|-----------------|-----------------|---------------|updateList        opaqueList        blendedList      systemList     hitTestList  |                  |                 |                 |            |GridLayer         GridLayer         GridLayer        GridLayer      GridLayerBackgroudLayer    BackgroudLayer    BackgroudLayerHudLayer           HudLayer         HudLayer                        HudLayerTimeBar                             TimeBar                         TimeBarPathBar                             PathBar                         PathBarXXXButton                           XXXButton                       XXXButtonXXXMenu                             XXXMenu                         XXXMenu

Layer 类提供了 update(...), renderOpaque (...), renderBlended (...) 接口，从上面 RenderView 的 onDrawFrame 绘制代码可以看到，这些接口被调用。

public abstract class Layer {    ... ...    public abstract void generate(RenderView view, RenderView.Lists lists);    public boolean update(RenderView view, float frameInterval) {        return false;    }    public void renderOpaque(RenderView view, GL11 gl) {    }    public void renderBlended(RenderView view, GL11 gl) {    }    ... ...}

GridLayer

GridLayer 中有个 GridDrawManager，专门负责绘制。

下面是 GridDrawManager 的构造函数，从其参数里可以看出些门道。

mDrawManager = new GridDrawManager(context, mCamera, mDrawables, sDisplayList, sDisplayItems, sDisplaySlots);