先看Surface

Surface的官方介紹：Handle onto a raw buffer that is being managed by the screen compositor，Surface是一個(gè)raw buffer的句柄，通過它在raw buffer上進(jìn)行繪制，可以通過Surface獲得一個(gè)Canvas。

Canvas canvas = mSurface.lockCanvas(null); mSurface.unlockCanvasAndPost(canvas);

SurfaceView

SurfaceView對(duì)Surface進(jìn)行了一次封裝，它內(nèi)部幫我們管理了一個(gè)Surface。我們使用SurfaceView其實(shí)最終都是獲取到這個(gè)Surface去繪制，可參看官方解釋：

Provides a dedicated drawing surface embedded inside of a view hierarchy. You can control the format of this surface and, if you like, its size; the SurfaceView takes care of placing the surface at the correct location on the screen

The surface is Z ordered so that it is behind the window holding its SurfaceView; the SurfaceView punches a hole in its window to allow its surface to be displayed. The view hierarchy will take care of correctly compositing with the Surface any siblings of the SurfaceView that would normally appear on top of it. This can be used to place overlays such as buttons on top of the Surface, though note however that it can have an impact on performance since a full alpha-blended composite will be performed each time the Surface changes.

The transparent region that makes the surface visible is based on the layout positions in the view hierarchy. If the post-layout transform properties are used to draw a sibling view on top of the SurfaceView, the view may not be properly composited with the surface.

Access to the underlying surface is provided via the SurfaceHolder interface, which can be retrieved by calling?getHolder().

The Surface will be created for you while the SurfaceView's window is visible; you should implement?SurfaceHolder.Callback#surfaceCreated?and?SurfaceHolder.Callback#surfaceDestroyed?to discover when the Surface is created and destroyed as the window is shown and hidden.

One of the purposes of this class is to provide a surface in which a secondary thread can render into the screen. If you are going to use it this way, you need to be aware of some threading semantics:

• All SurfaceView and?SurfaceHolder.Callback?methods will be called from the thread running the SurfaceView's window (typically the main thread of the application). They thus need to correctly synchronize with any state that is also touched by the drawing thread.
• You must ensure that the drawing thread only touches the underlying Surface while it is valid -- between?SurfaceHolder.Callback.surfaceCreated()?and?SurfaceHolder.Callback.surfaceDestroyed().

繪制過程：

• 通過SurfaceHolder．getSurface可以獲取到Surface；
• 通過Surface.lockCanvas可以獲取到Surface的Canvas；
• 使用Canvas繪制圖像；
• 使用Surface.unlockCanvasAndPost可以釋放Canvas。

GLSurfaceView

GLSurfaceView繼承自SurfaceView，對(duì)SurfaceView又做了一次封裝，方便我們在安卓中使用OpenGL。

GLSurfaceView提供了以下特性：

• 提供并且管理一個(gè)獨(dú)立的Surface；
• 提供并且管理一個(gè)EGL display，它能讓opengl把內(nèi)容渲染到上述的Surface上；
• 支持用戶自定義渲染器(Render)，通過setRenderer設(shè)置一個(gè)自定義的Renderer；
• 讓渲染器在獨(dú)立的GLThread線程里運(yùn)作，和UI線程分離；
• 支持按需渲染(on-demand)和連續(xù)渲染(continuous)兩種模式；
• GPU加速：GLSurfaceView的效率是SurfaceView的30倍以上，SurfaceView使用畫布進(jìn)行繪制，GLSurfaceView利用GPU加速提高了繪制效率；
• View的繪制onDraw(Canvas canvas)使用Skia渲染引擎渲染，而GLSurfaceView的渲染器Renderer的onDrawFrame(GL10 gl)使用opengl繪制引擎進(jìn)行渲染。

參看官方解釋：

An implementation of SurfaceView that uses the dedicated surface for displaying OpenGL rendering.

A GLSurfaceView provides the following features:

• Manages a surface, which is a special piece of memory that can be composited into the Android view system.
• Manages an EGL display, which enables OpenGL to render into a surface.
• Accepts a user-provided Renderer object that does the actual rendering.
• Renders on a dedicated thread to decouple rendering performance from the UI thread.
• Supports both on-demand and continuous rendering.
• Optionally wraps, traces, and/or error-checks the renderer's OpenGL calls.

總結(jié)

除了上述區(qū)別外，SurfaceView通用性更好，GLSurfaceView渲染更細(xì)膩，如果想讓普通的SurfaceView渲染效果更好，可以加抗鋸齒效果，不過抗鋸齒效果會(huì)有一定的性能消耗，硬解碼設(shè)置surface模式的話，直接用普通的SurfaceView。

一般兼容性比較好的播放器，會(huì)同時(shí)支持SurfaceView和GLSurfaceView兩種模式供用戶根據(jù)實(shí)際場景選擇，以大牛直播SDK(Github)的Android平臺(tái)RTSP和RTMP播放端為例：

/* Create rendering */private boolean CreateView() {if (sSurfaceView == null) {Log.i(TAG, "CreateView..");String manufacturer = Build.MANUFACTURER;Log.i(TAG, "CreateView, current manufacturer: " + manufacturer);if (is_enable_hardware_render_mode) {//hardware render模式，第二個(gè)參數(shù)設(shè)置為falsesSurfaceView = NTRenderer.CreateRenderer(this, false);} else {//這個(gè)字符串可以自己定義,例如判斷華為就填寫huawei,魅族就填寫meizuif ("huawei".equalsIgnoreCase(manufacturer)) {sSurfaceView = NTRenderer.CreateRenderer(this, true);} else {/** useOpenGLES2: If with true: Check if system supports openGLES, if* supported, it will choose openGLES. If with false: it will set* with default surfaceView;*/sSurfaceView = NTRenderer.CreateRenderer(this, true);}}}if (sSurfaceView == null) {Log.i(TAG, "Create render failed..");return false;}if (is_enable_hardware_render_mode) {SurfaceHolder surfaceHolder = sSurfaceView.getHolder();if (surfaceHolder == null) {Log.e(TAG, "CreateView, surfaceHolder with null..");}surfaceHolder.addCallback(this);}return true;}

感興趣的開發(fā)者可以參考官方文檔。

總結(jié)

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