Android 播放器SurfaceView播放后(前)清屏 Clear video frame from surfaceview on video complete， 播放开始出现上一次播放的残留画面

Android MediaPlayer某些播放场景下，由于SurfaceView的使用方式的问题，可能遇到 播放开始出现上一次播放的残留画面，为此需要在每次播放开始或结束时，对SurfaceView做清屏clear

方式一：  注意可能导致的问题 You can't clear it with Canvas draw commands because that will prevent you from playing movies on that surface again.

Paint paint = new Paint();
paint.setColor(0xff000000);
Canvas canvas = surface.lockCanvas(null);
canvas.drawColor(0x00000000, PorterDuff.Mode.CLEAR);
canvas.drawRect(0, 0, 0 + canvas.getWidth(), 0 + canvas.getHeight(), paint);
surface.unlockCanvasAndPost(canvas);

使用如下这种方式，lockCanvas后清空再unlockCanvasAndPost，会导致后续播放出问题，也就是如果当前要清空的SurfaceView后续要去作为player的输出surface就不能采用这种方式了

原因：参考 https://stackoverflow.com/questions/24902114/mediaplayer-cannot-render-to-textureview-after-image-render/24914966#24914966

//You can't do this, due to a limitation of the Android app framework (as of //Android 4.4 at least).

//The SurfaceTexture that underlies the TextureView is a buffer consumer. //The MediaPlayer is one example of a buffer producer, Canvas is another. //Once you attach a producer, you have to detach it before you can attach //a second producer.

//The trouble is that there is no way to detach a software-based (Canvas) //buffer producer. There could be, but isn't. So once you draw with Canvas, //you're stuck. (There's a note to that effect here.)

//You can detach a GLES producer. For example, in one of Grafika's video //player classes you can find a clearSurface() method that clears the //surface to black using GLES. Note the EGL context and window are //created and explicitly released within the scope of the method. You could //expand the method to show an image instead.

方式二：使用GLES 来清除

https://stackoverflow.com/questions/25660994/clear-video-frame-from-surfaceview-on-video-complete

https://github.com/autumnqin/grafika/blob/master/src/com/android/grafika/PlayMovieSurfaceActivity.java

直接上代码：自己体会哈哈哈

import android.opengl.EGL14;
import android.opengl.EGLConfig;
import android.opengl.EGLContext;
import android.opengl.EGLDisplay;
import android.opengl.EGLExt;
import android.opengl.EGLSurface;
import android.opengl.GLES20;

//=====

/**
 * Clears the playback surface to black.
 */
private void clearSurface(Surface surface) {
    EGLDisplay display = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY);
    int[] version = new int[2];
    EGL14.eglInitialize(display, version, 0, version, 1);

    int[] attribList = {
            EGL14.EGL_RED_SIZE, 8,
            EGL14.EGL_GREEN_SIZE, 8,
            EGL14.EGL_BLUE_SIZE, 8,
            EGL14.EGL_ALPHA_SIZE, 8,
            EGL14.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
            EGL14.EGL_NONE, 0,
            EGL14.EGL_NONE
    };
    EGLConfig[] configs = new EGLConfig[1];
    int[] numConfigs = new int[1];
    EGL14.eglChooseConfig(display, attribList, 0, configs, 0, configs.length, numConfigs, 0);

    EGLConfig config = configs[0];
    EGLContext context = EGL14.eglCreateContext(display, config, EGL14.EGL_NO_CONTEXT, new int[]{
            EGL14.EGL_CONTEXT_CLIENT_VERSION, 2,
            EGL14.EGL_NONE
    }, 0);

    EGLSurface eglSurface = EGL14.eglCreateWindowSurface(display, config, surface,
            new int[]{
                EGL14.EGL_NONE
            }, 0);

    EGL14.eglMakeCurrent(display, eglSurface, eglSurface, context);
    GLES20.glClearColor(0, 0, 0, 1);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
    EGL14.eglSwapBuffers(display, eglSurface);
    EGL14.eglDestroySurface(display, eglSurface);
    EGL14.eglMakeCurrent(display, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_CONTEXT);
    EGL14.eglDestroyContext(display, context);
    EGL14.eglTerminate(display);
}

每次播放结束时都销毁SurfaceView 是不会出现上次播放的残留画面的，也就不用考虑清屏了