今天遇到一个android系统在切换横竖屏时一直卡着不动，大概3秒以后才能转过来的问题。最后定位到是由于ScreenRotationAnimation类的构造函数调用了
SurfaceControl.screenshot(SurfaceControl.getBuiltInDisplay(
SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN), sur);
进行截屏导致的。
截屏函数最终是由SurfaceFlinger完成的。在surfaceflinger中加入日志调试。
nsecs_t st = systemTime();
result = flinger->captureScreenImplLocked(hw,
producer, reqWidth, reqHeight, minLayerZ, maxLayerZ);
nsecs_t et = systemTime();
ALOGI("surfaceflinger captureScreenImplLocked use time:%dms", (int)ns2ms(et - st));
得到以下输出：
03-11 14:12:44.550 2259-2797/? W/ScreenRotationAnimation: SurfaceControl.screenshot use 3142ms
03-11 14:13:01.950 2259-2669/? W/ScreenRotationAnimation: SurfaceControl.screenshot use 3282ms
03-11 14:23:26.250 2259-2669/? W/ScreenRotationAnimation: SurfaceControl.screenshot use 3176ms
03-11 14:23:36.790 2259-2668/? W/ScreenRotationAnimation: SurfaceControl.screenshot use 3239ms
为什么需要这么长时间？
最后研究发现这个时间跟SurfaceView的数量还有关系，每多一个SurfaceView截屏时间就多个500到600毫秒，我的界面总共添加了3个SurfaceView，所以截屏时间花了3秒。
如果一个SurfaceView都不添加，截屏只需要花费大概600毫秒的时间。
看了一眼captureScreenImplLocked这个函数的实现，发现这个函数很神奇，只调用了几个GL函数，截屏就完成了。
status_t SurfaceFlinger::captureScreenImplLocked(
const sp<const DisplayDevice>& hw,
const sp<IGraphicBufferProducer>& producer,
uint32_t reqWidth, uint32_t reqHeight,
uint32_t minLayerZ, uint32_t maxLayerZ)
{
ATRACE_CALL();
// get screen geometry
const uint32_t hw_w = hw->getWidth();
const uint32_t hw_h = hw->getHeight();
// if we have secure windows on this display, never allow the screen capture
if (hw->getSecureLayerVisible()) {
ALOGW("FB is protected: PERMISSION_DENIED");
return PERMISSION_DENIED;
}
if ((reqWidth > hw_w) || (reqHeight > hw_h)) {
ALOGE("size mismatch (%d, %d) > (%d, %d)",
reqWidth, reqHeight, hw_w, hw_h);
return BAD_VALUE;
}
reqWidth = (!reqWidth) ? hw_w : reqWidth;
reqHeight = (!reqHeight) ? hw_h : reqHeight;
// Create a surface to render into
sp<Surface> surface = new Surface(producer);
ANativeWindow* const window = surface.get();
// set the buffer size to what the user requested
native_window_set_buffers_user_dimensions(window, reqWidth, reqHeight);
// and create the corresponding EGLSurface
EGLSurface eglSurface = eglCreateWindowSurface(
mEGLDisplay, mEGLConfig, window, NULL);
if (eglSurface == EGL_NO_SURFACE) {
ALOGE("captureScreenImplLocked: eglCreateWindowSurface() failed 0x%4x",
eglGetError());
return BAD_VALUE;
}
if (!eglMakeCurrent(mEGLDisplay, eglSurface, eglSurface, mEGLContext)) {
ALOGE("captureScreenImplLocked: eglMakeCurrent() failed 0x%4x",
eglGetError());
eglDestroySurface(mEGLDisplay, eglSurface);
return BAD_VALUE;
}
renderScreenImplLocked(hw, reqWidth, reqHeight, minLayerZ, maxLayerZ, false);
// and finishing things up...
if (eglSwapBuffers(mEGLDisplay, eglSurface) != EGL_TRUE) {
ALOGE("captureScreenImplLocked: eglSwapBuffers() failed 0x%4x",
eglGetError());
eglDestroySurface(mEGLDisplay, eglSurface);
getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
return BAD_VALUE;
}
eglDestroySurface(mEGLDisplay, eglSurface);
getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
return NO_ERROR;
}
不明觉厉，这个函数我是改不了了，不过还好我们这个设备是墨水屏，刷新特别慢，在旋转时不需要动画，可以想办法去掉动画，这样就不用调用截屏函数了。
首先打印一下调用堆栈，看看谁调用的截屏函数。
try {
throw new Exception();
} catch(Exception e) {
e.printStackTrace();
}
long st = System.currentTimeMillis(); SurfaceControl.screenshot(SurfaceControl.getBuiltInDisplay(
SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN), sur);
long et = System.currentTimeMillis();
Slog.w(TAG, "SurfaceControl.screenshot use " + (et - st) + "ms");
得到以下输出：
03-11 14:27:39.840 2259-2439/? W/System.err: java.lang.Exception
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.ScreenRotationAnimation.<init>(ScreenRotationAnimation.java:260)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.WindowManagerService.startFreezingDisplayLocked(WindowManagerService.java:9945)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.WindowManagerService.updateRotationUncheckedLocked(WindowManagerService.java:5960)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.WindowManagerService.updateOrientationFromAppTokensLocked(WindowManagerService.java:3708)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.WindowManagerService.updateOrientationFromAppTokensLocked(WindowManagerService.java:3645)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.wm.WindowManagerService.updateOrientationFromAppTokens(WindowManagerService.java:3633)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.am.ActivityManagerService.setRequestedOrientation(ActivityManagerService.java:3596)
03-11 14:27:39.840 2259-2439/? W/System.err: at android.app.ActivityManagerNative.onTransact(ActivityManagerNative.java:955)
03-11 14:27:39.840 2259-2439/? W/System.err: at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:2084)
03-11 14:27:39.840 2259-2439/? W/System.err: at android.os.Binder.execTransact(Binder.java:404)
03-11 14:27:39.850 2259-2439/? W/System.err: at dalvik.system.NativeStart.run(Native Method)
根据日志查看WindowManagerService.java 9945行附近，有如下代码：
if (CUSTOM_SCREEN_ROTATION) {
mExitAnimId = exitAnim;
mEnterAnimId = enterAnim;
final DisplayContent displayContent = getDefaultDisplayContentLocked();
final int displayId = displayContent.getDisplayId();
ScreenRotationAnimation screenRotationAnimation =
mAnimator.getScreenRotationAnimationLocked(displayId);
if (screenRotationAnimation != null) {
screenRotationAnimation.kill();
}
// TODO(multidisplay): rotation on main screen only.
screenRotationAnimation = new ScreenRotationAnimation(mContext, displayContent,
mFxSession, inTransaction, mPolicy.isDefaultOrientationForced());
mAnimator.setScreenRotationAnimationLocked(displayId, screenRotationAnimation);
}
重点是if (CUSTOM_SCREEN_ROTATION) {判断条件，再搜索一下CUSTOM_SCREEN_ROTATION变量，发现只有一个初始值，中间没有任何赋值的地方。
/**
* If true, the window manager will do its own custom freezing and general
* management of the screen during rotation.
*/
static final boolean CUSTOM_SCREEN_ROTATION = true;
既然是这样，把CUSTOM_SCREEN_ROTATION 修改为false试试效果看。
哇！果然很快，就是效果有点儿差，能看得见黑屏。