网页网站设计培训班,seo排名优化哪家好,广东省医院建设协会网站首页,中华企业网站建设Android VirtualDisplay创建流程及原理
Android DisplayManager提供了createVirtualDisplay接口#xff0c;用于创建虚拟屏。虚拟屏可用于录屏#xff08;网上很多资料说这个功能#xff09;#xff0c;分屏幕#xff08;比如一块很长的屏幕#xff0c;通过虚拟屏分出不…Android VirtualDisplay创建流程及原理
Android DisplayManager提供了createVirtualDisplay接口用于创建虚拟屏。虚拟屏可用于录屏网上很多资料说这个功能分屏幕比如一块很长的屏幕通过虚拟屏分出不同的区域等等。
创建VirtualDisplay
DisplayManager中的函数原型如下。后两个Hide的API只有平台的应用才可以使用。
// frameworks/base/core/java/android/hardware/display/DisplayManager.java
public VirtualDisplay createVirtualDisplay(NonNull String name,int width, int height, int densityDpi, Nullable Surface surface, int flags) {
}public VirtualDisplay createVirtualDisplay(NonNull String name,int width, int height, int densityDpi, Nullable Surface surface, int flags,Nullable VirtualDisplay.Callback callback, Nullable Handler handler) {
}
/** hide */
public VirtualDisplay createVirtualDisplay(Nullable MediaProjection projection,NonNull String name, int width, int height, int densityDpi, Nullable Surface surface,int flags, Nullable VirtualDisplay.Callback callback, Nullable Handler handler,Nullable String uniqueId) {
}
/** hide */
public VirtualDisplay createVirtualDisplay(Nullable MediaProjection projection,NonNull VirtualDisplayConfig virtualDisplayConfig,Nullable VirtualDisplay.Callback callback, Nullable Handler handler) {
}补充一点MediaProjection中也提供了 createVirtualDisplay这个接口实际上也是通过调用DisplayManager实现的功能。 // frameworks/base/media/java/android/media/projection/MediaProjection.javapublic VirtualDisplay createVirtualDisplay(NonNull VirtualDisplayConfig virtualDisplayConfig,Nullable VirtualDisplay.Callback callback, Nullable Handler handler) {DisplayManager dm mContext.getSystemService(DisplayManager.class);// 调用DisplayManager的接口return dm.createVirtualDisplay(this, virtualDisplayConfig, callback, handler);}创建VirtualDisplay时需要传入Surface。**VirtualDisplay上要绘制的内容实际是通过传入的Surface显示出来的。**比如在主屏根据物理屏分配逻辑Display上创建了一个SurfaceView通过把这个SurfaceView传给VirtualDisplay。那么VirtualDisplay的 内容实际上是在主屏的SurfaceView上显示的。下面是一段Android原生的例子。
// frameworks/base/packages/SystemUI/tests/src/com/android/systemui/navigationbar/NavigationBarButtonTest.java
private Display createVirtualDisplay() {final String displayName NavVirtualDisplay;final DisplayInfo displayInfo new DisplayInfo();mContext.getDisplay().getDisplayInfo(displayInfo);final DisplayManager displayManager mContext.getSystemService(DisplayManager.class);// 创建ImageReader通过它得到一张SurfacemReader ImageReader.newInstance(displayInfo.logicalWidth,displayInfo.logicalHeight, PixelFormat.RGBA_8888, 2);assertNotNull(ImageReader must not be null, mReader);// 创建虚拟屏传入Surface。mVirtualDisplay displayManager.createVirtualDisplay(displayName, displayInfo.logicalWidth,displayInfo.logicalHeight, displayInfo.logicalDensityDpi, mReader.getSurface(),0 /*flags*/);assertNotNull(virtual display must not be null, mVirtualDisplay);waitForDisplayReady(mVirtualDisplay.getDisplay().getDisplayId());return mVirtualDisplay.getDisplay();
}上面的例子中创建虚拟屏返回Display实际上是VirtualDislay对象。有了Display对象我们就可以将View绑定到这个虚拟的Display上了绑定网上方法比较多可自行搜索。关于Surface的创建有很多种方法比如通过SurfaceContronBuffer这种方式也可以。VituralDisplay创建时需要提供flag。其值定义如下可通过 “或”将flag组合。 public static final int VIRTUAL_DISPLAY_FLAG_PUBLIC 1 0;public static final int VIRTUAL_DISPLAY_FLAG_PRESENTATION 1 1;public static final int VIRTUAL_DISPLAY_FLAG_SECURE 1 2;public static final int VIRTUAL_DISPLAY_FLAG_OWN_CONTENT_ONLY 1 3;public static final int VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR 1 4;public static final int VIRTUAL_DISPLAY_FLAG_CAN_SHOW_WITH_INSECURE_KEYGUARD 1 5;public static final int VIRTUAL_DISPLAY_FLAG_SUPPORTS_TOUCH 1 6;public static final int VIRTUAL_DISPLAY_FLAG_ROTATES_WITH_CONTENT 1 7;public static final int VIRTUAL_DISPLAY_FLAG_DESTROY_CONTENT_ON_REMOVAL 1 8;public static final int VIRTUAL_DISPLAY_FLAG_SHOULD_SHOW_SYSTEM_DECORATIONS 1 9;public static final int VIRTUAL_DISPLAY_FLAG_TRUSTED 1 10;public static final int VIRTUAL_DISPLAY_FLAG_OWN_DISPLAY_GROUP 1 11;DisplayManager公开的接口中有VirtualDisplay.Callback 提供了其状态的回调。 public static abstract class Callback {/*** Called when the virtual display video projection has been* paused by the system or when the surface has been detached* by the application by calling setSurface(null).* The surface will not receive any more buffers while paused.*/public void onPaused() { }/*** Called when the virtual display video projection has been* resumed after having been paused.*/public void onResumed() { }/*** Called when the virtual display video projection has been* stopped by the system. It will no longer receive frames* and it will never be resumed. It is still the responsibility* of the application to release() the virtual display.*/public void onStopped() { }}VirtualDisplay原理
关于VirtualDisplay的实现原理主要从AndroidFramework角度进行分析。
// /frameworks/base/core/java/android/hardware/display/DisplayManager.java
public VirtualDisplay createVirtualDisplay(NonNull String name,int width, int height, int densityDpi, Nullable Surface surface, int flags) {return createVirtualDisplay(name, width, height, densityDpi, surface, flags, null, null);
}public VirtualDisplay createVirtualDisplay(NonNull String name,int width, int height, int densityDpi, Nullable Surface surface, int flags,Nullable VirtualDisplay.Callback callback, Nullable Handler handler) {final VirtualDisplayConfig.Builder builder new VirtualDisplayConfig.Builder(name, width,height, densityDpi);builder.setFlags(flags);if (surface ! null) {builder.setSurface(surface);}return createVirtualDisplay(null /* projection */, builder.build(), callback, handler);
}// TODO : Remove this hidden API after remove all callers. (Refer to MultiDisplayService)
/** hide */
public VirtualDisplay createVirtualDisplay(Nullable MediaProjection projection,NonNull String name, int width, int height, int densityDpi, Nullable Surface surface,int flags, Nullable VirtualDisplay.Callback callback, Nullable Handler handler,Nullable String uniqueId) {final VirtualDisplayConfig.Builder builder new VirtualDisplayConfig.Builder(name, width,height, densityDpi);builder.setFlags(flags);if (uniqueId ! null) {builder.setUniqueId(uniqueId);}if (surface ! null) {builder.setSurface(surface);}return createVirtualDisplay(projection, builder.build(), callback, handler);
}/** hide */
public VirtualDisplay createVirtualDisplay(Nullable MediaProjection projection,NonNull VirtualDisplayConfig virtualDisplayConfig,Nullable VirtualDisplay.Callback callback, Nullable Handler handler) {// 走的这里会调用到DisplayManagerGlobal中。return mGlobal.createVirtualDisplay(mContext, projection, virtualDisplayConfig, callback,handler);
}DisplayManagerGlobal调用DMSDisplayManagerService服务创建虚拟屏得到DMS返回的DisplayID后通过DisplayID在Client端创建了VirtualDisplay对象。
// /frameworks/base/core/java/android/hardware/display/DisplayManager.java
public VirtualDisplay createVirtualDisplay(NonNull Context context, MediaProjection projection,NonNull VirtualDisplayConfig virtualDisplayConfig, VirtualDisplay.Callback callback,Handler handler) {VirtualDisplayCallback callbackWrapper new VirtualDisplayCallback(callback, handler);// 从MediaProjection过来的调用这个地方非空。IMediaProjection projectionToken projection ! null ? projection.getProjection() : null;int displayId;try {// 告知DMS创建虚拟屏并返回DisplayIDdisplayId mDm.createVirtualDisplay(virtualDisplayConfig, callbackWrapper,projectionToken, context.getPackageName());} catch (RemoteException ex) {throw ex.rethrowFromSystemServer();}if (displayId 0) {Log.e(TAG, Could not create virtual display: virtualDisplayConfig.getName());return null;}// 通过DisplayID取得Display对象信息也是调用DMS得到的Display display getRealDisplay(displayId);if (display null) {Log.wtf(TAG, Could not obtain display info for newly created virtual display: virtualDisplayConfig.getName());try {// 创建失败需要释放mDm.releaseVirtualDisplay(callbackWrapper);} catch (RemoteException ex) {throw ex.rethrowFromSystemServer();}return null;}// 创建VirtualDisplayreturn new VirtualDisplay(this, display, callbackWrapper,virtualDisplayConfig.getSurface());
}DisplayManagerService(DMS)中创建DisplayDevice并添加到Device列表中管理
// /frameworks/base/services/core/java/com/android/server/display/DisplayManagerService.java
Override // Binder call
public int createVirtualDisplay(VirtualDisplayConfig virtualDisplayConfig,IVirtualDisplayCallback callback, IMediaProjection projection, String packageName) {// 检查uid与包名是否相符。final int callingUid Binder.getCallingUid();if (!validatePackageName(callingUid, packageName)) {throw new SecurityException(packageName must match the calling uid);}if (callback null) {throw new IllegalArgumentException(appToken must not be null);}if (virtualDisplayConfig null) {throw new IllegalArgumentException(virtualDisplayConfig must not be null);}// 拿到client端传过来的surface对象final Surface surface virtualDisplayConfig.getSurface();int flags virtualDisplayConfig.getFlags();if (surface ! null surface.isSingleBuffered()) {throw new IllegalArgumentException(Surface cant be single-buffered);}// 下面开始针对Flag做一些逻辑判断。if ((flags VIRTUAL_DISPLAY_FLAG_PUBLIC) ! 0) {flags | VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR;// Public displays cant be allowed to show content when locked.if ((flags VIRTUAL_DISPLAY_FLAG_CAN_SHOW_WITH_INSECURE_KEYGUARD) ! 0) {throw new IllegalArgumentException(Public display must not be marked as SHOW_WHEN_LOCKED_INSECURE);}}if ((flags VIRTUAL_DISPLAY_FLAG_OWN_CONTENT_ONLY) ! 0) {flags ~VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR;}if ((flags VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR) ! 0) {flags ~VIRTUAL_DISPLAY_FLAG_OWN_DISPLAY_GROUP;}if (projection ! null) {try {if (!getProjectionService().isValidMediaProjection(projection)) {throw new SecurityException(Invalid media projection);}flags projection.applyVirtualDisplayFlags(flags);} catch (RemoteException e) {throw new SecurityException(unable to validate media projection or flags);}}if (callingUid ! Process.SYSTEM_UID (flags VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR) ! 0) {if (!canProjectVideo(projection)) {throw new SecurityException(Requires CAPTURE_VIDEO_OUTPUT or CAPTURE_SECURE_VIDEO_OUTPUT permission, or an appropriate MediaProjection token in order to create a screen sharing virtual display.);}}if (callingUid ! Process.SYSTEM_UID (flags VIRTUAL_DISPLAY_FLAG_SECURE) ! 0) {if (!canProjectSecureVideo(projection)) {throw new SecurityException(Requires CAPTURE_SECURE_VIDEO_OUTPUT or an appropriate MediaProjection token to create a secure virtual display.);}}if (callingUid ! Process.SYSTEM_UID (flags VIRTUAL_DISPLAY_FLAG_TRUSTED) ! 0) {if (!checkCallingPermission(ADD_TRUSTED_DISPLAY, createVirtualDisplay())) {EventLog.writeEvent(0x534e4554, 162627132, callingUid,Attempt to create a trusted display without holding permission!);throw new SecurityException(Requires ADD_TRUSTED_DISPLAY permission to create a trusted virtual display.);}}if (callingUid ! Process.SYSTEM_UID (flags VIRTUAL_DISPLAY_FLAG_OWN_DISPLAY_GROUP) ! 0) {if (!checkCallingPermission(ADD_TRUSTED_DISPLAY, createVirtualDisplay())) {throw new SecurityException(Requires ADD_TRUSTED_DISPLAY permission to create a virtual display which is not in the default DisplayGroup.);}}if ((flags VIRTUAL_DISPLAY_FLAG_TRUSTED) 0) {flags ~VIRTUAL_DISPLAY_FLAG_SHOULD_SHOW_SYSTEM_DECORATIONS;}// Sometimes users can have sensitive information in system decoration windows. An app// could create a virtual display with system decorations support and read the user info// from the surface.// We should only allow adding flag VIRTUAL_DISPLAY_FLAG_SHOULD_SHOW_SYSTEM_DECORATIONS// to trusted virtual displays.final int trustedDisplayWithSysDecorFlag (VIRTUAL_DISPLAY_FLAG_SHOULD_SHOW_SYSTEM_DECORATIONS| VIRTUAL_DISPLAY_FLAG_TRUSTED);if ((flags trustedDisplayWithSysDecorFlag) VIRTUAL_DISPLAY_FLAG_SHOULD_SHOW_SYSTEM_DECORATIONS !checkCallingPermission(INTERNAL_SYSTEM_WINDOW, createVirtualDisplay())) {throw new SecurityException(Requires INTERNAL_SYSTEM_WINDOW permission);}final long token Binder.clearCallingIdentity();try {// 调用内部实现return createVirtualDisplayInternal(callback, projection, callingUid, packageName,surface, flags, virtualDisplayConfig);} finally {Binder.restoreCallingIdentity(token);}
}// /frameworks/base/services/core/java/com/android/server/display/DisplayManagerService.java
private int createVirtualDisplayInternal(IVirtualDisplayCallback callback,IMediaProjection projection, int callingUid, String packageName, Surface surface,int flags, VirtualDisplayConfig virtualDisplayConfig) {synchronized (mSyncRoot) {if (mVirtualDisplayAdapter null) {Slog.w(TAG, Rejecting request to create private virtual display because the virtual display adapter is not available.);return -1;}// 为虚拟屏创建Device告知surfaceflinger创建DisplayDisplayDevice device mVirtualDisplayAdapter.createVirtualDisplayLocked(callback, projection, callingUid, packageName, surface, flags,virtualDisplayConfig);if (device null) {return -1;}// 发送添加Device通知这里比较重要mDisplayDeviceRepo.onDisplayDeviceEvent(device,DisplayAdapter.DISPLAY_DEVICE_EVENT_ADDED);// 检查Display是否创建成功final LogicalDisplay display mLogicalDisplayMapper.getDisplayLocked(device);if (display ! null) {return display.getDisplayIdLocked();}// Something weird happened and the logical display was not created.Slog.w(TAG, Rejecting request to create virtual display because the logical display was not created.);mVirtualDisplayAdapter.releaseVirtualDisplayLocked(callback.asBinder());mDisplayDeviceRepo.onDisplayDeviceEvent(device,DisplayAdapter.DISPLAY_DEVICE_EVENT_REMOVED);}return -1;
}接下来DMS开始调用SurfaceFlinger的接口创建Display。并将Display放入自身的List中管理。
// /frameworks/base/services/core/java/com/android/server/display/VirtualDisplayAdapter.java
public DisplayDevice createVirtualDisplayLocked(IVirtualDisplayCallback callback,IMediaProjection projection, int ownerUid, String ownerPackageName, Surface surface,int flags, VirtualDisplayConfig virtualDisplayConfig) {String name virtualDisplayConfig.getName();// VIRTUAL_DISPLAY_FLAG_SECURE 的用途是判断是否为安全的Display这个参数会告知SurfaceFlingerboolean secure (flags VIRTUAL_DISPLAY_FLAG_SECURE) ! 0;IBinder appToken callback.asBinder();// 调用SurfaceFligner创建DisplayDisplay的type是virtualIBinder displayToken mSurfaceControlDisplayFactory.createDisplay(name, secure);final String baseUniqueId UNIQUE_ID_PREFIX ownerPackageName , ownerUid , name ,;final int uniqueIndex getNextUniqueIndex(baseUniqueId);String uniqueId virtualDisplayConfig.getUniqueId();if (uniqueId null) {uniqueId baseUniqueId uniqueIndex;} else {uniqueId UNIQUE_ID_PREFIX ownerPackageName : uniqueId;}// 通过SurfaceFligner返回的displayToken创建Device对象VirtualDisplayDevice device new VirtualDisplayDevice(displayToken, appToken,ownerUid, ownerPackageName, surface, flags, new Callback(callback, mHandler),uniqueId, uniqueIndex, virtualDisplayConfig);// 放到虚拟屏的List中管理。mVirtualDisplayDevices.put(appToken, device);try {if (projection ! null) {projection.registerCallback(new MediaProjectionCallback(appToken));}appToken.linkToDeath(device, 0);} catch (RemoteException ex) {mVirtualDisplayDevices.remove(appToken);device.destroyLocked(false);return null;}// Return the display device without actually sending the event indicating// that it was added. The caller will handle it.return device;
}// /frameworks/base/services/core/java/com/android/server/display/DisplayDeviceRepository.java
// mDisplayDeviceRepo.onDisplayDeviceEvent(device,
// DisplayAdapter.DISPLAY_DEVICE_EVENT_ADDED);
// 这段代码会调用到下面的函数中。
private void handleDisplayDeviceAdded(DisplayDevice device) {synchronized (mSyncRoot) {DisplayDeviceInfo info device.getDisplayDeviceInfoLocked();if (mDisplayDevices.contains(device)) {Slog.w(TAG, Attempted to add already added display device: info);return;}Slog.i(TAG, Display device added: info);device.mDebugLastLoggedDeviceInfo info;// 需要是将Device就是上面创建的虚拟屏幕Device放入到DMS的管理listmDisplayDevices.add(device);// 通知Device添加会调用到LogicalDisplayMappe的handleDisplayDeviceAddedLocked中。sendEventLocked(device, DISPLAY_DEVICE_EVENT_ADDED);}
}
// /frameworks/base/services/core/java/com/android/server/display/LogicalDisplayMapper.java
private void handleDisplayDeviceAddedLocked(DisplayDevice device) {DisplayDeviceInfo deviceInfo device.getDisplayDeviceInfoLocked();// Internal Displays need to have additional initialization.// This initializes a default dynamic display layout for INTERNAL// devices, which is used as a fallback in case no static layout definitions// exist or cannot be loaded.if (deviceInfo.type Display.TYPE_INTERNAL) {initializeInternalDisplayDeviceLocked(device);}// Create a logical display for the new display deviceLogicalDisplay display createNewLogicalDisplayLocked(device, Layout.assignDisplayIdLocked(false /*isDefault*/));// 刷新布局和display配置applyLayoutLocked();updateLogicalDisplaysLocked();
}虚拟屏幕的创建Client端通过Surface告知的DisplayID创建VirtualDisplay对象。通过DisplayID与DMS打交道。DMS服务端通过SurfaceFlinger创建虚拟屏拿到SurfaceFligner的DisplayToken然后通过它创建VirtualDisplayDevice LogicalDisplay来管理虚拟屏幕。
如何上屏
创建虚拟屏幕的时候会传入了一张Surface比如绑定主屏的一张Buffer。虚拟屏通过这张Surface拿到Surface对应的Buffer将上屏内容绘制到这个Buffer上然后提交到画面流水线上SurfaceFlinger。通过SurfaceFlinger将这个这个Buffer最终由SurfaceFlinger描画并显示到Surface所在那张Display上根据VirtualDisplay位置去显示。
