概述

Android实现双屏异显的实现方式有2种。

方式一：在Android4.2及以上平台上，按照标准Android SDK提供的API，使用Presentation类，将一个APP的相关内容显示到指定的屏幕上，具体请参考https://developer.android.com/reference/android/app/Presentation.html。这种方式实现的是应用内的异显，也是View级别的异显。

方式二：通过修改Framework层的am,wm,display相关代码，从而在不同的显示设备上运行不同的应用，这种多任务的双屏异显方法实现了不同应用之间的异显，本文重点讲解这种双屏异显方法的实现方式。这种实现方式是基于某芯片厂商系列芯片，Android 6.0平台开发的。

这需要解决如下几个问题:

1.如何获取所有的TaskID?

在IActivityManager.java添加接口，public List getAllTaskIds() throws RemoteException。

ActivityManagerNative.java种实现了IActivityManger接口，具体实现如下：

@Override

public List getAllTaskIds() throws RemoteException{

List taskIds = new ArrayList();

List stackInfos = getAllStackInfos();

if(stackInfos != null && stackInfos.size() > 0){

for(StackInfo info : stackInfos){

int[] taskIdArray = info.taskIds;

reverseArray(taskIdArray);

if(taskIdArray != null && taskIdArray.length > 0){

for(int taskId : taskIdArray)

taskIds.add(taskId);

}

}

}

return taskIds;

}

2.如何确保两个应用同时运行，同时保持Resume状态？如何确保副屏Activity不会随着主屏应用同时销毁？在ActivityStack.java下activityPausedLocked方法添加如下代码：

if(r.task != null && r.task.taskId == mService.getSecondDisplayTaskId())

return;

上述代码禁止副屏应用进入Pased状态，副屏应用将一直保持Resume状态

3.主屏与副屏的应用如何切换，同显与异显如何切换?这是通过操作主屏与副屏的窗口实现的，WindowManagerService.java添加如下代码:

public void setOnlyShowInExtendDisplay(Session session,IWindow client,int transit){

long origId = Binder.clearCallingIdentity();

synchronized(mWindowMap){

if(mDisplayContents == null || mDisplayContents.size() <= 1){

return;

}

final int displayCount = mDisplayContents.size();

DisplayContent defaultContent = getDefaultDisplayContentLocked();

int displayId = 0;

DisplayContent secondDisplayContent = null;

for(int i = 0; i < displayCount;i++){

final DisplayContent content = mDisplayContents.valueAt(i);

if(content != defaultContent){

secondDisplayContent = content;

displayId = secondDisplayContent.getDisplayId();

break;

}

}

if(secondDisplayContent == null){

return;

}

if(!okToDisplay()){

return;

}

WindowState current = windowForClientLocked(session, client, false);

if(isHomeWindow(current)){

return;

}

AppWindowToken wtoken = current.mAppToken;

if(wtoken == null){

return;

}

int groupId = wtoken.mTask.mTaskId;

mH.sendMessage(mH.obtainMessage(H.DO_TASK_DISPLAY_CHANGED, groupId, -1));

}

Binder.restoreCallingIdentity(origId);

}

/**

move window to second display

*/

public void moveTransitionToSecondDisplay(int groupId,int transit){

//if(!isShowDualScreen()){

//    mSecondTaskIds.clear();

//}

//Settings.System.putInt(mContext.getContentResolver(), Settings.DUAL_SCREEN_ICON_USED, 0);

List allTaskIds = null;

try{

allTaskIds = mActivityManager.getAllTaskIds();

}catch (Exception e){

Log.i("DualScreen", "WindowManagerService->getAllTaskIds->e:" + e);

}

if(allTaskIds == null || allTaskIds.size() < 2)

return;

if(isShowDualScreen()){

moveWindowToSecondDisplayWithDualShow();

return;

}

long origId = Binder.clearCallingIdentity();

int curMoveTaskId = -1;

synchronized(mWindowMap){

if(mDisplayContents == null || mDisplayContents.size() <= 1){

return;

}

final int displayCount = mDisplayContents.size();

DisplayContent defaultContent = getDefaultDisplayContentLocked();

int displayId = 0;

DisplayContent secondDisplayContent = null;

for(int i = 0; i < displayCount;i++){

final DisplayContent content = mDisplayContents.valueAt(i);

if(content != defaultContent){

secondDisplayContent = content;

displayId = secondDisplayContent.getDisplayId();

break;

}

}

if(secondDisplayContent == null){

return;

}

if(!okToDisplay()){

return;

}

SurfaceControl.openTransaction();

WindowState win = null;

WindowList defaultWindows = defaultContent.getWindowList();

try{

WindowList secondDisplayAddList = new WindowList();

WindowList secondDisplayWindows = secondDisplayContent.getWindowList();

int topTaskId = -1;

if(allTaskIds != null && allTaskIds.size() > 0){

topTaskId = allTaskIds.get(0);

//mSecondTaskIds.add(topTaskId);

}

for(int i= defaultWindows.size()-1;i>=0;i--){

win = defaultWindows.get(i);

if(win == null){

continue;

}

if (win.mAppToken == null){

continue;

}

if(win.mAppToken.mTask == null){

continue;

}

int windowTaskId = win.mAppToken.mTask.mTaskId;

if(windowTaskId == topTaskId){

win.setPrimaryDisplay(true);

defaultWindows.remove(win);

mTempWindowList.add(win);

win.mDisplayContent = secondDisplayContent;

if(win.mWinAnimator != null){

int layerStack = secondDisplayContent.getDisplay().getLayerStack();

if(win.mWinAnimator.mSurfaceControl!= null){

win.mWinAnimator.mSurfaceControl.setLayerStack(layerStack);

}

}

secondDisplayAddList.add(0,win);

}

}

secondDisplayWindows.clear();

secondDisplayWindows.addAll(secondDisplayAddList);

for (int i = 0; i < displayCount; i++) {

final DisplayContent content = mDisplayContents.valueAt(i);

assignLayersLocked(content.getWindowList());

content.layoutNeeded = true;

}

Log.i("DualScreen", "WindowManagerService->allTaskIds:" + allTaskIds);

ArrayList allStacks = getAllStacks();

Log.i("DualScreen", "moveTransitionToSecondDisplay->allStacks:" + allStacks);

boolean isFind = false;

for(int i = allStacks.size() - 1; i >= 0; --i){

ActivityStack itemStack = allStacks.get(i);

//ArrayList getAllTasks()

List itemTasks = itemStack.getAllTasks();

if(itemTasks != null && itemTasks.size() > 0){

for(int k = itemTasks.size() - 1; k >= 0; --k){

TaskRecord itemTask = itemTasks.get(k);

List itemActivities = itemTask.mActivities;

for(int j = itemActivities.size() - 1; j >= 0; --j){

ActivityRecord itemActivity = itemActivities.get(j);

if(/*itemActivity.state == ActivityState.RESUMED && */itemTask.taskId != topTaskId){

curMoveTaskId = itemTask.taskId;

isFind = true;

break;

}

}

if(isFind)

break;

}

}

if(isFind)

break;

}

mSecondDisplayTaskId = topTaskId;

Log.i("DualScreen", "WindowManagerService->curMoveTaskId:" + curMoveTaskId);

misMovingToSecond = true;

Settings.System.putInt(mContext.getContentResolver(), Settings.DUAL_SCREEN_ICON_USED, 1);

switchFocusWindow(curMoveTaskId);

updateFocusedWindowLocked(UPDATE_FOCUS_WILL_PLACE_SURFACES, false);

mAppTransition.setReady();

performLayoutAndPlaceSurfacesLocked();

}finally{

SurfaceControl.closeTransaction();

}

//shouldAppMoveBack(-1);

}

Binder.restoreCallingIdentity(origId);

}

public void moveWindowToSecondDisplayWithDualShow(){

long origId = Binder.clearCallingIdentity();

int secondDisplayTaskId = getSecondDisplayTaskId();

int currentFocusedTaskId = -1;

int curMoveTaskId = secondDisplayTaskId;

if(mFocusedApp != null && mFocusedApp.mTask != null)

currentFocusedTaskId = mFocusedApp.mTask.mTaskId;

Log.i("DualScreen", "WindowManagerService->moveWindowToSecondDisplayWithDualShow->currentFocusedTaskId:" + currentFocusedTaskId);

//mSecondDisplayTaskId = currentFocusedTaskId;

synchronized(mWindowMap){

if(mDisplayContents == null || mDisplayContents.size() <= 1){

return;

}

final int displayCount = mDisplayContents.size();

DisplayContent defaultContent = getDefaultDisplayContentLocked();

int displayId = 0;

DisplayContent secondDisplayContent = null;

for(int i = 0; i < displayCount;i++){

final DisplayContent content = mDisplayContents.valueAt(i);

if(content != defaultContent){

secondDisplayContent = content;

displayId = secondDisplayContent.getDisplayId();

Log.d("DualScreen", "WindowManagerService->moveWindowToSecondDisplayWithDualShow->secondDisplayId:" + displayId);

break;

}

}

if(secondDisplayContent == null){

return;

}

if(!okToDisplay()){

return;

}

SurfaceControl.openTransaction();

WindowState win = null;

try{

WindowList secondDisplayAddList = new WindowList();

WindowList defaultDisplayAddList = new WindowList();

WindowList secondDisplayWindows = secondDisplayContent.getWindowList();

WindowList defaultWindows = defaultContent.getWindowList();

if(mTempWindowList != null && mTempWindowList.size() > 0)

defaultWindows.addAll(mTempWindowList);

mTempWindowList.clear();

for(int i= defaultWindows.size()-1;i>=0;i--){

win = defaultWindows.get(i);

if(win == null){

continue;

}

if (win.mAppToken == null){

continue;

}

if(win.mAppToken.mTask == null){

continue;

}

int windowTaskId = win.mAppToken.mTask.mTaskId;

if(windowTaskId == currentFocusedTaskId){

defaultWindows.remove(win);

win.mDisplayContent = secondDisplayContent;

if(win.mWinAnimator != null){

int layerStack = secondDisplayContent.getDisplay().getLayerStack();

if(win.mWinAnimator.mSurfaceControl!= null){

win.mWinAnimator.mSurfaceControl.setLayerStack(layerStack);

}

}

secondDisplayAddList.add(0,win);

}

}

for(int i= secondDisplayWindows.size()-1;i>=0;i--){

win = secondDisplayWindows.get(i);

if(win == null){

continue;

}

if (win.mAppToken == null){

continue;

}

if(win.mAppToken.mTask == null){

continue;

}

int windowTaskId = win.mAppToken.mTask.mTaskId;

if(windowTaskId == secondDisplayTaskId){

secondDisplayWindows.remove(win);

win.mDisplayContent = defaultContent;

if(win.mWinAnimator != null){

int layerStack = defaultContent.getDisplay().getLayerStack();

if(win.mWinAnimator.mSurfaceControl!= null){

win.mWinAnimator.mSurfaceControl.setLayerStack(layerStack);

}

}

defaultDisplayAddList.add(0,win);

}

}

//secondDisplayWindows.clear();

secondDisplayWindows.addAll(0,secondDisplayAddList);

//defaultWindows.clear();

defaultWindows.addAll(0, defaultDisplayAddList);

for (int i = 0; i < displayCount; i++) {

final DisplayContent content = mDisplayContents.valueAt(i);

assignLayersLocked(content.getWindowList());

content.layoutNeeded = true;

}

//Log.i("DualScreen", "WindowManagerService->moveWindowToSecondDisplayWithDualShow->allTaskIds:" + allTaskIds);

ArrayList allStacks = getAllStacks();

Log.i("DualScreen", "WindowManagerService->moveWindowToSecondDisplayWithDualShow->allStacks:" + allStacks);

mSecondDisplayTaskId = currentFocusedTaskId;

Log.i("DualScreen", "WindowManagerService->moveWindowToSecondDisplayWithDualShow->curMoveTaskId:" + curMoveTaskId);

misMovingToSecond = true;

Settings.System.putInt(mContext.getContentResolver(), Settings.DUAL_SCREEN_ICON_USED, 1);

switchFocusWindow(curMoveTaskId);

updateFocusedWindowLocked(UPDATE_FOCUS_WILL_PLACE_SURFACES, false);

mAppTransition.setReady();

performLayoutAndPlaceSurfacesLocked();

}finally{

SurfaceControl.closeTransaction();

}

//shouldAppMoveBack(-1);

}

Binder.restoreCallingIdentity(origId);

}

4.副屏页面如何全屏显示？修改PhoneWindowManager.java下layoutWindowLw方法添加代码如下：

pf.top = df.top = of.top = cf.top = vf.top = 0;

pf.right = df.right = of.right = cf.right = vf.right = width;

pf.bottom = df.bottom = of.bottom = cf.bottom = vf.bottom = height;

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作者：默默等待__007

来源：CSDN

原文：https://blog.csdn.net/u011365633/article/details/55001840

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