本文基于android9.0来写的。

一、产品需求：如下图，类似mac的桌面系统

(1)区域1是系统标题栏。

(2)区域2是长显示的窗口。

(3)区域3 普通app显示的窗口。

(4) 区域4 也是一个上显示的窗口,主要用于应用的点击启动。

二、下图是根据Android系统特性画的草图：

(1)区域1是系统statusBar。

(2)区域2是长显示的窗口,用WindowMananger添加的窗口。

(3)区域3 普通app显示的窗口，定制系统默认窗口大小，定位至区域3。

(4) 区域4 也是一个长显示的窗口，同样是用WindowMananger添加的窗口。

三、主要实现思路：通过freefrom 和添加悬浮window来实现。因为app只有在freeform模式才能任意定制多窗口大小和位置。

1、区域1无需改动，还是采用系统默认stausBar。

2、修改famework AMS ，以freeform模式启动Launcher。修改HOME的的区域为上图区域3。

3、Lancher启动时，同时启动两个两个service, 然后通过WindowManger来添加区域2和区域4。

4、区域4 的Icon点击以freeform模式启动其他APP。在framework拦截启动APP的入口，以freeform模式启动，同时设置窗口大小和位置(区域3)。

四、最终实现的demo如下：

五、具体实现方法如下：

1、开启freeform

google 默认freeform是关闭的，如果要测试需要手动开启。

配置config_freeformWindowManagement

WORKING_DIRECTORY/frameworks/base/core/res/res/values/config.xml

如下，将config_freeformWindowManagement配置为true

WORKING_DIRECTORY/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

private void retrieveSettings() {

final ContentResolver resolver = mContext.getContentResolver();

//获取是否支持freeform

final boolean freeformWindowManagement =

mContext.getPackageManager().hasSystemFeature(FEATURE_FREEFORM_WINDOW_MANAGEMENT)

|| Settings.Global.getInt(

resolver, DEVELOPMENT_ENABLE_FREEFORM_WINDOWS_SUPPORT, 0) != 0;

由上面代码可以看出有两种方法可以开启freeform

(1)  Settings 设置开启的属性

WORKING_DIRECTORY/frameworks/base/core/java/android/provider/Settings.java

/**

* Whether any activity can be resized. When this is true, any

* activity, regardless of manifest values, can be resized for multi-window.

* (0 = false, 1 = true)

* @hide

*/

public static final String DEVELOPMENT_FORCE_RESIZABLE_ACTIVITIES

= "force_resizable_activities";

/**

* Whether to enable experimental freeform support for windows.

* @hide

*/

public static final String DEVELOPMENT_ENABLE_FREEFORM_WINDOWS_SUPPORT

= "enable_freeform_support";

这个用命令就可以开启：

adb shell settings put global enable_freeform_support  1

adb shell settings put global force_resizable_activities  1

如果要在framework中默认开启，可以这样：

private void retrieveSettings() {

final ContentResolver resolver = mContext.getContentResolver();

//简单粗暴开启，哈哈

Settings.Global.putInt(resolver, DEVELOPMENT_ENABLE_FREEFORM_WINDOWS_SUPPORT, 1);

Settings.Global.putInt(resolver, DEVELOPMENT_FORCE_RESIZABLE_ACTIVITIES, 1);

final boolean freeformWindowManagement =

mContext.getPackageManager().hasSystemFeature(FEATURE_FREEFORM_WINDOW_MANAGEMENT)

|| Settings.Global.getInt(

resolver, DEVELOPMENT_ENABLE_FREEFORM_WINDOWS_SUPPORT, 0) != 0;

(2)给系统添加feature：android.software.freeform_window_management

其实android系统默认已经写好，这里可以找到：

WORKING_DIRECTORY/frameworks/native/data/etc

可以将android.software.freeform_window_management.xml 拷贝到WORKING_DIRECTORY/frameworks/base/data/etc

里面有个Android.mk在这里面添加如下：

########################

include $(CLEAR_VARS)

LOCAL_MODULE := android.software.freeform_window_management.xml

LOCAL_MODULE_CLASS := ETC

LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/permissions

LOCAL_SRC_FILES := $(LOCAL_MODULE)

include $(BUILD_PREBUILT)

它最终会被拷贝到手机的system/etc/permissions/目录下，开机时PMS会通过的读取此目录下xml配置开启freeform这个feature.

但是经过测试这个还是不够，还需要开启

Settings.Global.putInt(resolver, DEVELOPMENT_FORCE_RESIZABLE_ACTIVITIES, 1);

2、freeform模式启动app

Android为了支持多窗口，在运行时创建了多个Stack，Stack就是类似这里虚拟桌面的作用。

每个Stack会有一个唯一的Id，在WindowConfiguration.java中定义了这些Stack的Id：如下:

public class WindowConfiguration

implements android.os.Parcelable, java.lang.Comparable{

public WindowConfiguration() { throw new RuntimeException("Stub!"); }

public void writeToParcel(android.os.Parcel dest, int flags) { throw new RuntimeException("Stub!"); }

public int describeContents() { throw new RuntimeException("Stub!"); }

public void setBounds(android.graphics.Rect rect) { throw new RuntimeException("Stub!"); }

public void setAppBounds(android.graphics.Rect rect) { throw new RuntimeException("Stub!"); }

public android.graphics.Rect getAppBounds() { throw new RuntimeException("Stub!"); }

public android.graphics.Rect getBounds() { throw new RuntimeException("Stub!"); }

public void setWindowingMode(int windowingMode) { throw new RuntimeException("Stub!"); }

public int getWindowingMode() { throw new RuntimeException("Stub!"); }

public void setActivityType(int activityType) { throw new RuntimeException("Stub!"); }

public int getActivityType() { throw new RuntimeException("Stub!"); }

public void setTo(android.app.WindowConfiguration other) { throw new RuntimeException("Stub!"); }

public int compareTo(android.app.WindowConfiguration that) { throw new RuntimeException("Stub!"); }

public static final int ACTIVITY_TYPE_ASSISTANT = 4;

public static final int ACTIVITY_TYPE_HOME = 2;

public static final int ACTIVITY_TYPE_RECENTS = 3;

public static final int ACTIVITY_TYPE_STANDARD = 1;

public static final int ACTIVITY_TYPE_UNDEFINED = 0;

public static final int WINDOWING_MODE_FREEFORM = 5;

public static final int WINDOWING_MODE_FULLSCREEN = 1;

public static final int WINDOWING_MODE_FULLSCREEN_OR_SPLIT_SCREEN_SECONDARY = 4;

public static final int WINDOWING_MODE_PINNED = 2;

public static final int WINDOWING_MODE_SPLIT_SCREEN_PRIMARY = 3;

public static final int WINDOWING_MODE_SPLIT_SCREEN_SECONDARY = 4;

public static final int WINDOWING_MODE_UNDEFINED = 0;

}

例如以freeform启动activity

Intent intent = new Intent(this, AdjacentActivity.class);

intent.setFlags(Intent.FLAG_ACTIVITY_LAUNCH_ADJACENT | Intent.FLAG_ACTIVITY_NEW_TASK);

ActivityOptions activityOptions = ActivityOptions.makeBasic();

activityOptions.setLaunchWindowingMode(5);

int left = 100;

int top = 0;

int right = 720;

int bottom = 2280;

activityOptions.setLaunchBounds(new Rect(left,top,right,bottom));

Bundle bundle = activityOptions.toBundle();

startActivity(intent,bundle)

setLaunchWindowingMode 是个testApi，我们开发的时候获取不到，可以通过反射来调用

public static ActivityOptions getActivityOptions(Context context) {

ActivityOptions options = ActivityOptions.makeBasic();

int freeform_stackId = 5;

try {

Method method = ActivityOptions.class.getMethod("setLaunchWindowingMode", int.class);

method.invoke(options, freeform_stackId);

} catch (Exception e) { /* Gracefully fail */ }

return options;

}

具体详细用法可以参考

https://github.com/farmerbb/Taskbar

3、如何以freeform 启动launcher

/WORKING_DIRECTORY/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

boolean startHomeActivityLocked(int userId, String reason) {

if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL

&& mTopAction == null) {

// We are running in factory test mode, but unable to find

// the factory test app, so just sit around displaying the

// error message and don't try to start anything.

return false;

}

Intent intent = getHomeIntent();

ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);

if (aInfo != null) {

intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));

// Don't do this if the home app is currently being

// instrumented.

aInfo = new ActivityInfo(aInfo);

aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);

ProcessRecord app = getProcessRecordLocked(aInfo.processName,

aInfo.applicationInfo.uid, true);

if (app == null || app.instr == null) {

intent.setFlags(intent.getFlags() | FLAG_ACTIVITY_NEW_TASK);

final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid);

// For ANR debugging to verify if the user activity is the one that actually

// launched.

final String myReason = reason + ":" + userId + ":" + resolvedUserId;

//这里调用启动homeActivity

mActivityStartController.startHomeActivity(intent, aInfo, myReason);

}

} else {

Slog.wtf(TAG, "No home screen found for " + intent, new Throwable());

}

return true;

}

/WORKING_DIRECTORY/frameworks/base/services/core/java/com/android/server/am/ActivityStartController.java

void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason) {

mSupervisor.moveHomeStackTaskToTop(reason);

// 这里我设置了freefrom启动参数。

ActivityOptions activityOptions = ActivityOptions.makeBasic();

activityOptions.setLaunchWindowingMode(5);

Point size = new Point();

mService.mWindowManager.getInitialDisplaySize(0,size);

int left = 100;

int top = 0;

int right = size.x;

int bottom = size.y*6/7;

activityOptions.setLaunchBounds(new Rect(left,top,right,bottom));

Bundle bundle = activityOptions.toBundle();

mLastHomeActivityStartResult = obtainStarter(intent, "startHomeActivity: " + reason)

.setOutActivity(tmpOutRecord)

.setCallingUid(0)

.setActivityInfo(aInfo)

.setActivityOptions(bundle)

.execute();

mLastHomeActivityStartRecord = tmpOutRecord[0];

if (mSupervisor.inResumeTopActivity) {

// If we are in resume section already, home activity will be initialized, but not

// resumed (to avoid recursive resume) and will stay that way until something pokes it

// again. We need to schedule another resume.

mSupervisor.scheduleResumeTopActivities();

}

}

WORKING_DIRECTORY/frameworks/base/services/core/java/com/android/server/am/ActivityStarter.java

作如下修改：

// Note: This method should only be called from {@link startActivity}.

private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,

IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,

int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,

ActivityRecord[] outActivity) {

setInitialState(r, options, inTask, doResume, startFlags, sourceRecord, voiceSession,

voiceInteractor);

computeLaunchingTaskFlags();

computeSourceStack();

mIntent.setFlags(mLaunchFlags);

ActivityRecord reusedActivity = getReusableIntentActivity();

int preferredWindowingMode = WINDOWING_MODE_UNDEFINED;

int preferredLaunchDisplayId = DEFAULT_DISPLAY;

//在这里对启动的activity作拦截，用freeform启动，设置setLaunchWindowingMode 为5

Point size = new Point();

Display display = mSupervisor.mDisplayManager.getDisplay(0);

DisplayMetrics displayMetrics = new DisplayMetrics();

display.getMetrics(displayMetrics);

size.x = displayMetrics.widthPixels;

size.y = displayMetrics.heightPixels;

Slog.e("ZyTest", "myTestZize displayMetrics w = " + displayMetrics.widthPixels + " h = " + displayMetrics.heightPixels);

if (mOptions != null) {

preferredWindowingMode = mOptions.getLaunchWindowingMode();

preferredLaunchDisplayId = mOptions.getLaunchDisplayId();

Slog.e("ZyTest", "preferredWindowingMode = " + preferredWindowingMode );

int left = size.x /4;

int top = 0;

int right = size.x;

int bottom = size.y*6/7;;

mOptions.setLaunchBounds(new Rect(left,top,right,bottom));

mOptions.setLaunchWindowingMode(5);

}else {

mOptions = ActivityOptions.makeBasic();

int left = size.x /4;

int top = 0;

int right = size.x;

int bottom = size.y*6/7;;

mOptions.setLaunchBounds(new Rect(left,top,right,bottom));

mOptions.setLaunchWindowingMode(5);

Slog.e("ZyTest", "22222 preferredWindowingMode = " + preferredWindowingMode );

}

preferredWindowingMode = 5;

// windowing mode and preferred launch display values from {@link LaunchParams} take

// priority over those specified in {@link ActivityOptions}.

if (!mLaunchParams.isEmpty()) {

if (mLaunchParams.hasPreferredDisplay()) {

preferredLaunchDisplayId = mLaunchParams.mPreferredDisplayId;

}

if (mLaunchParams.hasWindowingMode()) {

preferredWindowingMode = mLaunchParams.mWindowingMode;

}

}

设置启动的目标栈的setWindowingMode为freeform,位置和大小自定义

private int setTaskFromReuseOrCreateNewTask(

TaskRecord taskToAffiliate, ActivityStack topStack) {

mTargetStack = computeStackFocus(mStartActivity, true, mLaunchFlags, mOptions);

boolean ishome = mStartActivity.isActivityTypeHome();

Slog.e("ZyTest", "is home llllllllll = " + ishome);

// if(ishome){

Point size = new Point();

// mService.mWindowManager.getInitialDisplaySize(0,size);

//设置目标栈的setWindowingMode、位置 、大小

Display display = mSupervisor.mDisplayManager.getDisplay(0);

DisplayMetrics displayMetrics = new DisplayMetrics();

display.getMetrics(displayMetrics);

size.x = displayMetrics.widthPixels;

size.y = displayMetrics.heightPixels;

int left = size.x /4;

int top = 0;

int right = size.x;

int bottom = size.y*6/7;

mTargetStack.setBounds(left,top,right,bottom);

mTargetStack.setWindowingMode(5);

// }

// Do no move the target stack to front yet, as we might bail if

// isLockTaskModeViolation fails below.

if (mReuseTask == null) {

final TaskRecord task = mTargetStack.createTaskRecord(

mSupervisor.getNextTaskIdForUserLocked(mStartActivity.userId),

mNewTaskInfo != null ? mNewTaskInfo : mStartActivity.info,

mNewTaskIntent != null ? mNewTaskIntent : mIntent, mVoiceSession,

mVoiceInteractor, !mLaunchTaskBehind /* toTop */, mStartActivity, mSourceRecord,

mOptions);

addOrReparentStartingActivity(task, "setTaskFromReuseOrCreateNewTask - mReuseTask");

updateBounds(mStartActivity.getTask(), mLaunchParams.mBounds);

if (DEBUG_TASKS) Slog.v(TAG_TASKS, "Starting new activity " + mStartActivity

+ " in new task " + mStartActivity.getTask());

} else {

addOrReparentStartingActivity(mReuseTask, "setTaskFromReuseOrCreateNewTask");

}

if (taskToAffiliate != null) {

mStartActivity.setTaskToAffiliateWith(taskToAffiliate);

}

if (mService.getLockTaskController().isLockTaskModeViolation(mStartActivity.getTask())) {

Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);

return START_RETURN_LOCK_TASK_MODE_VIOLATION;

}

if (mDoResume) {

mTargetStack.moveToFront("reuseOrNewTask");

}

return START_SUCCESS;

}