前文

Android U 多任务启动分屏——Launcher流程（下分屏）
前文说到通过ISplitScreen接口跨进程调用到了SystemUI进程，我们继续分析分屏在systemui中的实现。

wmshell实现分屏

实现ISplitScreen接口

代码路径：frameworks/base/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java

    /**
     * The interface for calls from outside the host process.
     */
    @BinderThread
    private static class ISplitScreenImpl extends ISplitScreen.Stub
            implements ExternalInterfaceBinder {
        ......
        @Override
        public void startTasks(int taskId1, @Nullable Bundle options1, int taskId2,
                @Nullable Bundle options2, @SplitPosition int splitPosition, float splitRatio,
                @Nullable RemoteTransition remoteTransition, InstanceId instanceId) {
            executeRemoteCallWithTaskPermission(mController, "startTasks",
                    (controller) -> controller.mStageCoordinator.startTasks(taskId1, options1,
                            taskId2, options2, splitPosition, splitRatio, remoteTransition,
                            instanceId));
        }
        ......
    }