需求：android10 禁止下拉状态栏，也就是禁止下拉如下图的快速设置面板（
Quick settings panel，也叫QS面板）

修改后：怎么拉都拉不下来，包括锁屏页面和正常桌面都无法下拉状态栏。

修改点：

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationStackScrollLayout.java

    @ShadeViewRefactor(RefactorComponent.INPUT)
    private final DragDownCallback mDragDownCallback = new DragDownCallback() {

        /* Only ever called as a consequence of a lockscreen expansion gesture. */
        @Override
        public boolean onDraggedDown(View startingChild, int dragLengthY) {
            //加上这个if即可在滑动锁屏页面禁止下拉
            if (mStatusBarState == StatusBarState.KEYGUARD) {
                return false;
            }
            if (mStatusBarState == StatusBarState.KEYGUARD
                    && hasActiveNotifications()) {
                mLockscreenGestureLogger.write(
                        MetricsEvent.ACTION_LS_SHADE,
                        (int) (dragLengthY / mDisplayMetrics.density),
                        0 /* velocityDp - N/A */);

                if (!mAmbientState.isDozing() || startingChild != null) {
                    // We have notifications, go to locked shade.
                    mShadeController.goToLockedShade(startingChild);
                    if (startingChild instanceof ExpandableNotificationRow) {
                        ExpandableNotificationRow row = (ExpandableNotificationRow) startingChild;
                        row.onExpandedByGesture(true /* drag down is always an open */);
                    }
                }

                return true;
            } else if (mDynamicPrivacyController.isInLockedDownShade()) {
                mStatusbarStateController.setLeaveOpenOnKeyguardHide(true);
                mStatusBar.dismissKeyguardThenExecute(() -> false /* dismissAction */,
                        null /* cancelRunnable */, false /* afterKeyguardGone */);
                return true;
            } else {
                // abort gesture.
                return false;
            }
        }
　   ......

frameworks/base/core/java/android/app/StatusBarManager.java

    @UnsupportedAppUsage
    public void disable(int what) {
        //加上这行what = what | DISABLE_EXPAND;
        what = what | DISABLE_EXPAND;
        try {
            final int userId = Binder.getCallingUserHandle().getIdentifier();
            final IStatusBarService svc = getService();
            if (svc != null) {
                svc.disableForUser(what, mToken, mContext.getPackageName(), userId);
            }
        } catch (RemoteException ex) {
            throw ex.rethrowFromSystemServer();
        }
    }

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarView.java

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        boolean barConsumedEvent = mBar.interceptTouchEvent(event);

        if (DEBUG_GESTURES) {
            if (event.getActionMasked() != MotionEvent.ACTION_MOVE) {
                EventLog.writeEvent(EventLogTags.SYSUI_PANELBAR_TOUCH,
                        event.getActionMasked(), (int) event.getX(), (int) event.getY(),
                        barConsumedEvent ? 1 : 0);
            }
        }
        // return barConsumedEvent || super.onTouchEvent(event);
        //在这里直接return true;
         return true;
    }

参考文章：
Android9.0禁止滑动锁下拉状态栏
Android源码分析

Android10 Frameworks专栏其他文章：
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android10 修改媒体音的默认值
android10 隐藏SystemUI锁屏下的多用户图标
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