How to catch long press Back button in Accessibility service?

I want to catch long press Back button in my Accessibility service. I use code below for it. Unluckily, something is wrong because I get log where is isLongPress = false. My question is how to catch KeyEvent properly.

This is my service:

package com.example.android.globalactionbarservice;
import android.accessibilityservice.AccessibilityService;
import android.util.Log;
import android.view.KeyEvent;
import android.view.accessibility.AccessibilityEvent;
import android.widget.FrameLayout;
import static android.content.ContentValues.TAG;
public class GlobalActionBarService extends AccessibilityService {
    FrameLayout mLayout;
    @Override
    protected void onServiceConnected() {
        Log.d(TAG, "MyAccessibilityService: onServiceConnected");
    }
    private long holdTime;
    @Override
    protected boolean onKeyEvent(KeyEvent event) {
        Log.d(TAG, "MyAccessibilityService: onKeyEvent: action = " + event.getAction() +
                "; key code = " + event.getKeyCode() +
                "; scan code = " + event.getScanCode() +
                "; meta state = " + event.getMetaState() +
                "; key = " + event.getNumber() +
                "; isLongPress = " + event.isLongPress());
        return super.onKeyEvent(event);
    }


    @Override
    public void onAccessibilityEvent(AccessibilityEvent event) {
            Log.d(TAG, "MyAccessibilityService: onAccessibilityEvent " + event.toString());
    }
    @Override
    public void onInterrupt() {
    }
}

This is the service xml:

<?xml version="1.0" encoding="utf-8"?>
<accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityFeedbackType="feedbackGeneric"
    android:accessibilityFlags="flagDefault|flagRequestFilterKeyEvents"
    android:canRetrieveWindowContent="true"
    android:canRequestFilterKeyEvents="true"
    android:accessibilityEventTypes="typeContextClicked|typeViewClicked"
    />

This is my log:

2019-09-09 22:02:28.690 11201-11201/com.example.android.demoservice D/ContentValues: MyAccessibilityService: onServiceConnected
2019-09-09 22:02:34.109 11201-11201/com.example.android.demoservice D/ContentValues: MyAccessibilityService: onKeyEvent: action = 0; key code = 4; scan code = 158; meta state = 0; key = ��; isLongPress = false
2019-09-09 22:02:36.345 11201-11201/com.example.android.demoservice D/ContentValues: MyAccessibilityService: onKeyEvent: action = 1; key code = 4; scan code = 158; meta state = 0; key = ��; isLongPress = false
2019-09-09 22:02:47.433 11201-11201/com.example.android.demoservice D/ContentValues: MyAccessibilityService: onAccessibilityEvent EventType: TYPE_VIEW_CLICKED; EventTime: 84040825; PackageName: com.android.settings; MovementGranularity: 0; Action: 0 [ ClassName: android.widget.Button; Text: [OK]; ContentDescription: null; ItemCount: -1; CurrentItemIndex: -1; IsEnabled: true; IsPassword: false; IsChecked: false; IsFullScreen: false; Scrollable: false; BeforeText: null; FromIndex: -1; ToIndex: -1; ScrollX: -1; ScrollY: -1; MaxScrollX: -1; MaxScrollY: -1; AddedCount: -1; RemovedCount: -1; ParcelableData: null ]; recordCount: 0

Thanks.