The Meizu mobile phone is connected to the computer via USB, but it cannot be debugged. After searching the Internet for a long time, I found the answer:

1. Phenomenon:

./adb devices
List of devices attached 
emulator-5554        device
????????????        no permissions

Two, cause

This was caused by the fact that our devices after 14 years were all updated using Meizu's own vids

See: http://bbs.flyme.cn/thread-111712-1-1.html
flyme's documentation: MX4 USB Reference Manual\Simplified\MX4_ADB_Reference Manual.txt

Three, the solution:

$echo 0x2a45 > ~/.android/adb_usb.ini
$adb kill-server
$adb devices

Ubuntu environment

Create or modify the file ~/.android/adb_usb.ini, add a line at the beginning or end of the file, the content is 0x2a45.
Create or modify the file /etc/udev/rules.d/51-android.rules
2.1 Modify file permissions:
sudo chmod a+rx /etc/udev/rules.d/51-android.rules

2.2 Add a line to the file:
SUBSYSTEM=="usb", ATTR{idVendor}=="2a45", MODE="0666", GROUP="plugdev"

mac

Mac corresponds to ~/.android/adb_usb.ini

windows

C:\Users\yiyuan.zhangyy.android\adb_usb.ini corresponding to windows is modified to the following

Modified file content

Check if ADB device is found (in command line program)

    adb kill-server
    adb devices

The problem of unauthorized is easy to solve. Versions 4.2.2 and above have RSA verification, and a prompt box will automatically pop up on the mobile phone. Click "OK" to authorize it.

4. Handling of similar problems with other mobile phones:

How to set the MAC:

Turn on the Android phone in debug mode and connect it to our Mac OS.
Select Mac's About This Machine -> More Information -> System Report -> Find the usb option, a series of USB-related devices will appear on the right side. We find our Android device and select it.
After selecting it, find the vendor ID or call the vendor ID. The vendor ID displayed on my MX4 mobile phone is: 0x2a454. Open the Mac terminal and enter: echo 0x2a45 >> ~/.android/adb_usb.ini and restart adb (I restart the Mac system ) and then open eclipse you will find that the device of the Android phone is displayed. This method can also solve the problem that other android devices on the Mac do not display.

Win7 setting method:

The easiest way to install the adb driver is to use pea pods or 91 assistants, as long as you connect it once, the installation is successful.
Open "Device Manager", find the mx4 device (Android Composite ADB Interface) inside, right-click properties, select "Details" tab, "Properties" select "Hardware ID", there will be two lines of values below, one of my lines is "USB\VID_2A45&PID_0C02&MI_01" see the VID_XXXX in it, and write down the XXXX value.
Find the C:\Users\XXX.android\adb_usb.ini file (XXX is your current operating system user name), and add "0xXXXX" (without quotation marks) to a new line in it. The preceding 0x indicates a hexadecimal number. Replace the following XXXX with the value you wrote down above. Restart the computer or exit eclipse, then kill the "adb" process in the task manager and re-enter eclipse. That's it.

Five, popular science VID:

The full name of VID is VendorID, and the Chinese translation is the vendor ID. Google gave some by default, but unfortunately Meizu's new VID is not included.

Meizu phone debugging and VID