使用evdev模拟触摸输入报错，寻求技术解决方案

Hey there! Let's break down why your touch emulation code is failing and get it working properly. The main issues are incomplete device capabilities and missing required touch-specific events. Here's how to fix it step by step:

Key Issues in Your Original Code #

1. Missing Multi-Touch (MT) Essentials
   Your current capability set only includes ABS_MT_POSITION_X, but touch devices require a full set of MT events (like position Y, tracking ID, and pressure) to be recognized correctly by the system.

2. Incorrect Key Events
   You've included KEY_A and KEY_B, which are irrelevant for touch input. Instead, touch devices need BTN_TOUCH (to signal a press) and BTN_TOOL_FINGER (to indicate a single-finger touch).

3. Malformed AbsInfo for MT X Position
   The tuple format (0, 255, 128, 0) for ABS_MT_POSITION_X doesn't match the expected AbsInfo structure (value, min, max, fuzz, flat, resolution). Always use the explicit AbsInfo object for consistency.

Corrected Code with Full Touch Emulation #

Here's a complete working example that creates a valid touch device and simulates a press, drag, and release:

from evdev import UInput, AbsInfo, ecodes as e
import time

# Define a valid touch device capability set
capabilities = {
    e.EV_KEY: [e.BTN_TOUCH, e.BTN_TOOL_FINGER],
    e.EV_ABS: [
        # Base X/Y axes (required by some systems)
        (e.ABS_X, AbsInfo(value=0, min=0, max=255, fuzz=0, flat=0, resolution=0)),
        (e.ABS_Y, AbsInfo(0, 0, 255, 0, 0, 0)),
        # Multi-touch mandatory events
        (e.ABS_MT_TRACKING_ID, AbsInfo(0, 0, 65535, 0, 0, 0)),  # Tracks individual touch points
        (e.ABS_MT_POSITION_X, AbsInfo(0, 0, 255, 0, 0, 0)),
        (e.ABS_MT_POSITION_Y, AbsInfo(0, 0, 255, 0, 0, 0)),
        (e.ABS_MT_PRESSURE, AbsInfo(0, 0, 255, 0, 0, 0))  # Optional but recommended for realism
    ]
}

try:
    # Create the virtual touch device
    ui = UInput(capabilities, name='custom-touch-emulator', version=0x1)
    print("Virtual touch device created successfully!")

    # Simulate touch press
    ui.write(e.EV_KEY, e.BTN_TOUCH, 1)
    ui.write(e.EV_KEY, e.BTN_TOOL_FINGER, 1)
    ui.write(e.EV_ABS, e.ABS_MT_TRACKING_ID, 0)  # Assign ID 0 to this touch point
    ui.write(e.EV_ABS, e.ABS_MT_POSITION_X, 50)
    ui.write(e.EV_ABS, e.ABS_MT_POSITION_Y, 50)
    ui.write(e.EV_ABS, e.ABS_X, 50)
    ui.write(e.EV_ABS, e.ABS_Y, 50)
    ui.write(e.EV_ABS, e.ABS_MT_PRESSURE, 200)
    ui.syn()  # Sync events to trigger system recognition
    time.sleep(0.5)

    # Simulate touch drag
    for pos in range(50, 201, 10):
        ui.write(e.EV_ABS, e.ABS_MT_POSITION_X, pos)
        ui.write(e.EV_ABS, e.ABS_MT_POSITION_Y, pos)
        ui.write(e.EV_ABS, e.ABS_X, pos)
        ui.write(e.EV_ABS, e.ABS_Y, pos)
        ui.syn()
        time.sleep(0.1)

    # Simulate touch release
    ui.write(e.EV_KEY, e.BTN_TOUCH, 0)
    ui.write(e.EV_KEY, e.BTN_TOOL_FINGER, 0)
    ui.write(e.EV_ABS, e.ABS_MT_TRACKING_ID, -1)  # Mark touch point as ended
    ui.write(e.EV_ABS, e.ABS_MT_PRESSURE, 0)
    ui.syn()
    time.sleep(0.5)

finally:
    # Clean up the device
    ui.close()
    print("Virtual touch device closed.")

Additional Troubleshooting Tips #

• Verify Input Group Membership: Even after adding yourself to the input group, log out and back in (or restart) to apply the permissions. Check with groups in the terminal to confirm.
• Load UINPUT Kernel Module: If you still get permission errors, ensure the uinput module is loaded with sudo modprobe uinput. To load it on boot, add uinput to /etc/modules-load.d/uinput.conf.
• Update Evdev: Make sure you're using the latest version of the library with pip install --upgrade evdev.

内容的提问来源于stack exchange，提问作者ovg