This tool allows to record and replay touch events on Android devices. The primary goal is for the replays to be consistent with each other as much as possible to allow for repeating touch gestures many times with statistical analysis to follow. Maintaining consistency with the original sequence of touches is only a secondary goal.
Recording on one device and replaying on another is likely not going to work because of differences in the structure of touch events. The way the kernel drivers emit the events depends heavily on device type and OS version.
Please use an optimized release build to minimize potential delays between emitted events. Here is how to build it:
# autoninja -C out/AndroidRelease touch_replay
This produces an executable only runnable on the device. Push it to the device:
# adb push out/AndroidRelease/touch_replay /data/local/tmp
Before running the tool make sure it will be invoked with root privileges:
adb root
Run the tool. All interaction with the screen will be recorded until you press Ctrl+C.
# adb shell '/data/local/tmp/touch_replay record /data/local/tmp/touch_events.dump'
To replay change record with replay in the command above.
The last piece of functionality of this tool is the help message:
# adb shell '/data/local/tmp/touch_replay --help' Usage: /data/local/tmp/touch_replay record|replay FILE Record input events to FILE or replay them from FILE.
It is important to be able to replay touch scenarios while the device is being traced. The cpu_profile tool is compatible with running the replay simultaneously. See about its usage in the Perfetto documentation.
Using Perfetto from the browser to record a trace on the device is less straightforward. While attached to the device, Perfetto may make the device invisible to the commandline adb tool:
adb: no device found
One workaround is to start replay and attach with Perfetto later:
adb shell 'nohup sh -c "sleep 15 && /data/local/tmp/touch_replay replay /data/local/tmp/touch_events.dump" >/dev/null 2>&1 &'
This will wait for 15 seconds before replaying. The adb command would return immediately. After that the tool runs on the device without depending on the existing adb session. This works by running the program as a daemon with the help of the nohup utility. Since both the sleeping and replaying needs to be daemonized, they are wrapped into a shell command together.
Immediately after invoking the command above it should be possible to connect to the device with Perfetto (within the specified time interval, 15 seconds in this case) and start profiling.