Android slow rendering

When the UI thread of an Android app is blocked for too long, an “Application Not Responding” (ANR) error is triggered . If the app is in the foreground, the system displays a dialog to the user, as shown in figure 1. The ANR dialog gives the user the opportunity to force quit the app.

Android vitals is an initiative by Google to improve the stability and performance of Android devices . When an opted-in user runs your app, their Android device logs various metrics, including data about app stability, app startup time, battery usage, render time, and permission denials.

The difference between a crash and an ANR is that a crash is a code exception whereas an ANR is an ongoing state of nonresponsiveness . So when a crash happens, the app itself terminates. When an ANR happens, the user simply cannot do anything in the app and will eventually force quit it.

A good way to try to detect the problem is by fetching the file /data/anr/traces. txt which is generated after a ANR happens on a device (beware that it is overridden after another ANR happens). That offers you a overview of what each thread was doing at the time of the ANR.