ANRs

Shake also detects ANRs — moments when your app's main thread freezes and stops responding to input.

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Introduction

A crash means your app threw an exception and shut down. An ANR is different: your app's main thread stops responding for several seconds, the UI locks up, and your user either waits it out, force-quits your app, or the system kills it for them. No exception is ever thrown, so without this feature none of that would reach your dashboard — a frozen screen simply disappeared without a trace.

This module reports ANRs the same way it reports crashes: with device info, activity history, black box, and everything else your Configuration and data settings already attach.

There's one difference worth knowing up front: since the main thread is frozen at the exact moment an ANR is detected, these reports never include a screenshot or a screen recording — there's no way to capture either while the UI isn't responding.

Detecting ANRs is enabled by default, and it's independent from crash reporting — you can turn one off without the other.

Enable

If you'd like to turn ANR detection off, set the setAnrDetectionEnabled flag to false before calling the Shake.start method.

Java

App.java

Shake.setAnrDetectionEnabled(false);

Kotlin

App.kt

Shake.setAnrDetectionEnabled(false)

Set the threshold

By default, an ANR is reported once your app's main thread has been unresponsive for 5000 ms — the same bar Android itself uses to decide an app isn't responding. You can tune this to match how strict you want detection to be. Setting it lower than 1000 ms isn't allowed, since anything shorter would start flagging ordinary UI stutter as an ANR.

Java

App.java

Shake.setAnrThresholdMs(5000);

Kotlin

App.kt

Shake.setAnrThresholdMs(5000)

What happens when an ANR is detected

• One report per ANR. A single, ongoing freeze is only reported once, no matter how long it lasts. If your app freezes again later, that's a separate report.
• Shake never closes your app. Detecting an ANR doesn't terminate it — if your app recovers, it keeps running normally and the report is simply sent in the background.
• Two outcomes are possible, and your dashboard tells you which one happened:
  • The app recovered — the main thread started responding again, and the session continued.
  • The app was terminated while frozen — the system (or your user, by force-quitting) ended the app before it recovered. This is the more severe of the two, since the session was lost.

note

If a debugger is attached to your app, ANR detection is automatically suppressed. Pausing at a breakpoint freezes your main thread too, and Shake has no way to tell that apart from a real ANR — so testing this feature should be done on a build that isn't being debugged.

Test it

Let's freeze your app on purpose to see what an ANR report looks like on your Shake dashboard.

ANR detection is on by default, so just add a button that blocks the main thread for longer than your threshold — 8 seconds is a safe margin for the 5000 ms default:

Java

MainActivity.java

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button buttonFreeze = findViewById(R.id.button_freeze);
        buttonFreeze.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    Thread.sleep(8000);
                } catch (InterruptedException e) {
                    // ignore
                }
            }
        });
    }
}

Kotlin

MainActivity.kt

public class MainActivity : Activity {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val buttonFreeze: Button = findViewById(R.id.button_freeze)
        buttonFreeze.setOnClickListener {
            Thread.sleep(8000)
        }
    }
}

Run your app without a debugger attached, then tap the button and wait — your screen will freeze for 8 seconds before recovering.

Visit your Shake dashboard

To see your report:

1. Visit your Shake dashboard
2. Switch to the Crashes tab in the left sidebar

If your report isn't visible instantly, wait a minute until the system processes it.