检查 BOOT_COMPLETED 是否已经在 Android 上被触发

Question

I have a Broadcast Receiver which handles multiple events. I need it to do some special things for me at boot so I registered the android.intent.action.BOOT_COMPLETED intent, which works fine. If the device is plugged in and is charging the android.intent.action.ACTION_POWER_CONNECTED intent is fired before BOOT_COMPLETED and does work before it's supposed to do stuff. (I'm using BOOT_COMPLETED as a sort of initializer).

Is there a way to check if the BOOT_COMPLETED event has been fired, so that I can run my initializing code in the event something gets fired too early?

Answer 1

When the BOOT_COMPLETED is fired, you need to set a flag in your SharedPreferences as "true".

So, now if your ACTION_POWER_CONNECTED gets fired before the BOOT_COMPLETED then you need to check the value of the flag from the SharedPreferences.

If the value is still false, that means that the BOOT_COMPLETED broadcast has not fired yet and you should not perform your actions.

Note - Also remember to reset the flag in SharedPreferences every time.

Answer 2

I found another solution which is consistent. (I couldn't use another approach as I'm not the one who decides the approach sadly.)

Using the answer from this post: How to get Android system boot time I can save the last boot time in SharedPreferences (or some other storage). Once the boot time is different than the last I know that it's a fresh boot and can apply my initialisations etc.

This is the code I've ended up writing:

private boolean checkIfRebooted(Context context) {
    SharedPreferences prefs = context.getSharedPreferences("package.name.class", Context.MODE_PRIVATE);

    long savedUptime = prefs.getLong("timestamp", 0);
    long currentUptime = System.currentTimeMillis() - SystemClock.elapsedRealtime();

    // Giving it a threshold of 10ms since the calculation may be off by one sometimes.
    if (Math.abs(currentUptime - savedUptime) < 10)
        return false;

    prefs.edit().putLong("timestamp", currentUptime).apply();
    return true;
}

Answer 3

You could use the kernel boot id from /proc/sys/kernel/random/boot_id. When the code receives BOOT_COMPLETED, store the boot_id in the shared preference. After that it is simple. If the boot_id from /proc is equal to the shared preference, then BOOT_COMPLETED has been handled. Otherwise, not yet.