How do I prevent an Android device from going to sleep programmatically?

How do I prevent an Android device from going to sleep pro开发者_开发技巧grammatically?

If you just want to prevent the sleep mode on a specific View, just call setKeepScreenOn(true) on that View or set the keepScreenOn property to true. This will prevent the screen from going off while the View is on the screen. No special permission required for this.

One option is to use a wake lock. Example from the docs:

PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
wl.acquire();

// screen and CPU will stay awake during this section

wl.release();

There's also a table on this page that describes the different kinds of wakelocks.

Be aware that some caution needs to be taken when using wake locks. Ensure that you always release() the lock when you're done with it (or not in the foreground). Otherwise your app can potentially cause some serious battery drain and CPU usage.

The documentation also contains a useful page that describes different approaches to keeping a device awake, and when you might choose to use one. If "prevent device from going to sleep" only refers to the screen (and not keeping the CPU active) then a wake lock is probably more than you need.

You also need to be sure you have the WAKE_LOCK permission set in your manifest in order to use this method.

I found another working solution: add the following line to your app under the onCreate event.

getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

My sample Cordova project looks like this:

package com.apps.demo;
import android.os.Bundle;
import android.view.WindowManager;
import org.apache.cordova.*;

public class ScanManActivity extends DroidGap {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        super.loadUrl("http://stackoverflow.com");
    }
}

After that, my app would not go to sleep while it was open. Thanks for the anwer goes to xSus.

android:keepScreenOn="true" could be better option to have from layout XML.

More info: https://developer.android.com/training/scheduling/wakelock.html

Set flags on Activity's Window as below

@Override public void onResume() {
 super.onResume();
 getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
}

@Override public void onPause() {
 super.onPause();
 getWindow().clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
}

From the root shell (e.g. adb shell), you can lock with:

echo mylockname >/sys/power/wake_lock    

After which the device will stay awake, until you do:

echo mylockname >/sys/power/wake_unlock    

With the same string for 'mylockname'.

Note that this will not prevent the screen from going black, but it will prevent the CPU from sleeping.

Note that /sys/power/wake_lock is read-write for user radio (1001) and group system (1000), and, of course, root.

A reference is here: http://lwn.net/Articles/479841/

what @eldarerathis said is correct in all aspects, the wake lock is the right way of keeping the device from going to sleep.

I don't know waht you app needs to do but it is really important that you think on how architect your app so that you don't force the phone to stay awake for more that you need, or the battery life will suffer enormously.

I would point you to this really good example on how to use AlarmManager to fire events and wake up the phone and (your app) to perform what you need to do and then go to sleep again: Alarm Manager (source: commonsware.com)

If you are a Xamarin user, this is the solution:

   protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle); //always call superclass first

        this.Window.AddFlags(WindowManagerFlags.KeepScreenOn);

        LoadApplication(new App());
    }