Develop Reference

Why the Screen didn't wake up when I call acquire in Android?

I am trying to wake the screen when the screen is off (dark).
I create a class like the following code:
public class ScreenWakeLock {
private static PowerManager.WakeLock WakeLock;
#SuppressLint("Wakelock")
static void acquireCpuWakeLock(Context context) {
Log.i("ScreenWakeLock", "acquireCpuWakeLock");
PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
WakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP,"okTag");
WakeLock.acquire();
}
static void releaseCpuLock() {
if (WakeLock != null) {
WakeLock.release();
WakeLock = null;
}
}
}
When the Screen is off , the App call ScreenWakeLock.acquireCpuWakeLock(getActivity());.
But the Screen didn't wake up. I have seen the acquireCpuWakeLock in the log , I am sure the function acquireCpuWakeLock has been called. I also add the <uses-permission android:name="android.permission.WAKE_LOCK" /> in Manifest.xml.
Why the Screen didn't wake up when I call acquire in Android ?
Did I missing something?
Thanks in advance.

Straight from the PowerManager documentation:
In addition, you can add two more flags, which affect behavior of the
screen only. These flags have no effect when combined with a
PARTIAL_WAKE_LOCK.
Use something else instead of PowerManager.PARTIAL_WAKE_LOCK. Try SCREEN_DIM_WAKE_LOCK and see if that's good enough for your use case; if not, try SCREEN_BRIGHT_WAKE_LOCK.

Check whether onPause state of activity is called due to screen lock

If my app is running and I press lock screen button, it will put the app in background.What is the method to check whether onPause() is called by screen lock?.Thanks in advance.

All you have to do is check if the screen is on or not.
#Override
protected void onPause() {
super.onPause();
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
boolean screenOn;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
screenOn = pm.isInteractive();
} else {
screenOn = pm.isScreenOn();
}
if (screenOn) {
// Screen is still on, so do your thing here
}
}

You Can Simply Know It By Using This Method
#Override
public void onPause() {
super.onPause(); // Always call the superclass method first
System.out.println("On Pause called");
}
For Keeping The Device Awake while lock screen. Documentation.
Ok in your case you would need Wake_Lock
To use a wake lock, the first step is to add the WAKE_LOCK permission to your application's manifest file:
<uses-permission android:name="android.permission.WAKE_LOCK" />
If your app includes a broadcast receiver that uses a service to do some work, you can manage your wake lock through a WakefulBroadcastReceiver, as described in Using a WakefulBroadcastReceiver. This is the preferred approach. If your app doesn't follow that pattern, here is how you set a wake lock directly:
PowerManager powerManager = (PowerManager) getSystemService(POWER_SERVICE);
Wakelock wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
"MyWakelockTag");
wakeLock.acquire();
To release the wake lock, call wakelock.release(). This releases your claim to the CPU. It's important to release a wake lock as soon as your app is finished using it to avoid draining the battery.
DO this after setting powermanager.
boolean screenOn;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
screenOn = powerManager.isInteractive();
} else {
screenOn = powerManager.isScreenOn();
}
if (screenOn) {
// Screen is still on, so do your thing here
}

You just want to know when onPause is called? You could override the super function and add logging to the function:
#Override
public void onPause() {
super.onPause();
System.out.println("On Pause called");
}

Android Turn screen Off

I can't turn off the screen using this code. I used PowerManager and wl.release() method, but it doesn't work. Can somebody show me an example?
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
wl = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK, "DoNotDimScreen");
This is part of my function:
stateString = "nextone";
if(stateString=="nextone"){
wl.release();
}
I also added permission in the manifest but no result.

I found the answer over here on stack overflow: Turn off screen on Android
Copied from there:
WindowManager.LayoutParams params = getWindow().getAttributes();
params.flags |= LayoutParams.FLAG_KEEP_SCREEN_ON;
params.screenBrightness = 0;
getWindow().setAttributes(params);
I tried this out and it seems to work.

If you don't use a permission, the program will crash with a SecurityException when it tries to lock, so that isn't the problem. The correct method is: (obtains WakeLock on start, gives it up when the application loses focus (onPause)
//declared globally so both functions can access this
public PowerManager.WakeLock wl;
///////////onCreate
//stop phone from sleeping
PowerManager powman = (PowerManager) getSystemService(Context.POWER_SERVICE);
wl = powman.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, "NameOfLock");
wl.acquire();
///////////onPause
wl.release();
//////////for completion's sake, onResume
if(!wl.isHeld()){
wl.acquire();
}
However, your problem is actually in this check
if(stateString=="nextone")
This should be if(stateString.equals("nextone"))

please check this link before proceeding with wake lock. if it does not solve your problem then you can proceed with wake lock.
Force Screen On

You can use
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

try
{
Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_OFF_TIMEOUT, 1000*15);
}
catch (NumberFormatException e)
{
Log.e("aa", "could not persist screen timeout setting", e);
}
How to detect switching between user and device

What should I do as power button do (turn off screen, lock keyboard)?

My goal is make same thing as power button do.
I try PARTIAL_WAKE_LOCK and this is my code..
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
wl.acquire();
after that I open WAKE_LOCK permission in AndroidManifest.xml
<uses-permission android:name="android.permission.WAKE_LOCK" />
But when I launch my application not thing happen.
Do I miss something ?
Thanks

From your question I'm not totally sure whether you:
Try to turn off the device by pressing a button
Want to make sure the device will not go to sleep (as this is what a WakeLock is supposed to help you with). It can't prevent user interaction though (just tested on HTC Desire).
For 1) You can't lock the device or turn it's power off without being signed as a system app, as written here: http://groups.google.com/group/android-developers/browse_thread/thread/36399f15724ac3ae/98d93e53616cf495?show_docid=98d93e53616cf495
For 2) You can prevent the device from sleeping using WakeLock, sample code can read like this:
/**
* Called when the activity is first created.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
wl = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK, TAG);
}
// Call me from a button
public void doLock(View view) {
Log.d(TAG, "Lock");
if (!wl.isHeld()) {
Log.d(TAG, "acquire");
wl.acquire();
} else {
Log.d(TAG, "release");
wl.release();
}
}

Turning on screen programmatically

I would like to unlock screen and switching it on to show a popup on an event trigger. I am able to unlock the screen using
newKeyguardLock = km.newKeyguardLock(HANDSFREE);
newKeyguardLock.disableKeyguard();
on KeyGuardService but I cannot turn on the screen. I am using
wl = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, HANDSFREE);
wl.acquire();
but with no success. The screen still remains off.
How can I achieve this?

Note from author: I wrote this back in 2012. I don't know if it works anymore. Be sure to check out the other more recent answers.
Amir's answer got me close, but you need the ACQUIRE_CAUSES_WAKEUP flag at least (Building against Android 2.3.3).
WakeLock screenLock = ((PowerManager)getSystemService(POWER_SERVICE)).newWakeLock(
PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "TAG");
screenLock.acquire();
//later
screenLock.release();

This is very popular question but the accepted answer now is outdated.
Below is latest way to Turn On Screen OR wake up your device screen from an activity:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1) {
this.setTurnScreenOn(true);
} else {
final Window window = getWindow();
window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
}
Use WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON but FLAG_TURN_SCREEN_ON flag has been deprecated in API level 27 so you can use Activity.setTurnScreenOn(true) from API level 27 onward.

In your main activity's OnCreate() write following code:
((PowerManager)getSystemService(POWER_SERVICE)).newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "TAG").acquire();
It causes the device to wake up.
Do not forget disableKeyguard() to unlock the device...

undefined's answer with NullPointer check and set timeout :
private void turnOnScreen() {
PowerManager.WakeLock screenLock = null;
if ((getSystemService(POWER_SERVICE)) != null) {
screenLock = ((PowerManager)getSystemService(POWER_SERVICE)).newWakeLock(
PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "TAG");
screenLock.acquire(10*60*1000L /*10 minutes*/);
screenLock.release();
}
}

This is how you can do it:
PowerManager powerManager = (PowerManager) context.getSystemService(context.POWER_SERVICE);
PowerManager.WakeLock wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK |
PowerManager.ACQUIRE_CAUSES_WAKEUP |
PowerManager.ON_AFTER_RELEASE, "appname::WakeLock");
//acquire will turn on the display
wakeLock.acquire();
make sure to set permission in the manifest :
<uses-permission android:name="android.permission.WAKE_LOCK"/>