check android application is in foreground or not?

I don't understand what you want, but You can detect currently foreground/background application with ActivityManager.getRunningAppProcesses() call.

Something like,

class ForegroundCheckTask extends AsyncTask<Context, Void, Boolean> {

  @Override
  protected Boolean doInBackground(Context... params) {
    final Context context = params[0].getApplicationContext();
    return isAppOnForeground(context);
  }

  private boolean isAppOnForeground(Context context) {
    ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
    if (appProcesses == null) {
      return false;
    }
    final String packageName = context.getPackageName();
    for (RunningAppProcessInfo appProcess : appProcesses) {
      if (appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND && appProcess.processName.equals(packageName)) {
        return true;
      }
    }
    return false;
  }
}

// Use like this:
boolean foregroud = new ForegroundCheckTask().execute(context).get();

Also let me know if I misunderstand..

UPDATE: Look at this SO question Determining the current foreground application from a background task or service fore more information..

Thanks..

Update Oct 2020: Checkout the Lifecycle extensions based solutions on this thread. The approach seems to be working, it's more elegant and modern.

---

The neatest and not deprecated way that I've found so far to do this, as follows:

@Override
public boolean foregrounded() {
    ActivityManager.RunningAppProcessInfo appProcessInfo = new ActivityManager.RunningAppProcessInfo();
    ActivityManager.getMyMemoryState(appProcessInfo);
    return (appProcessInfo.importance == IMPORTANCE_FOREGROUND || appProcessInfo.importance == IMPORTANCE_VISIBLE)
}

It only works with SDK 16+.

EDIT:

I removed the following code from the solution:

KeyguardManager km = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE);
// App is foreground, but screen is locked, so show notification
return km.inKeyguardRestrictedInputMode();

since that makes not getting the notifications if the screen locked. I had a look to the framework and the purpose of this is not entirely clear. I'd remove it. Checking the process info state would be enough :-)