Develop Reference

Android Debug Bridge force RTL option to apply without root

I have learned that using the ADB one can force the layout guides to show using the following commands:
adb shell setprop debug.layout true
adb shell service call activity 1599295570 # SYSPROPS_TRANSACTION
This allows developers to see the layout grid thanks to the SYSPROPS_TRANSACTION code.
The examples of which can be found here
However if I want to change something like RTL (right to left) - the SYSPROPS_TRANSACTION call does not force the re-render, I suspect because it needs to restart the activity, given that a rotation of the device will work:
adb shell setprop debug.force_rtl true
adb shell settings put system user_rotation 3 # landscape
adb shell settings put system user_rotation 0 # portrait
While I don't mind invalidating the activity I don't think I should have to be this "manual" about it. Is there a mechanism to refresh the screen without doing the rotation?
I have looked in the AOSP and found this:
private void writeToForceRtlLayoutSetting(boolean isEnabled) {
Settings.Global.putInt(mContext.getContentResolver(),
Settings.Global.DEVELOPMENT_FORCE_RTL,
isEnabled ? SETTING_VALUE_ON : SETTING_VALUE_OFF);
DisplayProperties.debug_force_rtl(isEnabled);
}
which is roughly the equivalent of:
adb shell settings put global debug.force_rtl 1.0 #or 0.0 for off
But I have noticed if I do this one and a rotation it does NOT change
I have been trying to find the appropriate broadcast intent so that it would work, but I can't find one that just tells the screen to re-render
adb shell am broadcast <SOMETHING HERE WOULD BE NICE>
I took a page out of the DarkModePreference and tried to tell it that the battery charge state had changed, but you can't do that from ADB:
adb shell am broadcast android.os.action.POWER_SAVE_MODE_CHANGED
But no luck there either - no refresh happening
NOTE:
It's interesting that the layout bounds and RTL elements are grouped in the android source code, yet don't use the same behaviour when changed

I noticed that if I use
adb shell wm size
I can read the size of the window, and as a bonus, when setting it, it causes a redraw regarding right to left. So now what I do is read the window size, save it, change it a little, set it to the changed value and set it back. My script looks something like:
run("adb shell settings put global debug.force_rtl 1.0")
old_size = run("adb shell wm size")
run("adb shell wm size 100x100")
run("adb shell wm size " + old_size)
And it will force the right to left. It's a bit hacky but it works.

Permanently hide Android Status Bar

I'm trying to hide the system Status Bar on an Android 4.4 device. This is for a kiosk-mode where my app will be the only app ever run on the device. The target device for now is a 2013 Nexus 7.
The device is rooted, and I've been able to completely remove the bottom Navigation Bar with some info from this post.
For the top Status Bar, everything I have tried only hides the bar temporarily. If my users motion down at the top of the screen, the status bar reappears. I don't want to allow them to see the time, get to settings or even see notifications.
Posts I've found and already tried:
Hide System Bar in Tablets
Permanently hide navigation bar on activity
Hide status bar on android
Disable/Hide status bar in Android
Any suggestions?
Ideally, I'd love to be able to edit build.prop to do this, since I'm already doing that for the navigation bar, and could do this at the same time. I'm trying to not have to build my own android image.
Update:
After some more work, this seems to depend somewhat on the exact build of android, or the device its running on.
Some devices, such as the Nexus series I've been working with allow the user to swipe to make the bar reappear.
However, I've recently tried this on a Verizon Eclipse, and the bar does not reappear, which is what I was looking for.
I'm still looking for a better solution to target all devices, but it will probably come down to creating my own build of android.

We could not prevent the status appearing in full screen mode in kitkat devices, so made a hack which still suits the requirement ie block the status bar from expanding.
For that to work, the app was not made full screen. We put a overlay over status bar and consumed all input events. It prevented the status from expanding.
note:
customViewGroup is custom class which extends any
layout(frame,relative layout etc) and consumes touch event.
to consume touch event override the onInterceptTouchEvent method of
the view group and return true
Updated
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
customViewGroup implementation
Code :
WindowManager manager = ((WindowManager) getApplicationContext()
.getSystemService(Context.WINDOW_SERVICE));
WindowManager.LayoutParams localLayoutParams = new WindowManager.LayoutParams();
localLayoutParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ERROR;
localLayoutParams.gravity = Gravity.TOP;
localLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|
// this is to enable the notification to recieve touch events
WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |
// Draws over status bar
WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
localLayoutParams.width = WindowManager.LayoutParams.MATCH_PARENT;
localLayoutParams.height = (int) (50 * getResources()
.getDisplayMetrics().scaledDensity);
localLayoutParams.format = PixelFormat.TRANSPARENT;
customViewGroup view = new customViewGroup(this);
manager.addView(view, localLayoutParams);
Hope this helps you

I did try the workaround provided by #gonglong, but I wasn't happy with the result because of a flash in the UI as the workaround kicked in.
Instead, I was able to do this as root:
settings put secure user_setup_complete 0
I think on a normal device, this would cause the initial device setup to start, but on my devices, I've removed that APK from system so that doesn't happen.
This isn't documented anywhere I can find, but has a nice effect, where the top settings UI can't be dragged down. The notifications area can still be dragged down.
Another setting that I found useful was:
settings put global device_provisioned 0
This hides the Airplane Mode and Silent Mode options from the Power menu, which is an added bonus for my application.
There might be more side effects, but I've yet to find any that matter to me.
Full List
This list was taken from a Nexus 7 2013 LTE running brand new Android 4.4.3 (KTU84L). The number in square brackets is the value when I pulled the db file, which was after basic setup device setup and enabling developer/USB, but before making any other changes in settings
This file was found at data/data/com.android.providers.settings/databases/settings.db
Note: Some URLS required adding an extra space character to bypass SO filters
system namespace
volume_music [11]
volume_ring [5]
volume_system [7]
volume_voice [4]
volume_alarm [6]
volume_notification [5]
volume_bluetooth_sco [7]
mode_ringer_streams_affected [174]
mute_streams_affected [46]
vibrate_when_ringing [0]
dim_screen [1]
dtmf_tone_type [0]
hearing_aid [0]
tty_mode [0]
screen_brightness [87]
screen_brightness_mode [1]
window_animation_scale [1.0]
transition_animation_scale [1.0]
accelerometer_rotation [1]
haptic_feedback_enabled [1]
notification_light_pulse [1]
dtmf_tone [1]
sound_effects_enabled [1]
lockscreen_sounds_enabled [1]
pointer_speed [0]
alarm_alert [content://media/internal/audio/media/11]
notification_sound [content://media/internal/audio/media/27]
ringtone [content://media/internal/audio/media/35]
next_alarm_formatted []
radio.data.stall.recovery.action [0]
screen_off_timeout [30000]
global namespace
airplane_mode_on [0]
airplane_mode_radios [cell,bluetooth,wifi,nfc,wimax]
airplane_mode_toggleable_radios [bluetooth,wifi,nfc]
auto_time [1]
auto_time_zone [1]
stay_on_while_plugged_in [0]
wifi_sleep_policy [2]
mode_ringer [2]
package_verifier_enable [1]
wifi_networks_available_notification_on [1]
bluetooth_on [0]
cdma_cell_broadcast_sms [1]
data_roaming [0]
mobile_data [1]
netstats_enabled [1]
install_non_market_apps [0]
usb_mass_storage_enabled [1]
wifi_max_dhcp_retry_count [9]
wifi_display_on [0]
lock_sound [/system/media/audio/ui/Lock.ogg]
unlock_sound [/system/media/audio/ui/Unlock.ogg]
power_sounds_enabled [1]
low_battery_sound [/system/media/audio/ui/LowBattery.ogg]
dock_sounds_enabled [0]
desk_dock_sound [/system/media/audio/ui/Dock.ogg]
desk_undock_sound [/system/media/audio/ui/Undock.ogg]
car_dock_sound [/system/media/audio/ui/Dock.ogg]
car_undock_sound [/system/media/audio/ui/Undock.ogg]
wireless_charging_started_sound [/system/media/audio/ui/WirelessChargingStarted.ogg]
dock_audio_media_enabled [1]
set_install_location [0]
default_install_location [0]
emergency_tone [0]
call_auto_retry [0]
preferred_network_mode [9]
subscription_mode [1]
low_battery_sound_timeout [3600000]
wifi_watchdog_on [1]
audio_safe_volume_state [1]
send_action_app_error [1]
web_autofill_query_url [http:// android.clients.google.com/proxy/webautofill]
sms_short_codes_content_url [http://www.gstatic.com/android/config_update/07172013-sms-blacklist.txt]
sms_short_codes_metadata_url [http://www.gstatic.com/android/config_update/07172013-sms-metadata.txt]
cert_pin_metadata_url [http://www.gstatic.com/android/config_update/10142013-metadata.txt]
cert_pin_content_url [http://www.gstatic.com/android/config_update/10142013-pins.txt]
wifi_on [1]
assisted_gps_enabled [1]
wifi_scan_always_enabled [1]
device_provisioned [1]
bugreport_in_power_menu [0]
development_settings_enabled [1]
adb_enabled [1]
wifi_country_code [us]
secure namespace
wifi_watchdog_watch_list [GoogleGuest]
mock_location [0]
backup_enabled [0]
backup_transport [com.google.android.backup/.BackupTransportService]
mount_play_not_snd [1]
mount_ums_autostart [0]
mount_ums_prompt [1]
mount_ums_notify_enabled [1]
accessibility_script_injection [0]
accessibility_web_content_key_bindings [0x13=0x01000100; 0x14=0x01010100; 0x15=0x02000001; 0x16=0x02010001; 0x200000013=0x02000601; 0x200000014=0x02010601; 0x200000015=0x03020101; 0x200000016=0x03010201; 0x200000023=0x02000301; 0x200000024=0x02010301; 0x200000037=0x03070201; 0x200000038=0x03000701:0x03010701:0x03020701;]
long_press_timeout [500]
touch_exploration_enabled [0]
speak_password [0]
accessibility_script_injection_url [https://ssl.gstatic.com/accessibility/javascript/android/AndroidVox_v1.js]
lockscreen.disabled [0]
screensaver_enabled [1]
screensaver_activate_on_dock [1]
screensaver_activate_on_sleep [0]
screensaver_components [com.google.android.deskclock/com.android.deskclock.Screensaver]
screensaver_default_component [com.google.android.deskclock/com.android.deskclock.Screensaver]
accessibility_display_magnification_enabled [0]
accessibility_display_magnification_scale [2.0]
accessibility_display_magnification_auto_update [1]
android_id [a0ef8b2a9ade982c]
enabled_input_methods [com.google.android.inputmethod.latin/com.android.inputmethod.latin.LatinIME:com.google.android.googlequicksearchbox/com.google.android.voicesearch.ime.VoiceInputMethodService]
input_methods_subtype_history []
selected_input_method_subtype [-1]
selected_spell_checker [com.google.android.inputmethod.latin/com.android.inputmethod.latin.spellcheck.AndroidSpellCheckerService]
selected_spell_checker_subtype [0]
lock_screen_owner_info_enabled [0]
voice_recognition_service [com.google.android.googlequicksearchbox/com.google.android.voicesearch.serviceapi.GoogleRecognitionService]
default_input_method [com.google.android.inputmethod.latin/com.android.inputmethod.latin.LatinIME]
enabled_print_services [com.google.android.apps.cloudprint/com.google.android.apps.cloudprint.printdialog.services.CloudPrintService:com.hp.android.printservice/com.hp.android.printservice.ServiceAndroidPrint]
enabled_on_first_boot_system_print_services [com.google.android.apps.cloudprint/com.google.android.apps.cloudprint.printdialog.services.CloudPrintService:com.hp.android.printservice/com.hp.android.printservice.ServiceAndroidPrint]
bluetooth_name [Nexus 7]
masterLocationPackagePrefixBlacklist [com.google.,com.semaphoremobile.zagat.android]
serial_blacklist [827,864]
dropbox:data_app_anr [disabled]
dropbox:data_app_wtf [disabled]
ssl_session_cache [file]
pubkey_blacklist [5f3ab33d55007054bc5e3e5553cd8d8465d77c61,783333c9687df63377efceddd82efa9101913e8e]
facelock_liveliness_recognition_threshold [2.2]
facelock_detection_threshold [0.0]
dropbox:data_app_crash [disabled]
masterLocationPackagePrefixWhitelist [com.google.android.gms]
lockscreen.options [enable_facelock]
facelock_max_center_movement [10.0]
bluetooth_address [AC:22:0B:A5:AF:3D]
bluetooth_addr_valid [1]
config_update_certificate [ truncated base64 content ]
location_providers_allowed [gps,network]
allowed_geolocation_origins [http://www.google.co.uk http:// www.google.com]
locationPackagePrefixBlacklist []
user_setup_complete [1]
locationPackagePrefixWhitelist []
last_setup_shown [eclair_1]

I know this is an old question but hopefully it will help someone. Here are two very simple calls to disable and enable the status bar that I have used before. Can be used from the command line or executed by a Java app:
Disable:
service call activity 42 s16 com.android.systemui
Enable:
am startservice -n com.android.systemui/.SystemUIService

I've used this answer to hide the softkeys: https://stackoverflow.com/a/27003890/1525867
And for disabling the StatusBar (this may harm your device so do it carfully. I've ruined my device several times before I managed to do it) Tested on Asus Tinker Board, Android 6:
Download apktool from here https://bitbucket.org/iBotPeaches/apktool/downloads/ and add it to pathin your favorite way
pull SystemUI.apk from your device:
adb pull /system/priv-app/SystemUI/SystemUI.apk the path to SystemUI.apk may be different
pull framework-res.apk from your device adb pull /system/framework/framework-res.apk the path to framework-res.apk may be different
run apktool if framework-res.apk
run apktool if SystemUI.apk
run apktool d SystemUI.apk
Open SystemUI\res\layout\status_bar.xml and add android:visibility="gone" to the top most xml element (for me it was com.android.systemui.statusbar.phone.PhoneStatusBarView)
run apktool b SystemUI
Go to SystemUI\original and copy AndroidManifest.xml and META-INF to SystemUI\build\apk\
run apktool b SystemUI again
Go to SystemUI\dist\ and override the device's original SystemUI.apk with the one at SystemUI\dist\SystemUI.apk with adb push SystemUI\dist\SystemUI.apk /system/priv-app/SystemUI/SystemUI.apk
Restart device
Based on this thread https://forum.xda-developers.com/showthread.php?t=2203166

I don't have a perfect solution but a workaround here. The basic idea is to listen the system ui status changes and force navigation/status bar as invisible. It takes effect as similar as setting IMMERSIVE_STICKY mode but disappearing navigation/status bar quicker than IMMERSIVE_STICKY.
here it is:
set system ui style in onCreate() and on onResume function, and set system ui change listener
mDecroView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE);
mDecroView.setOnSystemUiVisibilityChangeListener(this);
force system bar as invisible in onSystemUiVisibilityChange, setting system ui some seconds later otherwise it would take on effect(does not know exactly why, maybe system just ignores the system ui setting request when system bar showing not yet completed)
public void onSystemUiVisibilityChange(int visibility) {
// TODO Auto-generated method stub
Log.d(TAG, "onSystemUiVisibilityChange called with visibility " + visibility);
if((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0){
if(null == mHandler){
mHandler = new MyHandler();
}
if(null != mHandler){
mHandler.removeMessages(MSG_HIDE_SYSTEM_BAR);
mHandler.sendEmptyMessageDelayed(MSG_HIDE_SYSTEM_BAR, 50);
}
//the deccro view is not in full screen
Log.d(TAG, "setSystemUiVisibility");
Log.d(TAG, "current system ui is " + mDecroView.getSystemUiVisibility());
}
}
then you can set system ui like this:
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
switch(msg.what){
case MSG_HIDE_SYSTEM_BAR:
mDecroView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE);
break;
}
}

A great solution I found for that issue, setting each Activity theme & windowSoftInputMode to the following values :
<activity android:name=".MyActivity"
android:theme="#android:style/Theme.NoTitleBar.Fullscreen"
android:windowSoftInputMode="adjustResize"> <!-- theme : to set the activity to a full screen mode without a status bar(like in some games) -->
</activity> <!-- windowSoftInputMode : to resize the activity so that it fits the condition of displaying a softkeyboard -->
for more info refer here.

try this code:
disable statusbar and navbar
adb shell
su
pm disable com.android.systemui
reboot
enable statusbar and navbar
adb shell
su
pm enable com.android.systemui
reboot
It works on Android 5.1.1 but the usb camera is down
Another way (my device worked without any problems)
Remove System Navigation Bar ¶
The Android System Navigation Bar is the bar at the bottom of the screen which presents the back, home, and app-switch soft-keys.
As the system navigation bar is independent from any installed Android application in particular, removing it is done in the Android OS.
To accomplish this on a rooted installed device you can set the qemu.hw.mainkeys property to 1 by editing /system/build.prop:
qemu.hw.mainkeys=1
To accomplish this at build time you would set the 'config_showNavigationBar' value to false in your device overlay (ie device/gateworks/ventana/overlay/frameworks/base/core/res/res/values/config.xml):
<bool name="config_showNavigationBar">false</bool>
Note you could also make build.prop modifications at build time by adding to the PRODUCT_DEFAULT_PROPERTY_OVERRIDES or ADDITIONAL_BUILD_PROPERTIES variables which can be found in your device target configuration (ie imx6.mk and BoardConfig.mk in device/gateworks/ventana/).
Additionally, you can hide the navigation bar (and status bar) within an application by setting the SYSTEM_UI_FLAG_HIDE_NAVIGATION flag however it will pop back if the user touches anywhere on the screen.
http://trac.gateworks.com/wiki/Android/Kiosk

For rooted devices, I use the follwing code to change visibility from within my apps. It sets the visibility of the System UI and then reboots the device to make the setting changes actually happen. You can also use "pm "hide" com.android.systemui"... via adb, of course.
Please note that on some older devices, the command parameters were "enable" / "disable". For newer Android versions (9+), I observed that only "unhide" and "hide" were working for me.
fun setSystemUiEnabled(enabled: Boolean) {
try {
val p = Runtime.getRuntime().exec("su")
val os = DataOutputStream(p.outputStream)
os.writeBytes(
"pm ${if (enabled) "unhide" else "hide"} com.android.systemui\n"
)
os.writeBytes("reboot\n")
os.writeBytes("exit\n")
os.flush()
} catch (e: IOException) {
Timber.w(e, "Error while setting system-ui enabled-state to $enabled")
e.printStackTrace()
}
}

add this before : setContentView(R.layout.x);
this.requestWindowFeature(Window.FEATURE_NO_TITLE); // Removes title bar
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.x);

Android logcat message: SurfaceTextureClient

My app is generating this logcat message almost every second:
SurfaceTextureClient [STC::queueBuffer] (this:0x5e774a58) fps:2.00, dur:1496.57, max:499.96, min:498.21
and it's just a hello world with a custom logo in the actionbar and saves things in SharedPreferences. My activity layout is a LinearLayout with two edittexts and one button. No strange things.
This is the only style I use:
<style name="MyTheme" parent="#android:style/Theme.Holo.Light.DarkActionBar"></style>
I've searched in google but I have found nothing.
When I touch the button this appears:
Provider/Settings invalidate [system]: current 1 != cached 0
Provider/Settings from db cache, name = sound_effects_enabled , value = 0
It's annoying.
EDIT
Maybe is my smarphone. I've installed the same app in a tablet and the messages don't appear. Maybe I have touch something in settings? It's very strange. (My phone is a Jiayu 3gs with Android 4.2.1, but until today nothing wrong had happened).
Ok, the message appears in the general log so it's not associated with my app.
I'm starting to think that I have a virus. I have a lot of messages of this kind without doing anything in the phone:
ADB_SERVICES create_local_service_socket() name=shell:ls -l /
ADB_SERVICES adb: unable to open /proc/14420/oom_adj
ADB_SERVICES adb fdevent_process list (31) (20) (77)
ADB_SERVICES closing because is_eof=1 r=1 s->fde.force_eof=0
SurfaceFlinger [SurfaceFlinger] fps:2.002652,dur:1498.01,max:499.41,min:499.22
UsbDeviceManager onReceive - BATTERY_CHANGED - mPlugType: 2, mSettingUsbCharging: false, mConnected: true, mSettingUsbBicr: false
And I have a lot of files in my / with date creation of 1970-01-01 01:00. Files like init, init.modem.rc, init.rc, init.usb.rc, ..., emmc#android, ..
Maybe I'm just paranoid.
Furthermore I can't access to all options in "Developer options settings". This is all I can see:

Different phones have different kind and amount of log messages. Not much you can do about it, besides filtering the output based on the tag you use.

How to hide bottom system bar in android tablet

I am developing an application for tablet only, where the requirement is to run the app on the full screen of the tablet.
For this I have used following code in my main activity:
getWindow().requestFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
This code snippet only removes the title bar and action bar. But in tablets, there is a bottom system bar (having home and back button). I also want to remove or hide this system bar too.
I have searched but there is only following solution:
There is no API to remove or hide the system bar.
You can use some android app to hide system bar. (for example:
surelock, hidebar, etc)
My question is :
Is it really not possible in android?
Above available app (i.e surelock, hide bar, etc) also hiding bar.
It means they are using something to do so. Can be use this
something in our app so the user will not require to download these
app seperatly.
Please guide me.
I know this is not a good idea. But My app is only for tablet having Android 4.0 or greater and that tablet will run only this single app so we do not need to go back and use home button. That's why my requirement is to use the app in full screen.

If you have root access you can use this code other wise it is not allowed
try{
//REQUIRES ROOT
Build.VERSION_CODES vc = new Build.VERSION_CODES();
Build.VERSION vr = new Build.VERSION();
String ProcID = "79"; //HONEYCOMB AND OLDER
//v.RELEASE //4.0.3
if(vr.SDK_INT >= vc.ICE_CREAM_SANDWICH){
ProcID = "42"; //ICS AND NEWER
}
//REQUIRES ROOT
Process proc = Runtime.getRuntime().exec(new String[]{"su","-c","service call activity "+ ProcID +" s16 com.android.systemui"}); //WAS 79
proc.waitFor();
}catch(Exception ex){
Toast.makeText(getApplicationContext(), ex.getMessage(), Toast.LENGTH_LONG).show();
}
See this

From Android API 4.0 and later you can use the following code to hide the bottom system bar.
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);

This is not possible unless you've root access. Alternatively, you can create a launcher application.
Otherwise it will be beyond the scope of your Application to Hide System/Navigation bar.

After a lot of searching on the internet, I managed to get the System Bar to hide and appear in a 4.2 device using:
To Hide:
Runtime.getRuntime().exec("service call activity 42 s16 com.android.systemui");
Or use 79 instead of 42 for API less than 14. You may also need to include the SET_DEBUG_APP permission, in which case you need to have the application signed with the system key or installed in the /system/app/ directory.
To Show:
Runtime.getRuntime().exec("am startservice --user 0 -n com.android.systemui/.SystemUIService");
Alternatively some people have used the -a (instead of -n) option, though this was causing an error on my device:
Error: Not found; no service started.

Hiding Systembar in android 3.0(honeycomb)

How do I hide the system bar in android 3.0(honeycomb)?

The systembar cannot be removed (on non-rooted devices). You can go into "lights out mode" which dims it and only shows dots where the buttons are using the following code (ref):
View v = findViewById(R.id.view_id);
v.setSystemUiVisibility(View.STATUS_BAR_HIDDEN);
This was also asked before here, remember to search first.

We tinkered around with Honeycomb and found a way to hide and restore the bar, although root is required here. You can find a detailed answer in our article here.

I tested some ways to kill system bar:
Kill by adb shell: - su; ps, look for com.android.systemui; kill - success, sys-bar removed.
Settings, "Sytem UI" force stop - success, sys-bar removed.
Root explorer, delete /system/app/systemui.apk - got circle of error messages "com.android.systemui crashed, blabla...". Reboot, tablet started without system bar, no any errors, so success.
My app:
Code:
android.os.Process.killProcess(android.os.Process.getUidForName("com.android.systemui"));
failed, as expected, because my app can not kill process started by another app.
My app:
permission - android.permission.KILL_BACKGROUND_PROCESSES
Code:
final Context context = getApplicationContext();
servMng = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
servMng.killBackgroundProcesses("com.android.systemui");
Failed, no idea why.
Run script in my app to execute "ps", look for PID and execute "kill", not tested.

Hiding the systembar in honeycomb can be done with Hide Bar. The home page is at http://ppareit.github.com/HideBar/. The code can be found at https://github.com/ppareit/HideBar.