[Galaxy S II Themes and Apps] gerryS2:
I solved it with the guide of [MENTION=3065070]Goldie[/MENTION], I have created a method in PhoneStatusbar and I have insert a custom id in the line of Digital Clock like this:

<com.android.systemui.statusbar.policy.DigitalClock android:textSize="@dimen/status_bar_clock_text_size" android:textColor="#ff959595" android:ellipsize="none" android:gravity="left|center" android:id="@id/digitalclock_view" android:visibility="gone" android:paddingLeft="3.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" android:singleLine="true" android:includeFontPadding="false" />

Insert this line in ids.xml:

<item type="id" name="digitalclock_view">false</item>

In PhoneStatusbar insert this method at the end of the file:

.method digitalclock_view()V
.locals 6

iget-object v1, p0, Lcom/android/systemui/SystemUI;->mContext:Landroid/content/Context;

invoke-virtual {v1}, Landroid/content/Context;->getContentResolver()Landroid/content/ContentResolver;

move-result-object v1

const-string v2, "enable_digitalclock"

const/4 v3, 0x1

invoke-static {v1, v2, v3}, Landroid/provider/Settings$System;->getInt(Landroid/content/ContentResolver;Ljava/lang/String;I)I

move-result v3

if-nez v3, :cond_0

const v3, 0x8

:cond_0
iget-object v5, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mStatusBarWindow:Lcom/android/systemui/statusbar/phone/StatusBarWindowView;

const p0, 0x7f0d01e0

invoke-virtual {v5, p0}, Lcom/android/systemui/statusbar/phone/StatusBarWindowView;->findViewById(I)Landroid/view/View;

move-result-object v4

invoke-virtual {v4, v3}, Lcom/android/systemui/statusbar/policy/DigitalClock;->setVisibility(I)V

return-void
.end method

0x7f0d01e0 is the public id of "digitalclock_view"

"enable_digitalclock" is the key for checkbox (android:key="enable_digitalclock")

After I have insert this line in a part of method makestatusbarview:

invoke-virtual {p0}, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->digitalclock_view()V

iget-object v9, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mClearButton:Landroid/view/View;

const/4 v10, 0x0

invoke-virtual {v9, v10}, Landroid/view/View;->setAlpha(F)V

iget-object v9, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mClearButton:Landroid/view/View;

const/4 v10, 0x4

invoke-virtual {v9, v10}, Landroid/view/View;->setVisibility(I)V

invoke-virtual {p0}, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->digitalclock_view()V

iget-object v9, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mClearButton:Landroid/view/View;

const/4 v10, 0x0

invoke-virtual {v9, v10}, Landroid/view/View;->setEnabled(Z)V

iget-object v9, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mStatusBarWindow:Lcom/android/systemui/statusbar/phone/StatusBarWindowView;

const v10, 0x7f0d004f

invoke-virtual {v9, v10}, Lcom/android/systemui/statusbar/phone/StatusBarWindowView;->findViewById(I)Landroid/view/View;

move-result-object v9

check-cast v9, Lcom/android/systemui/statusbar/policy/DateView;

If you have this on-fly you must have PhoneStatusBar$SettingsObserver.smali and add this line in two method:

.method observe()V
.locals 3

const/4 v2, 0x0

iget-object v1, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar$SettingsObserver;->this$0:Lcom/android/systemui/statusbar/phone/PhoneStatusBar;

iget-object v1, v1, Lcom/android/systemui/statusbar/phone/PhoneStatusBar;->mContext:Landroid/content/Context;

invoke-virtual {v1}, Landroid/content/Context;->getContentResolver()Landroid/content/ContentResolver;

move-result-object v0

const-string v1, "enable_digitalclock"

invoke-static {v1}, Landroid/provider/Settings$System;->getUriFor(Ljava/lang/String;)Landroid/net/Uri;

move-result-object v1

invoke-virtual {v0, v1, v2, p0}, Landroid/content/ContentResolver;->registerContentObserver(Landroid/net/Uri;ZLandroid/database/ContentObserver;)V

.method public onChange(Z)V
.locals 1

iget-object v0, p0, Lcom/android/systemui/statusbar/phone/PhoneStatusBar$SettingsObserver;->this$0:Lcom/android/systemui/statusbar/phone/PhoneStatusBar;

invoke-virtual {p0}, Lcom/android/systemui/statusbar/phone/PhoneStatusBar$SettingsObserver;->digitalclock_view()V

Thanks [MENTION=3065070]Goldie[/MENTION] for his guide of smali code :D