NullPointerException at ActionBarImplICS (using app compat) on long-press

Question 1

The ActionBar is null. That's because you're using an activity without a title (and thus also without an actionbar):

requestWindowFeature(Window.FEATURE_NO_TITLE);

There are two ways to fix it.

Simple:
Make YourActivity NOT extends ActionBarActivity but normal Activity.

More difficult:
Make transparent ActionBar with no title, no icon, no home button etc. How to do this? First, define ActionBar style and new theme that extends YourAppTheme:

<!-- Your App Theme-->
<style name="YourAppTheme.Light" parent="@style/Theme.AppCompat.Light">
    <...>
</style>

<!-- Transparent ActionBar Style -->
<style name="YourAppTheme.Light.ActionBar.Transparent" parent="@style/Widget.AppCompat.Light.ActionBar">
    <item name="android:background">@android:color/transparent</item>
    <item name="background">@android:color/transparent</item>
</style>

<!-- Fullscreen Activity Theme -->
<style name="YourAppTheme.FullScreen.Light" parent="@style/YourAppTheme.Light">
    <item name="android:actionBarStyle">@style/YourAppTheme.Light.ActionBar.Transparent</item>
    <item name="actionBarStyle">@style/YourAppTheme.Light.ActionBar.Transparent</item>
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:backgroundDimEnabled">false</item>
    <item name="android:windowActionBarOverlay">true</item>
    <item name="windowActionBarOverlay">true</item>
</style>

Next, set this theme to your fullscreen activity:

<activity
    android:name="your.package.name.YourFullscreenActivity"
    android:label="@string/app_name"
    android:theme="@style/YourAppTheme.FullScreen.Light" />

Finally, add following lines to YourFullscreenActivity#onCreate method:

getSupportActionBar().setDisplayHomeAsUpEnabled(false);
getSupportActionBar().setDisplayShowHomeEnabled(false);
getSupportActionBar().setDisplayShowTitleEnabled(false);

I hope it will help.

Question 2

I think I have a better solution to this issue.

Remove requestWindowFeature(Window.FEATURE_NO_TITLE); from activity and <item name="android:windowNoTitle">true</item> from activity theme.

To your activity code add:

To onCreate() method

View actionBar = getActionBarView();
if (actionBar != null) {
    actionBar.setVisibility(View.GONE);
}

To activity class:

public View getActionBarView() {
    Window window = getWindow();
    View v = window.getDecorView();
    int resId;

    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
        resId = getResources().getIdentifier(
                "action_bar_container", "id", getPackageName());
    } else {
        resId = Resources.getSystem().getIdentifier(
                "action_bar_container", "id", "android");
    }
    if (resId != 0) {
        return v.findViewById(resId);
    } else {
        return null;
    }
}

@Override
public void onSupportActionModeStarted(ActionMode mode) {
    super.onSupportActionModeStarted(mode);
    View actionBar = getActionBarView();
    if (actionBar != null) {
        actionBar.setVisibility(View.VISIBLE);
    }
}

@Override
public void onSupportActionModeFinished(ActionMode mode) {
    super.onSupportActionModeFinished(mode);
    View actionBar = getActionBarView();
    if (actionBar != null) {
        actionBar.setVisibility(View.GONE);
    }
}

This is remove action bar and at the same time allows you to manipulate text in edit text with action mode buttons.

Cheers

Question 3

The second solution to the above answer works, but causes the top row that would have been covered by the actionbar to be unclickable. Set the height item to zero in the actionbar style to solve this issue:

<item name="android:height">0dp</item>

Question 4

I think erakitin is a VERY good answer, and quiet simple if you take the "DO NOT extend ActionBarActivity, but in case anyone needs or want to avoid making that change, I'm leaving another answer which I think is also very simple and solves the problem PERFECTLY.

Try adding this to your activity's theme.

<item name="android:windowActionBar">false</item>

Question 5

public class MainActivity extends ActionBarActivity

Change to:

public class MainActivity extends Activity