eclipse xml editor indent using spaces

Question

My eclipse version is Mars Release (4.5.0).Preferences->XML－>XML Files->Editor,I can not set the value of Indentation size. The "+" and "-"　can not be clicked . I can not input value yet!

Answer 1

Had the same problem, I found the following workaround:

1. open with a text editor this file in your workspace folder: .metadata/.plugins/org.eclipse.core.runtime/.settings/org.eclipse.wst.xml.core.prefs
2. change or add the following line ("4" is just an example): indentationSize=4
3. (Re)start Eclipse