// Derived from http://stackoverflow.com/a/3054692/250076
public static File getRelativeFile(File targetFile, File baseFile) {
try {
targetFile = targetFile.getCanonicalFile();
baseFile = baseFile.getCanonicalFile();
} catch (IOException ignored) {
}
String pathSeparator = File.separator;
String basePath = baseFile.getAbsolutePath();
String normalizedTargetPath = normalize(targetFile.getAbsolutePath(), pathSeparator);
String normalizedBasePath = normalize(basePath, pathSeparator);
String[] base = normalizedBasePath.split(Pattern.quote(pathSeparator));
String[] target = normalizedTargetPath.split(Pattern.quote(pathSeparator));
StringBuilder common = new StringBuilder();
int commonIndex = 0;
while (commonIndex < target.length
&& commonIndex < base.length
&& target[commonIndex].equals(base[commonIndex])) {
common.append(target[commonIndex]).append(pathSeparator);
commonIndex++;
}
if (commonIndex == 0) {
throw new Error(
"No common path element found for '"
+ normalizedTargetPath
+ "' and '"
+ normalizedBasePath
+ '\'');
}
boolean baseIsFile = true;
if (baseFile.exists()) {
baseIsFile = baseFile.isFile();
} else if (basePath.endsWith(pathSeparator)) {
baseIsFile = false;
}
StringBuilder relative = new StringBuilder();
if (base.length != commonIndex) {
int numDirsUp = baseIsFile ? base.length - commonIndex - 1 : base.length - commonIndex;
for (int i = 0; i < numDirsUp; i++) {
relative.append("..").append(pathSeparator);
}
}
relative.append(normalizedTargetPath.substring(common.length()));
return new File(relative.toString());
}
