How do I count the number of files with a specific extension on Android?

In the app I'm developing for Android I'm letting users create files specific to my application with the extension ".rbc". So far I have been successful in creating, writing to, and reading from these files.

Right now I am trying to count the number of these files that exists. I'm not particularly familiar with Java and I'm just beginning programming for Android so I feel a bit lost. All of my attempts so far at doing this have not been able to locate any files with my extension.

So I bas开发者_StackOverflow中文版ically have two questions I need answered so that I can figure this out:

Where is the default directory where Android stores files created by an application?

Do you have any examples do you can give me of counting files with a specific extension on Android?

Thank you very much in advance for your time.

Some tests showed me that the default directory where Android stores files created by an application using Context.getFilesDir() is /data/data/<your_package_name>/files

To count the files in any given directory you use File.listFiles(FileFilter) over the root dir. Your FileFilter should then be something like this (to filter for ".rbc" files):

public static class RBCFileFilter implements FileFilter {

    @Override
    public boolean accept(File pathname) {
        String suffix = ".rbc";
        if( pathname.getName().toLowerCase().endsWith(suffix) ) {
            return true;
        }
        return false;
    }

}

If you have some kind of directory structure you need to recursively search then you will have to File.listFiles(FileFilter) over the entire directory structure. And it should be something like:

public static List<File> listFiles(File rootDir, FileFilter filter, boolean recursive) {
    List<File> result = new ArrayList<File>();
    if( !rootDir.exists() || !rootDir.isDirectory() ) 
        return result;


    //Add all files that comply with the given filter
    File[] files = rootDir.listFiles(filter);
    for( File f : files) {
        if( !result.contains(f) )
            result.add(f);
    }

    //Recurse through all available dirs if we are scanning recursively
    if( recursive ) {
        File[] dirs = rootDir.listFiles(new DirFilter());
        for( File f : dirs ) {
            if( f.canRead() ) {
                result.addAll(listFiles(f, filter, recursive));
            }
        }
    }

    return result;
}

And where DirFilter would implements FileFilter this way:

public static class DirFilter implements FileFilter {

    @Override
    public boolean accept(File pathname) {
        if( pathname.isDirectory() ) 
            return true;

        return false;
    }

}

Android usually stores files created by an application in data/data/package_name_of_launching_Activity and there you'll find a few folders where files can be stored. You can get a cache directory within that path by calling getCacheDir().

A quick strategy for counting specific extensions could be as follows:

If you have a folder, say File folder = new File(folderPath) where folderPath is the absolute path to a folder. You could do the following:

String[] fileNames = folder.list();
int total = 0;
for (int i = 0; i< filenames.length; i++)
{
  if (filenames[i].contains(".rbc"))
    {
      total++;
     }
  }

This can give you a count of the total files with ".rbc" as the extension. Although this may not be the best/efficient way of doing it, it still works.

For counting files you can try this code:

# public static List getFiles(File aStartingDir)   
# {  
#     List result = new ArrayList();  
#    
#     File[] filesAndDirs = aStartingDir.listFiles();  
#     List filesDirs = Arrays.asList(filesAndDirs);  
#     Iterator filesIter = filesDirs.iterator();  
#     File file = null;  
#     while ( filesIter.hasNext() ) {  
#       file = (File)filesIter.next();  
#       result.add(file); //always add, even if directory  
#       if (!file.isFile()) {  
#         //must be a directory  
#         //recursive call!  
#         List deeperList = getFileListing(file);  
#         result.addAll(deeperList);  
#       }  
#    
#     }  
#     Collections.sort(result);  
#     return result;  
#   }  

You can use fileFilter parameter for listFiles() method to return files with .rbc extension.

EDIT: Sorry, missed one question. Files will be placed in your application package which will be there in data/data.. You can view them in File Explorer in Eclipse with DDMS mode.

Here is a java 8+ example:

var total=Arrays.asList(new File(pathToDirectory).list())
                      .stream()
                      .filter(x -> x.contains(".rbc"))
                      .collect(Collectors.counting());

or

var fileNames = Arrays.asList(tempDir.list())
                       .stream()
                       .filter(x -> x.contains(".rbc"))
                       .collect(Collectors.toList());
var total=fileNames.size();