Sort the file list in order, by implementing Comparator.

In the previous example of our file explorer, the files listed not in order. To list it in order, we have to implement our own custom Comparator, filecomparator, to compare the file name.

Involve our comparator on files by calling Arrays.sort(files, filecomparator).



Modify from last post Back in history for File Explorer.

package com.AndroidListFiles;

import java.io.File;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Stack;

import android.app.ListActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.webkit.MimeTypeMap;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class AndroidListFilesActivity extends ListActivity {
 
 private List<String> fileList = new ArrayList<String>();
 
 Stack<File> history;

   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
      
       history = new Stack<File>();
      
       File root = new File(Environment
         .getExternalStorageDirectory()
         .getAbsolutePath());
       ListDir(root);

   }
  
   @Override
 protected void onListItemClick(ListView l, View v, int position, long id) {
  // TODO Auto-generated method stub
    File selected = new File(fileList.get(position));
    if(selected.isDirectory()){
     ListDir(selected);
    }else {
     Uri selectedUri = Uri.fromFile(selected);
     String fileExtension
      = MimeTypeMap.getFileExtensionFromUrl(selectedUri.toString());
     String mimeType
      = MimeTypeMap.getSingleton().getMimeTypeFromExtension(fileExtension);
     
     Toast.makeText(AndroidListFilesActivity.this,
       "FileExtension: " + fileExtension + "\n" +
       "MimeType: " + mimeType,
       Toast.LENGTH_LONG).show();
     
     //Start Activity to view the selected file
     Intent intent;
     intent = new Intent(Intent.ACTION_VIEW);
     intent.setDataAndType(selectedUri, mimeType);
     startActivity(intent);

    }
 }

 void ListDir(File f){
  
  history.push(f);
  
    File[] files = f.listFiles();
    
  Arrays.sort(files, filecomparator);
    
    fileList.clear();
    for (File file : files){
     fileList.add(file.getPath());  
    }
    
    ArrayAdapter<String> directoryList
    = new ArrayAdapter<String>(this,
      android.R.layout.simple_list_item_1, fileList);
    setListAdapter(directoryList); 
   }
 
 Comparator<? super File> filecomparator = new Comparator<File>(){
  public int compare(File file1, File file2) {
   return String.valueOf(file1.getName()).compareTo(file2.getName());
  } 
 };

 @Override
 public void onBackPressed() {
  // TODO Auto-generated method stub
  
  history.pop(); //remove current directory
  
  if(history.empty()){
   super.onBackPressed();
  }else{
   File selected = history.pop(); //Get the File on Top of history
   ListDir(selected);
  }
  
 }

}

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