Question

I’ve been trying to open a text file and and save each line as the contents of an arraylist. Once this has been completed I would like to save it back to a file. I have been running into errors for so long and have tried numerous techniques. I found that for some reason, the files themselves are not being created. It may just be a simple error I’m overlooking but if you could provide any help I will be thankful.

Here’s the code:

public void addToFile(){

File root = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/appName/savedlocations");
root.mkdirs();
File fileName = new File(root, "locationslatitude.txt");
File fileName2 = new File(root, "locationslongitude.txt");

String file = fileName.toString();
String file2 = fileName2.toString();

String theContent = Double.toString(currLatitude);
String theContent2 = Double.toString(currLongitude);

s = new Scanner(file);
    while (s.hasNext()){
        fileList.add(s.next());
    }
    s.close();
    fileList.add(theContent);



    s2 = new Scanner(file2);
    while (s2.hasNext()){
        fileList2.add(s2.next());
    }
    s2.close();
    fileList2.add(theContent2);


try {//works for latitude file
        FileWriter writer = new FileWriter(file); 
        for(String str: fileList) { 
          writer.write(str);
          writer.write("\r\n");
        }
        writer.close();
        } catch (java.io.IOException error) {
          //do something if an IOException occurs.
            Toast.makeText(this, "Cannot Save Back To A File", Toast.LENGTH_LONG).show();
    }
//save the arraylist back to its appropriate file
    try {//works for longitude file
        FileWriter writer = new FileWriter(file2); 
        for(String str2: fileList2) { 
          writer.write(str2);
          writer.write("\r\n");
        }
        writer.close();
    } catch (java.io.IOException error) {
      //do something if an IOException occurs.
        Toast.makeText(this, "Cannot Save Back To A File", Toast.LENGTH_LONG).show();
    }
}

I believe I found the answer to the problem and I wanted to post it back on here so if anyone else faces the same problem this might help them.

The problem was that it wasn’t creating the file. The directory was created using “root.mkdirs();”. However, the files were not created and I was trying to read from non-existing files. This is what I believe caused the error. So, in order to fix this problem I altered the code to this:

  try{

        s = new Scanner(fileName);
        while (s.hasNext()){
            fileList.add(s.next());
        }
        s.close();
                fileList.add(theContent);

}catch (FileNotFoundException ex){
    ex.printStackTrace();
    try{
        fileName.createNewFile();
    }catch (IOException e){
        e.printStackTrace();
        Toast.makeText(this, "Hit IOException for file one", Toast.LENGTH_SHORT).show();
    }
}

try{  
        s2 = new Scanner(fileName2);
        while (s2.hasNext()){
            fileList2.add(s2.next());
        }
        s2.close();
                fileList2.add(theContent2);
}catch (FileNotFoundException ex){
    ex.printStackTrace();
    try{
        fileName2.createNewFile();
    }catch (IOException e){
        e.printStackTrace();
        Toast.makeText(this, "Hit IOException for file two", Toast.LENGTH_SHORT).show();
    }
}

This was the only piece of code I had to alter. The code which saved back to the file worked. I hope this will be of use to someone and thanks everyone for your help.

Answer 1

This code works in my project. You can use it to save ArrayList contents to text file. Make sure that the directory is created beforehand. Just iterate through your list and use println method to write it to txt file.

FileWriter outFile = new FileWriter(Environment.getExternalStorageDirectory().getAbsolutePath() + "/appName/savedlocations/nameoftextfile.txt");
PrintWriter out = new PrintWriter(outFile);
out.println("PRINT LINES WITH ME");
out.print("NOT NECCESSARILY A NEW LINE");
out.close(); // at the very end

Do not forget to catch IOException.