Write to txt file, but not overwrite

问题

I got a little problem, it seems simple (personally I think it is), but I couldn't find a answer. But atleast I don't know how to fix it.

I write some lines to a .txt file when I hit the button Save. Then after that, when I type something else, and hit Save again, it overwrites my first lines.

But I want that it writes at a new line. Also when I close and restart the app again, and hit save again, it must save the text on a new line again.

So basically: How can I write text to a .txt file, without overwriting previous lines. I can write to a file, so that is not the problem, but only how to NOT overwrite.

This is the "little" part of my code:

   public void Data_save_contacts(View v) {

        Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);

        try {

                writer_contact = new BufferedWriter(new FileWriter(root + "/Save/Contacten.txt"));
                writer_contact.write("Perceel "+str_boer_teler_nummer+" = "+str_boer_teler);
                writer_contact.newLine();   

        } catch (IOException e) {
            System.err.println(e);
        }
}

Please put me in the good directions.

Thanks already, Bigflow

回答1:

You have to do

writer_contact = new BufferedWriter(new FileWriter(root + "/Save/Contacten.txt",true));

Just as said in java documentation:

FileWriter

public FileWriter(File file,
              boolean append)
       throws IOException

Constructs a FileWriter object given a File object. If the second argument is true, then bytes will be written to the end of the file rather than the beginning.

Parameters:
file - a File object to write to
append - if true, then bytes will be written to the end of the file rather than the beginning

回答2:

try:

public FileWriter (File file, boolean append)

set the append to true

回答3:

Well given this is just a little of your code (and I'm assuming you chunked it out so as to not reveal other parts) what I suspect is going on is that you're opening the file root + "/Save/Contacten.txt" in a non-append mode. The first time you call it the file is created and written to. Subsequent times you call it, it finds the file, and recreates (or deletes content) and then writes to it.

Try using:

writer_contact = new BufferedWriter(new FileWriter(root + "/Save/Contacten.txt", true));

Of course the first time you open/create the file you'll want it to be false (unless you ALWAYS want to append if the file already exists).

Give that a spin.

回答4:

you can check for if file exits or not ?

or you can also append old file.

If not exits then and then only create new one.

来源：https://stackoverflow.com/questions/10041007/write-to-txt-file-but-not-overwrite

标签

android

file

overwrite