Saving a file in sdcard

Many a times, you want to save some contents permanently from your program. If the data is few words, you can save them in shared preferences. But for larger contents, you need to use a file.

To save a file in sdcard, first of all you should have the permission in your app. You should add this line in AndroidManifest.xml file. 

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>   

Next in code, you should open the file.

                File fl = new File("/mnt/sdcard/yourdirname","yourfilename");
                try {
   FileWriter wr = new FileWriter(fl);
   wr.write(str);//str is the string to be written to file
   wr.close();
  } catch (IOException e) {
    
   e.printStackTrace();
  }

For the File constructor, first parameter is directory name and second is filename. It is always better to write to another directory in sdcard. What happens if the directory does not exist? Your program will crash.

First ensure that the directory where you want to store file exists. If it does not, create it. Then create the file. To do that, you can use exists() function of File class.
could open the file.

               File dir = new File("/mnt/sdcard/yourdirname"); 
               if (!dir.exists() ){
                    if (!dir.mkdir()){ 
                       Toast.makeToast(context,"Unable to create directory",Toast.LENGTH_LONG).show(); 
                       return; 
                   } 
               } 
               File fl = new File(dir,"yourfilename");
              try {
                  FileWriter wr = new FileWriter(fl);
                  wr.write(str);//str is the string to be written to file
                  wr.close();
              } catch (IOException e) {

                  e.printStackTrace();
              }

If the directory does not exist, dir.exists() will be false. Then our code tries to create directory by using dir.mkdir().  If due to any reason, directory creation fails, mkdir() method returns false, and our code exits the function.

Once we have ensured that directory exists, we open the file and write to it.

If necessary the file can opened for appending, so that the contents are added to the end of existing file.

      FileWriter wr = new FileWriter(fl,true);//true to append, false to create new file
      wr.append(str);