Android file management

i use the code below to write a file to the sd card and read the content of it:

try {
        if (root.canWrite())
        {
                File rootdir = Environment.getExternalStorageDirectory();
                File yourFile = new File(rootdir, "tomato50.txt");
                FileWriter filewriter = new FileWriter(file,true);                                                                     
                BufferedWriter out = new BufferedWriter(filewriter);
            for (int k=0; k<assignArr.size(); k++)
            {
               out.write(assignArr.get(k) + "\n");
               Toast.makeText(MainActivity.this, "out: " + assignArr.get(k), Toast.LENGTH_LONG).show();
            }
            out.close();
          }
          } catch (IOException e) {
          Log.e("TAG", "Could n开发者_开发技巧ot write file " + e.getMessage());


try { 
       File rootdir = Environment.getExternalStorageDirectory();
       File yourFile = new File(rootdir, "tomato50.txt");
       FileReader filereader = new FileReader(yourFile);
       BufferedReader br = new BufferedReader(filereader);
       String line; 
       while((line = br.readLine()) != null) 
       {
           assignArrBe.add(line); 
           Toast.makeText(MainActivity.this, "Read from file: " + line, Toast.LENGTH_LONG).show();
        } 
      br.close();
       }
      catch (IOException e) 
     { 
        e.printStackTrace(); 
     }

Question is: how can i write to the phone memory and read from it?

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You will need to root your phone in order to get write access to any phone folder.

If what you want is to write in the app-specific internal storage, then you can follow this guide: http://developer.android.com/guide/topics/data/data-storage.html#filesInternal

---

First of all you have to put in your manifest file this line:

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

If it is not enough, can you explain the problem with more details?