Android How to - Write and read file in External Storage Directory

The following code shows how to Write and read file in External Storage Directory.

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.java2s.myapplication3.app" >
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="java2s.com"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.java2s.myapplication3.app.MainActivity"
            android:label="java2s.com"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Main activity Java code

package com.java2s.myapplication3.app;
//  w w  w . ja v  a 2  s.  co m
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    private static final String FILENAME = "data.txt";
    private static final String DNAME = "myfiles";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView tv = new TextView(this);
        setContentView(tv);

        File rootPath = new File(Environment.getExternalStorageDirectory(), DNAME);
        if(!rootPath.exists()) {
            rootPath.mkdirs();
        }
        File dataFile = new File(rootPath, FILENAME);
        if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            Toast.makeText(this, "Cannot use storage.", Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        try {
            FileOutputStream mOutput = new FileOutputStream(dataFile, false);
            String data = "THIS DATA WRITTEN TO A FILE";
            mOutput.write(data.getBytes());
            mOutput.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        //Read the created file and display to the screen
        try {
            FileInputStream mInput = new FileInputStream(dataFile);
            byte[] data = new byte[128];
            mInput.read(data);
            mInput.close();

            String display = new String(data);
            tv.setText(display.trim());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        dataFile.delete();
    }
}