android read write sd card operation write data read data example

package com.example.sdcardtest;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.app.Activity;
public class MainActivity extends Activity {
    final String FILE_NAME = "/lxp.bin";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button write = (Button) findViewById(R.id.main_btn1);
        Button read = (Button) findViewById(R.id.main_btn2);
        final EditText edit1 = (EditText) findViewById(R.id.main_edit1);
        final EditText edit2 = (EditText) findViewById(R.id.main_edit2);
        write.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                write(edit1.getText().toString().trim());
                edit1.setText("");
            }
        });
        read.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                edit2.setText(read());
            }
        });
    }
    private void write(String content){
        try {
            if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                // To obtain SD The card catalog 
                File sdCardDir = Environment.getExternalStorageDirectory();
                File targetFile = new File(sdCardDir.getCanonicalPath() + FILE_NAME);
                // To create a specified file RandomAccessFile object 
                RandomAccessFile raf = new RandomAccessFile(targetFile, "rw");
                // Move the file record pointer to the end 
                raf.seek(targetFile.length());
                // Output file content 
                raf.write(content.getBytes());
                raf.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private String read(){
        try {
            if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                // To obtain SD The storage directory corresponding to the card 
                File sdCardDir = Environment.getExternalStorageDirectory();
                // Gets the input stream for the specified file 
                FileInputStream fis = new FileInputStream(sdCardDir.getCanonicalPath() + FILE_NAME);
                // Wraps the specified input stream as BufferReader
                BufferedReader br = new BufferedReader(new InputStreamReader(fis));
                StringBuilder sb = new StringBuilder("");
                String line = null;
                // Loop reads the contents of the file 
                while((line = br.readLine()) != null){
                    sb.append(line);
                }
                br.close();
                return sb.toString();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

Finally, don't forget to add access to read SD in AndroidManafest.xml.