實驗程式碼：

package com.example.test1102;  
  
import java.io.BufferedReader;  
import java.io.BufferedWriter;  
import java.io.FileInputStream;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStreamReader;  
import java.io.OutputStreamWriter;  
  
import android.app.Activity;  
import android.content.Context;  
import android.os.Bundle;  
import android.os.Environment;  
import android.text.TextUtils;  
import android.view.Menu;  
import android.widget.EditText;  
import android.widget.Toast;  
  
public class MainActivity extends Activity  
{  
  private EditText edit;  
    @Override  
    protected void onCreate(Bundle savedInstanceState)  
    {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        edit = (EditText) findViewById(R.id.edit);  
        String inputText=load();  
        if (!TextUtils.isEmpty(inputText)) {  
            edit.setText(inputText);  
            edit.setSelection(inputText.length());  
            Toast.makeText(this, "Restoring succeeded", Toast.LENGTH_SHORT).show();  
        }  
          
          if(isHavedSDcard()){  
                try {  
                    writeStr2SDCard(inputText);  
                } catch (Exception e) {  
                    e.printStackTrace();  
                }  
            }  
            else{  
                showToast("您的手機沒有記憶體卡哦!");  
            }  
  
          
      }  
     public boolean isHavedSDcard() {  
            if (Environment.getExternalStorageState().equals(  
                    Environment.MEDIA_MOUNTED))  
                return true;  
            else  
                return false;  
        }  
     public String getRootPath() {  
            return Environment.getExternalStorageDirectory().toString();  
        }  
      public void showToast(String text) {  
            Toast.makeText(this, text, Toast.LENGTH_SHORT).show();  
        }  
           
        private void writeStr2SDCard(String str) throws Exception{  
            FileOutputStream fos = new FileOutputStream(getRootPath()+"/test.txt");  
            fos.write(str.getBytes());  
        }  
  
    @Override  
    protected void onDestroy()  
    {  
        // TODO Auto-generated method stub  
        super.onDestroy();  
        String inputText = edit.getText().toString();  
        save(inputText);  
    }  
  
    private void save(String inputText)  
    {  
        // TODO Auto-generated method stub  
        FileOutputStream out = null;  
        BufferedWriter writer = null;  
        try {  
            out = openFileOutput("data", Context.MODE_PRIVATE);  
            writer = new BufferedWriter(new OutputStreamWriter(out));  
            writer.write(inputText);  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            try {  
                if (writer != null) {  
                    writer.close();  
                }  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
          
    }  
    public String load() {  
        FileInputStream in = null;  
        BufferedReader reader = null;  
        StringBuilder content = new StringBuilder();  
        try {  
            in = openFileInput("data");  
            reader = new BufferedReader(new InputStreamReader(in));  
            String line = "";  
            while ((line = reader.readLine()) != null) {  
                content.append(line);  
            }  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            if (reader != null) {  
                try {  
                    reader.close();  
                } catch (IOException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
        return content.toString();  
    }  
  
  
    @Override  
    public boolean onCreateOptionsMenu(Menu menu)  
    {  
        // Inflate the menu; this adds items to the action bar if it is present.  
        getMenuInflater().inflate(R.menu.main, menu);  
        return true;  
    }  
  
}