读写SD

 public class SD_Files_RW extends Activity implements OnClickListener{

     private String Text_of_input;

     private Button button_01,button_02;
     private EditText ed_text;
     private TextView text_view;

     private File sdCardDir;
     private File saveFile;
     private FileOutputStream outStream;
     private FileInputStream inStream;

     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         sdCardDir = Environment.getExternalStorageDirectory();
         saveFile = new File(sdCardDir,"wms.txt");

         ed_text = (EditText) findViewById(R.id.edit_01);
         text_view = (TextView) findViewById(R.id.text_01);

         button_01 = (Button)findViewById(R.id.button_01);
         button_01.setOnClickListener(this);

         button_02 = (Button)findViewById(R.id.button_02);
         button_02.setOnClickListener(this);
     }

     // Button 监听
     @Override
     public void onClick(View v)
     {
         // TODO Auto-generated method stub
         switch(v.getId())
         {
         case R.id.button_01:
             {
                 Toast.makeText(SD_Files_RW.this, "开始写入文件！", Toast.LENGTH_SHORT).show();
                 Write_Files();
                 //text_view.setText(ed_text.getText().toString());
             }break;
         case R.id.button_02:
             {
                 Toast.makeText(SD_Files_RW.this, "开始读出文件！", Toast.LENGTH_SHORT).show();
                 Read_Files();

             }break;
         }

     }

     private void Write_Files()
     {

         //得到用户输入字符
         Text_of_input = ed_text.getText().toString();

         if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){

         //创建  初始化 流对象
         try{

         outStream = new FileOutputStream(saveFile);
         }
         catch (FileNotFoundException e){
             Toast.makeText(this, "文件不存在！", Toast.LENGTH_SHORT).show();
             return ;
         }

         try {

         //把内容写入文件
         outStream.write(Text_of_input.getBytes());

         } catch (FileNotFoundException e) {

         // TODO Auto-generated catch block
             Toast.makeText(this, "文件未发现异常！", Toast.LENGTH_SHORT).show();

         } catch (IOException e) {

         // TODO Auto-generated catch block
             Toast.makeText(this, "文件读写异常！", Toast.LENGTH_SHORT).show();

         }
         catch (NullPointerException e){
             Toast.makeText(this, "文件读写空指针异常！", Toast.LENGTH_SHORT).show();
           }
         finally {

         try {

         //关闭文件输出流

         outStream.close();

         } catch (IOException e) {

         // TODO Auto-generated catch block
             Toast.makeText(this, "文件读写异常！", Toast.LENGTH_SHORT).show();            

         }

         Toast.makeText(this, "文件写入成功！", Toast.LENGTH_SHORT).show();

         }

         }else {
             Toast.makeText(this, "内存卡不存在！", Toast.LENGTH_SHORT).show();
             return ;
          }

     }

     private void Read_Files()
     {

         int len;

         //然后创建一个字节数组输出流
         byte[] buffer = new byte[1024];

         ByteArrayOutputStream ostream = new ByteArrayOutputStream();

         if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){

             //创建  初始化 流对象
             try{

             inStream = new FileInputStream(saveFile);
             Log.v("Instance inStream", "实例化inStream！");
             }
             catch (FileNotFoundException e){
                 Toast.makeText(this, "文件不存在！", Toast.LENGTH_SHORT).show();
                 return ;
             }

             try{

             Log.v("Read", "读数据！");

             while((len=inStream.read(buffer))!=-1){
                 ostream.write(buffer, 0, len);

             }

             Log.v("Read", "读成功！");

             }catch (IOException e){
                 Toast.makeText(this, "读 异常！", Toast.LENGTH_SHORT).show();
             }

             try{
             //最后关闭输入流和输出流
             inStream.close();
             ostream.close();

             Log.v("Read", "读成功！");

             }catch (IOException e){
                 Toast.makeText(this, "读 异常！", Toast.LENGTH_SHORT).show();
             }

             String str = new String(ostream.toByteArray());

             Log.v("Disp", "文本显示！");

             text_view.setText(str);

     }else{
         Toast.makeText(this, "内存卡不存在！", Toast.LENGTH_SHORT).show();
         return ;
     }
     }

 }