1.在AndroidManifest文件下添加SDCard的读写权限view plain    
              
              
              
       2.文件操作的各种模式如下代码：（注意通过getExternalStorageDirectory方法获取SDCard的文件路径）view plain    package com.hoo.file;      import java.io.ByteArrayOutputStream;      import java.io.File;      import java.io.FileInputStream;      import java.io.FileOutputStream;      import android.content.Context;      import android.os.Environment;      public class FileService       {          private Context context;          public FileService(Context context)           {              this.context = context;          }                    /**          * 读取文件的内容          * @param filename 文件名称          * @return          * @throws Exception          */          public String readFile(String filename) throws Exception          {              //获得输入流              FileInputStream inStream = context.openFileInput(filename);              //new一个缓冲区              byte[] buffer = new byte[1024];              int len = 0;              //使用ByteArrayOutputStream类来处理输出流              ByteArrayOutputStream outStream = new ByteArrayOutputStream();              while( (len = inStream.read(buffer))!= -1)              {                  //写入数据                  outStream.write(buffer, 0, len);              }              //得到文件的二进制数据              byte[] data = outStream.toByteArray();              //关闭流              outStream.close();              inStream.close();              return new String(data);          }          /**          * 以默认私有方式保存文件内容至SDCard中          * @param filename           * @param content           * @throws Exception          */          public void saveToSDCard(String filename, String content) throws Exception          {              //通过getExternalStorageDirectory方法获取SDCard的文件路径              File file = new File(Environment.getExternalStorageDirectory(), filename);              //获取输出流              FileOutputStream outStream = new FileOutputStream(file);              outStream.write(content.getBytes());              outStream.close();          }                    /**          * 以默认私有方式保存文件内容，存放在手机存储空间中          * @param filename           * @param content           * @throws Exception          */          public void save(String filename, String content) throws Exception          {              //              FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_PRIVATE);              outStream.write(content.getBytes());              outStream.close();          }                    /**          * 以追加的方式保存文件内容          * @param filename 文件名称          * @param content 文件内容          * @throws Exception          */          public void saveAppend(String filename, String content) throws Exception          {                 FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_APPEND);              outStream.write(content.getBytes());              outStream.close();          }                    /**          * 以允许其他应用从该文件中读取内容的方式保存文件(Context.MODE_WORLD_READABLE)          * @param filename 文件名称          * @param content 文件内容          * @throws Exception          */          public void saveReadable(String filename, String content) throws Exception          {              FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_READABLE);              outStream.write(content.getBytes());              outStream.close();          }                    /**          * 以允许其他应用往该文件写入内容的方式保存文件          * @param filename 文件名称          * @param content 文件内容          * @throws Exception          */          public void saveWriteable(String filename, String content) throws Exception          {              FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_WRITEABLE);              outStream.write(content.getBytes());              outStream.close();          }                    /**          * 以允许其他应用对该文件读和写的方式保存文件(MODE_WORLD_READABLE与MODE_WORLD_WRITEABLE)          * @param filename 文件名称          * @param content 文件内容          * @throws Exception          */          public void saveRW(String filename, String content) throws Exception          {              FileOutputStream outStream = context.openFileOutput(filename,                      Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);              //Context.MODE_WORLD_READABLE(1) + Context.MODE_WORLD_WRITEABLE(2),其实可用3替代              outStream.write(content.getBytes());              outStream.close();          }      }   3.写入数据前判断sdcard是否存在于手机上，是否有写保护view plain    package com.hoo.file;      import android.app.Activity;      import android.os.Bundle;      import android.os.Environment;      import android.util.Log;      import android.view.View;      import android.widget.Button;      import android.widget.EditText;      import android.widget.Toast;      public class MainActivity extends Activity       {          private static final String TAG = "MainActivity";          private FileService fileService;                    @Override          public void onCreate(Bundle savedInstanceState)           {              super.onCreate(savedInstanceState);              setContentView(R.layout.main);                         fileService = new FileService(this);              //使用下面的方法可以快速获取当前文件夹的位置，              //这样可以在后面追加路径从而避免使用绝对路径              //File filedir = this.getFilesDir();              Button button = (Button) this.findViewById(R.id.button);              button.setOnClickListener(new View.OnClickListener()               {                  @Override                  public void onClick(View v)                   {                      //获取EditText中的内容                      EditText filenameText = (EditText) findViewById(R.id.filename);                      EditText contentText = (EditText) findViewById(R.id.filecontent);                      String filename = filenameText.getText().toString();                      String content = contentText.getText().toString();                      try                       {                          //使用通常文件保存方式,默认保存在data/data/包名/file/XXX里面                          //fileService.save(filename, content);                                                    //判断sdcard是否存在于手机上而且没有写保护                          //Android2.2版本以后sdcard的路径在mnt/sdcard，2.2之前在/sdcard                          if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))                          {                              //保存到SDCard中                              fileService.saveToSDCard(filename, content);                              //提示保存成功                              Toast.makeText(MainActivity.this, R.string.success, 1).show();                          }                          else                          {                              //提示保存失败                              Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show();                          }                      }                       catch (Exception e)                      {                          Log.e(TAG, e.toString());                          Toast.makeText(MainActivity.this, R.string.error, 1).show();                      }                  }              });          }