android 读写SD卡文件

参考：

http://www.oschina.net/code/snippet_176897_7336#11699

写文件：

private void SavedToText(Context context, String stringToWrite) {
        if (Environment.MEDIA_MOUNTED.equals(Environment
                .getExternalStorageState())) {
            String foldername = Environment.getExternalStorageDirectory()
                    .getPath() + "/log";
            File folder = new File(foldername);
            if (folder == null || !folder.exists()) {
                folder.mkdir();
            }
            String fileName = "/locLog" + ".txt";
            File targetFile = new File(foldername + fileName);
            OutputStreamWriter osw;
            try {
                if (!targetFile.exists()) {
                    targetFile.createNewFile();
                    osw = new OutputStreamWriter(new FileOutputStream(
                            targetFile), "utf-8");
                    osw.write(stringToWrite);
                    osw.close();
                } else {
                    osw = new OutputStreamWriter(new FileOutputStream(
                            targetFile, true), "utf-8");
                    osw.write("\n" + stringToWrite);
                    osw.flush();
                    osw.close();
                }
            } catch (Exception e) {
                // Toast.makeText(context,e.toString(),Toast.LENGTH_LONG).show();
            }
        } else {
            // Toast.makeText(context,"未发现SD卡！",Toast.LENGTH_LONG).show();
        }

}

读文件：

private String readFromFile(Context context){

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

            String foldername = Environment.getExternalStorageDirectory().getPath()+ "/eryaApp";
            File folder = new File(foldername);

            if (folder == null || !folder.exists()) {
                folder.mkdir();
            }

            File targetFile=new File("/sdcard/eryaApp/eryaShoppingList.txt");
            String readedStr="";

             try{
                if(!targetFile.exists()){
                    targetFile.createNewFile();
                    return "No File error ";
                }else{
                     InputStream in = new BufferedInputStream(new FileInputStream(targetFile));
                     BufferedReader br= new BufferedReader(new InputStreamReader(in, "UTF-8"));
                     String tmp;

                     while((tmp=br.readLine())!=null){
                         readedStr+=tmp;
                     }
                     br.close();
                     in.close();

                     return readedStr;
                }
             } catch (Exception e) {
                    Toast.makeText(context,e.toString(),Toast.LENGTH_LONG).show();
                    return e.toString();
             }
        }else{
            Toast.makeText(context,"未发现SD卡！",Toast.LENGTH_LONG).show();
            return "SD Card error";
        }

    }