Android的SD卡文件读写的帮助类——FileHelper，以及查询SD卡是否存在及其容量的方法

FileHelper.java是文件的帮助类，完成文件创建、删除、读。

在开始之前别忘了加权限：<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

public class FileHelper { 

    private Context context; 

    /** SD卡是否存在**/ 

    private boolean hasSD = false; 

    /** SD卡的路径**/ 

    private String SDPATH; 

    /** 当前程序包的路径**/ 

    private String FILESPATH; 

    public FileHelper(Context context) { 

        this.context = context; 

        hasSD = Environment.getExternalStorageState().equals( 

                android.os.Environment.MEDIA_MOUNTED); 

        SDPATH = Environment.getExternalStorageDirectory().getPath(); 

        FILESPATH = this.context.getFilesDir().getPath(); 

    } 

    /**

     * 在SD卡上创建文件

     * 

     * @throws IOException

     */ 

    public File createSDFile(String fileName) throws IOException { 

        File file = new File(SDPATH + "//" + fileName); 

        if (!file.exists()) { 

            file.createNewFile(); 

        } 

        return file; 

    } 

    /**

     * 删除SD卡上的文件

     * 

     * @param fileName

     */ 

    public boolean deleteSDFile(String fileName) { 

        File file = new File(SDPATH + "//" + fileName); 

        if (file == null || !file.exists() || file.isDirectory()) 

            return false; 

        return file.delete(); 

    } 

    /**

     * 读取SD卡中文本文件

     * 

     * @param fileName

     * @return

     */ 

    public String readSDFile(String fileName) { 

        StringBuffer sb = new StringBuffer(); 

        File file = new File(SDPATH + "//" + fileName); 

        try { 

            FileInputStream fis = new FileInputStream(file); 

            int c; 

            while ((c = fis.read()) != -1) { 

                sb.append((char) c); 

            } 

            fis.close(); 

        } catch (FileNotFoundException e) { 

            e.printStackTrace(); 

        } catch (IOException e) { 

            e.printStackTrace(); 

        } 

        return sb.toString(); 

    } 

    public String getFILESPATH() { 

        return FILESPATH; 

    } 

    public String getSDPATH() { 

        return SDPATH; 

    } 

    public boolean hasSD() { 

        return hasSD; 

    } 

}

Environment 常用方法：

* 方法：getDataDirectory()

解释：返回 File ，获取 Android 数据目录。

* 方法：getDownloadCacheDirectory()

解释：返回 File ，获取 Android 下载/缓存内容目录。

* 方法：getExternalStorageDirectory()

解释：返回 File ，获取外部存储目录即 SDCard

* 方法：getExternalStoragePublicDirectory(String type)

解释：返回 File ，取一个高端的公用的外部存储器目录来摆放某些类型的文件

* 方法：getExternalStorageState()

解释：返回 File ，获取外部存储设备的当前状态

* 方法：getRootDirectory()

解释：返回 File ，获取 Android 的根目录

public void getSDPath(){ 
File sdDir = null; 
File sdDir1 = null;
File sdDir2 = null;
boolean sdCardExist = Environment.getExternalStorageState() 
.equals(android.os.Environment.MEDIA_MOUNTED); //判断sd卡是否存在 
if (sdCardExist) 
{ 
sdDir = Environment.getExternalStorageDirectory();//获取跟目录 
sdDir1 = Environment.getDataDirectory();
sdDir2 =Environment.getRootDirectory();
} 
System.out.println("getExternalStorageDirectory(): "+sdDir.toString()); 
System.out.println("getDataDirectory(): "+sdDir1.toString()); 
System.out.println("getRootDirectory(): "+sdDir2.toString()); 
}

//判断一个路径下的文件（文件夹）是否存在

public class IsExist {
public static void main(String[] args) {
isExist("e://12");
}
/**
* 
* @param path 文件夹路径
*/
public static void isExist(String path) {
File file = new File(path);
//判断文件夹是否存在,如果不存在则创建文件夹
if (!file.exists()) {
file.mkdir();
}
}
}

//1.在SD卡上创建一个文件夹
public class make extends Activity { 
/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.main); 
File sd=Environment.getExternalStorageDirectory(); 
String path=sd.getPath()+"/notes"; 
File file=new File(path); 
if(!file.exists()) 
file.mkdir(); 

}

Android 判断SD卡是否存在及容量查询的简单方法如下：

首先要在AndroidManifest.xml中增加SD卡访问权限

<!-- 在SDCard中创建与删除文件权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!-- 往SDCard写入数据权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

SD卡剩余空间

public long getSDFreeSize(){
      //取得SD卡文件路径
      File path = Environment.getExternalStorageDirectory(); 
      StatFs sf = new StatFs(path.getPath()); 
      //获取单个数据块的大小(Byte)
      long blockSize = sf.getBlockSize(); 
      //空闲的数据块的数量
      long freeBlocks = sf.getAvailableBlocks();
      //返回SD卡空闲大小
      //return freeBlocks * blockSize;  //单位Byte
      //return (freeBlocks * blockSize)/1024;   //单位KB
      return (freeBlocks * blockSize)/1024 /1024; //单位MB
    }

SD卡总容量

public long getSDAllSize(){
      //取得SD卡文件路径
      File path = Environment.getExternalStorageDirectory(); 
      StatFs sf = new StatFs(path.getPath()); 
      //获取单个数据块的大小(Byte)
      long blockSize = sf.getBlockSize(); 
      //获取所有数据块数
      long allBlocks = sf.getBlockCount();
      //返回SD卡大小
      //return allBlocks * blockSize; //单位Byte
      //return (allBlocks * blockSize)/1024; //单位KB
      return (allBlocks * blockSize)/1024/1024; //单位MB
    }