android文件处理

1. 获取文件大小

public
 
static
 final 
int
 MAX_ATTACHMENT_UPLOAD_SIZE = (5 * 1024 * 1024);

File file = new
 File(
"/sdcard/default/aaa.txt"
);
long
 size =  file.length();  
//获取文件大小,单位为bytes
if
(size > Email.MAX_ATTACHMENT_UPLOAD_SIZE)  
//判断文件大小，最大5MB = 5 * 1024 * 1024 bytes
{
     Toast.makeText(this
, 
"File exceed 5MB, too large to attach"
,Toast.LENGTH_LONG)
                    .show();
}

public static final int MAX_ATTACHMENT_UPLOAD_SIZE = (5 * 1024 * 1024);
File file = new File("/sdcard/default/aaa.txt"); 
long size =  file.length();  //获取文件大小,单位为bytes
if(size > Email.MAX_ATTACHMENT_UPLOAD_SIZE)  //判断文件大小，最大5MB = 5 * 1024 * 1024 bytes
{
     Toast.makeText(this, "File exceed 5MB, too large to attach",Toast.LENGTH_LONG)
                    .show();		
}

2. 判断文件后缀

File folder = 
new
 File(
"/sdcard/data"
);
PickerFilter filter = new
 PickerFilter();
File [] files = folder.listFiles(filter);
int
 fileCount = files.length;    
//获取当前目录下文件的个数
String fileName = files[0].getName(); //获取第一个文件的名字

/* 先将文件名转换为小写，因为endsWith函数会区分大小写，若后缀为.Txt，
   判断时会出现不匹配于.txt导致判断有误 */
fileName = fileName.toLowerCase();
boolean isTxt = fileName.endsWith(".txt"
);

File folder = new File("/sdcard/data");
PickerFilter filter = new PickerFilter();
File [] files = folder.listFiles(filter);
int fileCount = files.length;    //获取当前目录下文件的个数
String fileName = files[0].getName(); //获取第一个文件的名字
/* 先将文件名转换为小写，因为endsWith函数会区分大小写，若后缀为.Txt，
   判断时会出现不匹配于.txt导致判断有误 */
fileName = fileName.toLowerCase();
boolean isTxt = fileName.endsWith(".txt"); 

3. 文件大小 单位转换

public
 
static
 String formatSize(
float
 size)
 {
     long
 kb = 1024;
     long
 mb = (kb * 1024);
     long
 gb  = (mb * 1024);
     if
 (size < kb) {
         return
 String.format(
"%d B"
, (
int
) size);
     }
     else
 
if
 (size < mb) {
         return
 String.format(
"%.2f KB"
, size / kb); 
//保留两位小数
     }
     else
 
if
 (size < gb) {
         return
 String.format(
"%.2f MB"
, size / mb);
     }
     else
 {
         return
 String.format(
"%.2f GB"
, size / gb);
     }
 }

public static String formatSize(float size)
 {
     long kb = 1024;
     long mb = (kb * 1024);
     long gb  = (mb * 1024);
     if (size < kb) {
         return String.format("%d B", (int) size);
     }
     else if (size < mb) {
         return String.format("%.2f KB", size / kb); //保留两位小数
     }
     else if (size < gb) {
         return String.format("%.2f MB", size / mb);
     }
     else {
         return String.format("%.2f GB", size / gb);
     }
 }

4. android在SD卡上创建文件保存信息

     1）判断是否存在SD卡

     2）获取SD卡目录

     3）在SD卡目录下创建文件

     4）写入信息到文件中

//判断SD卡是否存在
boolean sdCardExist = Environment.getExternalStorageState()
                      .equals(android.os.Environment.MEDIA_MOUNTED)
if
 (sdCardExist)
{
    //获取SD卡目录
    File sdDir = Environment.getExternalStorageDirectory();
    //在SD卡目录下创建文件smsLog.txt文件，true表示当文件存在时，信息追加在文件尾
    FileWriter fw = new
 FileWriter( sdDir.toString() + 
"/smsLog.txt"
, 
true
);
    //获取当前时间
    Calendar calendar = Calendar.getInstance();
    Date d = calendar.getTime();

    fw.write("短信接收时间："
 + d.toString());
    fw.write("\r\n"
); 
//写入换行
     fw.write("短信内容："
);
    fw.write("\r\n"
);

    //关闭文件
    fw.close();
  }

评论

1 楼 enefry 2010-09-07  

未知楼主 是否有读写大文件的代码....比如几十M