【ListViewJSON】【com.demo.app.common】【FileUtils】源码分析及其在工程中作用

源码如下：

package com.demo.app.common;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

import android.content.Context;
import android.os.Environment;
import android.os.StatFs;
import android.util.Log;

/** 
 * 文件操作工具包
 * @version 1.0
 * @created 2012-3-21
 */
public class FileUtils 
{
    /**
     * 写文本文件
     * 在Android系统中，文件保存在 /data/data/PACKAGE_NAME/files 目录下
     * @param context
     * @param msg
     */
    public static void write(Context context, String fileName, String content) 
    { 
        if( content == null )    content = "";
        
        try 
        {
            FileOutputStream fos = context.openFileOutput(fileName, Context.MODE_PRIVATE);
            fos.write( content.getBytes() ); 
            
            fos.close();
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        } 
    }
    
    /**
     * 读取文本文件
     * @param context
     * @param fileName
     * @return
     */
    public static String read( Context context, String fileName ) 
    {
        try 
        {
            FileInputStream in = context.openFileInput(fileName);
            return readInStream(in);
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
        return "";
    } 
    
    private static String readInStream(FileInputStream inStream)
    {
        try 
        {
           ByteArrayOutputStream outStream = new ByteArrayOutputStream();
           byte[] buffer = new byte[512];
           int length = -1;
           while((length = inStream.read(buffer)) != -1 )
           {
               outStream.write(buffer, 0, length);
           }
           
           outStream.close();
           inStream.close();
           return outStream.toString();
        } 
        catch (IOException e)
        {
           Log.i("FileTest", e.getMessage()); 
        }
        return null;
    }
    
    public static File createFile( String folderPath, String fileName )
    {
        File destDir = new File(folderPath);
        if (!destDir.exists()) 
        {
            destDir.mkdirs();
        }
        return new File(folderPath,  fileName + fileName );
    }
    
    /**
     * 向手机写图片
     * @param buffer   
     * @param folder
     * @param fileName
     * @return
     */
    public static boolean writeFile( byte[] buffer, String folder, String fileName )
    {
        boolean writeSucc = false;
        
        boolean sdCardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);
        
        String folderPath = "";
        if( sdCardExist )
        {
            folderPath = Environment.getExternalStorageDirectory() + File.separator +  folder + File.separator;
        }
        else
        {
            writeSucc =false;
        }
        
        File fileDir = new File(folderPath);
        if(!fileDir.exists()) 
        {
            fileDir.mkdirs();
        }
          
        File file = new File( folderPath + fileName );
        FileOutputStream out = null;
        try 
        {
            out = new FileOutputStream( file );
            out.write(buffer);
            writeSucc = true;
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
        finally
        {
            try {out.close();} catch (IOException e) {e.printStackTrace();}
        }
        
        return writeSucc;
    }
    
    /**
     * 根据文件绝对路径获取文件名
     * @param filePath
     * @return
     */
    public static String getFileName( String filePath )
    {
        if( StringUtils.isEmpty(filePath) )    return "";
        return filePath.substring( filePath.lastIndexOf( File.separator )+1 );
    }
    /**
     * 根据文件的绝对路径获取文件名但不包含扩展名
     * @param filePath
     * @return
     */
    public static String getFileNameNoFormat( String filePath){
        if(StringUtils.isEmpty(filePath)){
            return "";
        }
        int point = filePath.lastIndexOf('.');
        return filePath.substring(filePath.lastIndexOf(File.separator)+1,point);
    }
    
    /**
     * 获取文件扩展名
     * @param fileName
     * @return
     */
    public static String getFileFormat( String fileName )
    {
        if( StringUtils.isEmpty(fileName) )    return "";
        
        int point = fileName.lastIndexOf( '.' );
        return fileName.substring( point+1 );
    }
    
    /**
     * 获取文件大小
     * @param filePath
     * @return
     */
    public static long getFileSize( String filePath )
    {
        long size = 0;
        
        File file = new File( filePath );
        if(file!=null && file.exists())
        {
            size = file.length();
        } 
        return size;
    }
    
    /**
     * 获取文件大小
     * @param size 字节
     * @return
     */
    public static String getFileSize(long size) 
    {
        if (size <= 0)    return "0";
        java.text.DecimalFormat df = new java.text.DecimalFormat("##.##");
        float temp = (float)size / 1024;
        if (temp >= 1024) 
        {
            return df.format(temp / 1024) + "M";
        }
        else 
        {
            return df.format(temp) + "K";
        }
    }

    /**
     * 转换文件大小
     * @param fileS
     * @return B/KB/MB/GB
     */
    public static String formatFileSize(long fileS) {
        java.text.DecimalFormat df = new java.text.DecimalFormat("#.00");
        String fileSizeString = "";
        if (fileS < 1024) {
            fileSizeString = df.format((double) fileS) + "B";
        } else if (fileS < 1048576) {
            fileSizeString = df.format((double) fileS / 1024) + "KB";
        } else if (fileS < 1073741824) {
            fileSizeString = df.format((double) fileS / 1048576) + "MB";
        } else {
            fileSizeString = df.format((double) fileS / 1073741824) + "G";
        }
        return fileSizeString;
    }

    /**
     * 获取目录文件大小
     * @param dir
     * @return
     */
    public static long getDirSize(File dir) {
        if (dir == null) {
            return 0;
        }
        if (!dir.isDirectory()) {
            return 0;
        }
        long dirSize = 0;
        File[] files = dir.listFiles();
        for (File file : files) {
            if (file.isFile()) {
                dirSize += file.length();
            } else if (file.isDirectory()) {
                dirSize += file.length();
                dirSize += getDirSize(file); //递归调用继续统计
            }
        }
        return dirSize;
    }
    
    /**
     * 获取目录文件个数
     * @param f
     * @return
     */
    public long getFileList(File dir){
        long count = 0;
        File[] files = dir.listFiles();
        count = files.length;
        for (File file : files) {
            if (file.isDirectory()) {
                count = count + getFileList(file);//递归
                count--;
            }
        }
        return count;  
    }
    
    public static byte[] toBytes(InputStream in) throws IOException 
    {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int ch;
        while ((ch = in.read()) != -1)
        {
            out.write(ch);
        }
        byte buffer[]=out.toByteArray();
        out.close();
        return buffer;
    }
    
    /**
     * 检查文件是否存在
     * @param name
     * @return
     */
    public static boolean checkFileExists(String name) {
        boolean status;
        if (!name.equals("")) {
            File path = Environment.getExternalStorageDirectory();
            File newPath = new File(path.toString() + name);
            status = newPath.exists();
        } else {
            status = false;
        }
        return status;

    }
    
    /**
     * 计算SD卡的剩余空间
     * @return 返回-1，说明没有安装sd卡
     */
    public static long getFreeDiskSpace() {
        String status = Environment.getExternalStorageState();
        long freeSpace = 0;
        if (status.equals(Environment.MEDIA_MOUNTED)) {
            try {
                File path = Environment.getExternalStorageDirectory();
                StatFs stat = new StatFs(path.getPath());
                long blockSize = stat.getBlockSize();
                long availableBlocks = stat.getAvailableBlocks();
                freeSpace = availableBlocks * blockSize / 1024;
            } catch (Exception e) {
                e.printStackTrace();
            }
        } else {
            return -1;
        }
        return (freeSpace);
    }

    /**
     * 新建目录
     * @param directoryName
     * @return
     */
    public static boolean createDirectory(String directoryName) {
        boolean status;
        if (!directoryName.equals("")) {
            File path = Environment.getExternalStorageDirectory();
            File newPath = new File(path.toString() + directoryName);
            status = newPath.mkdir();
            status = true;
        } else
            status = false;
        return status;
    }

    /**
     * 检查是否安装SD卡
     * @return
     */
    public static boolean checkSaveLocationExists() {
        String sDCardStatus = Environment.getExternalStorageState();
        boolean status;
        if (sDCardStatus.equals(Environment.MEDIA_MOUNTED)) {
            status = true;
        } else
            status = false;
        return status;
    }

    /**
     * 删除目录(包括：目录里的所有文件)
     * @param fileName
     * @return
     */
    public static boolean deleteDirectory(String fileName) {
        boolean status;
        SecurityManager checker = new SecurityManager();

        if (!fileName.equals("")) {

            File path = Environment.getExternalStorageDirectory();
            File newPath = new File(path.toString() + fileName);
            checker.checkDelete(newPath.toString());
            if (newPath.isDirectory()) {
                String[] listfile = newPath.list();
                // delete all files within the specified directory and then
                // delete the directory
                try {
                    for (int i = 0; i < listfile.length; i++) {
                        File deletedFile = new File(newPath.toString() + "/"
                                + listfile[i].toString());
                        deletedFile.delete();
                    }
                    newPath.delete();
                    Log.i("DirectoryManager deleteDirectory", fileName);
                    status = true;
                } catch (Exception e) {
                    e.printStackTrace();
                    status = false;
                }

            } else
                status = false;
        } else
            status = false;
        return status;
    }

    /**
     * 删除文件
     * @param fileName
     * @return
     */
    public static boolean deleteFile(String fileName) {
        boolean status;
        SecurityManager checker = new SecurityManager();

        if (!fileName.equals("")) {

            File path = Environment.getExternalStorageDirectory();
            File newPath = new File(path.toString() + fileName);
            checker.checkDelete(newPath.toString());
            if (newPath.isFile()) {
                try {
                    Log.i("DirectoryManager deleteFile", fileName);
                    newPath.delete();
                    status = true;
                } catch (SecurityException se) {
                    se.printStackTrace();
                    status = false;
                }
            } else
                status = false;
        } else
            status = false;
        return status;
    }
}