import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.os.Environment;
import android.os.StatFs;
import android.util.Log;

public class FileUtil {
    private static int bufferd = 1024;

    private FileUtil() {
    }

    /*
     * <!-- 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"/>
     */

    // =================get SDCard information===================
    public static boolean isSdcardAvailable() {
        String status = Environment.getExternalStorageState();
        if (status.equals(Environment.MEDIA_MOUNTED)) {
            return true;
        }
        return false;
    }

    public static long getSDAllSizeKB() {
        // get path of sdcard
        File path = Environment.getExternalStorageDirectory();
        StatFs sf = new StatFs(path.getPath());
        // get single block size(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) / 1024; // KB
    }

    /**
     * free size for normal application
     *
     * @return
     */
    public static long getSDAvalibleSizeKB() {
        File path = Environment.getExternalStorageDirectory();
        StatFs sf = new StatFs(path.getPath());
        long blockSize = sf.getBlockSize();
        long avaliableSize = sf.getAvailableBlocks();
        return (avaliableSize * blockSize) / 1024;// KB
    }

    // =====================File Operation==========================
    public static boolean isFileExist(String director) {
        File file = new File(Environment.getExternalStorageDirectory()
                + File.separator + director);
        return file.exists();
    }

    /**
     * create multiple director
     *
     * @param path
     * @return
     */
    public static boolean createFile(String director) {
        if (isFileExist(director)) {
            return true;
        } else {
            File file = new File(Environment.getExternalStorageDirectory()
                    + File.separator + director);
            if (!file.mkdirs()) {
                return false;
            }
            return true;
        }
    }

    public static File writeToSDCardFile(String directory, String fileName,
            String content, boolean isAppend) {
        return writeToSDCardFile(directory, fileName, content, "", isAppend);
    }

    /**
     *
     * @param director
     *            (you don't need to begin with
     *            Environment.getExternalStorageDirectory()+File.separator)
     * @param fileName
     * @param content
     * @param encoding
     *            (UTF-8...)
     * @param isAppend
     *            : Context.MODE_APPEND
     * @return
     */
    public static File writeToSDCardFile(String directory, String fileName,
            String content, String encoding, boolean isAppend) {
        // mobile SD card path +path
        File file = null;
        OutputStream os = null;
        try {
            if (!createFile(directory)) {
                return file;
            }
            file = new File(Environment.getExternalStorageDirectory()
                    + File.separator + directory + File.separator + fileName);
            os = new FileOutputStream(file, isAppend);
            if (encoding.equals("")) {
                os.write(content.getBytes());
            } else {
                os.write(content.getBytes(encoding));
            }
            os.flush();
        } catch (IOException e) {
            Log.e("FileUtil", "writeToSDCardFile:" + e.getMessage());
        } finally {
            try {
                if(os != null){
                    os.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return file;
    }

    /**
     * write data from inputstream to SDCard
     */
    public File writeToSDCardFromInput(String directory, String fileName,
            InputStream input) {
        File file = null;
        OutputStream os = null;
        try {
            if (createFile(directory)) {
                return file;
            }
            file = new File(Environment.getExternalStorageDirectory()
                    + File.separator + directory + fileName);
            os = new FileOutputStream(file);
            byte[] data = new byte[bufferd];
            int length = -1;
            while ((length = input.read(data)) != -1) {
                os.write(data, 0, length);
            }
            // clear cache
            os.flush();
        } catch (Exception e) {
            Log.e("FileUtil", "" + e.getMessage());
            e.printStackTrace();
        } finally {
            try {
                os.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return file;
    }

    /**
     * this url point to image(jpg)
     *
     * @param url
     * @return image name
     */
    public static String getUrlLastString(String url) {
        String[] str = url.split("/");
        int size = str.length;
        return str[size - 1];
    }

}

下面对代码进行了测试，使用了AndroidJunitTest，当然另外还需要对SDCard查看操作的权限。

1、对android项目的mainfest.xml进行配置，需要注意targetPacket应当与包名保持一致。

//在mainfest标签下
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<instrumentation
        android:name="android.test.InstrumentationTestRunner"
        android:targetPackage="com.example.mygeneralutil" >
</instrumentation>

//在mainfest的application标签下
<uses-library android:name="android.test.runner"/>

2、简单的测试代码如下：

import android.test.AndroidTestCase;
import android.util.Log;

public class FileUtilTest extends AndroidTestCase {

    public void testIsSdcardAvailable() {
        FileUtil.isSdcardAvailable();
        Log.e("FileUtil", ""+FileUtil.isSdcardAvailable());
    }

    public void testGetSDAllSizeKB() {
        FileUtil.getSDAllSizeKB();
        Log.e("FileUtil", ""+(float)FileUtil.getSDAllSizeKB()/1024/1024);
    }

    public void testGetSDAvalibleSizeKB() {
        FileUtil.getSDAvalibleSizeKB();
        Log.e("FileUtil", ""+(float)FileUtil.getSDAvalibleSizeKB()/1024/1024);
    }

    public void testIsFileExist() {
        FileUtil.isFileExist("example");
        Log.e("FileUtil", ""+FileUtil.isFileExist("example"));
    }

    public void testCreateFile() {
        Log.e("FileUtil", ""+FileUtil.createFile("forexample"));
    }

    public void testWriteToSDCardFileStringStringStringBoolean() {

        fail("Not yet implemented");
    }

    public void testWriteToSDCardFileStringStringStringStringBoolean() {
        FileUtil.writeToSDCardFile("forexample", "123.txt",
                "FileUtil.writeToSDCardFile", "utf-8", true);
    }

    public void testWriteToSDCardFromInput() {
        fail("Not yet implemented");
    }

    public void testGetUrlLastString() {
        fail("Not yet implemented");
    }

}