FileCache.java

package com.daifan.service;

import android.content.Context;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.Date;

public class FileCache {

    private File cacheDir;
    private File imgDir;

    public FileCache(Context context) {
        //Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
            cacheDir = new File(android.os.Environment.getExternalStorageDirectory(), "51daifan");
        else
            cacheDir = context.getCacheDir();
        if (!cacheDir.exists())
            cacheDir.mkdirs();

        imgDir = new File(cacheDir, "images");
        if (!imgDir.exists())
            imgDir.mkdirs();
    }

    public File getCacheDir(){
        return this.cacheDir;
    }

    public File getFile(String url) {
        //I identify images by hashcode. Not a perfect solution, good for the demo.
        String filename = String.valueOf(url.hashCode());
        //Another possible solution (thanks to grantland)
        //String filename = URLEncoder.encode(url);
        File f = new File(cacheDir, filename);
        return f;
    }

    public File createTmpImg() throws IOException {
        String timeStamp =
                new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "jpg-" + timeStamp + "_";
        File image = File.createTempFile(
                imageFileName,
                ".jpg",
                this.imgDir
        );
        return image;
    }

    public void clear() {
        File[] files = cacheDir.listFiles();
        if (files == null)
            return;
        for (File f : files)
            f.delete();
    }

}