How do I delete a file stored in cache? (android)

Question

I am not able delete file that is stored in cache. I am using the cache for several purposes. I am reading and writing but not able to delete. Can someone please help me with this?

//write
   public static void writeObject(Context context, String key, Object object)
                                  throws IOException {
            Log.d("Cache", "WRITE: context");
            FileOutputStream fos = context.openFileOutput(key, Context.MODE_PRIVATE);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(object);
            oos.close();
            fos.close();
   }

//read
   public static Object readObject(Context context, String key) throws IOException,
         ClassNotFoundException {
      FileInputStream fis = context.openFileInput(key);
      ObjectInputStream ois = new ObjectInputStream(fis);
      Object object = ois.readObject();
      return object;
   }

//delete
   public static void clearCahe(String key) throws IOException,ClassNotFoundException {
        File file = new File(key);
        file.delete();
   }

please log the return type of delete method . and please print stack trace might be particular file is not available. — mcd, Apr 27 '15 at 10:39

score 2 · Accepted Answer · answered Apr 27 '15 at 10:56

2

context.openFileOutput(key writes the file to internal memory. The path you can find with getFilesDir() and looks like /data/data/<yourpackagename>/files.

So if you want to delete the file 'key' you have to set up the path for File file = new File(path) as String path = getFilesDir().getAbsolutePath() + "/" + key;.

And use file.exists() to check if the file exists!

answered Apr 27 '15 at 10:56

greenapps

11,154
2
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19

can be defined like this; File file = new File(getFilesDir(), fileName); – kaya Sep 15 '17 at 09:22

score 0 · Answer 2 · answered Apr 27 '15 at 10:41

use this to clear application data.

  public void clearApplicationData() 
    {
        File cache = getCacheDir();
        File appDir = new File(cache.getParent());
        if (appDir.exists()) {
            String[] children = appDir.list();
            for (String s : children) {
                if (!s.equals("lib")) {
                    deleteDir(new File(appDir, s));Log.i("TAG", "**************** File /data/data/APP_PACKAGE/" + s + " DELETED *******************");
                }
            }
        }
    }

    public static boolean deleteDir(File dir) 
    {
        if (dir != null &amp;&amp; dir.isDirectory()) {
            String[] children = dir.list();
            for (int i = 0; i < children.length; i++) {
                boolean success = deleteDir(new File(dir, children[i]));
                if (!success) {
                    return false;
                }
            }
        }
        return dir.delete();
    }

score 0 · Answer 3 · edited May 23 '17 at 12:22

Files

Like the cache directory, your app also has an app-specific directory for holding files. Files in this directory will exist until the app explicitly deletes them or the app is uninstalled. You typically access this directory with Context.getFilesDir(). This can show up as various things on the app info screen, but in your screenshot this is "USB Storage Data".

NOTE: If you want to explicitly place on external media (typically SD card), you can use Context.getExternalFilesDir(String type).

Simple cache manager:

public class CacheManager {

    private static final long MAX_SIZE = 5242880L; // 5MB

    private CacheManager() {

    }

    public static void cacheData(Context context, byte[] data, String name) throws IOException {

        File cacheDir = context.getCacheDir();
        long size = getDirSize(cacheDir);
        long newSize = data.length + size;

        if (newSize > MAX_SIZE) {
            cleanDir(cacheDir, newSize - MAX_SIZE);
        }

        File file = new File(cacheDir, name);
        FileOutputStream os = new FileOutputStream(file);
        try {
            os.write(data);
        }
        finally {
            os.flush();
            os.close();
        }
    }

    public static byte[] retrieveData(Context context, String name) throws IOException {

        File cacheDir = context.getCacheDir();
        File file = new File(cacheDir, name);

        if (!file.exists()) {
            // Data doesn't exist
            return null;
        }

        byte[] data = new byte[(int) file.length()];
        FileInputStream is = new FileInputStream(file);
        try {
            is.read(data);
        }
        finally {
            is.close();
        }

        return data;
    }

    private static void cleanDir(File dir, long bytes) {

        long bytesDeleted = 0;
        File[] files = dir.listFiles();

        for (File file : files) {
            bytesDeleted += file.length();
            file.delete();

            if (bytesDeleted >= bytes) {
                break;
            }
        }
    }

    private static long getDirSize(File dir) {

        long size = 0;
        File[] files = dir.listFiles();

        for (File file : files) {
            if (file.isFile()) {
                size += file.length();
            }
        }

        return size;
    }
}

NOTE: The purpose of the cache is to cut down on network activity, long processes, and provide a responsive UI in your app.

Reference: When to clear the cache dir in Android?.

How do I delete a file stored in cache? (android)

3 Answers3