error : cache_dir must be a directory?

[Harlowton]

I am working with Magento 1.7 and suddenly I have this error when I go to cache management:
cache_dir must be a directory
I tried this solution to change this file lib/Zend/Cache/Backend/File.php
'cache_dir' => 'null' to 'cache_dir' => 'tmp/' but does not work

[Harmony]

找到lib\Zend\Cache\Backend\File.php这个文件
protected $_options = array(
'cache_dir' => null,
'file_locking' => true,
'read_control' => true,
'read_control_type' => 'crc32',
'hashed_directory_level' => 0,
'hashed_directory_umask' => 0700,
'file_name_prefix' => 'zend_cache',
'cache_file_umask' => 0600,
'metadatas_array_max_size' => 100
);
将以上的代码修改成如下代码，

protected $_options = array(
'cache_dir' => 'var/cache',
'file_locking' => true,
'read_control' => true,
'read_control_type' => 'crc32',
'hashed_directory_level' => 0,
'hashed_directory_umask' => 0700,
'file_name_prefix' => 'zend_cache',
'cache_file_umask' => 0600,
'metadatas_array_max_size' => 100
);

这样修改 问题就解决了，去后台刷新一下，成功解决