Android client caching mechanism is a very important work in Android application development, the use of caching mechanism can not only save 3G traffic for users, but also a very good choice in user experience. For example, some news clients support offline mode, which is also achieved by caching mechanism. The cache mechanism is divided into two parts, one is the text cache, the other is the multimedia file cache. Text cache can be implemented in two ways: 1) Json data or XML data obtained by interaction with the server can be stored in the SD card, and records of the data can be added in the database. When adding database records, provide two key fields, one is the REQUESTED URL and the other is the local saved file address, 2) Load the JSON data into the List object after parsing, and then traverse the List to write all the data into the corresponding database table structure. In the future, the database can be retrieved before each request to the server, if there is a direct return. Multimedia file cache: refers to the image cache cache can according to the current date and time for the name buffer to the specified image cache directory of SD card, make a corresponding record in the database at the same time, record method can be controlled by two key fields, one field is the image URL, another field is the image of the machine address. Retrieve the image according to the URL in the data, if not, connect to the server to download, after downloading the corresponding record cache file deletion policy in the server: 1. For each module, the cache file of the corresponding module will be deleted and the new cache file will be downloaded every time the client updates automatically or manually. 2. Provide the function of deleting cache in the setting interface. Click to delete all caches of the machine.