Android Application Development Cookbook: 93 Recipes for Building Winning Apps

Recipe 10.4 Saving Files to the Cache Directory

Android versions

Level 1 and above

Permissions

None

Source code to download from Wrox.com

Cache.zip

Files stored in the files folder are persistent; they will always be there until you explicitly delete them. Sometimes, however, you may not want this to happen because you only need to save the files temporarily and do not need them again later. For this purpose, you should save the files into the cache folder.

NOTE Files stored in the cache folder are not persistent and will be removed by the OS when it is low on internal storage. However, it is always a good practice to clean up the folder yourself and restrict your application to using no more than 1MB.

Solution

To save files to the cache directory, use the getCacheDir() method to return the absolute path to the application-specific cache directory on the filesystem. You can then use the File class to create a full path for the file that you want to store in the cache folder.

The following code snippet shows how to save a file into the cache folder and then read back its content:

package net.learn2develop.cache;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast; public class MainActivity extends Activity { static final int READ_BLOCK_SIZE ...