android 获取路径的获取

1 内部存储
1.1 根目录(applicationDir)：applicationDir/cache，通过Context.getCacheDir()获取。
应用文件目录：$applicationDir/files，通过Context.getFilesDir()获取。Context.getFileStreamPath(String name)返回以name为文件名的子文件目录，若name为空，则返回文件根目录。假设我们的应用程序包名为com.learn.test，路径如下：

Environment.getDataDirectory():      /data
Context.getCacheDir():               /data/data/com.learn.test/cache
Context.getFilesDir():               /data/data/com.learn.test/files
Context.getFileStreamPath(""):       /data/data/com.learn.test/files
Context.getFileStreamPath("test"):   /data/data/com.learn.test/files/test

2 外部存储
2.1 根目录(applicationDir)：applicationDir/cache，通过Context.getExternalCacheDir()获取。
应用文件目录：$applicationDir/files，通过Context.getExternalFilesDir(String type)，type为空字符串时获取。type系统给我们提供了很多常用的类型，比如图片和下载等等:

public static String DIRECTORY_MUSIC = "Music";
public static String DIRECTORY_ALARMS = "Alarms";
public static String DIRECTORY_NOTIFICATIONS = "Notifications";
public static String DIRECTORY_PICTURES = "Pictures";
public static String DIRECTORY_MOVIES = "Movies";
public static String DIRECTORY_DOWNLOADS = "Download";
public static String DIRECTORY_DCIM = "DCIM";
public static String DIRECTORY_DOCUMENTS = "Documents";

Environment.getExternalStorageDirectory():               /storage/emulated/0
Context.getExternalCacheDir():                           /storage/emulated/0/Android/data/com.learn.test/cache
Context.getExternalFilesDir(""):                         /storage/emulated/0/Android/data/com.learn.test/files
Context.getExternalFilesDir("test"):                     /storage/emulated/0/Android/data/com.learn.test/files/test
Context.getExternalFilesDir(Environment.DIRECTORY_PICTURES):    /storage/emulated/0/Android/data/com.learn.test/files/Pictures

3 公共存储目录

Environment.getExternalStorageDirectory():                     /storage/emulated/0
Environment.getExternalStoragePublicDirectory(""):             /storage/emulated/0
Environment.getExternalStoragePublicDirectory("test"):         /storage/emulated/0/test
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)：  /storage/emulated/0/Pictures