Android 如何使用 Environment.getExternalStorageDirectory()

Question

我如何使用Environment.getExternalStorageDirectory()从 SD 卡读取存储的图像，或者有更好的方法吗？

Answer 1

Environment.getExternalStorageDirectory().getAbsolutePath()

Gives you the full path the SDCard. You can then do normal File I/O operations using standard Java.

Here's a simple example for writing a file:

String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
String fileName = "myFile.txt";

// Not sure if the / is on the path or not
File f = new File(baseDir + File.separator + fileName);
f.write(...);
f.flush();
f.close();

Edit:

Oops - you wanted an example for reading ...

String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
String fileName = "myFile.txt";

// Not sure if the / is on the path or not
File f = new File(baseDir + File.Separator + fileName);
FileInputStream fiStream = new FileInputStream(f);

byte[] bytes;

// You might not get the whole file, lookup File I/O examples for Java
fiStream.read(bytes); 
fiStream.close();

Answer 2

Have in mind though, that getExternalStorageDirectory() is not going to work properly on some phones eg my Motorola razr maxx, as it has 2 cards /mnt/sdcard and /mnt/sdcard-ext - for internal and external SD cards respectfully. You will be getting the /mnt/sdcard only reply every time. Google must provide a way to deal with such a situation. As it renders many SD card aware apps (ie card backup) failing miserably on these phones.

Answer 3

As described in Documentation Environment.getExternalStorageDirectory() :

Environment.getExternalStorageDirectory() Return the primary shared/external storage directory.

This is an example of how to use it reading an image :

String fileName = "stored_image.jpg";
 String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
 String pathDir = baseDir + "/Android/data/com.mypackage.myapplication/";

 File f = new File(pathDir + File.separator + fileName);

        if(f.exists()){
          Log.d("Application", "The file " + file.getName() + " exists!";
         }else{
          Log.d("Application", "The file no longer exists!";
         }

Answer 4

要获取目录，您可以使用以下代码：

File cacheDir = new File(Environment.getExternalStorageDirectory() + File.separator + "");