在外存存储图片的一个典型示例

void createExternalStoragePublicPicture() {
// Create a path where we will place our picture in the user's
// public pictures directory.  Note that you should be careful about
// what you place here, since the user often manages these files.  For
// pictures and other media owned by the application, consider
// Context.getExternalMediaDir().
File path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES);
File file = new File(path, "DemoPicture.jpg");

try {
// Make sure the Pictures directory exists.
path.mkdirs();

// Very simple code to copy a picture from the application's
// resource into the external file.  Note that this code does
// no error checking, and assumes the picture is small (does not
// try to copy it in chunks).  Note that if external storage is
// not currently mounted this will silently fail.
InputStream is = getResources().openRawResource(R.drawable.balloons);
OutputStream os = new FileOutputStream(file);
byte[] data = new byte[is.available()];
is.read(data);
os.write(data);
is.close();
os.close();

// Tell the media scanner about the new file so that it is
// immediately available to the user.
MediaScannerConnection.scanFile(this,
new String[] { file.toString() }, null,
new MediaScannerConnection.OnScanCompletedListener() {
public void onScanCompleted(String path, Uri uri) {
Log.i("ExternalStorage", "Scanned " + path + ":");
Log.i("ExternalStorage", "-> uri=" + uri);
}
});
} catch (IOException e) {
// Unable to create file, likely because external storage is
// not currently mounted.
Log.w("ExternalStorage", "Error writing " + file, e);
}
}

void deleteExternalStoragePublicPicture() {
// Create a path where we will place our picture in the user's
// public pictures directory and delete the file.  If external
// storage is not currently mounted this will fail.
File path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES);
File file = new File(path, "DemoPicture.jpg");
file.delete();
}

boolean hasExternalStoragePublicPicture() {
// Create a path where we will place our picture in the user's
// public pictures directory and check if the file exists.  If
// external storage is not currently mounted this will think the
// picture doesn't exist.
File path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES);
File file = new File(path, "DemoPicture.jpg");
return file.exists();
}