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();}

原文链接：http://developer.android.com/reference/android/os/Environment.html