存储卡sd注意事项及创建目录

try { 
        String filePath = Environment.getExternalStorageDirectory() 
                + "/myappdir/" + appName + ".apk"; 
 
        File file = new File(filePath); 
        file.getParentFile().mkdirs(); 
        file.createNewFile(); 
 
        BufferedOutputStream objectOut = new BufferedOutputStream( 
                new FileOutputStream(file)); 
 
        objectOut.write(appByteArray); 
 
        objectOut.close(); 
 
    } catch (Exception e) { 
        e.printStackTrace(); 
    }

 在下载到sd卡中 最好不要直接存储在根目录，因为sd卡根目录数量是有限的，还要有权限啊

android.permission.WRITE_EXTERNAL_STORAGE