相关疑难解决方法(0)

我希望我的应用程序将应用程序DB存档到SD卡.在我的代码中,我检查目录是否canWrite()存在,如果不存在,则抛出一个IOException.在这个特定的实例中,我试图将db文件复制到SD卡上的根目录,但它正在抛出一个IOException.如何更改文件夹/文件的权限才能写入？

我写SD卡时遇到问题,这里是代码:(对不起代码的布局,只需复制它)

public class SaveAndReadManager {

 private String result;
 private String saveFileName = "eventlist_savefile";

 public String writeToFile( ArrayList<Event> arrlEvents ){
  FileOutputStream fos = null;
  ObjectOutputStream out = null;

  try{
   File root = Environment.getExternalStorageDirectory();

   if( root.canWrite() ){
    fos = new FileOutputStream( saveFileName );
    out = new ObjectOutputStream( fos );
    out.writeObject( arrlEvents );

    result = "File written";

    out.close();
   }else{
    result = "file cant write";
   }
  }catch( IOException e ){
   e.printStackTrace();
   result = "file not written";
  }

  return result;
 }

 public boolean readFromFile(){
  return …