android - Fileobserver 的 onevent 方法触发但我如何在删除任何文件之前获取文件

Question

我想在从任何文件管理器或图库中删除图像之前复制文件，但是 FileObserver 的 onEvent 触发，但我只想在用户删除任何文件时专门获取事件来自 FileObserver 的观察路径

observer = new FileObserver(pathToWatch) { // set up a file observer to watch this directory on sd card
        @Override
        public void onEvent(int event, String fileName) {
            if (fileName == null) {
                return;
            }
            //a new file or subdirectory was created under the monitored directory

            if ((FileObserver.DELETE & event) != 0) {
                //handle deleted file
                Log.e(TAG, "onEvent: DELETE");
                Log.e(TAG, "onEvent:exists(): " + new File(pathToWatch + fileName).exists());
            }
        }
    };
    observer.startWatching();

上面的代码运行良好，当用户删除任何文件时也会打印日志，但当时文件不存在并返回 false 我认为可能是文件被删除，这就是为什么它返回 false 但我想删除用于备份目的的文件。由 Dumpster 完成，请帮助我!!

Answer 1

File Observer onEvent() 方法在任何文件被删除后调用。所以你无法复制任何已删除的文件。

我知道这个解决方案不合适，但你可以试试这个来复制已删除的文件。

1. 为您要观察的每个文件创建 fileInputStream 对象。确保该对象不会被垃圾收集。

2. 当您在任何特定文件的 onEvent() 方法中收到删除事件时，通过使用该特定文件的文件输入流，您可以复制该文件。

   public class RecoverFileObserver extends FileObserver {
   
     private final String TAG = RecoverFileObserver.class.getSimpleName();
     String originMd5="xyz";
     FileInputStream fileInputStream;
     String path;
     String newPath;
     private int length = 0;
     String extension;
   
   public RecoverFileObserver(String path) {
       super(path, FileObserver.ALL_EVENTS);
       this.path = path;
       Log.d(TAG, "patException:" + path);
       if (path.lastIndexOf(".") != -1) {
           extension = path.substring(path.lastIndexOf("."));
           this.newPath = RECOVERY_DIR + "/" + MD5Utils.getMD5Str(path) + extension;
       } else {
           this.newPath = RECOVERY_DIR + "/" + MD5Utils.getMD5Str(path);
       }
   
       try {
           fileInputStream = new FileInputStream(path);
           length = fileInputStream.available();
       } catch (IOException e) {
           e.printStackTrace();
       }
       RecoverInfo info = new RecoverInfo();
       info.originMd5 = originMd5;
       info.recoveryPath = newPath;
       recoverInfoHashMap.put(path, info);
       Log.e(TAG, "actualpath:" + path + "\n orignalmd5:" + originMd5);
   
   }
   
   @Override
   public void onEvent(int event, String path) {
       if (event == FileObserver.ACCESS) return;
       Log.v(TAG, this.path + " | " + path + " : " + event);
       switch (event) {
   
           case FileObserver.ACCESS:
               Log.d("xyzabc", "inside Access");
               break;
   
           case FileObserver.ALL_EVENTS:
               Log.d("xyzabc", "inside AllEvents");
               break;
   
           case FileObserver.CLOSE_NOWRITE:
               Log.d("xyzabc", "inside CLOSE_NOWRITE");
               break;
   
   
           case FileObserver.CLOSE_WRITE:
               Log.d("xyzabc", "inside CLOSE_WRITE");
               break;
   
           case FileObserver.CREATE:
               Log.d("xyzabc", "inside CREATE");
               break;
   
           case FileObserver.MODIFY:
               Log.d("xyzabc", "inside MODIFY");
               break;
   
           case FileObserver.MOVED_FROM:
               Log.d("xyzabc", "inside MOVED_FROM");
               break;
   
           case FileObserver.MOVED_TO:
               Log.d("xyzabc", "inside MOVED_TO");
               break;
   
           case FileObserver.MOVE_SELF:
               Log.d("xyzabc", "inside MOVE_SELF");
               break;
   
           case FileObserver.OPEN:
               Log.d("xyzabc", "inside OPEN");
               break;
   
           case FileObserver.ATTRIB:
               Log.d("xyzabc", "inside attrib");
               copyFile(fileInputStream, this.path, this.newPath, length, originMd5);
               break;
   
           case FileObserver.DELETE:
               Log.d("xyzabc", "inside delete");
               copyFile(fileInputStream, this.path, this.newPath, length, originMd5);
               break;
   
           case FileObserver.DELETE_SELF:
               Log.d("xyzabc", "inside delete self");
               copyFile(fileInputStream, this.path, this.newPath, length, originMd5);
               break;
   
           case 32768:
               Log.d("xyzabc", "inside 32768");
               stopWatching();
               File file = new File(this.path);
               if (file.exists()) {
                   RecoverFileObserver fileObserver = new RecoverFileObserver(this.path);
                   fileObserver.startWatching();
                   myFileObserverHashMap.put(file, fileObserver);
               } else {
                   myFileObserverHashMap.remove(file);
               }
               break;
           default:
               break;
       }
   }
   
   
   @Override
   protected void finalize() {
   
       Log.d("xyzabc", "inside finalize");
       super.finalize();
   
   }
   

此解决方案适用于少量文件。否则你会遇到很多文件打开错误。希望对您有所帮助。