Android(安卓)多文件监听的实现

android.os下的FileObserver类是一个用于监听文件访问、创建、修改、删除、移动等操作的监听器，但是该监听只针对监听的那个文件目录下的一级子文件起作用，

而对它子目录下的文件目录则不能够实现。如下示例：

import com.example.androidemail.R;import com.example.androidemail.R.layout;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.os.FileObserver;public class AndroidFileListenerActivity extends Activity {    private FileObserver mFileObserver;        /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                if(null == mFileObserver) {            mFileObserver = new SDCardFileObserver(Environment.getExternalStorageDirectory().getPath());            mFileObserver.startWatching(); //开始监听        }    }    public void onDestory() {        if(null != mFileObserver) mFileObserver.stopWatching(); //停止监听    }        static class SDCardFileObserver extends FileObserver {        //mask:指定要监听的事件类型，默认为FileObserver.ALL_EVENTS        public SDCardFileObserver(String path, int mask) {            super(path, mask);        }        public SDCardFileObserver(String path) {            super(path);        }        @Override        public void onEvent(int event, String path) {            final int action = event & FileObserver.ALL_EVENTS;            switch (action) {            case FileObserver.ACCESS:                System.out.println("event: 文件或目录被访问, path: " + path);                break;                            case FileObserver.DELETE:                System.out.println("event: 文件或目录被删除, path: " + path);                break;                            case FileObserver.OPEN:                System.out.println("event: 文件或目录被打开, path: " + path);                break;                            case FileObserver.MODIFY:                System.out.println("event: 文件或目录被修改, path: " + path);                break;                            case FileObserver.CREATE:            System.out.println("event: 文件或目录被创建, path: " + path);            break;            }        }            }}

onEvent是回调，系统监听到事件后会触发此事件，参数event就是上面所说的事件类型，参数path就是触发事件的目录，鉴定只针对于该层目录，其他层次无效。

我们大多数需要监听path目录下的所有文件对象的相关操作，那该如何是好呢？解决问题方法之一就是重新实现FileObserver类，

下面是对FileObserver类的重写实现过程

import java.io.File;import java.util.ArrayList;import java.util.List;import java.util.Stack;import android.os.FileObserver;import android.util.Log;@SuppressWarnings(value = { "rawtypes", "unchecked" }) public class MultiFileObserver extends FileObserver {     /** Only modification events */  public static int CHANGES_ONLY = CREATE | MODIFY |DELETE | CLOSE_WRITE  | DELETE_SELF | MOVE_SELF | MOVED_FROM | MOVED_TO;  private List<SingleFileObserver> mObservers;  private String mPath;  private int mMask;  public MuityFileObserver(String path) {  this(path, ALL_EVENTS);  }  public MuityFileObserver(String path, int mask) {  super(path, mask);  mPath = path;  mMask = mask;  }  @Override  public void startWatching() {  if (mObservers != null)  return;  mObservers = new ArrayList<SingleFileObserver>();  Stack<String> stack = new Stack<String>();  stack.push(mPath);  while (!stack.isEmpty()) {  String parent = stack.pop();  mObservers.add(new SingleFileObserver(parent, mMask));  File path = new File(parent);  File[] files = path.listFiles();  if (null == files)  continue;  for (File f : files) {  if (f.isDirectory() && !f.getName().equals(".")  && !f.getName().equals("..")) {  stack.push(f.getPath());  }  }  }  for (int i = 0; i < mObservers.size(); i++) {  SingleFileObserver sfo = mObservers.get(i);  sfo.startWatching();  }  };  @Override  public void stopWatching() {  if (mObservers == null)  return;  for (int i = 0; i < mObservers.size(); i++) {  SingleFileObserver sfo = mObservers.get(i);  sfo.stopWatching();  }   mObservers.clear();  mObservers = null;  };      @Override     public void onEvent(int event, String path) {         switch (event) {         case FileObserver.ACCESS:             Log.i("RecursiveFileObserver", "ACCESS: " + path);             break;         case FileObserver.ATTRIB:             Log.i("RecursiveFileObserver", "ATTRIB: " + path);             break;         case FileObserver.CLOSE_NOWRITE:             Log.i("RecursiveFileObserver", "CLOSE_NOWRITE: " + path);             break;         case FileObserver.CLOSE_WRITE:             Log.i("RecursiveFileObserver", "CLOSE_WRITE: " + path);             break;         case FileObserver.CREATE:             Log.i("RecursiveFileObserver", "CREATE: " + path);             break;         case FileObserver.DELETE:             Log.i("RecursiveFileObserver", "DELETE: " + path);             break;         case FileObserver.DELETE_SELF:             Log.i("RecursiveFileObserver", "DELETE_SELF: " + path);             break;         case FileObserver.MODIFY:             Log.i("RecursiveFileObserver", "MODIFY: " + path);             break;         case FileObserver.MOVE_SELF:             Log.i("RecursiveFileObserver", "MOVE_SELF: " + path);             break;         case FileObserver.MOVED_FROM:             Log.i("RecursiveFileObserver", "MOVED_FROM: " + path);             break;         case FileObserver.MOVED_TO:             Log.i("RecursiveFileObserver", "MOVED_TO: " + path);             break;         case FileObserver.OPEN:             Log.i("RecursiveFileObserver", "OPEN: " + path);             break;         default:             Log.i("RecursiveFileObserver", "DEFAULT(" + event + " : " + path);             break;         }     }      /**     * Monitor single directory and dispatch all events to its parent, with full     * path.     */     class SingleFileObserver extends FileObserver {         String mPath;          public SingleFileObserver(String path) {             this(path, ALL_EVENTS);             mPath = path;         }          public SingleFileObserver(String path, int mask) {             super(path, mask);             mPath = path;         }          @Override         public void onEvent(int event, String path) {             String newPath = mPath + "/" + path;             RecursiveFileObserver.this.onEvent(event, newPath);         }     } }

修改之后的FileObserver就可以实现对path目录下所有文件的操作都能监听到了。

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