本篇内容主要讲解“Android怎么监测文件夹内容变化”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Android怎么监测文件夹内容变化”吧!
android.os包下的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，基于linux的INotify。FileObserver是个抽象类，必须继承它才能使用。每个FileObserver对象监听一个单独的文件或者文件夹，如果监视的是一个文件夹，那么文件夹下所有的文件和级联子目录的改变都会触发监听的事件。
FileObserver简介Android.os包下的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，基于Linux的INotify。
FileObserver是个抽象类，必须继承它才能使用。每个FileObserver对象监听一个单独的文件或者文件夹，如果监视的是一个文件夹，那么文件夹下所有的文件和级联子目录的改变都会触发监听的事件。
ACCESS，即文件被访问
MODIFY，文件被 修改
ATTRIB，文件属性被修改，如 chmod、chown、touch 等
CLOSE_WRITE，可写文件被 close
CLOSE_NOWRITE，不可写文件被 close
OPEN，文件被 open
MOVED_FROM，文件被移走,如 mv
MOVED_TO，文件被移来，如 mv、cp
CREATE，创建新文件
DELETE，文件被删除，如 rm
DELETE_SELF，自删除，即一个可执行文件在执行时删除自己
MOVE_SELF，自移动，即一个可执行文件在执行时移动自己
CLOSE，文件被关闭，等同于(IN_CLOSE_WRITE | IN_CLOSE_NOWRITE)
ALL_EVENTS，包括上面的所有事件
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; MultiFileObserver .this.onEvent(event, newPath); } } }到此，相信大家对“Android怎么监测文件夹内容变化”有了更深的了解，不妨来实际操作一番吧！这里是亿速云网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
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