无法使用单独的方法停止侦听器

Question

我已经使用org.apache.commons.io.monitor.FileAlterationMonitor创建了一个文件监视器。正确捕获文件更改。但是我想用另一种方法停止监视器任务。不管用。源代码如下:

import java.io.File;
import java.io.IOException;
import java.util.Scanner;
import org.apache.commons.io.FileDeleteStrategy;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.commons.io.monitor.FileEntry;
public class FileMonitor2 {

    //public final class FileMonitorExample {
        private static final String EXAMPLE_PATH =
                "D:\testrail\install.txt";
        private static final String PARENT_DIR1 =
                "D:\ibi\DevStudio77\client\wfc\etc";
        private static final String PARENT_DIR2 =
                "D:\ibi\DevStudio77\config";
        public static void runExample(boolean b) {
            System.out.println("File Monitor example...");
            FileAlterationMonitor monitor=new FileAlterationMonitor();
            // FileEntry
            // We can monitor changes and get information about files
            // using the methods of this class.
            if(b){
            FileEntry entry = new FileEntry(FileUtils.getFile(EXAMPLE_PATH));
            System.out.println("File monitored: " + entry.getFile());
            System.out.println("File name: " + entry.getName());
            System.out.println("Is the file a directory?: " + entry.isDirectory());

            // File Monitoring
            // Create a new observer for the folder and add a listener
            // that will handle the events in a specific directory and take action.
            File parentDir = FileUtils.getFile(PARENT_DIR1);
            FileAlterationObserver observer = new FileAlterationObserver(parentDir);
            observer.addListener(new FLA2());
            File parentDir1 = FileUtils.getFile(PARENT_DIR2);
            FileAlterationObserver observer2 = new FileAlterationObserver(parentDir1);
           // observer.addListener(new FLA());
            observer2.addListener(new FLA());
            // Add a monior that will check for events every x ms,
            // and attach all the different observers that we want.
            monitor.addObserver(observer);
            //monitor = new FileAlterationMonitor(500, observer);
            monitor.addObserver(observer2);
            try {
                monitor.start();
                System.out.println("Started");
                // After we attached the monitor, we can create some files and directories
                // and see what happens!
                //monitor.stop();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
            }else{
            /*System.out.println("type the value");
            Scanner sc=new Scanner(System.in);  
            String ss=sc.next();
            if(ss.equals("aa")){*/
            try {
                monitor.stop();
                System.out.println("stopped");
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
          //  }
            }
        }
        public static void main(String args[]) throws InterruptedException{
            runExample(true);
            System.out.println("After start");
            Thread.sleep(1000);
            runExample(false);
        }
    //}
}

Answer 1

第二次调用runExample(false)时，将重新创建monitor。您需要在调用runExample(true)时创建的实例上调用monitor.stop()。您可以在第一次创建monitor之后将其保存到static变量中。随后对runExample(false)的任何调用都可以访问monitor的原始实例。

您可以通过在runExample方法之外声明monitor来修复这个问题，并且仅在传递true时创建一个新的监视器:

static FileAlterationMonitor monitor;
public static void runExample(boolean b) {
    if (b) {
        monitor = new FileAlterationMonitor();
    } else {
        if (monitor == null) return;
        monitor.stop();
    }
}