java - 无法使用单独的方法停止侦听器

Question

我使用 org.apache.commons.io.monitor.FileAlterationMonitor 创建了一个文件观察器。文件更改被正确捕获。但我想使用单独的方法停止监视任务。它不工作。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

当runExample(false)第二次调用时，将monitor重新创建。您需要调用调用monitor.stop()时创建的实例runExample(true)。您可以在第一次创建变量后将其保存monitor到变量中。对then 的static任何后续调用都可以访问.runExample(false)monitor

monitor您可以通过在方法外部声明来解决此问题runExample，并且仅在传递 true 时才创建新监视器：

static FileAlterationMonitor monitor;

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