如何使用Java检测PC已空闲30秒？

Question

如何使用Java检测PC已空闲30秒？

已编辑

空闲是指没有用户活动。用户在 30 秒内没有执行任何操作。我想做一个像Windows这样的应用程序，它检测到用户什么都不做并进入待机状态。

Answer 1

我遇到过这个使用 JNA 检测系统范围空闲时间的优秀示例。 Java Native Access (JNA) 是一个库，可提供对 Java Native Interface (JNI) 的访问，而无需您实际编写本机代码。

这是示例，非常接近您的要求。

Answer 2

直接从java这是不可能的。您必须找到一些本机库并为其创建一个 JNI 包装器。

Answer 3

不可能按照要求，但您可以使用 java.lang.management API 创建解决方法。 JNI 实现也可以在 javaworld 上找到。

Answer 4

这并不容易，请查看 OperatingSystemMXBean 方法 getSystemLoadAverage() 仅自 java 6 起可用，您可以跟踪它，如果一段时间内相同，则确定电脑处于空闲状态。

这假设空闲 CPU 处于空闲状态

操作系统MXBean 操作系统MxBean = ManagementFactory.getOperatingSystemMXBean();

Answer 5

可以使用 Jana Native Access (JNA)

旧示例代码不再适用于最新的 JNA 版本（例如 JNA 5.15.0）。请参阅下面更新的代码。

所需的依赖项：

• https://mvnrepository.com/artifact/net.java.dev.jna/jna/5.15.0
• https://mvnrepository.com/artifact/net.java.dev.jna/jna-platform

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

import com.sun.jna.Native;
import com.sun.jna.Structure;
import com.sun.jna.Structure.FieldOrder;
import com.sun.jna.win32.StdCallLibrary;

/**
 * Utility method to retrieve the idle time on Windows and sample code to test it.
 * JNA shall be present in your classpath for this to work (and compile).
 * 
 * @author ochafik
 */
public class Win32IdleTime {
    public interface Kernel32 extends StdCallLibrary {
        Kernel32 INSTANCE = Native.load("kernel32", Kernel32.class);

        /**
         * Retrieves the number of milliseconds that have elapsed since the system was started.
         * 
         * @see http://msdn2.microsoft.com/en-us/library/ms724408.aspx
         * @return number of milliseconds that have elapsed since the system was started.
         */
        public int GetTickCount();
    };

    public interface User32 extends StdCallLibrary {
        User32 INSTANCE = Native.load("user32", User32.class);

        /**
         * Contains the time of the last input.
         * 
         * @see https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-lastinputinfo
         */
        @FieldOrder({ "cbSize", "dwTime" })
        public static class LASTINPUTINFO extends Structure {
            public int cbSize = 8;
            /// Tick count of when the last input event was received.
            public int dwTime;
        }

        /**
         * Retrieves the time of the last input event.
         * 
         * @see https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getlastinputinfo
         * @return time of the last input event, in milliseconds
         */
        public boolean GetLastInputInfo(LASTINPUTINFO result);
    };

    /**
     * Get the amount of milliseconds that have elapsed since the last input event
     * (mouse or keyboard)
     * 
     * @return idle time in milliseconds
     */
    public static int getIdleTimeMillisWin32() {
        User32.LASTINPUTINFO lastInputInfo = new User32.LASTINPUTINFO();
        User32.INSTANCE.GetLastInputInfo(lastInputInfo);
        return Kernel32.INSTANCE.GetTickCount() - lastInputInfo.dwTime;
    }

    enum State {
        UNKNOWN,
        ONLINE,
        IDLE,
        AWAY
    };

    /**
     * State:
     * 
     * <pre>
     * idle time 0-30 sec       -> ONLINE
     * idle time 30 sec - 5 min -> IDLE
     * idle time > 5 min        -> AWAY
     * </pre>
     * 
     */
    public static void main(String[] args) {
        if (!System.getProperty("os.name").contains("Windows")) {
            System.err.println("ERROR: Only implemented on Windows");
            System.exit(1);
        }
        State state = State.UNKNOWN;
        DateFormat dateFormat = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss");
        while (true) {
            int idleSec = getIdleTimeMillisWin32() / 1000;
            // System.out.println(idleSec);
            State newState = idleSec < 30 ? State.ONLINE : idleSec > 5 * 60 ? State.AWAY : State.IDLE;
            if (newState != state) {
                state = newState;
                System.out.println(dateFormat.format(new Date()) + " # " + state);
            }
            try {
                Thread.sleep(1000);
            } catch (Exception ex) {
            }
        }
    }
}