java - DataLine 中的 isRunning() 和 isActive() 有什么区别？

Question

DataLine 中的 isRunning() 和 isActibe() 有什么区别？当线路实际处理数据时，这两个标志似乎都已设置。

更新

那里有两对方法:

1) 打开/关闭

2) 启动/停止

还有三个标志

1) 正在打开

2) 正在运行

3) 处于 Activity 状态

有人可以推断出他们之间和/或彼此之间的一些关系吗？例如，很明显，isRunning 意味着 isOpen，isActive 意味着 isOpen，但是 isActive 是否意味着 isRunning，或者反之亦然？或者他们是独立的？

我猜 Line 在调用 open() 后立即变为 isOpen 。所以 isOpen 用于检查是否调用了 open()。

我可以检查一下我是否调用了start()吗？也许一些 isActive 或 isRunning 就是为了这个？但哪一个呢？

更新1

以下代码旨在将音频从默认系统声音输入播放到默认系统声音输出。

public static void main(String[] args) throws LineUnavailableException, InterruptedException {

    AudioFormat audioFormat = new AudioFormat(16000f, 16, 1, true, false);

    final SourceDataLine outputLine;
    final TargetDataLine inputLine;


    outputLine = AudioSystem.getSourceDataLine(audioFormat);
    inputLine = AudioSystem.getTargetDataLine(audioFormat);

    Thread player = new Thread("player") {
        @Override
        public void run() {

            byte[] b = new byte[2048];
            int readen;

            log.info("Starting transfer");

            while( !inputLine.isOpen() ) {
                try {
                    log.info("TargetDataLine is closed, waiting");
                    sleep(1000);
                } catch (InterruptedException e) {
                    interrupt();
                }
            }

            while( !inputLine.isRunning() ) {
                try {
                    log.info("TargetDataLine is not running, waiting");
                    sleep(100);
                } catch (InterruptedException e) {
                    interrupt();
                }
            }

            while((readen = inputLine.read(b,0,b.length))>=0 && !isInterrupted()) {
                outputLine.write(b,0,readen);
            }

        }
    };
    player.start();

    outputLine.open();
    outputLine.start();

    inputLine.open();
    inputLine.start();

    player.join();

}

代码的输出如下:

15:20:01.369 [player] INFO  tests.DataLineFlags01 - Starting transfer
15:20:01.371 [player] INFO  tests.DataLineFlags01 - TargetDataLine is closed, waiting
15:20:02.371 [player] INFO  tests.DataLineFlags01 - TargetDataLine is not running, waiting
15:20:02.471 [player] INFO  tests.DataLineFlags01 - TargetDataLine is not running, waiting
15:20:02.571 [player] INFO  tests.DataLineFlags01 - TargetDataLine is not running, waiting
15:20:02.671 [player] INFO  tests.DataLineFlags01 - TargetDataLine is not running, waiting
15:20:02.771 [player] INFO  tests.DataLineFlags01 - TargetDataLine is not running, waiting
...

这证明 TargetDataLine 在调用 start() 后不会进入“运行”状态。

对于 isActive() 标志也会发生同样的情况。

这意味着

(1) 无法知道是否调用了 start()(2) isRunning() 和 isActive() 标志没有用

这样对吗？它们对于 SourceDataLine 对象可能有用吗？

更新2

以下应用

package testing.Test_TargetDataLine_01;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.TargetDataLine;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class App 
{

private static Logger log = LoggerFactory.getLogger(App.class);

private final AudioFormat audioFormat;
private final TargetDataLine targetDataLine;

private final Thread observer = new Thread("observer") {

    {
        setDaemon(true);
    }

    public void run() {

        while( !isInterrupted() ) {
            if( targetDataLine != null ) {
                log.info("targetDataLine: Opened={}, Active={}, Running={}", targetDataLine.isOpen(), targetDataLine.isActive(), targetDataLine.isRunning());
            }
            else {
                log.info("targetDataLine: is null");
            }
            try {
                sleep(10);
            } catch (InterruptedException e) {
            }
        }

    };
};

public App() throws LineUnavailableException, InterruptedException {

    byte[] buffer = new byte[160*2]; // 1/100 of second 

    log.info("App starting");

    log.info("Observer starting");
    observer.start();

    log.info("Sleeping 500");
    Thread.sleep(500);

    log.info("Creating targetDataLine");
    audioFormat = new AudioFormat(16000, 16, 1, true, false);
    targetDataLine = AudioSystem.getTargetDataLine(audioFormat);

    log.info("Sleeping 500");
    Thread.sleep(500);

    log.info("Opening targetDataLine");
    targetDataLine.open();

    log.info("Sleeping 500");
    Thread.sleep(500);

    log.info("Starting targetDataLine");
    targetDataLine.start();

    log.info("Sleeping 500");
    Thread.sleep(500);

    log.info("Reading target data line for 5 seconds");
    for(int i=0; i<50; ++i) {

        targetDataLine.read(buffer, 0, buffer.length);
        log.info("Stage " + i);
    }

    log.info("Stopping targetDataLine");
    targetDataLine.stop();

    log.info("Sleeping 500");
    Thread.sleep(500);

    log.info("Closing targetDataLine");
    targetDataLine.close();

    log.info("Sleeping 500");
    Thread.sleep(500);

    //log.info("Interrupting observer");
    //observer.interrupt();

}



public static void main( String[] args ) throws LineUnavailableException, InterruptedException
{
    new App();
}
}

产生以下输出:

20:58:23,360 0    [main] INFO  testing.Test_TargetDataLine_01.App  - App starting20:58:23,362 2    [main] INFO  testing.Test_TargetDataLine_01.App  - Observer starting20:58:23,362 2    [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:23,362 2    [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,372 12   [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null...20:58:23,842 482  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,852 492  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,862 502  [main] INFO  testing.Test_TargetDataLine_01.App  - Creating targetDataLine20:58:23,862 502  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,872 512  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null...20:58:23,912 552  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,922 562  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: is null20:58:23,929 569  [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:23,933 573  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:23,943 583  [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false...20:58:24,413 1053 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:24,423 1063 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:24,430 1070 [main] INFO  testing.Test_TargetDataLine_01.App  - Opening targetDataLine20:58:24,433 1073 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:24,443 1083 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false...20:58:24,483 1123 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:24,493 1133 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:24,501 1141 [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:24,503 1143 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:24,513 1153 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false...20:58:24,983 1623 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:24,993 1633 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:25,002 1642 [main] INFO  testing.Test_TargetDataLine_01.App  - Starting targetDataLine20:58:25,002 1642 [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:25,003 1643 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:25,013 1653 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false...20:58:25,483 2123 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:25,493 2133 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:25,502 2142 [main] INFO  testing.Test_TargetDataLine_01.App  - Reading target data line for 5 seconds20:58:25,502 2142 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 020:58:25,502 2142 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 120:58:25,503 2143 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 220:58:25,503 2143 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=true, Running=true20:58:25,503 2143 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 320:58:25,503 2143 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 4...20:58:25,512 2152 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 4820:58:25,512 2152 [main] INFO  testing.Test_TargetDataLine_01.App  - Stage 4920:58:25,512 2152 [main] INFO  testing.Test_TargetDataLine_01.App  - Stopping targetDataLine20:58:25,513 2153 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=true, Running=true20:58:25,521 2161 [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:25,523 2163 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:25,533 2173 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false...20:58:26,003 2643 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:26,013 2653 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=true, Active=false, Running=false20:58:26,021 2661 [main] INFO  testing.Test_TargetDataLine_01.App  - Closing targetDataLine20:58:26,023 2663 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:26,026 2666 [main] INFO  testing.Test_TargetDataLine_01.App  - Sleeping 50020:58:26,033 2673 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:26,043 2683 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false...20:58:26,513 3153 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false20:58:26,523 3163 [observer] INFO  testing.Test_TargetDataLine_01.App  - targetDataLine: Opened=false, Active=false, Running=false

这表明两个标志无法区分。

Answer 1

如果你查看 API 文档，它会说:

isRunning():指示线路是否正在运行。默认为 false。当响应启动方法的调用而呈现第一个数据时，开放线开始运行，并继续运行，直到响应停止调用或因为播放完成而停止呈现为止。

isActive():指示线路是否正在进行 Activity I/O(例如播放或捕获)。当不活动线路变为 Activity 线路时，它会向其监听器发送 START 事件。同样，当 Activity 线路变为非 Activity 状态时，它会发送 STOP 事件。

查看 start() 方法，我们发现 start() 允许该行变为非 Activity 状态，因此我们可以说 isRunning() 告诉我们线路是否可以激活，isActive() 告诉我们线路是否正在使用(即数据正在以播放或录制的形式传输)

所以，简而言之，

isRunning() - 在使用此行之前我们需要调用start()吗？

isActive() - 此行现在正在使用吗？

如果您必须知道何时调用 start()，请使用:

final HashSet<Line> openLines = new HashSet<Line>();
...
DataLine myLine = getDataLine();
myLine.addListener(new LineListener(){
    public void update(LineEvent evt)
    {
        if(evt.getType().equals(LineEvent.Type.START)) openLines.add(evt.getLine());
        else if(evt.getType().equals(LineEvent.Type.STOP)) openLines.remove(evt.getLine());
    }
});

...
public boolean isLineStarted(DataLine l)
{
    return openLines.contains(l);
}