這是我的代碼......我怎樣才能讓它工作，以便在用戶按住按鈕時運行循環(huán)并在用戶釋放按鈕時停止？public void nextPrimeNum(){ x = false; int b = 2; ArrayList<Integer> next = new ArrayList<Integer>(); while(x) { next = factors(b); if(next.size()==2) { System.out.println(b); } b++; } System.out.println("End");}public void keyPressed(KeyEvent e){ if(e.getKeyCode() == 401) { x = true; }}public void keyRealesed(KeyEvent e){ if(e.getKeyCode() == 402) { x = false; }}
2 回答
慕哥6287543
TA貢獻1831條經驗 獲得超10個贊
所以，答案是——這很復雜。它涵蓋了廣泛的主題，例如并發(fā)（一般）、GUI 開發(fā)、特定 API (Swing) 的最佳實踐
該示例提供了兩種執(zhí)行“循環(huán)”的doInBackground方法（在CalculateWorker類的方法中提供）。
您可以按住JButton或按住 [kbd]Space[kbd] 欄，兩者都會導致“主循環(huán)”運行，更新JTextArea結果...
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.KeyStroke;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea ta;
private CalculateWorker worker;
public TestPane() {
setLayout(new BorderLayout());
ta = new JTextArea(20, 20);
ta.setEditable(false);
add(new JScrollPane(ta));
worker = new CalculateWorker(ta);
JButton btn = new JButton("Press");
btn.getModel().addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
System.out.println("...isRunning = " + worker.isRunning());
if (!worker.isRunning()) {
return;
}
System.out.println("...isPressed = " + btn.getModel().isPressed());
System.out.println("...isPaused = " + worker.isPaused());
if (btn.getModel().isPressed()) {
worker.pause(false);
} else {
worker.pause(true);
}
}
});
add(btn, BorderLayout.SOUTH);
worker.execute();
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0, false), "Space.released");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0, true), "Space.pressed");
am.put("Space.released", new CalculateAction(false, worker));
am.put("Space.pressed", new CalculateAction(true, worker));
}
public class CalculateWorker extends SwingWorker<List<String>, String> {
private AtomicBoolean run = new AtomicBoolean(true);
private AtomicBoolean paused = new AtomicBoolean(false);
private ReentrantLock pausedLocked = new ReentrantLock();
private Condition pausedCondition = pausedLocked.newCondition();
private JTextArea ta;
public CalculateWorker(JTextArea ta) {
this.ta = ta;
pause(true);
}
public void stop() {
run.set(false);
pausedLocked.lock();
pausedCondition.signalAll();
pausedLocked.unlock();
}
public void pause(boolean pause) {
paused.set(pause);
pausedLocked.lock();
pausedCondition.signalAll();
pausedLocked.unlock();
}
public boolean isPaused() {
return paused.get();
}
public boolean isRunning() {
return run.get();
}
@Override
protected List<String> doInBackground() throws Exception {
List<String> values = new ArrayList<>(256);
long value = 0;
System.out.println("!! Start running");
while (run.get()) {
while (paused.get()) {
System.out.println("!! I'm paused");
pausedLocked.lock();
try {
pausedCondition.await();
} finally {
pausedLocked.unlock();
}
}
System.out.println("!! Start loop");
while (!paused.get() && run.get()) {
value++;
values.add(Long.toString(value));
publish(Long.toString(value));
Thread.sleep(5);
}
System.out.println("!! Main loop over");
}
System.out.println("!! Run is over");
return values;
}
@Override
protected void process(List<String> chunks) {
for (String value : chunks) {
ta.append(value);
ta.append("\n");
}
ta.setCaretPosition(ta.getText().length());
}
}
public class CalculateAction extends AbstractAction {
private boolean start;
private CalculateWorker worker;
public CalculateAction(boolean start, CalculateWorker worker) {
putValue(NAME, "Calculate");
this.start = start;
this.worker = worker;
}
@Override
public void actionPerformed(ActionEvent e) {
worker.pause(start);
}
}
}
}
有沒有更簡單的解決方案？
當然，我總是先找最難、最難理解的解決方案（諷刺）
雖然“可能”降低復雜性是可能的，但該示例提供了許多“最佳實踐”概念，您可以很好地學習和理解這些概念。
該解決方案也可以根據(jù)所使用的 API 以不同方式完成，因此，它是特定 API 選擇的“最簡單”解決方案。
我想從控制臺做到這一點！
Java 不能這樣做 - 它的控制臺支持充其量只是基本的，并且不支持“按鍵按下/釋放”操作的概念（因為它在單個線程中運行，否則它不可能這樣做）。
您可能會嘗試“有”解決方案，但它們需要鏈接到本機二進制文件的第三方庫才能實現(xiàn)，這（可能）會減少它運行的平臺數(shù)量
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