我有一个Jframe，它是我的应用程序窗口(以下代码中的appFrame)，其中包含很多逻辑，并且加载大约需要1秒左右的时间。同时，我想向我的用户展示一个非常不错的加载框架(initFrame)。但是，当我运行此代码时，initFrame确实会出现，但是它上的JLabel中的文本不会立即显示-实际上，在加载应用程序框架之前，它实际上根本不会出现。
如果我注释掉所有appFrame，并且仅启动initFrame，则立即加载文本，根本没有等待时间。为什么会这样呢？这可能是并发问题吗？
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() { //as per best practice for concurrency in swing - see http://docs.oracle.com/javase/tutorial/uiswing/concurrency/
@Override
public void run() {
final JFrame initFrame = new InitFrame();
initFrame.setVisible(true);
final AppFrame appFrame = new AppFrame();
appFrame.setVisible(true);
initFrame.setVisible(false);
initFrame.dispose();
}
});
}
最佳答案
这是AppFrame中可能出问题的示例。
您可以使用线程运行测试:
java SplashTest true
有无
java SplashTest
启用线程后，您会看到
SplashFrame和AppFrame每250ms更新一次，或多或少。如果未启用线程，则将看到带有且未显示组件的
SplashFrame，应用程序“挂起”了4秒钟，然后看到了AppFrame。该示例有些人为设计，但可能会给您一些想法。
请注意，
SplashFrame与AppFrame没有“直接”连接。所有通信都是通过AppFrameWorkListener接口进行的。我还将“工作”放在
AppFrame中。但是实际上，如果有很多处理要做，应该将其从UI代码中提取出来，并在单独的Thread中运行，并且任务将以与当前AppFrame相同的方式通知SplashFrame进度。import javax.swing.*;
class SplashTest {
static boolean useThread = false;
public static void main(String[] args) {
// Pass true at the command line to turn on threading.
// No args, or any value other than true will turn off threading.
if (args.length > 0) {
useThread = new Boolean(args[0]);
}
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
SplashFrame splashFrame = new SplashFrame();
splashFrame.setVisible(true);
new AppFrame(splashFrame).setVisible(true);
}});
}
private static class BaseFrame extends JFrame {
public BaseFrame() {
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setSize(200, 200);
setTitle(getClass().getSimpleName());
}
}
private static class SplashFrame extends BaseFrame implements AppFrameWorkListener {
JLabel status;
public SplashFrame() {
setLocation(0, 0);
status = new JLabel("Splash Frame");
getContentPane().add(status);
}
public void appFrameWorkStart() {
status.setText("Work started");
}
public void appFrameWorkProgress(long timeElapsed) {
status.setText("Work has taken " + timeElapsed + "ms so far");
}
public void appFrameWorkDone() {
// http://stackoverflow.com/questions/1234912/how-to-programmatically-close-a-jframe
setVisible(false);
dispose();
}
}
private static class AppFrame extends BaseFrame {
JLabel status;
AppFrameWorkListener listener;
public AppFrame(AppFrameWorkListener listener) {
setLocation(200, 200);
status = new JLabel("App Frame");
getContentPane().add(status);
this.listener = listener;
// None of this 'heavy lifting' should be in a constructor.
if (useThread) {
new Thread(new Runnable() {
@Override
public void run() {
doLotsOfWork(4);
}
}).start();
} else {
doLotsOfWork(4);
onWorkDone();
}
}
private void doLotsOfWork(int workLengthSeconds) {
// We're starting. Ensure onWorkStart is called on the EDT,
// as this method may be called from a different Thread.
invokeOnWorkStartOnEDT();
long start = System.currentTimeMillis();
// Hammer the CPU for "workLengthSeconds" number of seconds.
// And do some contrived progress reporting.
long workLengthMs = workLengthSeconds * 1000;
while (System.currentTimeMillis() - start < workLengthMs) {
long innerStart = System.currentTimeMillis();
// Consume 250ms CPU before issuing progress update.
while (System.currentTimeMillis() - innerStart < 250);
invokeOnWorkProgressOnEDT(System.currentTimeMillis() - start);
}
// We're done now. Ensure onWorkDone is called on the EDT,
// as this method may be called from a different Thread.
invokeOnWorkDoneOnEDT();
}
private void invokeOnWorkStartOnEDT() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
onWorkStart();
}
});
}
private void invokeOnWorkProgressOnEDT(final long timeElapsed) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
onWorkProgress(timeElapsed);
}
});
}
private void invokeOnWorkDoneOnEDT() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
onWorkDone();
}
});
}
private void onWorkStart() {
status.setText("Work Started");
if (null != listener) {
// Tell someone who's interested in the work status.
listener.appFrameWorkStart();
}
}
private void onWorkProgress(long timeElapsed) {
status.setText("Work has taken " + timeElapsed + "ms so far");
if (null != listener) {
// Tell someone who's interested in the work status.
listener.appFrameWorkProgress(timeElapsed);
}
}
private void onWorkDone() {
status.setText("Work Done");
if (null != listener) {
// Tell someone who's interested in the work status.
listener.appFrameWorkDone();
}
}
}
interface AppFrameWorkListener {
public void appFrameWorkDone();
public void appFrameWorkStart();
public void appFrameWorkProgress(long timeElapsed);
}
}