问题
我有一个应用程序的预加载器,处理特定于应用程序的初始化。现在我正在尝试扩展它,以便预加载器还显示已下载的应用程序JAR文件的进度。
简述
为什么在第二阶段期间,预加载程序未被加载,因为这应该处理
PreloaderFx :: handleProgressNotification();
来跟踪JAR的下载,我想知道是什么原因?2016年3月14日更新:使用DownloadServiceListener解决这个问题的方式是什么?如何将其连接到JavaFX舞台?
文档
根据Oracle的说法, 应用程序启动时有4个阶段:
- 第一阶段: 初始化: Java Runtime的初始化和初始检查确定必须在启动应用程序之前加载和执行的组件。 在此阶段,会显示一个启动画面。默认情况下是这个:
第二阶段:加载和准备:必要的资源从网络或磁盘缓存中加载,并进行验证程序。所有执行模式都可以看到默认的或自定义的预加载器。在此阶段,应该显示我的自定义预加载器。
第三阶段:应用程序特定初始化:应用程序已启动,但可能需要加载其他资源或执行其他漫长的准备工作,才能完全发挥功能。目前,正在显示我的自定义预加载器:
- 第四阶段:应用程序执行:应用程序被显示并准备好使用。在我的情况下,会显示一个登录窗口,用户可以继续操作。
我的案例
我注意到的第一件事是,在第二阶段中,处理应用程序JAR文件下载的默认JavaFX预加载程序未显示。由于这个原因,用户会感觉程序没有启动或提前终止,导致他们多次打开JNLP文件。一旦JAR文件被下载,我们进入第三阶段并显示预加载程序。
然而,我希望我的自定义预加载程序也能在ProgressBar中处理下载进度(第二阶段)。我尽可能简单地跟踪了应用程序启动期间发生的事件。这是基于 Jewelsea的示例和Oracle的示例:
预加载程序:
public class PreloaderFX extends Preloader {
Stage stage;
//boolean noLoadingProgress = true;
public static final String APPLICATION_ICON
= "http://cdn1.iconfinder.com/data/icons/Copenhagen/PNG/32/people.png";
public static final String SPLASH_IMAGE
= "http://fxexperience.com/wp-content/uploads/2010/06/logo.png";
private Pane splashLayout;
private ProgressBar loadProgress;
private Label progressText;
private static final int SPLASH_WIDTH = 676;
private static final int SPLASH_HEIGHT = 227;
@Override
public void init() {
ImageView splash = new ImageView(new Image(
SPLASH_IMAGE
));
loadProgress = new ProgressBar();
loadProgress.setPrefWidth(SPLASH_WIDTH - 20);
progressText = new Label("Loading . . .");
splashLayout = new VBox();
splashLayout.getChildren().addAll(splash, loadProgress, progressText);
progressText.setAlignment(Pos.CENTER);
splashLayout.setStyle(
"-fx-padding: 5; "
+ "-fx-background-color: white; "
+ "-fx-border-width:5; "
);
splashLayout.setEffect(new DropShadow());
}
@Override
public void start(Stage stage) throws Exception {
System.out.println("PreloaderFx::start();");
//this.stage = new Stage(StageStyle.DECORATED);
stage.setTitle("Title");
stage.getIcons().add(new Image(APPLICATION_ICON));
stage.initStyle(StageStyle.UNDECORATED);
final Rectangle2D bounds = Screen.getPrimary().getBounds();
stage.setScene(new Scene(splashLayout));
stage.setX(bounds.getMinX() + bounds.getWidth() / 2 - SPLASH_WIDTH / 2);
stage.setY(bounds.getMinY() + bounds.getHeight() / 2 - SPLASH_HEIGHT / 2);
stage.show();
this.stage = stage;
}
@Override
public void handleProgressNotification(ProgressNotification pn) {
System.out.println("PreloaderFx::handleProgressNotification(); progress = " + pn.getProgress());
//application loading progress is rescaled to be first 50%
//Even if there is nothing to load 0% and 100% events can be
// delivered
if (pn.getProgress() != 1.0 /*|| !noLoadingProgress*/) {
loadProgress.setProgress(pn.getProgress() / 2);
/*if (pn.getProgress() > 0) {
noLoadingProgress = false;
}*/
}
}
@Override
public void handleStateChangeNotification(StateChangeNotification evt) {
//ignore, hide after application signals it is ready
System.out.println("PreloaderFx::handleStateChangeNotification(); state = " + evt.getType());
}
@Override
public void handleApplicationNotification(PreloaderNotification pn) {
if (pn instanceof ProgressNotification) {
//expect application to send us progress notifications
//with progress ranging from 0 to 1.0
double v = ((ProgressNotification) pn).getProgress();
System.out.println("PreloaderFx::handleApplicationNotification(); progress = " + v);
//if (!noLoadingProgress) {
//if we were receiving loading progress notifications
//then progress is already at 50%.
//Rescale application progress to start from 50%
v = 0.5 + v / 2;
//}
loadProgress.setProgress(v);
} else if (pn instanceof StateChangeNotification) {
System.out.println("PreloaderFx::handleApplicationNotification(); state = " + ((StateChangeNotification) pn).getType());
//hide after get any state update from application
stage.hide();
}
}
}
第三阶段处理的代码来自与预加载程序交互的主应用程序,这是在进度条中看到的内容:
public class MainApp extends Application {
BooleanProperty ready = new SimpleBooleanProperty(false);
public static void main(String[] args) throws Exception {
launch(args);
}
@Override
public void start(final Stage initStage) throws Exception {
System.out.println("MainApp::start();");
this.mainStage = initStage;
longStart();
ready.addListener((ObservableValue<? extends Boolean> ov, Boolean t, Boolean t1) -> {
if (Boolean.TRUE.equals(t1)) {
Platform.runLater(() -> {
System.out.println("MainApp::showMainStage();");
showMainStage();
});
}
});
}
private void longStart() {
//simulate long init in background
Task task = new Task<Void>() {
@Override
protected Void call() throws Exception {
int max = 10;
for (int i = 1; i <= max; i++) {
Thread.sleep(500);
System.out.println("longStart " + i);
// Send progress to preloader
notifyPreloader(new ProgressNotification(((double) i)/max)); //this moves the progress bar of the preloader
}
// After init is ready, the app is ready to be shown
// Do this before hiding the preloader stage to prevent the
// app from exiting prematurely
ready.setValue(Boolean.TRUE);
notifyPreloader(new StateChangeNotification(
StateChangeNotification.Type.BEFORE_START));
return null;
}
};
new Thread(task).start();
}
private void showMainStage() {
//showing the login window
}
}
JNLP
<jnlp spec="1.0+" xmlns:jfx="http://javafx.com" codebase="<***>/preloadertest/jnlp" href="launch.jnlp">
<information>
...
</information>
<resources>
<j2se version="1.6+" href="http://java.sun.com/products/autodl/j2se" />
... //whole bunch of JARS
<jar href="lib/preloader-1.1.1.jar" download="progress" />
</resources>
<security>
<all-permissions/>
</security>
<applet-desc width="1024" height="768" main-class="com.javafx.main.NoJavaFXFallback" name="JavaFX Client">
<param name="requiredFXVersion" value="8.0+"/>
</applet-desc>
<jfx:javafx-desc width="1024" height="768" main-class="GUI.MainApp" name="JavaFX Client" preloader-class="GUI.PreloaderFX" />
<update check="background"/>
</jnlp>
调试
启动文件时,我密切关注了Java控制台(启用显示日志,禁用显示跟踪),并注意到以下事项:
在第2阶段期间,Java控制台中没有任何内容显示(控制台在此阶段后关闭)。
在第3阶段期间,生成以下输出(在新的控制台窗口中):
PreloaderFx::start();
PreloaderFx::handleProgressNotification(); progress = 1.0
PreloaderFx::handleStateChangeNotification(); state = BEFORE_LOAD
PreloaderFx::handleStateChangeNotification(); state = BEFORE_INIT
PreloaderFx::handleStateChangeNotification(); state = BEFORE_START
MainApp::start();
MainApp::longstart();
longStart 1
PreloaderFx::handleApplicationNotification(); progress = 0.1
longStart 2
PreloaderFx::handleApplicationNotification(); progress = 0.2
longStart 3
PreloaderFx::handleApplicationNotification(); progress = 0.3
longStart 4
PreloaderFx::handleApplicationNotification(); progress = 0.4
longStart 5
PreloaderFx::handleApplicationNotification(); progress = 0.5
longStart 6
PreloaderFx::handleApplicationNotification(); progress = 0.6
longStart 7
PreloaderFx::handleApplicationNotification(); progress = 0.7
longStart 8
PreloaderFx::handleApplicationNotification(); progress = 0.8
longStart 9
PreloaderFx::handleApplicationNotification(); progress = 0.9
longStart 10
PreloaderFx::handleApplicationNotification(); progress = 1.0
MainApp::showMainStage();
PreloaderFx::handleApplicationNotification(); state = BEFORE_START
2016年3月13日更新:
- 调整了代码,使用传入方法的阶段而不是创建新的,并注释掉与
noLoadingProgress
布尔值相关的所有内容(由nhylated建议) - 在MainApp中添加了一些额外的
System.out.println()
解决方案
只需在JNLP文件中添加<jfx:javafx-runtime version="8.0+"/>
即可解决问题。添加此行后,预加载程序将在第二阶段显示。我还修改了j2se version="1.6+"
为j2se version="1.8+"
。结果如下:
前50%是处理JAR下载,由handleProgressNotification()
方法完成。后50%是实际初始化MainApp (longstart()
通知预加载程序),由handleApplicationNotification()
完成。