我正在进行Web服务调用。我正在显示进度条，直到Web服务响应未来。但它挂起（停止递增值）或一段时间它会显示错误。 我们可以克服这个问题。
这是我的代码
public class MyApp extends UiApplication
{
public static void main(String[] args)
{
// Create a new instance of the application and make the currently
// running thread the application's event dispatch thread.
MyApp theApp = new MyApp();
theApp.enterEventDispatcher();
}
public MyApp()
{
MyScreen.progressBar=new ProgressBar("Loading data", 100, 90);
MyScreen.progressBar.start();
// Push a screen onto the UI stack for rendering.
pushScreen(new MyScreen());
}
}
====================================================================
public final class MyScreen extends MainScreen
{
public static ProgressBar progressBar;
/**
* Creates a new MyScreen object
*/
public MyScreen()
{
// Set the displayed title of the screen
setTitle("MyTitle");
add(new LabelField("Test"));
for (int i = 0; i <10000; i++) {
System.out.println("i");
}
// TODO Auto-generated method stub
if ( ProgressBar.popup.isDisplayed()){
ProgressBar.popup.close();
ProgressBar.remove();
}
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
// TODO Auto-generated method stub
UiApplication.getUiApplication().pushScreen(new SecondScreen()) ;
}
});
}
}
===========================================================
public class SecondScreen extends MainScreen {
protected void onDisplay() {
ConnectJsonWebService conjsonTocService = new ConnectJsonWebService();
conjsonTocService.jsonResult("http://50.57.145.165:8080/FirstGroupRailApps/jservices/rest/"+"a/"+"destinationdashboard"+"?crsCode="+"PAD"+"&device_pin="+Integer.toHexString(DeviceInfo.getDeviceId()));
System.out.println("**************Destination Response**********************"+conjsonTocService.response);
// TODO Auto-generated method stub
super.onDisplay();
}
public SecondScreen() {
// TODO Auto-generated constructor stub
}
}
=====================================================================
package mypackage;
///////////////////////////////////////////////////////////////////////////////////////////////////////////
//File Name : ProgressBar.Java
//Created On : 22 April 2010
//Created By : Ekansh Srivastava
//Purpose : This source file contains class which is a thread used for
// showing cinnecting PopUpWindow after LOGIN
//Change History
//Date Modified By Change
///////////////////////////////////////////////////////////////////////////////////////////////////////////
import net.rim.device.api.system.Display;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.GaugeField;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.PopupScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
////////////////////////////////////////////////////////////////////////////////////////////////////////////
//Class Name : ProgressBar
//Created On : 22 April 2010
//Created By : Ekansh Srivastava
//Purpose : This class is a thrad which is used for Displaying Connecting PopUp after LogIn
////////////////////////////////////////////////////////////////////////////////////////////////////////////
public class ProgressBar extends Thread {
private int maximum, timeout;
private static boolean useful;
public static PopupScreen popup;
public static GaugeField gaugeField;
public static LabelField gaugetitleField;
private ButtonField stopBtn;
int iterations = 0;
public static ProgressBar instance;
////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Function Name : ProgressBar (Constructor)
// Created On : 22 April 2010
// Created By : Ekansh Srivastava
// Input Parameters : String title, int maximum, int timeout
// Output : void
// Purpose : Executes the class, set the values and displays the Progress Bar
// Change History
// Date Modified By Change
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////
public ProgressBar(String title, int maximum, int timeout)
{
try
{
this.maximum = maximum;
this.timeout = timeout;
VerticalFieldManager manager = new VerticalFieldManager(VerticalFieldManager.VERTICAL_SCROLL);
HorizontalFieldManager buttonManager = new HorizontalFieldManager();
popup = new PopupScreen(manager){
public void sublayout(int width, int height){
super.sublayout(width,height);
setPosition(12,2*Display.getHeight()/3);
}
};
gaugeField = new GaugeField(null, 1, maximum, 1, GaugeField.NO_TEXT);
stopBtn = new ButtonField("CANCEL")
{
protected boolean navigationClick(int status,int time)
{
remove();
onClose();
return true;
}
};
// Font fon = Utility.getsFont(1);
// buttonManager.add(new SeparatorFieldClass(65,0));
// stopBtn.setFont(fon);
gaugetitleField=new LabelField(title,Field.USE_ALL_WIDTH);
manager.add(gaugetitleField);
manager.add(gaugeField);
manager.add(buttonManager);
instance = this;
}
catch(Exception e)
{
System.out.println("Exception in ProgressBAr : ProgressBar()" + e.toString());
}
}
public void run()
{
try
{
useful = true;
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
UiApplication.getUiApplication().pushScreen(popup);
}
});
while (useful) {
try {
Thread.sleep(timeout);
} catch (Exception e) {
}
if (++iterations > maximum)
iterations = 1;
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
// TODO Auto-generated method stub
gaugeField.setValue(iterations);
}
});
}
if (popup.isDisplayed()) {
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
UiApplication.getUiApplication().popScreen(popup);
}
});
}
}
catch(Exception e)
{
System.out.println("Exception in ProgressBAr : run()" + e.toString());
}
}
/* To remove Progress Bar*/
public static synchronized void remove()
{
useful = false;
}
public static ProgressBar getInstance()
{
if(instance == null)
{
instance = new ProgressBar("Connecting..",100,50);
}
return instance;
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Function Name : onClose
// Created On : 22 April 2010
// Created By : Ekansh Srivastava
// Input Parameters : None
// Output : Void
// Purpose : This method is remove Progress Bar and Close the Application
// Change History
// Date Modified By Change
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////
public boolean onClose()
{
try
{
Dialog.inform("Application will exit");
}
catch(Exception e)
{
System.out.println("Exception in ProgressBar : onClose() "+e.toString());
}
return true;
}
}
================================================
package mypackage;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import net.rim.device.api.io.IOUtilities;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.component.Dialog;
public class ConnectJsonWebService extends Thread {
private String url;
public String response;
private String myinterface = ";deviceside=true";
public void run() {
HttpConnection conn = null;
InputStream in = null;
int code;
try {
conn = (HttpConnection) Connector.open(this.url + NetworkAvailabilityCheck.getUrl(), Connector.READ);
conn.setRequestMethod(HttpConnection.GET);
code = conn.getResponseCode();
if (code == HttpConnection.HTTP_OK) {
in = conn.openInputStream();
byte[] buffer = IOUtilities.streamToBytes(in);
this.response = new String(buffer,"UTF-8");
if (in != null){
in.close();
}
if (conn != null){
conn.close();
}
}
} catch (Exception e) {
Dialog.inform(e.toString());
}
}
public String jsonResult(String url){
this.url = url;
// this.start();
this.run();
return response;
}
}
答案 0 :(得分：0)
此代码中还有其他一些奇怪之处，但最重要的是：
public String jsonResult(String url){
this.url = url;
// this.start();
this.run();
return response;
}
this.run（）会立即执行连接代码，这可能不是您想要的，因为您在事件线程上运行，因此实际上您阻止了事件线程，因此阻止了所有Ui更新。网络代码是阻塞的，因此不应在事件线程上执行。有关详细信息，请参阅此处：
Blocking operation not permitted on Event Thread
因此，您应该启动它而不是运行您的线程。搜索有关使用Java线程的更多信息，例如，请参阅此处：
如果你以非阻塞的方式运行它，那么你将异步地获得响应，所以你需要查看Observer模式之类的东西。
所有这些都已在本论坛和其他论坛上多次介绍过，因此我建议您查找人们专门为BlackBerry开发的其他代码示例，以下载和处理数据。
<强>更新
你问道： “你能让我演示一个演示，以便我理解它的基本原理”我不确定如何制作比已经存在的许多样本更好的东西，包括BB网站本身的样本，如下所示：
您提供的链接
Implement Simplified Observer Pattern to Avoid BlackBerry UI Lockup
似乎是使用观察者模式的一个很好的例子，我看到你发现了我写的一些样本，它们涵盖了相同的基础。我认为适合您的操作是按原样实现其中一个示例，通过代码并尝试理解它。
事件线程并不容易，也不是网络，我认为任何人都不能挥动魔杖并让你理解它。我想你需要自己解决这个问题。
祝你好运。