以下代码需要27秒才能加载51张图像，每张图像约为22 KB（我插入的开始和结束警报之间的时间间隔）。是否有可能使它更有效率（我想在3秒内达到它）？
起初我以为是数据库所以我把警报放进去确认并发现它是这个代码。
此致
格林
public void renderYMAwardsTable(List<YouthMemberAwards> ymAwardsList) {
if (!ymAwardsList.isEmpty()) {
flexTableLink.clear();
int linkRow = 0;
int linkCol = 0;
flexTableLeadership.clear();
int leadershipRow = 0;
int leadershipCol = 0;
flexTableBoomerang.clear();
int boomerangRow = 0;
int boomerangCol = 0;
flexTableAchievement.clear();
int achievementRow = 0;
int achievementCol = 0;
flexTableSpecialInterest.clear();
int specialInterestRow = 0;
int specialInterestCol = 0;
totalAwards = 0;
Window.alert("Start populating page.");
for (final YouthMemberAwards ymAwards : ymAwardsList) {
// Display awards and, if applicable, date awarded
if (((ymAwards.getCaAwardedDate() != null)
|| (ymAwards.getAwArchivedDate() == null)
|| (ymAwards.getCaAwardStarted().equals("Y"))
) && (ymAwards.getAwStartedDate().before(ymEndDate))) {
//Display each award in the correct area with:
// the date awarded, if applicable, and
// the date box shaded if the award has been started but not awarded
String imageDataString = ymAwards.getAwAwardPicture();
Image image = new Image(imageDataString);
image.setWidth("75px");
image.setHeight("75px");
image.setStyleName("gwt-Selectable");
final DateBox awardedDate = new DateBox();
awardedDate.setFormat(new DefaultFormat(DateTimeFormat.getFormat("dd/MM/yyyy")));
awardedDate.setValue(ymAwards.getCaAwardedDate());
awardedDate.setWidth("75px");
awardedDate.setFireNullValues(true);
//Check if the Youth Member has started the Award,
//if they have then colour the date box Green.
if (ymAwards.getCaAwardStarted()!= null){
if ((ymAwards.getCaAwardedDate() == null)
&& (ymAwards.getCaAwardStarted().equals("Y"))){
awardedDate.setStyleName("gwt-Green-Background");
}else{
awardedDate.setStyleName("gwt-Label-Login");
}
}else{
awardedDate.setStyleName("gwt-Label-Login");
}
//Tally the number of Awards the Youth Member has been awarded.
if (ymAwards.getCaAwardedDate() != null){
totalAwards = totalAwards + 1;
}
//Display each Award in the appropriate category.
if (ymAwards.getAwAwardType().equals("Link")){
flexTableLink.setWidget(linkRow, linkCol, image);
flexTableLink.setWidget(linkRow + 1, linkCol, awardedDate);
if (linkCol < 10){
linkCol = linkCol + 1;
}else{
linkCol = 0;
linkRow = linkRow + 2;
}
}else{
if (ymAwards.getAwAwardType().equals("Leadership")){
flexTableLeadership.setWidget(leadershipRow, leadershipCol, image);
flexTableLeadership.setWidget(leadershipRow + 1, leadershipCol, awardedDate);
if (leadershipCol < 10){
leadershipCol = leadershipCol + 1;
}else{
leadershipCol = 0;
leadershipRow = leadershipRow + 2;
}
}else{
if (ymAwards.getAwAwardType().equals("Boomerang")){
flexTableBoomerang.setWidget(boomerangRow, boomerangCol, image);
flexTableBoomerang.setWidget(boomerangRow + 1, boomerangCol, awardedDate);
if (boomerangCol < 10){
boomerangCol = boomerangCol + 1;
}else{
boomerangCol = 0;
boomerangRow = boomerangRow + 2;
}
}else{
if (ymAwards.getAwAwardType().equals("Achievement")){
flexTableAchievement.setWidget(achievementRow, achievementCol, image);
flexTableAchievement.setWidget(achievementRow + 1, achievementCol, awardedDate);
if (achievementCol < 10){
achievementCol = achievementCol + 1;
}else{
achievementCol = 0;
achievementRow = achievementRow + 2;
}
}else{
if (ymAwards.getAwAwardType().equals("Special Interest")){
flexTableSpecialInterest.setWidget(specialInterestRow, specialInterestCol, image);
flexTableSpecialInterest.setWidget(specialInterestRow + 1, specialInterestCol, awardedDate);
if (specialInterestCol < 10){
specialInterestCol = specialInterestCol + 1;
}else{
specialInterestCol = 0;
specialInterestRow = specialInterestRow + 2;
}
}else{
//If not found then default to Special Interest.
flexTableSpecialInterest.setWidget(specialInterestRow, specialInterestCol, image);
flexTableSpecialInterest.setWidget(specialInterestRow + 1, specialInterestCol, awardedDate);
if (specialInterestCol < 10){
specialInterestCol = specialInterestCol + 1;
}else{
specialInterestCol = 0;
specialInterestRow = specialInterestRow + 2;
}
}
}
}
}
}
//Add a click handler to the image
image.addClickHandler(new ClickHandler(){
public void onClick(ClickEvent event){
//Store the data from this view for use in subsequent Views (ScoutAwardView).
AsyncCallback<ViewData> callback = new ViewDataStoreHandler<ViewData>();
rpc.setViewData(accountId, accountLevel, youthMemberID, ymAwards.getAwId(), "0", callback);
//If the Award has sub groups then display the Groups and allow one the
//be selected to display the details. Otherwise, display the details.
if (ymAwards.getAwGrouped().equals("Y")) {
//Go to the AwardGroupView
navHandler2.go("AwardGroup");
}else{
//Go to the ScoutAwardView
navHandler2.go("ScoutAward");
}
}
});
//Add change handler for the awarded date.
//Only a Leader or Administrator can update the date
if (accountLevel.equals("Leader") || accountLevel.equals("Administrator")) {
awardedDate.addValueChangeHandler(new ValueChangeHandler<java.util.Date>() {
public void onValueChange(ValueChangeEvent<java.util.Date> event) {
//Check for a null date and handle it for dateBoxArchived and dateBoxPackOut
java.sql.Date sqlDateAwarded = awardedDate.getValue() == null ? null : new java.sql.Date(awardedDate.getValue().getTime());
AsyncCallback<Void> callback = new YMAwardedDateHandler<Void>();
rpc.updateYMAwarded(youthMemberID, ymAwards.getAwId(), sqlDateAwarded, callback);
@SuppressWarnings("unused")
AdjustAwardStock adjustAwardStock = new AdjustAwardStock(sqlDateAwarded, ymAwards.getAwId());
}
});
}
}
}
}
Window.alert("Finish populating page.");
//Hide "Loading please wait" popup.
popup.hide();
//Display the number of Awards earned.
String totalAwardsString = Integer.toString(totalAwards);
textBoxTotalAwards.setText(totalAwardsString);
}
答案 0 :(得分：6)
首先，尺寸为75x75像素的图像不应为22kB。即使是这种尺寸的PNG-24图像也只有3kB，更不用说GIF了。以正确的尺寸和相应的文件格式存储图像（使用PNG或GIF）。对于51个图像，这意味着1MB到150kB之间的差异。这是第一次重大改进。
其次，如果您使用有限数量的图像，请将它们组合成一个精灵。这会将往返服务器调用的次数从51（在您的示例中）减少到1.这是另一个巨大的改进。
您不需要手动制作此精灵（除非您愿意）。您可以使用GWT ImageResource ClientBundle。请注意，此精灵可以缓存，因此每次用户访问此页面时，浏览器都不需要加载它。
其他建议（比如使用switch语句）有利于代码的可读性和维护，但是它们不会给你带来显着的性能提升，因为你的Java代码被编译成JavaScript，并且编译器非常聪明。 / p>
答案 1 :(得分：0)
对于组合图像和其他JS文件，您始终可以使用浏览器支持的gzip功能，以便所有文件都可以压缩并发送到浏览器进行解压缩。它将大量的网络时间和转移的数据大小将大大减少。