我有两个不同的视图控制器显示几乎相同的获取请求。其中一个显示的信息比另一个更多，也用于编辑数据。第二个只是展示。
有没有办法加速，因为两者都显示完全相同的数据？我在我的代码中寻找一些东西，这使得第一次显示第二个视图控制器后整个重新排序很慢。换句话说：最初在我的主视图控制器中重新排序非常快。然后你只显示第二个视图控制器并切换回来，然后主视图控制器中的重新排序变慢。我有理由认为这是因为他们使用相同的提取。
我在两个viewDidLoad方法中启动了获取请求，如下面的代码片段所示。第一个是我的主视图控制器，也是启动应用程序时显示的第一个：
- (void)setupFetchedResultsController
{
self.managedObjectContext = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"MainCategory"];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"position" ascending:YES]];
self.fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil cacheName:@"MainCategoryCache"];
}
这是我的第二个：
- (void)setupFetchedResultsController
{
self.managedObjectContext = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"MainCategory"];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"position" ascending:YES]];
self.fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:@"NetCache"];
}
以下是我的主视图控制器的加载和cellForRowAtIndexPath视图：
- (void)viewDidLoad
{
[super viewDidLoad];
[self setupFetchedResultsController];
//Edit/Done button
UIBarButtonItem *editButton = [[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Edit", nil) style:UIBarButtonItemStyleBordered target:self action:@selector(editTable:)];
[self.navigationItem setRightBarButtonItem:editButton];
//Budget at bottom
self.sumTitleLabel.text = [NSString stringWithFormat:@"%@%@:",NSLocalizedString(@"Budget", nil),NSLocalizedString(@"PerMonth", nil)];
self.sumLabel.text = [[DatabaseFetches budgetPerMonthForManagedObjectContext:self.managedObjectContext] getLocalizedCurrencyString];
//Layout
self.view.backgroundColor = [UIColor clearColor];
[self styleTableView];
[self styleBudgetTotal];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
//Data model and cell setup
static NSString *CellIdentifier = @"MainCategoryCell";
MainCategoryTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
MainCategory *mainCategory = [self.fetchedResultsController objectAtIndexPath:indexPath];
//Clear background color
cell.backgroundColor = [UIColor clearColor];
//Setup the cell texts
cell.title.text = mainCategory.name;
int numberOfSubcategories = [[mainCategory getNumberOfSpendingCategories] integerValue];
if (numberOfSubcategories == 1) {
cell.subcategories.text = [NSString stringWithFormat:@"%i %@", numberOfSubcategories, NSLocalizedString(@"subcategory", nil)];
} else {
cell.subcategories.text = [NSString stringWithFormat:@"%i %@", numberOfSubcategories, NSLocalizedString(@"subcategories", nil)];
}
cell.costs.text = [[mainCategory getMonthlyCostsOfAllSpendingCategories] getLocalizedCurrencyString];
//Delegation
cell.title.delegate = self;
//Format text
cell.title.font = [Theme tableCellTitleFont];
cell.title.textColor = [Theme tableCellTitleColor];
cell.title.tag = indexPath.row;
cell.subcategories.font = [Theme tableCellSubTitleFont];
cell.subcategories.textColor = [Theme tableCellSubTitleColor];
cell.costs.font = [Theme tableCellValueFont];
cell.costs.textColor = [Theme tableCellValueColor];
//Icon
UIImage *icon;
if(!mainCategory.icon){
icon = [UIImage imageNamed:@"DefaultIcon.png"];
} else {
icon = [UIImage imageNamed:mainCategory.icon];
}
[cell.iconButton setImage:icon forState: UIControlStateNormal];
cell.icon.image = icon;
cell.iconButton.tag = indexPath.row;
//Background image
cell.cellBackground.image = [[UIImage imageNamed:@"content-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
//Selection
//cell.title.highlightedTextColor = cell.title.textColor;
cell.subcategories.highlightedTextColor = cell.subcategories.textColor;
cell.costs.highlightedTextColor = cell.costs.textColor;
return cell;
}
完成第二个视图控制器：
@interface NetIncomeViewController()
@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;
@end
@implementation NetIncomeViewController
@synthesize incomeTitleLabel = _incomeTitleLabel;
@synthesize incomeValueTextField = _incomeValueTextField;
@synthesize incomeBackground = _incomeBackground;
@synthesize incomeValueBackground = _incomeValueBackground;
@synthesize netIncomeTitleLabel = _netIncomeTitleLabel;
@synthesize netIncomeValueLabel = _netIncomeValueLabel;
@synthesize netIncomeBackground = _netIncomeBackground;
@synthesize netIncomeValueBackground = _netIncomeValueBackground;
@synthesize managedObjectContext = _managedObjectContext;
#pragma mark Initializer and view setup
- (void)setupFetchedResultsController
{
self.managedObjectContext = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"MainCategory"];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"position" ascending:YES]];
self.fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
}
#pragma mark View lifecycle
- (void)awakeFromNib{
[super awakeFromNib];
//Title (necessary here because otherwise the tab bar would be only localized after first click
//on the respective tab bar and not from beginning
self.title = NSLocalizedString(@"Net Income", nil);
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self updateNetIncome];
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self setupFetchedResultsController];
//Edit/Done button
UIBarButtonItem *editButton = [[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Edit", nil) style:UIBarButtonItemStyleBordered target:self action:@selector(editIncome:)];
[self.navigationItem setRightBarButtonItem:editButton];
//Get or set and get the gross income
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSNumber *grossIncome = [defaults objectForKey:@"income"];
if (!grossIncome) {
[defaults setDouble:0 forKey:@"income"];
[defaults synchronize];
grossIncome = [defaults objectForKey:@"income"];
}
self.incomeValueTextField.enabled = NO;
self.incomeValueTextField.delegate = self;
self.incomeValueTextField.keyboardType = UIKeyboardTypeDecimalPad;
self.incomeValueTextField.text = [grossIncome getLocalizedCurrencyString];
[self styleTableViewAndIncome];
}
- (void)styleTableViewAndIncome
{
self.view.backgroundColor = [UIColor clearColor];
self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
self.tableView.backgroundColor = [UIColor clearColor];
self.incomeTitleLabel.textColor = [Theme budgetValueTitleColor];
self.incomeTitleLabel.font = [Theme budgetValueTitleFont];
self.incomeValueTextField.textColor = [Theme budgetValueColor];
self.incomeValueTextField.font = [Theme budgetValueTitleFont];
self.netIncomeTitleLabel.textColor = [Theme budgetValueTitleColor];
self.netIncomeTitleLabel.font = [Theme budgetValueTitleFont];
self.netIncomeValueLabel.textColor = [Theme budgetValueColor];
self.netIncomeValueLabel.font = [Theme budgetValueFont];
self.incomeTitleLabel.text = [NSString stringWithFormat:@"%@:",NSLocalizedString(@"Income", nil)];
self.netIncomeTitleLabel.text = [NSString stringWithFormat:@"%@%@:",NSLocalizedString(@"Net", nil),NSLocalizedString(@"PerMonth", nil)];
self.incomeBackground.image = [[UIImage imageNamed:@"content-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
self.incomeValueBackground.image = [[UIImage imageNamed:@"price-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
self.netIncomeBackground.image = [[UIImage imageNamed:@"content-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
}
#pragma mark Table view delegate methods
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"CategoryCostCell";
CategoryCostTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
cell.backgroundColor = [UIColor clearColor];
// Configure the cell layout
MainCategory *mainCategory = [self.fetchedResultsController objectAtIndexPath:indexPath];
// Configure the cell layout
cell.categoryBackground.image = [[UIImage imageNamed:@"content-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
if(!mainCategory.icon){
cell.categoryImage.image = [UIImage imageNamed:@"DefaultIcon.png"];
} else {
cell.categoryImage.image = [UIImage imageNamed:mainCategory.icon];
}
cell.categoryName.text = mainCategory.name;
NSNumber *expenditures = [mainCategory getMonthlyCostsOfAllSpendingCategories];
double expendituresDouble =-[expenditures doubleValue];
if (expendituresDouble == 0) {
expenditures = [NSNumber numberWithDouble: 0];
} else {
expenditures = [NSNumber numberWithDouble: expendituresDouble];
}
cell.categoryCosts.text = [expenditures getLocalizedCurrencyString];
//Format the text
cell.categoryName.font = [Theme tableCellSmallTitleFont];
cell.categoryName.textColor = [Theme tableCellSmallTitleColor];
cell.categoryCosts.font = [Theme tableCellSmallValueFont];
cell.categoryCosts.textColor = [Theme tableCellSmallValueColor];
return cell;
}
#pragma mark TextField delegate methods
-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
if(self.editing){
return YES;
} else {
return NO;
}
}
-(void)textFieldDidBeginEditing:(UITextField *)textField
{
textField.text = [NSString stringWithFormat:@"%.2f",[NSNumber getUnLocalizedCurrencyDoubleWithString:textField.text]];
}
-(void)textFieldDidEndEditing:(UITextField *)textField
{
textField.text = [[NSNumber numberWithDouble:[textField.text doubleValue]] getLocalizedCurrencyString];
}
-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
//Handle the enter button
[textField resignFirstResponder];
[self endEdit];
//Since this method is called AFTER DidEndEditing, we have to call editTable or in this case since we have put all the endEdit code in a seperate method this method directly in order to format the table back from edit mode to normal.
return YES;
}
#pragma mark Edit/Add/Delete action
- (IBAction) editIncome:(id)sender
{
if(self.editing)
{
[self endEdit];
} else {
[self beginEdit];
}
}
- (void) beginEdit
{
//Change to editing mode
[super setEditing:YES animated:YES];
//Exchange the edit button with done button
[self.navigationItem.rightBarButtonItem setTitle:NSLocalizedString(@"Done", nil)];
[self.navigationItem.rightBarButtonItem setStyle:UIBarButtonItemStyleDone];
self.incomeValueTextField.borderStyle = UITextBorderStyleRoundedRect;
self.incomeValueTextField.enabled = YES;
self.incomeValueBackground.hidden = YES;
self.incomeValueTextField.textColor = [Theme budgetValueTitleColor];
}
- (void) endEdit
{
//Change to editing no
[super setEditing:NO animated:YES];
//Remove Done button and exchange it with edit button
[self.navigationItem.rightBarButtonItem setTitle:NSLocalizedString(@"Edit", nil)];
[self.navigationItem.rightBarButtonItem setStyle:UIBarButtonItemStylePlain];
self.incomeValueTextField.borderStyle = UITextBorderStyleNone;
self.incomeValueTextField.enabled = NO;
self.incomeValueBackground.hidden = NO;
self.incomeValueTextField.textColor = [Theme budgetValueColor];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setDouble:[NSNumber getUnLocalizedCurrencyDoubleWithString:self.incomeValueTextField.text] forKey:@"income"];
[self updateNetIncome];
//[defaults synchronize];
}
#pragma mark Net income
- (void) updateNetIncome {
double grossIncome = [NSNumber getUnLocalizedCurrencyDoubleWithString:self.incomeValueTextField.text];
double budget = [[DatabaseFetches budgetPerMonthForManagedObjectContext:self.managedObjectContext] doubleValue];
double netIncome = grossIncome - budget;
if(netIncome >0){
self.netIncomeValueBackground.image = [[UIImage imageNamed:@"price-bkg_green"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
} else if(netIncome <0) {
self.netIncomeValueBackground.image = [[UIImage imageNamed:@"price-bkg_red"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
} else {
self.netIncomeValueBackground.image = [[UIImage imageNamed:@"price-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
}
self.netIncomeValueLabel.text = [[NSNumber numberWithDouble:netIncome] getLocalizedCurrencyString];
}
@end
答案 0 :(得分：1)
看起来你正在使用cellForRowAtIndexPath方法创建UIImage，这会导致速度减慢。
最好将背景UIImage创建为实例变量并在viewDidLoad中设置其图像，然后在cellForRowAtIndexPath方法中引用它。像这样：
//Declare the instance variable
UIImage *backgroundImage
//Set it in viewDidLoad
self.backgroundImage = [[UIImage imageNamed:@"content-bkg"] resizableImageWithCapInsets:UIEdgeInsetsMake(10, 10, 10, 10)];
//Assign it in cellForRowAtIndexPath
cell.backgroundImage = self.backgroundImage;
对于必须为每一行设置的图标，您需要将实际图像加载移出主线程。您可以使用dispatch_async（）或NSOperationQueue执行此操作。 （从这里拉出来：Understanding dispatch_async）
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){
UIImage *icon;
if(!mainCategory.icon){
icon = [UIImage imageNamed:@"DefaultIcon.png"];
} else {
icon = [UIImage imageNamed:mainCategory.icon];
}
dispatch_async(dispatch_get_main_queue(), ^(void){
[cell.iconButton setImage:icon forState: UIControlStateNormal];
cell.icon.image = icon;
cell.iconButton.tag = indexPath.row;
});
});
注意如何在后台线程中调用imageNamed方法，但实际的赋值发生在主线程上。您必须这样做，因为除了主线程之外，您不允许更新UI元素。