我有一个tableView
,显示来自用户iPod库的歌曲列表。每个单元调用太多方法,这可能是为什么滚动如此迟缓(我认为'调用方法'是正确的术语,我对编程来说相当新),就像这样:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Configure the cell...
cell.textLabel.text= [self titleForRow:indexPath]; //getting song title
cell.detailTextLabel.text = [self subtitleForRow:indexPath]; //get song artist
cell.imageView.image = [self artworkForRow:indexPath]; //get song image
return cell;
}
这些是方法:
- GET SONG TITLE
-(NSString *)titleForRow:(NSIndexPath *)indexpath{
NSMutableArray* rowArray=[[NSMutableArray alloc]initWithCapacity:0];
rowArray=[self getArrayOfRowsForSection:indexpath.section];
NSString *titleToBeDisplayed=[rowArray objectAtIndex:indexpath.row];
return titleToBeDisplayed;
}
-(NSMutableArray *)getArrayOfRowsForSection:(NSInteger)section
{
NSString *rowTitle;
NSString *sectionTitle;
NSMutableArray *rowContainer=[[NSMutableArray alloc]initWithCapacity:0];
for (int i=0; i<self.alphabetArray.count; i++)
{
if (section==i) // check for right section
{
sectionTitle= [self.alphabetArray objectAtIndex:i]; //getting section title
for (MPMediaItem *song in songs)
{
NSString *title = [song valueForProperty:MPMediaItemPropertyTitle];
rowTitle= [title substringToIndex:1]; //modifying the statement to its first alphabet
if ([rowTitle isEqualToString:sectionTitle]) //checking if modified statement is same as section title
{
[rowContainer addObject:title]; //adding the row contents of a particular section in array
}
}
}
}
return rowContainer;
}
- 获取艺术家
-(NSString *)subtitleForRow:(NSIndexPath *)indexpath{
NSMutableArray* subtitleRowArray=[[NSMutableArray alloc]initWithCapacity:0];
subtitleRowArray=[self getSubtitle:indexpath.section];
NSString *subtitleToBeDisplayed=[subtitleRowArray objectAtIndex:indexpath.row];
return subtitleToBeDisplayed;
}
-(NSMutableArray *)getSubtitle:(NSInteger)section
{
NSString *rowTitle;
NSString *sectionTitle;
NSMutableArray *rowContainer=[[NSMutableArray alloc]initWithCapacity:0];
for (int i=0; i<self.alphabetArray.count; i++)
{
if (section==i) // check for right section
{
sectionTitle= [self.alphabetArray objectAtIndex:i]; //getting section title
for (MPMediaItem *song in songs)
{
NSString *title = [song valueForProperty:MPMediaItemPropertyTitle];
NSString *subtitle = [song valueForProperty:MPMediaItemPropertyArtist];
rowTitle= [title substringToIndex:1]; //modifying the statement to its first alphabet
if ([rowTitle isEqualToString:sectionTitle]) //checking if modified statement is same as section title
{
if (subtitle){
[rowContainer addObject:subtitle]; //adding the row contents of a particular section in array
}
else {
[rowContainer addObject:@"Unknown Artist"];
}
}
}
}
}
return rowContainer;
}
- 获取图片
-(UIImage *)artworkForRow:(NSIndexPath *)indexpath{
NSMutableArray* artworkRowArray=[[NSMutableArray alloc]initWithCapacity:0];
artworkRowArray=[self getArtwork:indexpath.section];
UIImage *artworkToBeDisplayed=[artworkRowArray objectAtIndex:indexpath.row];
return artworkToBeDisplayed;
}
-(NSMutableArray *)getArtwork:(NSInteger)section
{
NSString *rowTitle;
NSString *sectionTitle;
NSMutableArray *rowContainer=[[NSMutableArray alloc]initWithCapacity:0];
for (int i=0; i<self.alphabetArray.count; i++)
{
if (section==i) // check for right section
{
sectionTitle= [self.alphabetArray objectAtIndex:i]; //getting section title
for (MPMediaItem *song in songs)
{
NSString *title = [song valueForProperty:MPMediaItemPropertyTitle];
MPMediaItemArtwork *artwork = [song valueForProperty:MPMediaItemPropertyArtwork];
UIImage *artworkImage = [artwork imageWithSize: CGSizeMake (50, 50)];
rowTitle= [title substringToIndex:1]; //modifying the statement to its first alphabet
if ([rowTitle isEqualToString:sectionTitle]) //checking if modified statement is same as section title
{
if (artworkImage){
[rowContainer addObject:artworkImage]; //adding the row contents of a particular section in array
}
else {
[rowContainer addObject:[UIImage imageNamed:@"noArtworkSongsCell"]];
}
}
}
}
}
return rowContainer;
}
有没有办法让滚动滚动到这里?每种方法都很重要。
非常感谢任何帮助,谢谢!
答案 0 :(得分:4)
您不应该在cellForRowAtIndexPath中调用您使用的方法 - 每次需要在单元格中填充标签时,您都不应该创建这些数组。应该在cellForRowAtIndexPath之外创建一次数组,然后在该方法中查询以从数组中获取正确的项。
答案 1 :(得分:0)
在绘制表格之前,请始终准备好数据。在诸如cellForRow,heightForCellAtIndexPath等方法中,您应该只访问您的数据,而不是修改它和/或操纵它。在您的示例中,您不仅要为每个单元格迭代数组,甚至还要调用极慢的方法,例如字符串比较。你可以在cellForRowAtIndex路径中放一个断点,看看它在滚动过程中调用了多少次,然后想象一下你想做多少工作。