在UITableViewCell的委托中，当我得到一个指向先前分配的UIButton的指针…UIButton* PWR_RX_tracking_button = (UIButton*) [cell。contentView viewWithTag: BASE_UIBUTTON_TAG + cell_uibutton_index++];．..如果我这样做，这个指针将休息为nil (0):PWR_RX_tracking_button。标签= 0;．..或者设置为任意值
我显示了一个UITableView，显示了2个单元格。第一次调用cellForRowAtIndexPath()时，为第一个单元格分配UI控件，并显示一组16个UI控件(图像，标签，文本，一些按钮)。
第二次调用cellForRowAtIndexPath():为第二个单元格分配UI控件，并且该单元格为空白。
稍后，需要显示2组控件，所以:第三次调用cellForRowAtIndexPath():"细胞。到最后一个按钮的contentView viewWithTag现在是0 (nil)!!!!它不再被分配。所以只显示第一组16个UI控件中的一些。然而，同一单元格内的第二组UI控件显示ok——它的UI控件仍然被分配。
这是内存管理问题吗?我是不是忘记了?我使用的是XCODE 5.0.2有自动ARC，因为如果我添加自动释放等，它会产生错误。
下面是cellForRowAtIndexPath()代码:
。m文件 ...............
UITableView* device_charge_tableView[TOTAL_TX_CHANNELS];
-(void)init_table
{
device_charge_tableView[ channel ] = [[UITableView alloc]initWithFrame:tableFrame style:UITableViewStylePlain];
device_charge_tableView[ channel ].rowHeight = device_charge_row_height;
device_charge_tableView[ channel ].sectionFooterHeight = 0;
device_charge_tableView[ channel ].sectionHeaderHeight = 0;
device_charge_tableView[ channel ].scrollEnabled = YES;
//new_system_device_tableView.showsVerticalScrollIndicator = YES;
// device_charge_tableView[ channel ].userInteractionEnabled = YES;
device_charge_tableView[ channel ].bounces = YES;
device_charge_tableView[ channel ].delegate = self;
device_charge_tableView[ channel ].dataSource = self;
device_charge_tableView[ channel ].allowsSelection = NO;
device_charge_tableView[ channel ].tag = channel;
// device_charge_tableView[ channel ].autoresizingMask = UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleWidth;
charge_record_index = expected_charge_index = 0;
[device_charge_tableView[ channel ] reloadData]; // display channel's TableView
[[self view] addSubview: device_charge_tableView[ channel ]];
}
-(void)redisplay
{
...
[device_charge_tableView[ 0 ] reloadData];
...
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 2; // add 1 row for a nice looking blank cell at end
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return device_charge_row_height;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
...
NSString *CellIdentifier = [NSString stringWithFormat:@"%s_%d",device_off_table ? "OFF" : "CHG", table_cell_index];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle: UITableViewCellStyleDefault reuseIdentifier: CellIdentifier];
/* Though it's UITableViewCellStyleDefault, the three defaults (image, label, detail label) are nil
if not set. */
// UI controls must be preset for re-use, to prevent memory leak:
// Allocate contiguous range of tags for each type of UI control for all devices, in this cell, once per boot:
int instance;
for( instance=0; instance < total_cell_UILabels; ++instance )
{
/////////////// A L L O C A T E C E L L L A B E L S ///////////////
UILabel* cell_UILabel = [[UILabel alloc] initWithFrame: CGRectZero]; // allocate next UI control
[cell.contentView addSubview: cell_UILabel ]; // add it permanently to the cell
cell_UILabel.tag = BASE_UILABEL_TAG + instance; // assign unique ID for later lookup
if( dbg_cell ) printf( " tag_%d ", cell_UILabel.tag );
}
for( instance=0; instance < total_cell_UITextViews; ++instance )
{
/////////////// A L L O C A T E C E L L T E X T V I E W S ///////////////
UITextView* cell_UITextView = [[UITextView alloc] initWithFrame: CGRectZero];
[cell.contentView addSubview: cell_UITextView ];
cell_UITextView.tag = BASE_UITEXTVIEW_TAG + instance;
if( dbg_cell ) printf( " tag_%d ", cell_UITextView.tag );
}
for( instance=0; instance < total_cell_UIImageViews ; ++instance )
{
/////////////// A L L O C A T E C E L L I M A G E V I E W S ///////////////
UIImageView* cell_UIImageView = [[UIImageView alloc] initWithFrame: CGRectZero];
[cell.contentView addSubview: cell_UIImageView ];
cell_UIImageView.tag = BASE_UIIMAGEVIEW_TAG + instance;
if( dbg_cell ) printf( " tag_%d ", cell_UIImageView.tag );
}
// Allocate invisible buttons:
for( instance=0; instance < total_cell_UIButtons ; ++instance )
{
/////////////// A L L O C A T E C E L L B U T T O N S ///////////////
UIButton* cell_UIButton = [UIButton buttonWithType: UIButtonTypeCustom];
[cell_UIButton setTitle:@"" forState:UIControlStateNormal];
cell_UIButton.frame = CGRectZero;
[cell.contentView addSubview: cell_UIButton ];
cell_UIButton.tag = BASE_UIBUTTON_TAG + instance;
if( dbg_cell ) printf( " tag_%d ", cell_UIButton.tag );
}
if( dbg_cell ) printf("n");
}
...
for(;;) // LOOP for times, to display 4 sets of UI controls next to each other:
{
// Get pointers to all possible UI controls of this UITableViewCell:
UILabel* PWR_RX_title = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* PWR_RX_footer = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* PWR_RX_voltage = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* PWR_RX_rssi = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* PWR_RX_power = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* client_type_label = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* battery_percent_text = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UILabel* client_device_title = (UILabel*) [cell.contentView viewWithTag: BASE_UILABEL_TAG + cell_UILabel_index++ ];
UITextView* PWR_RX_cover_box = (UITextView*) [cell.contentView viewWithTag: BASE_UITEXTVIEW_TAG + cell_UITextView_index++ ];
UIImageView* device_icon_UIImageView = (UIImageView*)[cell.contentView viewWithTag: BASE_UIIMAGEVIEW_TAG + cell_UIImageView_index++ ];
UIImageView* energy_glow_UIImageView = (UIImageView*)[cell.contentView viewWithTag: BASE_UIIMAGEVIEW_TAG + cell_UIImageView_index++ ];
UIImageView* battery_level_icon = (UIImageView*)[cell.contentView viewWithTag: BASE_UIIMAGEVIEW_TAG + cell_UIImageView_index++ ];
UIButton* PWR_RX_charge_button = (UIButton*) [cell.contentView viewWithTag: BASE_UIBUTTON_TAG + cell_UIButton_index++ ];
UIButton* invisible_drag_button = (UIButton*) [cell.contentView viewWithTag: BASE_UIBUTTON_TAG + cell_UIButton_index++ ];
UIButton* PWR_RX_tracking_button = (UIButton*) [cell.contentView viewWithTag: BASE_UIBUTTON_TAG + cell_UIButton_index++ ];
…
PWR_RX_tracking_button.frame = CGRectMake (x,y + h * 2/3, w, h/3); // lower quarter of icon !!! NORMAL
PWR_RX_tracking_button.tag = area_device_status[ channel ][ PWR_RX_status_index ].serno_value;
>>>>>>>>>>>>> ERROR IS: <<<<<<<<<<<<<<<<
1ST TIME PWR_RX_tracking_button IS OKAY.
2ND TIME, PWR_RX_tracking_button = 0 !!!!!!!!!!!!!!!!!!!!!
[PWR_RX_tracking_button addTarget:self
action:@selector( delegate_tracking_button: )
forControlEvents: UIControlEventTouchUpInside ];
...
++cell_record_index; // select next device record
++device_per_row_index; // select next display device of row
if( device_per_row_index < devices_per_cell ) // another device to display on this row?
continue; // GO DISPLAY NEXT SET OF THE 4 SETS OF UI CONTROLS
else
break; // ALL SETS have been shown
}
// CHECK FOR DESIGN ERROR, IF UI control array limited exceeded:
if( cell_UILabel_index > total_cell_UILabels + UI_controls_per_cell * table_cell_index
|| cell_UIImageView_index > total_cell_UIImageViews + UI_controls_per_cell * table_cell_index
|| cell_UITextView_index > total_cell_UITextViews + UI_controls_per_cell * table_cell_index
|| cell_UIButton_index > total_cell_UIButtons + UI_controls_per_cell * table_cell_index )
{
printf("n cell_UILabel_index cell_UIImageView_index cell_UITextView_index cell_UIButton_index %d %d %d %d", cell_UILabel_index, cell_UIImageView_index, cell_UITextView_index, cell_UIButton_index );
printf("n total_cell_UILabels total_cell_UITextViews total_cell_UIImageViews %d %d %d %d",
total_cell_UILabels, total_cell_UITextViews, total_cell_UIImageViews, total_cell_UIButtons );
printf(" <<< MAX EXCEEDED!! HALTED.");
for(;;) sleep(1);
}
save_record_index( cell_record_index, expected_cell_index, device_off_table );
if( dbg_cell ) printf(" HHH n");
return cell;
} // cellForRowAtIndexPath()
废话!
问题:我使用。tag有两个不同的目的。它的主要目的是索引UI控件以便重用。但是，我在重新分配UIButton .tag的数据，当按钮被按下时读取。因此，通过破坏。tag, UIButton就不能再被查找了。
解决方案:我可以将数据放入由单元格(行)索引索引的数组中。然后:这里有一个关于UIButton委托如何查找单元格索引的很酷的答案