iOS. 仿淘宝剪切板

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// app从后台进入前台都会调用这个方法
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationBecomeActive) name:UIApplicationWillEnterForegroundNotification object:nil];

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//读取剪切板的内容只从系统剪切板读区
//应用内保存到剪切板的内容在主动读取的时候需要过滤掉
@implementation PasteboardUtils

• (NSString *)read {
  //创建系统剪切板
  UIPasteboard *systemBoard = [UIPasteboard generalPasteboard];
  if(!systemBoard.numberOfItems) {
  //剪切板为空
  return nil;
  }
  if([self hasMark]) {
  //剪切板数据已经标记过了，则数据来自当前应用，不予处理
  return nil;
  }
  return systemBoard.string;
  }

• (void)save:(NSString *)content {
  //创建系统剪切板
  UIPasteboard *systemBoard = [UIPasteboard generalPasteboard];
  //将文本写入剪切板
  systemBoard.string = content;
  //给剪切板加入一条标记性的数据，只是为了检测剪切板的数据是否来自当前应用
  NSDictionary *item = @{PASTEBOARD_MARK:content};
  [systemBoard addItems:@[item]];
  }

• (void)clear {
  //创建系统剪切板
  UIPasteboard *systemBoard = [UIPasteboard generalPasteboard];
  systemBoard.string = @"";
  }

• (BOOL)hasMark{
  //创建系统剪切板
  UIPasteboard *systemBoard = [UIPasteboard generalPasteboard];
  if(!systemBoard.numberOfItems) {
  return YES;
  }
  NSArray *> *items = systemBoard.items;
  long count = systemBoard.numberOfItems;
  for(int i=0; i < count; i++){
  NSDictionary *item = [items objectAtIndex:i];
  if([[item allKeys] containsObject:PASTEBOARD_MARK]){
  return YES;
  }
  }
  return NO;
  }