TextField Enter text length limit (cannot be entered after exceeding)

First step new TextField

_tf=[[uitextfield Alloc]initwithframe:cgrectmake (50, 150, 200, 30)];

_tf.backgroundcolor=[uicolor Whitecolor];

_tf.delegate=self;//Open Agent

_tf.autocapitalizationtype = Uitextautocapitalizationtypenone;

[Self.view ADDSUBVIEW:_TF];
The second step is to open the listening method for TextField

[_TF addtarget:self Action: @selector (infoaction:) forcontrolevents:uicontroleventeditingchanged];

Implementation Monitoring

-(void) Infoaction: (Uitextfield *) TextField

{

NSString *tobestring = Textfield.text;

Uitextrange *selectedrange = [TextField markedtextrange];

Get the highlighted section

NSString *newtext=[textfield Textinrange:selectedrange];

if (newtext.length>0) {

Return If there is a highlighted section, the TextField literal length is not computed at this time

}else{

if ([self textlength:tobestring] >16) {

Nsuinteger asciilength = 0;

for (Nsuinteger i = 0; I <textField.text.length; i++) {

Unichar UC = [Textfield.text characteratindex:i];

Asciilength + = Isascii (UC)? 1:2;

if (asciilength==16) {

Textfield.text = [Textfield.text substringtoindex:i+1];

Return

}

if (asciilength>16) {

Textfield.text = [Textfield.text substringtoindex:i];

Return

}

}

}

}

}
The third step is to set the proxy method

-(BOOL) TextField: (Uitextfield *) TextField Shouldchangecharactersinrange: (nsrange) range replacementstring: ( NSString *) string{

if (SELF.TF = = TextField) {

Uitextrange *selectedrange = [TextField markedtextrange];

NSString *newtext=[textfield Textinrange:selectedrange];

if (newtext.length>0) {

return YES;

}else{

if (string.length = 0) return YES;

Nsuinteger existedlength =[self TextLength:textField.text];

Nsuinteger selectedlength = range.length;

Nsuinteger replacelength = string.length;

if (Existedlength-selectedlength + replacelength > 16) {

return NO;

}

}

}

return YES;

}//Judge string length (Kanji two bytes)

-(Nsuinteger) TextLength: (NSString *) text{

Nsuinteger asciilength = 0;

for (Nsuinteger i = 0; i < text.length; i++) {

Unichar UC = [text characteratindex:i];

Asciilength + = Isascii (UC)? 1:2;

}

Nsuinteger unicodelength = asciilength;

return unicodelength;

}