47 lines
1.3 KiB
Markdown
47 lines
1.3 KiB
Markdown
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# MaxLength
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- **功能描述：** 在文本编辑框里限制文本的最大长度
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- **使用位置：** UPROPERTY
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- **引擎模块：** String/Text Property
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- **元数据类型：** int32
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- **限制类型：** FName/FString/Fext
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- **常用程度：** ★★★★★
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在文本编辑框里限制文本的最大长度。但在C++或蓝图层面还是可以自己任意写入值的。
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## 测试代码：
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```cpp
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UPROPERTY(EditAnywhere, Category = MaxLengthTest, meta = (MaxLength = 10))
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FString MyString_MaxLength10 = TEXT("Hello");
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```
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## 测试效果：
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## 原理：
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在文本框里字符串改变的时候，检查当前的长度，超过则报错。
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如果是FName属性，则会把MaxLength 继续限制在NAME_SIZE (1024)以内。
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```cpp
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MaxLength = PropertyHandle->GetIntMetaData(NAME_MaxLength);
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if (InPropertyEditor->PropertyIsA(FNameProperty::StaticClass()))
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{
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MaxLength = MaxLength <= 0 ? NAME_SIZE - 1 : FMath::Min(MaxLength, NAME_SIZE - 1);
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}
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bool SPropertyEditorText::OnVerifyTextChanged(const FText& Text, FText& OutError)
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{
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const FString& TextString = Text.ToString();
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if (MaxLength > 0 && TextString.Len() > MaxLength)
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{
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OutError = FText::Format(LOCTEXT("PropertyTextTooLongError", "This value is too long ({0}/{1} characters)"), TextString.Len(), MaxLength);
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return false;
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}
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}
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```
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