如何以正确的方式从 EditText 获得双倍？

Question

Does anyone know how to parse a double from an EditText?

I know how to do it, but it isn't the right way I think. Does anyone have best practises?

Thank you.

Answer 1

you can try this:

double value;
String text =your_edittext.getText().toString();
if(!text.isEmpty())
try
{
   value= Double.parseDouble(text);
   // it means it is double
} catch (Exception e1) {
   // this means it is not double 
   e1.printStackTrace();
}

Answer 2

Whatever you type in EditText is String.

How to check if edittext is empty?

String str = edit_text.getText().toString();
if (str.trim().equals("")
Toast.makeText(getApplicationContext(),
                    "EditText is empty.",
                    Toast.LENGTH_SHORT).show();

Answer 3

Parse a double from an EditText (Kotlin)

• toDouble() function works great but if the string is not a valid representation of a number. Throw NumberFormatException Exception.

• toDoubleOrNull() function returns a double value. if the string is not a valid representation of a number return null

Implementation

fun parseToDouble(value :Editable): Double { 
    if(value.isNotEmpty()){
        val result = value.trim().toString().toDoubleOrNull()
        if(result != null) 
            return result
        else 
            return 0.0
    }else { 
      return 0.0
   }
}

Or above code can be simplified usingExtension functions

fun Editable.parseToDouble(): Double { 
    if(this.isNotEmpty()){
        val result = this.trim().toString().toDoubleOrNull()
        if(result != null) 
            return result
        else 
            return 0.0
    }else { 
      return 0.0
   }
}

• The " this " keyword inside an extension function corresponds to the receiver object. it can also be remove

Or above code can be simplified using Kotlin When expression

fun Editable.parseToDouble(): Double { 
    return when(isNotEmpty()){
    true -> {
        val result = trim().toString().toDoubleOrNull()
        if(result != null) result else 0.0
      }
   else -> 0.0
}

Or above code can be simplified by Convert to expression body ( “return” vs expression body )

fun Editable.parseToDouble(): Double = when(isNotEmpty()){
    true -> {
        val result = trim().toString().toDoubleOrNull()
        if(result != null) result else 0.0
      }
   else -> 0.0
}

Or above code can be simplified using Kotlin Elvis Operator

fun Editable.parseToDouble() = when(isNotEmpty()){
    true -> trim().toString().toDoubleOrNull()?: 0.0
    else -> 0.0
}

Simplest version (best)

fun Editable.parseToDouble() = trim().toString().toDoubleOrNull()?: 0.0

Or

fun Editable.parseToDouble() = toString().toDoubleOrNull()?: 0.0

Notes : similarly you can create parseToInt and parseToLong function