Summary: I have a string from which I can print and use substring, but can't use attributes such as length or functions such as .toInt() or .compareTo(), why would this be the case?
var s = "20"
val myToast = Toast.makeText(this, s, Toast.LENGTH_SHORT)
myToast.show()
//20
val myToast2 = Toast.makeText(this, s.length, Toast.LENGTH_SHORT)
myToast2.show()
//The app crashes with the error: android.content.res.Resources$NotFoundException: String resource ID #0x2
I can call substring on string s, but I can't call length, toInt(), compareTo(), etc.
The string clearly exists since I can print it and use substring but if that is true why does my app throw an error when I try to use other attributes and functions from it?
There are two overloads of Toast.makeText(). One accepts a String as the second argument, and displays that string. The other accepts an Int as the second argument, and displays whatever string resource has that integer id. (Normally you'd pass something like R.string.my_string here.)
When you call .length on your String, you'll get an Int back. And that means you wind up calling the second overload, which then looks for a string resource with the id 2. That doesn't exist, so you crash.
If you want to just display the number 2, then you need to make this a String again. You can use .toString() or "${s.length}", and so on.
Add .toString at the end of length,toInt(),compareTo(), etc. because s.length
return int :not String
Here is your modified answer
var s = "20"
val myToast = Toast.makeText(this, s, Toast.LENGTH_SHORT)
myToast.show()
//20
val myToast2 = Toast.makeText(this, s.length.toString(), Toast.LENGTH_SHORT)
myToast2.show()
Related
Is there an easier approach to convert an Intellij IDEA environment variable into a list of Tuples?
My environment variable for Intellij is
GROCERY_LIST=[("egg", "dairy"),("chicken", "meat"),("apple", "fruit")]
The environment variable gets accessed into Kotlin file as String.
val g_list = System.getenv("GROCERY_LIST")
Ideally I'd like to iterate over g_list, first element being ("egg", "dairy") and so on.
And then ("egg", "dairy") is a tuple/pair
I have tried to split g_list by comma that's NOT inside quotes i.e
val splitted_list = g_list.split(",(?=(?:[^\\\"]*\\\"[^\\\"]*\\\")*[^\\\"]*\$)".toRegex()).toTypedArray()
this gives me first element as [("egg", second element as "dairy")] and so on.
Also created a data class and tried to map the string into data class using jacksonObjectMapper following this link:
val mapper = jacksonObjectMapper()
val g_list = System.getenv("GROCERY_LIST")
val myList: List<Shopping> = mapper.readValue(g_list)
data class Shopping(val a: String, val b: String)
You can create a regular expression to match all strings in your environmental variable.
Regex::findAll()
Then loop through the strings while creating a list of Shopping objects.
// Raw data set.
val groceryList: String = "[(\"egg\", \"dairy\"),(\"chicken\", \"meat\"),(\"apple\", \"fruit\")]"
// Build regular expression.
val regex = Regex("\"([\\s\\S]+?)\"")
val matchResult = regex.findAll(groceryList)
val iterator = matchResult.iterator()
// Create a List of `Shopping` objects.
var first: String = "";
var second: String = "";
val shoppingList = mutableListOf<Shopping>()
var i = 0;
while (iterator.hasNext()) {
val value = iterator.next().value;
if (i % 2 == 0) {
first = value;
} else {
second = value;
shoppingList.add(Shopping(first, second))
first = ""
second = ""
}
i++
}
// Print Shopping List.
for (s in shoppingList) {
println(s)
}
// Output.
/*
Shopping(a="egg", b="dairy")
Shopping(a="chicken", b="meat")
Shopping(a="apple", b="fruit")
*/
data class Shopping(val a: String, val b: String)
Never a good idea to use regex to match parenthesis.
I would suggest a step-by-step approach:
You could first match the name and the value by
(\w+)=(.*)
There you get the name in group 1 and the value in group 2 without caring about any subsequent = characters that might appear in the value.
If you then want to split the value, I would get rid of start and end parenthesis first by matching by
(?<=\[\().*(?=\)\])
(or simply cut off the first and last two characters of the string, if it is always given it starts with [( and ends in )])
Then get the single list entries from splitting by
\),\(
(take care that the split operation also takes a regex, so you have to escape it)
And for each list entry you could split that simply by
,\s*
or, if you want the quote character to be removed, use a match with
\"(.*)\",\s*\"(.*)\"
where group 1 contains the key (left of equals sign) and group 2 the value (right of equals sign)
In a function i have this:
val sunRise = SunEquation(2459622)
binding.timeDisplay.setText("$sunRise.n")
The SunEquation-Class looks like this:
class SunEquation(var jDate: Int,) {
val jYear = 2451545
val ttOffset = .0008
var n = jDate - jYear + ttOffset
}
the button- text that appears is:
com.example.soluna.SunEquation#6d1a94b.n
i would expect a double-value
You have to add curly brackets around the value you want to inject into the String, like this:
binding.timeDisplay.setText("${sunRise.n}")
The shorthand syntax without brackets only works for a single variable, but not
for access to a nested field or other more complex expressions.
In your case, this results in the object itself being injected into the String, which is resembled by com.example.soluna.SunEquation#6d1a94b based on the result of the corresponding toString() call, which defaults to the class name and the reference id of the object. Followed by the literal String .n.
Alternatively, you could extract the value into a val beforehand and reference that.
val customN = sunRise.n
binding.timeDisplay.setText("$customN")
I want to send data (number) from "edit text section" of Sub-Activity1 (users input a simple number)and receive in another Sub-activity2, and depending on the number I want to show different sets of text. I am a beginner and I am stuck where in Sub-Activity 2 as it returns error for val str where I want to receive and manipulate the number received from Sub-Activity 1 editText.
Sub-Activity 1 :
<Send & Open Sub-Activity2>
getResult.setOnClickListener {
val intent = Intent(this, subactivity::class.java)
val name: String = editTextID.getText().toString()
intent.putExtra(name:"editTextID",value:"7.0")
startActivity(intent)
This returns no error.
Sub-Activity 2: <Receive & Manipulate the text>
class subactivity2 : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_subactivity2)
val str =intent.getStringExtra("editTextID")
when str == 7.0 {
infoTextView.textview.text= "textIwannaShow"
}
}
Franz might be right about you wanting to pass a Double, but since you're passing it as a String and also naming your val str, I'll assume you do want to pass a string (that just happens to represent a number). In which case you need to compare to a string
if (str == "7.0") {
infoTextView.textview.text = "textIwannaShow"
}
or if you do want a when block
when(str) {
"7.0" -> infoTextView.textview.text = "textIwannaShow"
}
If you actually want to work with numbers you'll have to call toDouble() on your string at some point to convert it to one. toDoubleOrNull would be better if you're taking that number from a text input (in case the user doesn't enter a valid number), but you're not actually using the value taken from the EditText
In your Sub-Activity 2, you are receiving a String not an Integer.
So, you should change your code from this
val str =intent.getStringExtra("editTextID")
To this
val str =intent.getIntExtra("editTextID", 0)
Anyway, in the example you are passing 7.0 which is Double, so you probably need this instead of above code
val str =intent.getDoubleExtra("editTextID", 0.0)
I have written a code that reads a text file. The text files contain placeholders which I would like to replace. The substitution does not work this way and the string is printed with the placeholders. Here is the code that I have written for this:
class TestSub(val sub: Sub) {
fun create() = template()
fun template() = Files.newBufferedReader(ClassPathResource(templateId.location).file.toPath()).readText()
}
data class Sub(val name: String, val age: Int)
Here is the main function that tries to print the final string:
fun main(args: Array<String>) {
val sub = Sub("Prashant", 32)
println(TestSub(sub).create())
}
However, when, instead of reading a file, I use a String, the following code works (Replacing fun template())
fun template() = "<h1>Hello ${sub.name}. Your age is ${sub.age}</h1>"
Is there a way to make string Substitution work when reading the content of a file?
Kotlin does not support String templates from files. I.e. code like "some variable: $variable" gets compiled to "some variable: " + variable. String templates are handled at compile time, which means it does not work with text loaded from files, or if you do something else to get the String escaped into a raw form. Either way, it would, as danielspaniol mentioned, be a security threat.
That leaves three options:
String.format(str)
MessageFormat.format(str)
Creating a custom engine
I don't know what your file contains, but if it's the String you used in the template function, change it to:
<h1>Hello {0}. Your age is {1,integer}</h1>
This is for MessageFormat, which is my personal preference. If you use String.format, use %s instead, and the other appropriate formats.
Now, use that in MessageFormat.format:
val result = MessageFormat.format(theString, name, age);
Note that if you use MessageFormat, you'll need to escape ' as ''. See this.
String substitution using ${...} is part of the string literals syntax and works roughly like this
val a = 1
val b = "abc ${a} def" // gets translated to something like val b = "abc " + a + " def"
So there is no way for this to work when you load from a text file. This would also be a huge security risk as it would allow for arbitrary code execution.
However I assume that Kotlin has something like a sprintf function where you can have placeholders like %s in your string and you can replace them with values
Take a look here. It looks like the easiest way is to use String.format
You are looking for something similar to Kotlin String templates for raw Strings, where placeholders like $var or ${var} are substituted by values, but this functionality needs to be available at runtime (for text read from files).
Methods like String.format(str) or MessageFormat.format(str) use other formats than the notation with the dollar prefix of Kotlin String templates. For "Kotlin-like" placeholder substitution you could use the function below (which I developed for similar reasons). It supports placeholders as $var or ${var} as well as dollar escaping by ${'$'}
/**
* Returns a String in which placeholders (e.g. $var or ${var}) are replaced by the specified values.
* This function can be used for resolving templates at RUNTIME (e.g. for templates read from files).
*
* Example:
* "\$var1\${var2}".resolve(mapOf("var1" to "VAL1", "var2" to "VAL2"))
* returns VAL1VAL2
*/
fun String.resolve(values: Map<String, String>): String {
val result = StringBuilder()
val matcherSimple = "\\$([a-zA-Z_][a-zA-Z_0-9]*)" // simple placeholder e.g. $var
val matcherWithBraces = "\\$\\{([a-zA-Z_][a-zA-Z_0-9]*)}" // placeholder within braces e.g. ${var}
// match a placeholder (like $var or ${var}) or ${'$'} (escaped dollar)
val allMatches = Regex("$matcherSimple|$matcherWithBraces|\\\$\\{'(\\\$)'}").findAll(this)
var position = 0
allMatches.forEach {
val range = it.range
val placeholder = this.substring(range)
val variableName = it.groups.filterNotNull()[1].value
val newText =
if ("\${'\$'}" == placeholder) "$"
else values[variableName] ?: throw IllegalArgumentException("Could not resolve placeholder $placeholder")
result.append(this.substring(position, range.start)).append(newText)
position = range.last + 1
}
result.append(this.substring(position))
return result.toString()
}
String templates only work for compile-time Sting literals, while what u read from a file is generated at runtime.
What u need is a template engine, which can render templates with variables or models at runtime.
For simple cases, String.format or MessageFormat.format in Java would work.
And for complex cases, check thymeleaf, velocity and so on.
I have a object that I want to print it into string [key1=value1&key2=value2...etc] without the null value key value pair and comma into &.
So first of all i think of putting it into a map but it won't work and I don know how it work either.
val wxPayOrderObj = WxPayOrder(appid = "wx0b6dcsad20b379f1", mch_id =
"1508334851", nonce_str = UUID.randomUUID().toString(),sign = null,
body = "QQTopUp", out_trade_no = "20150806125346", total_fee = req.total_fee,
spbill_create_ip = "123.12.12.123",
trade_type = "JSAPI", openid = "oUpF8uMuAJO_M2pxb1Q9zNjWeS6o")
so the output will be
appid=wx0b6dc78d20b379f1&mch_id=150788851&nonce_str=UUID.randomUUID().toString()&
body=QQTopUp&out_trade_no=20150806125346&total_fee=req.total_fee&
spbill_create_ip=123.12.12.123&trade_type=JSAPI&openid=oUpF8uMuAJO_M2pxb1Q9zNjWeS6o
anyone please help me, thanks in advances.
I don't really get your question, but you want to convert object to string (to a format that you want)?
Override the object's toString() to return "[key1=value1&key2=value2...etc]"
example
override fun toString(){
// make sure you compute the data first
val answer = "[key1=$value1&key2=$value2...etc]"
return answer
}
The $ is used in string templates (That's directly writing the name of a variable, the value will be used later to be concatenated) with other strings)