An InputFilter for Android EditText that limits the number of newlines the user can type into it.
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import android.text.InputFilter | |
import android.text.Spanned | |
class NewlineLimitingInputFilter(val maxLines: Int) : InputFilter { | |
var monitor: LimitMonitor? = null | |
var numNewlines = 0 | |
override fun filter(source: CharSequence, start: Int, end: Int, dest: Spanned, dstart: Int, dend: Int): CharSequence? { | |
// subtract all newlines in dest range | |
for (char in dest.subSequence(dstart, dend)) { | |
if (char == '\n') { | |
numNewlines-- | |
} | |
} | |
var replacement: StringBuilder? = null | |
// add newlines in source | |
var char: Char | |
for (i in start until end) { | |
char = source[i] | |
if (replacement != null) { | |
if (char != '\n') | |
replacement.append(char) | |
else if (numNewlines >= maxLines) | |
monitor?.onLimitExceeded(this) | |
else | |
numNewlines++ | |
} | |
else if (char == '\n') { | |
if (numNewlines >= maxLines) { | |
monitor?.onLimitExceeded(this) | |
replacement = StringBuilder(source.subSequence(start, i)) | |
} | |
else | |
numNewlines++ | |
} | |
} | |
return replacement | |
} | |
interface LimitMonitor { | |
fun onLimitExceeded(filter: InputFilter) | |
} | |
} |
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