Set unchangeable some part of editText android

Question

I have some EditText for mobile number input. App must add unique text for every country. For example for Armenia is must add +374 , and user must fill other nu

Answer 1

I opted for a solution, similar to another one submitted, of extending EditText and modifying onSelectionChanged. This prevents the user from even entering that region.

Here's what I'm using:

import android.content.Context
import android.text.Editable
import android.util.AttributeSet
import androidx.appcompat.widget.AppCompatEditText

class PrefixEditText(context: Context, attrs: AttributeSet?) : AppCompatEditText(context, attrs) {
    private var prefix: String? = null

    fun setPrefix(prefix: String) {
        this.prefix = prefix
        setText(prefix)

        addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) = Unit
            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) = Unit

            override fun afterTextChanged(s: Editable?) {
                // Block deleting the prefix
                if (s?.startsWith(prefix) == false) {
                    setText(prefix)
                }
            }
        })
    }

    override fun onSelectionChanged(selStart: Int, selEnd: Int) {
        var newStart = selStart
        var newEnd = selEnd
        prefix?.length?.let {
            newStart = if (selStart < it) it else selStart
            newEnd = if (selEnd < it) it else selEnd
        }

        if (selStart != newStart || selEnd != newEnd) {
            setSelection(newStart, newEnd)
        } else {
            super.onSelectionChanged(selStart, selEnd)
        }
    }

    // Here to conform to EditText's API
    // Could also just override getText()
    fun getPostText(): Editable? {
        return prefix?.let {
            Editable.Factory.getInstance().newEditable(text)?.delete(0, it.length)
        } ?: run {
            text
        }
    }

    // Here for convenience, to avoid instantiating a new Editable, if the text is all you need
    fun getPostCharSeq(): CharSequence? {
        return prefix?.let {
            text?.substring(it.length)
        } ?: run {
            text
        }
    }
}

With tests:

import android.view.ViewGroup
import android.widget.FrameLayout
import androidx.test.ext.junit.runners.AndroidJUnit4
import androidx.test.rule.ActivityTestRule
import com.roosterteeth.roosterteeth.TestActivity
import org.junit.Assert
import org.junit.Rule
import org.junit.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class PrefixEditTextTest {
    @Rule
    @JvmField
    var activityRule: ActivityTestRule = ActivityTestRule(TestActivity::class.java, true, true)

    private fun setupView(prefix: String, message: String): PrefixEditText {
        val editText = PrefixEditText(activityRule.activity, null)
        val lp = FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
        activityRule.activity.addContentView(editText, lp)

        editText.setPrefix(prefix)
        editText.append(message)

        return editText
    }

    @Test
    fun testSelection() {
        activityRule.runOnUiThread {
            val prefix = "pre: "
            val message = "hello world"
            val editText = setupView(prefix, message)

            editText.setSelection(0)
            Assert.assertEquals(editText.selectionStart, prefix.length)
            Assert.assertEquals(editText.selectionEnd, prefix.length)
            editText.setSelection(0, editText.length())
            Assert.assertEquals(editText.selectionStart, prefix.length)
            Assert.assertEquals(editText.selectionEnd, editText.length())
        }
    }

    @Test
    fun testGetPostText() {
        activityRule.runOnUiThread {
            val prefix = "pre: "
            val message = "hello world"
            val editText = setupView(prefix, message)

            Assert.assertEquals(message, editText.getPostText().toString())
            // This test is after to make sure that getting the post text did not actually modify the contents
            Assert.assertEquals("pre: $message", editText.text.toString())
        }
    }

    @Test
    fun testGetPostCharSeq() {
        activityRule.runOnUiThread {
            val prefix = "pre: "
            val message = "hello world"
            val editText = setupView(prefix, message)

            Assert.assertEquals(message, editText.getPostCharSeq())
            // This test is after to make sure that getting the post text did not actually modify the contents
            Assert.assertEquals("pre: $message", editText.text.toString())
        }
    }
}