Formatted String Resource Not Appearing When Dark Theme Enabled

Question

I've been running through the first two parts of this Android Developer CodeLab. I've created a working tip-calculator with no issues until I've implemented Dark Theme. Without Dark Theme enabled, my application appears as below:

Upon enabling Dark Theme, text which was formatted (see code below) no longer appears.

The text was formatted as follows:

    private fun displayTip(tip : Double) {
        val formattedTip = NumberFormat.getCurrencyInstance().format(tip)
        binding.tipResult.text = getString(R.string.tip_amount, formattedTip)
    }

Where the string resource 'tip_amount' is defined as:

<string name="tip_amount">Tip Amount: %s</string>

Where tip is calculated as shown below:

    private fun calculateTip() {
        val serviceCost = binding.costOfService.text.toString()
        val cost = serviceCost.toDoubleOrNull()
        if (cost == null || cost == 0.0) {
            displayTip(0.0)
            return
        }
        val tipPercentage = when (binding.tipOptions.checkedRadioButtonId) {
            R.id.option_fifteen_percent -> 0.15
            R.id.option_eighteen_percent -> 0.18
            else -> 0.20
        }
        var tip = tipPercentage * cost
        if (binding.roundUpSwitch.isChecked) {
            tip = kotlin.math.ceil(tip)
        }
        displayTip(tip)
    }

I am using view bindings as instructed in the CodeLab:

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
        binding.calculateButton.setOnClickListener{calculateTip()}
    }

The textview corresponding to the text that disappears upon enabling Dark Theme is below (Note: nothing appears until the user provides input and presses a button):

    <TextView
        android:id="@+id/tip_result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:textSize="34sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/calculate_button"
        tools:text="Tip Amount: $10" />

And finally my night/themes.xml file is below:

<resources xmlns:tools="http://schemas.android.com/tools">
    <!-- Base application theme. -->
    <style name="Theme.TipCalculator" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
        <!-- Primary brand color. -->
        <item name="colorPrimary">@color/green_light</item>
        <item name="colorPrimaryVariant">@color/green</item>
        <item name="colorOnPrimary">@color/black</item>
        <!-- Secondary brand color. -->
        <item name="colorSecondary">@color/blue_light</item>
        <item name="colorSecondaryVariant">@color/blue_light</item>
        <item name="colorOnSecondary">@color/black</item>
        <!-- Status bar color. -->
        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
        <!-- Customize your theme here. -->
    </style>
</resources>

Why does my semicolon and formatted text disappear when enabling Dark Theme? Why does the rest of the text in the TextView remain?

Answer 1

As discussed here, the problem was that the string resource appeared differently in values/strings.xml and night/strings.xml. The string resource in night/strings.xml was not edited to use string formatting, a very simple but time consuming mistake. If you receive a similar error, I suggest checking that all string resources are defined identically across all resource files.

values/strings.xml had resource defined as:

    <string name="tip_amount">Tip Amount: %1$s</string>

While night/strings.xml defined as:

    <string name="tip_amount">Tip Amount: </string>