如何在Android Studio中居中应用顶部的标题文本？

Hey there! I see you're trying to center the "Login to Notely" title in your app's top action bar, and you’ve set android:gravity="center" in your activity tag—unfortunately, that property controls the alignment of the activity’s content, not the action bar title itself. Let’s fix this with a few straightforward methods:

Method 1: Set Title Alignment via Activity Code #

This is the quickest approach if you only need the title centered for this specific activity.

Kotlin Code #

Add this to your ActivityLogin.kt file inside the onCreate method:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_login)
    
    // Center the action bar title
    supportActionBar?.apply {
        setDisplayOptions(ActionBar.DISPLAY_SHOW_CENTERED)
    }
}

Java Code #

If you’re using Java, add this to ActivityLogin.java:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    
    ActionBar actionBar = getSupportActionBar();
    if (actionBar != null) {
        // Center the action bar title
        actionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CENTERED);
    }
}

Method 2: Center Title Using Theme Styles #

Use this if you want the centered title style to apply across multiple activities, or prefer styling via XML.

1. Open your res/values/styles.xml file and add these styles:

<!-- Custom action bar style with centered title -->
<style name="CenteredActionBar" parent="@style/Widget.MaterialComponents.ActionBar.Solid">
    <item name="titleTextStyle">@style/CenteredTitleText</item>
</style>

<!-- Style for centered title text -->
<style name="CenteredTitleText" parent="@style/TextAppearance.MaterialComponents.Headline6">
    <item name="android:gravity">center</item>
</style>

2. Update your app’s theme (or create a custom theme) to use this action bar style:

<style name="AppTheme.CenteredTitle" parent="Theme.MaterialComponents.Light.DarkActionBar">
    <!-- Keep your existing theme properties, then add this -->
    <item name="actionBarStyle">@style/CenteredActionBar</item>
</style>

3. Apply this theme to your ActivityLogin in AndroidManifest.xml:

<activity 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:label="Login to Notely" 
    android:name=".ActivityLogin"
    android:theme="@style/AppTheme.CenteredTitle"/>

Method 3: Use a Custom Toolbar (Recommended for Modern Apps) #

If you’re using a custom Toolbar (which gives you more control over the action bar), follow these steps:

1. Add a Toolbar to your activity’s layout file (e.g., activity_login.xml):

<androidx.appcompat.widget.Toolbar
    android:id="@+id/login_toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    app:title="Login to Notely"
    android:gravity="center"
    app:titleTextColor="@android:color/white"/>

2. Set this Toolbar as your activity’s action bar in code:

Kotlin #

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_login)
    
    val toolbar = findViewById<Toolbar>(R.id.login_toolbar)
    setSupportActionBar(toolbar)
}

Java #

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    
    Toolbar toolbar = findViewById(R.id.login_toolbar);
    setSupportActionBar(toolbar);
}

All these methods will successfully center your "Login to Notely" title. Pick the one that best fits your app’s structure!

内容的提问来源于stack exchange，提问作者user13750693