[android] How can you get the Manifest Version number from the App's (Layout) XML variables?

I would like to have a way to reference the project's manifest version number in the main part of the code. What I have been doing up until now is to link the version number in a String XML file to the manifest (@string/Version). What I would like to do is to do it the other way around, link a string XML variable to the version in the manifest. The reason? I'd like to only have to change the version number in one location, the manifest file. Is there any way to do this? Thanks!

IF you are using Gradle you can use the build.gradle file to programmatically add value to the xml resources at compile time.

Example Code extracted from: https://medium.com/@manas/manage-your-android-app-s-versioncode-versionname-with-gradle-7f9c5dcf09bf

buildTypes {
    debug {
        versionNameSuffix ".debug"
        resValue "string", "app_version", "${defaultConfig.versionName}${versionNameSuffix}"
    }
    release {
        resValue "string", "app_version", "${defaultConfig.versionName}"
    }
}

now use @string/app_version as needed in XML

It will add .debug to the version name as describe in the linked article when in debug mode.

Easiest solution is to use BuildConfig.

I use BuildConfig.VERSION_NAME in my application.

You can also use BuildConfig.VERSION_CODE to get version code.

I use BuildConfig.VERSION_NAME.toString();. What's the difference between that and getting it from the packageManager?

No XML based solutions have worked for me, sorry.

I solved this issue by extending the Preference class.

package com.example.android;

import android.content.Context;
import android.preference.Preference;
import android.util.AttributeSet;

public class VersionPreference extends Preference {
    public VersionPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        String versionName;
        final PackageManager packageManager = context.getPackageManager();
        if (packageManager != null) {
            try {
                PackageInfo packageInfo = packageManager.getPackageInfo(context.getPackageName(), 0);
                versionName = packageInfo.versionName;
            } catch (PackageManager.NameNotFoundException e) {
                versionName = null;
            }
            setSummary(versionName);
        }
    }
}

Then in my preferences XML:

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <com.example.android.VersionPreference android:title="Version" />
</PreferenceScreen>

I believe that was already answered here.

String versionName = getPackageManager().getPackageInfo(getPackageName(), 0).versionName;

OR

int versionCode = getPackageManager().getPackageInfo(getPackageName(), 0).versionCode;

You can use the versionName in XML resources, such as activity layouts. First create a string resource in the app/build.gradle with the following snippet in the android node:

applicationVariants.all { variant ->
    variant.resValue "string", "versionName", variant.versionName
}

So the whole build.gradle file contents may look like this:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion '24.0.0 rc3'
    defaultConfig {
        applicationId 'com.example.myapplication'
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 17
        versionName '0.2.3'
        jackOptions {
            enabled true
        }
    }
    applicationVariants.all { variant ->
        variant.resValue "string", "versionName", variant.versionName
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    productFlavors {
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
} 

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.android.support:design:23.3.0'
    compile 'com.android.support:support-v4:23.3.0'
}

Then you can use @string/versionName in the XML. Android Studio will mark it red, but the app will compile without issues. For example, this may be used like this in app/src/main/res/xml/preferences.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">

    <PreferenceCategory
        android:title="About"
        android:key="pref_key_about">

        <Preference
            android:key="pref_about_build"
            android:title="Build version"
            android:summary="@string/versionName" />

    </PreferenceCategory>


</PreferenceScreen>

You can't use it from the XML.

You need to extend the widget you are using in the XML and add the logic to set the text using what's mentioned on Konstantin Burov's answer.

Late to the game, but you can do it without @string/xyz by using ?android:attr

    <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="?android:attr/versionName"
     />
    <!-- or -->
    <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="?android:attr/versionCode"
     />