What should I do if (Qt Creator)))) cannot find my Android SDK/NDK?

Building Qt 5.15.15 for Android on Ubuntu 22.04.3 LTS

Building Qt for Android can be a complex task due to the number of dependencies and configuration steps involved. This guide walks you through the complete process of setting up your environment, compiling Qt, and troubleshooting common issues like the crtbegin_so.o not found error. This guide assumes that you're working in a WSL2 (Windows Subsystem for Linux) environment, which adds its own layer of complexity, but we’ll cover the necessary steps to make it work.

Prerequisites

Before beginning the Qt build process, ensure you have the necessary tools installed:

Ubuntu 22.04.3 LTS running in WSL2.

Android SDK (API 31).

Android NDK
21e.

Java Development Kit (JDK 8 or higher).

CMake, GCC, and other standard development tools.

Step 1: Install Dependencies

Start by installing all required dependencies, including the Android SDK and NDK, along with the necessary build tools for Ubuntu.

1.1 Install system dependencies

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sudo apt update sudo apt install -y build-essential libfontconfig1-dev libdbus-1-dev libssl-dev libglib2.0-dev \ libpulse-dev libudev-dev pkg-config cmake qt5-qmake qtbase5-dev qtchooser \ openjdk-8-jdk unzip curl

1.2 Install Android NDK and SDK

To download and install the Android SDK and NDK, follow the instructions below:

Download the Android SDK command-line tools from here.

Unzip the SDK and place it in a directory (e.g., /opt/android-sdk/).

Then, install the required SDK packages:

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cd /opt/android-sdk ./tools/bin/sdkmanager --licenses ./tools/bin/sdkmanager "platform-tools" "platforms;android-31" "build-tools;31.0.0" "ndk;21.4.7075529"
Step 2: Set Up Environment Variables

Now, set up the environment variables to let Qt know where to find the Android SDK and NDK.

2.1 Configure Environment Variables

Add the following lines to your .bashrc (or .zshrc if you're using Zsh):

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export ANDROID_SDK_ROOT=/opt/android-sdk export ANDROID_NDK_ROOT=/opt/android-sdk/ndk/21.4.7075529 export PATH=$PATH:$ANDROID_SDK_ROOT/platform-tools:$ANDROID_SDK_ROOT/tools:$ANDROID_NDK_ROOT
Reload the .bashrc file to apply the changes:

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source ~/.bashrc
Step 3: Download Qt Source Code

You can download the source code for Qt 5.15.15 from the official Qt Git repository or from a tarball.

3.1 Clone Qt Git repository

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git clone git://code.qt.io/qt/qt5.git --branch 5.15 --single-branch cd qt5 git submodule update --init --recursive
Alte
atively, you can download the tarball from here.

Step 4: Configure Qt for Android

Before building Qt, you need to configure it to build for Android.

4.1 Run the Configuration Script

Navigate to the qt5 directory, then run the configure script for Android:

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./configure -xplatform android-clang -prefix /path/to/qt-android -android-sdk $ANDROID_SDK_ROOT -android-ndk $ANDROID_NDK_ROOT -android-arch arm64-v8a -opensource -confirm-license -nomake tests -nomake examples
Here’s a breakdown of the important flags:

-xplatform android-clang: Specifies the target platform.

-prefix /path/to/qt-android: Specifies where the compiled Qt libraries should be installed.

-android-sdk $ANDROID_SDK_ROOT: Points to the Android SDK.

-android-ndk $ANDROID_NDK_ROOT: Points to the Android NDK.

-android-arch arm64-v8a: Specifies the target architecture (can be armeabi-v7a, x86, etc. depending on your needs).

-opensource -confirm-license: Accepts the open-source license.

4.2 Fix Missing Dependencies (Optional)

Sometimes, you may face issues where certain Android-specific files (like crtbegin_so.o) are not found. This usually happens because the NDK is either not properly linked or there's a mismatch between the SDK and NDK versions.

If you see the error message like:

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error: crtbegin_so.o: No such file or directory
You should check if your NDK has the appropriate libraries. Here's how you can fix it:

Check the Android NDK version:

Qt 5.15.15 works best with NDK
21e, which you already have installed. Other versions (like
22) can sometimes cause issues.

Ensure NDK paths are set correctly:

Double-check that the NDK path is correctly set in your environment variables. You can check if the crtbegin_so.o file exists by searching the NDK folder:

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find $ANDROID_NDK_ROOT -name crtbegin_so.o
Workaround for Missing crtbegin_so.o:

If the file is still missing, sometimes a simple workaround is to symlink the file from a working NDK or copy it manually.

Step 5: Build Qt

Once you’ve configured Qt, you can proceed with the build process:

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make -j$(nproc)
The -j$(nproc) flag allows the build to run in parallel, utilizing all available CPU cores.

Step 6: Install Qt for Android

After building Qt, you can install it to the specified prefix directory:

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make install
This will install the Qt libraries and tools to the directory you specified in the configure step (/path/to/qt-android).

Step 7: Set Up Qt Creator

Finally, you need to configure Qt Creator to use the Android toolchain.

7.1 Install Qt Creator

On Ubuntu, you can install Qt Creator via apt:

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sudo apt install qtcreator

7.2 Configure Qt Creator for Android

Open Qt Creator.

Go to Tools > Options > Kits.

Add a new kit for Android and set the following:

Compiler: Set the compiler to the Android toolchain (clang for the ARM or x86 target).

Qt Version: Add the Qt version you just compiled (located in /path/to/qt-android).

Debugger: Make sure you have the Android debugger (gdb) set up.

Ensure the Android SDK and NDK paths are correctly set under Tools > Options > Devices > Android.

Step 8: Test the Setup

You can now create a basic Android project in Qt Creator and deploy it to an Android device or emulator.

FAQ

Q1: Why am I getting the crtbegin_so.o not found error?

This issue occurs when the necessary startup files for the Android toolchain are missing or incorrectly configured. Check that you’ve set the correct NDK path in your environment variables. Ensure you're using the correct version of the NDK (e.g.,
21e) as newer versions may have changes that break compatibility.

Q2: What should I do if Qt Creator cannot find my Android SDK/NDK?

Ensure that the Android SDK and NDK paths are set correctly in your environment variables. In Qt Creator, go to Tools > Options > Devices > Android, and double-check the paths for both the SDK and NDK.

Q3: How can I verify if my NDK has the necessary libraries?

Use the following command to search for crtbegin_so.o:

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find $ANDROID_NDK_ROOT -name crtbegin_so.o
If it’s missing, you may need to download or install the correct NDK version, or manually copy the required file from a different source.

Q4: How do I install the missing dependencies in Ubuntu?

You can install all necessary dependencies using the following command:

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sudo apt install -y build-essential libfontconfig1-dev libdbus-1-dev libssl-dev libglib2.0-dev \ libpulse-dev libudev-dev pkg-config cmake qt5-qmake qtbase5-dev qtchooser \ openjdk-8-jdk unzip curl
Q5: Can I use a different version of Qt for Android?

Yes, while this guide specifically covers Qt 5.15.15, you can build other versions of Qt by checking out a different branch in the Qt Git repository or by downloading another version of the source.

Conclusion

Building Qt 5.15.15 for Android on Ubuntu 22.04.3 LTS (especially within a WSL2 environment) is a detailed and complex process. However, by following the steps outlined above, you should be able to overcome the most common errors and build a working Qt for Android environment. If you run into any issues, the FAQs provide answers to the most frequent problems. Remember that Qt 5.15.15 is a stable release and should work well with Android SDK
31 and NDK
21e, as long as paths and dependencies are correctly set.