When using Qt to develop apps for Android, sometimes our app will carry some resource files, such as png, jpg, etc., or there may be some configuration files, such as xml, etc. Where are these files placed?

There are two ways:

1. qrc
2. assets

Let's take a look at each.

the Qt Resource System

Qrc, Qt's resource file system, very easy to use. Look at a picture:

Figure 1 qrc schematic

Files you put in qrc, such as copy.png , will be compiled into the exe file (Android application is libapplication.so ). These resources are also loaded into memory when you run the app. If your resources are large, this is a problem.

If it's on the Android platform, you have another option.

Android assets

There is an assets directory in the Android project directory. The files placed in this directory will be packaged into the APK. The APK will not be installed into the application directory when the Android system is installed. Note that it is still in the APK. But the app can access the resources in this folder!

Qt uses this mechanism to implement the assets virtual file system. Our common QFile, QPixmap, QImage, etc. can access the files in assets through "assets:/".

With the assets virtual file system, your resource files are not loaded into memory at program startup, saving resources.

Look at a picture:

Figure 2 Asset diagram

How to put the resource file? Very simple, just put it in the android/assets folder in the Qt project directory. Figure 3:

Figure 3 Directory structure using assets

As long as you put it in, Qt compiles the files in assets into APKs and then accesses them in C++ code.

Android example using assets

ReferenceQt on Android: Graphical explanation of the whole process of Hello World》Build a project for Android.

Create AndroidManifest.xml and place a beauty.jpg in the android/assets directory. Delete the widget.h and widget.cpp of the project. Modify main.cpp as follows:

#include <QApplication>#include <QLabel>#include <QPixmap>int main(int argc, char *argv[]){    QApplication a(argc, argv);    QLabel label;    QPixmap pixmap("assets:/beauty.jpg");    label.setPixmap(pixmap);    label.show();    return a.exec();}

Compile, run, you can see Figure 4:

Figure 4 Qt on Android example using assets

OK, this is the end.

Review the Qt on Android series:

Qt on Android: Graphical explanation of the whole process of Hello World Getting started with Qt 5.2 for Android development under Windows Qt for Android deployment process analysis Qt on Android: Output Qt debugging information to logcat Qt on Android: Qt 5.3.0 release, improved instructions for Android Qt on Android Episode 1 (translation) Qt on Android Episode 2 (translation) Qt on Android Episode 3 (translation) Qt on Android Episode 4 (translation) Qt for Android compiles pure C project Qt for Android compiles Android C language executable program under Windows Qt on Android: Android SDK installation Qt on Android: http download and Json analysis Qt on Android settings app is called Chinese Qt on Android: Let Qt Widgets and Qt Quick apps display full screen Qt on Android: How to adapt to different screen sizes

 Qt on Android: Using JNI with third-party jar packages