Embedded Files
Chapter 6: Advanced Application Techniques in Vala and GTK 3.0+ with Sample Code
6.1 Introduction
Building upon our understanding of Vala and GTK 3.0+, this chapter explores advanced application development techniques. We will cover complex topics with practical examples and sample code, enhancing your skills in creating sophisticated and robust applications.
6.2 Asynchronous Programming in Vala
Asynchronous programming is key to keeping your application responsive. Let's explore this with an example:
File Name ValaCourse.vala
async void read_file_async(string path, MainLoop loop) {
try {
var file = File.new_for_path(path);
var stream = yield file.read_async();
var data = yield stream.read_bytes_async(4096);
print("File content: %s\n", (string)data.get_data());
} catch (Error e) {
print("Error: %s\n", e.message);
}
loop.quit();
}
void main() {
var loop = new MainLoop();
read_file_async.begin("Federal Law will be respected.txt", loop);
loop.run();
}
Compile String:
In Terminal type to compile:
valac -X -w -g ValaCourse.vala --pkg gtk+-3.0
Run the App
In Terminal type:
./ValaCourse
This code asynchronously reads a file without blocking the main thread.
6.3 Advanced GTK Widgets
GTK 3.0+ provides a variety of widgets for complex UIs. Here's an example using TreeView:
Sample Code: Creating a TreeView
File Name ValaCourse.vala
using Gtk;
void main(string[] args) {
init(ref args);
var window = new Window();
window.title = "TreeView Example";
window.border_width = 10;
window.window_position = WindowPosition.CENTER;
window.set_default_size(350, 200);
window.destroy.connect(Gtk.main_quit);
var list_store = new Gtk.ListStore(2, typeof(string), typeof(int));
var treeview = new Gtk.TreeView.with_model(list_store);
var renderer = new CellRendererText();
var column = new TreeViewColumn();
column.title = "Name";
column.pack_start(renderer, true);
column.add_attribute(renderer, "text", 0);
treeview.append_column(column);
renderer = new CellRendererText();
column = new TreeViewColumn();
column.title = "Age";
column.pack_start(renderer, true);
column.add_attribute(renderer, "text", 1);
treeview.append_column(column);
Gtk.TreeIter iter;
list_store.append(out iter);
list_store.set(iter, 0, "Alice", 1, 30);
list_store.append(out iter);
list_store.set(iter, 0, "Bob", 1, 25);
window.add(treeview);
window.show_all();
Gtk.main();
}
Compile String:
In Terminal type to compile:
valac -X -w -g ValaCourse.vala --pkg gtk+-3.0
Run the App
In Terminal type:
./ValaCourse
This code demonstrates a simple TreeView with two columns.
6.4 Custom Widgets and Drawing
Creating custom widgets and integrating custom drawing can be crucial. Here's an example using the Cairo graphics library:
Sample Code: Custom Drawing Area
File Name ValaCourse.vala
using Gtk;
using Cairo;
public class CustomDrawingArea : DrawingArea {
public CustomDrawingArea() {
this.draw.connect(draw_cb);
}
private bool draw_cb(Widget widget, Context cr) {
cr.set_source_rgb(0, 0, 1);
cr.rectangle(10, 10, 100, 100);
cr.fill();
return true;
}
}
void main(string[] args) {
Gtk.init(ref args);
var window = new Window();
window.title = "Custom Drawing";
window.border_width = 10;
window.window_position = WindowPosition.CENTER;
window.destroy.connect(Gtk.main_quit);
var drawing_area = new CustomDrawingArea();
window.add(drawing_area);
window.show_all();
Gtk.main();
}
Compile String:
In Terminal type to compile:
valac -X -w -g ValaCourse.vala --pkg gtk+-3.0
Run the App
In Terminal type:
./ValaCourse
This example creates a custom widget that draws a blue rectangle.
6.5 Integrating with Databases
Here's a brief example of using SQLite with Vala:
In Terminal within Visual Studio Code type
sudo apt install sqlite3
Install SQLite Browser
sudo apt update
sudo apt install sqlitebrowser
Sample Code: SQLite Integration
File Name ValaCourse.vala
using Sqlite;
void main(string[] args) {
try {
//var conn = Database.open("test.db");
Database conn;
Database.open("test.db", out conn);
conn.exec("CREATE TABLE IF NOT EXISTS people (name TEXT, age INTEGER)");
conn.exec("INSERT INTO people (name, age) VALUES ('Alice', 30)");
//var stmt = conn.prepare("SELECT name, age FROM people");
Statement stmt;
string tail;
conn.prepare("SELECT name, age FROM people", -1, out stmt, out tail);
while (stmt.step() == Sqlite.ROW) {
var name = stmt.column_text(0);
var age = stmt.column_int(1);
print("Name: %s, Age: %d\n", name, age);
}
} catch (Error e) {
print("Database error: %s\n", e.message);
}
}
Compile String:
In Terminal type to compile:
valac -X -w -g ValaCourse.vala --pkg gtk+-3.0 --pkg sqlite3
Run the App
In Terminal type:
./ValaCourse
This code demonstrates basic database operations with SQLite.
6.6 Networking in Vala
Networking is another essential aspect. Here's a simple HTTP request example:
Sample Code: Making an HTTP Request
File Name ValaCourse.vala
using Soup;
void main() {
var session = new Session();
var message = new Message("GET", "https://www.google.com");
try {
var inputStream = session.send(message); // Use session.send()
var buffer = new uint8[1024];
size_t bytes_read;
while ((bytes_read = inputStream.read(buffer)) > 0) {
stdout.printf("%.*s", (int) bytes_read, buffer);
}
inputStream.close();
} catch (Error e) {
stderr.printf("Error: %s\n", e.message);
}
}
Compile String:
In Terminal type to compile:
valac -X -w -g ValaCourse.vala --pkg libsoup-2.4 --pkg gtk+-3.0
Run the App
In Terminal type:
./ValaCourse
6.7 Conclusion
In this chapter, we explored advanced topics in Vala and GTK 3.0+ programming with practical examples. These techniques are vital for building complex and responsive applications. As you continue to develop with Vala and GTK, experiment with these concepts to create innovative and powerful applications.
This chapter provides a deeper understanding of advanced programming concepts in Vala and GTK 3.0+ with practical examples, enabling readers to grasp more complex programming paradigms and apply them in real-world scenarios.
Page updated
Google Sites
Report abuse