Was bored so revisited FFM (java Foreign Function & Memory - allows access to things outside the JVM)
Example for Windows only and Java 21+
Example for Windows only and Java 21+
B4X:
Sub AppStart (Form1 As Form, Args() As String)
MainForm = Form1
MainForm.RootPane.LoadLayout("Layout1")
MainForm.Show
End Sub
Sub Button1_Click
'**********************
'java 21+ Windows only (needs --enable-preview if used < java 22)
'**********************
Dim title As String = MainForm.Title ' save title
MainForm.Title="find me cos I am hiding" ' change name to make it easy to find
Log("HWND = " & Me.as(JavaObject).RunMethod("getHWND",Array(MainForm.title)))
MainForm.title=title ' restore it to original
End Sub
#if java
import java.lang.foreign.*;
import java.lang.invoke.*;
import java.nio.charset.*;
public static long getHWND(String title) throws Throwable {
Linker linker = Linker.nativeLinker();
SymbolLookup user32 = SymbolLookup.libraryLookup("C:/windows/system32/user32.dll", Arena.global());
MethodHandle findWindow = linker.downcallHandle(
user32.find("FindWindowW").orElseThrow(),
FunctionDescriptor.of(ValueLayout.JAVA_LONG, ValueLayout.ADDRESS, ValueLayout.ADDRESS)
);
try (Arena arena = Arena.ofConfined()) {
byte[] utf16le = (title + "\0").getBytes(StandardCharsets.UTF_16LE);
MemorySegment lpWindowName = arena.allocate(utf16le.length, 2);
lpWindowName.copyFrom(MemorySegment.ofArray(utf16le));
Long hwnd = (long)findWindow.invoke(MemorySegment.NULL, lpWindowName);
// for testing
MethodHandle getWindowText = linker.downcallHandle(
user32.find("GetWindowTextW").orElseThrow(),
FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.JAVA_LONG, ValueLayout.ADDRESS, ValueLayout.JAVA_INT)
);
try (Arena arena1 = Arena.ofConfined()) {
MemorySegment buffer = arena1.allocate(512 * 2); // 512 WCHARs
int charsCopied = (int) getWindowText.invoke(hwnd, buffer, 512);
String actualTitle = decodeWideString(buffer, charsCopied);
IO.println("Chk = " + actualTitle);
}
return hwnd;
}
}
static String decodeWideString(MemorySegment segment, int length) {
byte[] bytes = new byte[length * 2]; // WCHAR = 2 bytes
for (int i = 0; i < bytes.length; i++) {
bytes[i] = segment.get(ValueLayout.JAVA_BYTE, i);
}
return new String(bytes, StandardCharsets.UTF_16LE);
}
#End If
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