Thank you for the answer, much appreciated. I actually don't need to trigger the android save dialog, I just want to make a screenshot outside of the sandbox. I have tried to create an extension for GMS(1), because "screen_save" and "surface_save_part" works, but save the .png files to the restricted location, available only for rooted devices (/data/data/<package name>). This is the .java script I'm trying to create

package ${YYAndroidPackageName};
import ${YYAndroidPackageName}.R;
public class android_screenshot {
    public void take_scr() {
     adb shell screencap /sdcard/screen.png
     adb pull /sdcard/screen.png
     }
}

File > Create Application > Error

BUILD FAILED

Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:9: error: ';' expected adb shell screencap /sdcard/screen.png ^
Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:9: error: not a statement adb shell screencap /sdcard/screen.png ^
Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:9: error: ';' expected adb shell screencap /sdcard/screen.png ^
Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:10: error: ';' expected adb pull /sdcard/screen.png ^
Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:10: error: not a statement adb pull /sdcard/screen.png ^
Z:\com.companyname.screenshot2\src\main\java\com\companyname\screenshot2\scr_capture.java:10: error: ';' expected adb pull /sdcard/screen.png ^
6 errors
:com.companyname.screenshot2:compileReleaseJavaWithJavac FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':com.companyname.screenshot2:compileReleaseJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
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I've got these 2 android commands from here
http://adbshell.com/commands/adb-shell-screencap

some other info
https://adbinstaller.com/commands/adb-shell-screencap-5b69ae0032e0461ad1db1ca8

https://code.google.com/archive/p/android-fb2png/

https://stackoverflow.com/questions/32883784/which-commands-line-are-used-to-take-a-screenshot-on-android-device-except-scre

https://stackoverflow.com/questions/45133089/take-screenshot-with-adb-and-retrieve-it-in-java-without-writing-a-file

https://stackoverflow.com/questions/27766712/using-adb-to-capture-the-screen?lq=1
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I believe it's not that hard to achieve this, but with little help...