Flávio S. Glock

We've had another hackathon at work.

Yati, Bas, Luca and I hacked on the Perlito Perl5-to-Java compiler and also a bit of Perl5-to-JavaScript.

The changes are in GitHub and will be published in the next CPAN release.

The latest cool addition is an Android App example:

Import to Perl space all Java libraries we will need:

use strict;
use warnings;

package header { java_path => 'org.perlito.perlitosample' };
package Android::Activity { import => 'android.support.v7.app.AppCompatActivity' };
package Android::Bundle { import => 'android.os.Bundle' };
package String {};
package Button   { import => 'android.widget.Button' };
package TextView { import => 'android.widget.TextView' };
package EditText { import => 'android.widget.EditText' };
package View     { import => 'android.view.View' };

Setup a class extending "Android::Activity" - this is our App entry point, and it involves a bit of Android-side magic using use Java::inline:

package MainActivity {
    extends => 'Android::Activity',
    decl    => ['public'],
    'Java::inline' => '
        static {
            Main.init();
        }
        public void onCreate(Bundle saved) {
            super.onCreate(saved);
            setContentView(R.layout.activity_main);
            Button button = (Button) findViewById(R.id.button_ok);
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                  EditText txt = (EditText) findViewById(R.id.value);
                  String x = txt.getText().toString();
                  TextView tv = (TextView) findViewById(R.id.text);
                  String val = doit(x);
                  tv.setText(val);
                }
          });
        }
    ',
    methods => [
        doit => {
            decl   => ['public'],
            return => 'String',
            args   => ['String'],
            code   => 'main::doit',
        }
    ],
}

The header declares that the "doit()" method is implemented in Perl, in the subroutine "main::doit".

Now we define the subroutine:

sub doit {
    my $this = shift;
    my $x = shift;
    if ($x eq 'die') { die "Death to you"; }
    if (0+$x eq $x) {
        return "The result (calculated in Perl) is ". (2 * $x);
    }
    else {
        return "The result (calculated in Perl) is ". ($x x 2);
    }
}

We called this file "mainactivity.pl" [Perl5 source code] and it compiles to "MainActivity.java" [Java source code].

We then compiled this with Android Studio using an Android project file [project file] and tested on a real phone!