intent

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class LaunchActivity extends Activity {

  public Button mLaunchButton;
  public int mFuelLevel;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_launch);

    // mFuelLevel is set elsewhere.
    // Code ommitted for brevity!

    mLaunchButton = (Button)findViewById(R.id.launchButton);
    mLaunchButton.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
      intent.putExtra("FUEL_LEVEL",mFuelLevel);
        Intent intent = new Intent(LaunchActivity.this, FlightActivity.class);
        startActivity(intent);
      }
    });
  }
}