#1 Tutorial Android - Criando projeto, AVD e Iniciando Desenvolvimento

Fontes Java:
package com.infoplace.helloworld;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends Activity {

private Button btnHello;

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

btnHello = (Button) findViewById(R.id.btnHello);

btnHello.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, "Hello World!! Infoplace Sistemas", Toast.LENGTH_SHORT).show();
}
});

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}

@Override public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();

//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}

return super.onOptionsItemSelected(item);
}
}


Arquivo XML:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

<TextView android:text="@string/infoplace" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/textView" />

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/btnHello"
android:id="@+id/btnHello"
android:layout_below="@+id/textView"
android:layout_alignParentStart="true" />


</RelativeLayout>