activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="tech.alvarez.intents.MainActivity">

    <Button
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:onClick="abrirTelefono"
        android:text="@string/abrir_telefono" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:onClick="abrirWeb"
        android:text="@string/abrir_web" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:onClick="enviarCorreo"
        android:text="@string/enviar_correo" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:onClick="abrirMapa"
        android:text="@string/abrir_mapa" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:onClick="llamar"
        android:text="@string/llamar" />

</LinearLayout>

MainActivity.java

package tech.alvarez.intents;

import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void abrirTelefono(View view) {
        Uri numero = Uri.parse("tel:77242526");
        Intent intent = new Intent(Intent.ACTION_DIAL);
        startActivity(intent);
    }

    public void abrirWeb(View view) {
        Uri web = Uri.parse("http://alvarez.tech/android-umsa");
        Intent i = new Intent(Intent.ACTION_VIEW, web);
        startActivity(i);
    }

    public void enviarCorreo(View view) {
        Log.i("MIAPP", "Se presiono el boton de enviar correo");

        Intent i = new Intent(Intent.ACTION_SEND);
        i.setType("text/plain");
        i.putExtra(Intent.EXTRA_EMAIL, new String[]{"[email protected]", "[email protected]"});
        i.putExtra(Intent.EXTRA_SUBJECT, "Asunto");
        i.putExtra(Intent.EXTRA_TEXT, "Este es el contenido del correo");
        startActivity(i);
    }

    public void abrirMapa(View view) {
//        Uri lugar = Uri.parse("geo:-16.510947,-68.122074?z=8");
        Uri lugar = Uri.parse("geo:0,0?q=Perez+Velasco,+La+Paz,+Bolivia");

        Intent i = new Intent(Intent.ACTION_VIEW, lugar);
        startActivity(i);
    }

    public void llamar(View view) {

        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.CALL_PHONE) == PackageManager.PERMISSION_GRANTED) {

            Uri numero = Uri.parse("tel:74858056");
            Intent intent = new Intent(Intent.ACTION_CALL, numero);
            startActivity(intent);

        } else {

            if (ActivityCompat.shouldShowRequestPermissionRationale(this, android.Manifest.permission.CALL_PHONE)) {
                Log.i("MIAPP", "mostrar mensaje dar permiso manual");
            } else {
                ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.CALL_PHONE}, 777);
            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == 777) {

            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Log.i("MIAPP", "El usuario SI dio permiso");
            } else {
                Log.i("MIAPP", "El usuario NO dio permiso");
            }

        }
    }
}

strings.xml

<resources>
    <string name="app_name">Intents</string>
    <string name="abrir_telefono">Abrir teléfono</string>
    <string name="abrir_web">Abrir web</string>
    <string name="enviar_correo">Enviar correo</string>
    <string name="abrir_mapa">Abrir mapa</string>
    <string name="llamar">Llamar</string>
</resources>