<?xml version="1.0" encoding="utf-8"?><android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.blogspot.c.appbasic.MainActivity">
    <LinearLayout        android:layout_width="0dp"        android:layout_height="0dp"        android:orientation="vertical"        android:weightSum="1"        app:layout_constraintBottom_toBottomOf="parent"        app:layout_constraintHorizontal_bias="0.0"        app:layout_constraintLeft_toLeftOf="parent"        app:layout_constraintRight_toRightOf="parent"        app:layout_constraintTop_toTopOf="parent"        app:layout_constraintVertical_bias="0.0">
         <Button            android:id="@+id/btntoast"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:text="@string/btntoast" />
        <Button            android:id="@+id/btnalert"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:text="@string/btnalert"            android:textAlignment="center" />

        <LinearLayout/>

 

public class MainActivity extends AppCompatActivity {

    private Button btntoast, btnalert,     @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);
        Toast.makeText(this, "Aplikasi tampil", Toast.LENGTH_LONG).show();
        inisialisasikomponen();        actionButton();
    }

    private void actionButton() {
        btntoast.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "ini toast", Toast.LENGTH_SHORT).show();            }
        });        btnalert.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View v) {
                new AlertDialog.Builder(MainActivity.this).setTitle("Show Toast")
                        .setMessage("Tampilkan Toast?")
                        .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                            @Override                            public void onClick(DialogInterface dialog, int which) {
                                //perintah atau aksi setelah menekan tombol yes                                //menanmpilkan toastm                                Toast.makeText(MainActivity.this, "Tampil Toast", Toast.LENGTH_SHORT).show();                                Toast.makeText(MainActivity.this, "teks", Toast.LENGTH_SHORT).show();                            }
                        })
                        .setNegativeButton("No", new DialogInterface.OnClickListener() {
                            @Override                            public void onClick(DialogInterface dialog, int which) {
                                //abaikan / tidak ada aksi
                            }
                        })
                        .setNeutralButton("Cancel", new DialogInterface.OnClickListener() {
                            @Override                            public void onClick(DialogInterface dialog, int which) {
                                //abaikan                            }
                        })
                        .show();