Android_Alert.java

/**
* Alert 1
* Normal Alert
*/
AlertDialog.Builder alertDialog = new AlertDialog.Builder(your_activity.this); // we build alert
alertDialog.setMessage("Alert_text") // alert text with setMessage() method
.setCancelable(true); // user can cancel this alert for 'true'

AlertDialog alert = alertDialog.create(); // we create alert for show
alert.setTitle("Alert_title");
alert.show(); // display alert

// alertDialog, your_activity, Alert_text, setCancelable(), alert, Alert_title

/**
* Alert 2
* Alert with positive and nagative button
*/
AlertDialog.Builder alertDialog = new AlertDialog.Builder(your_activity.this); // we build alert
alertDialog.setMessage("Alert_text") // alert text with setMessage() method
.setCancelable(true) // user can't cancel this alert for false
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
	@Override
	public void onClick(DialogInterface dialogInterface, int i) {
		// what we want to do
	}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
	@Override
	public void onClick(DialogInterface dialogInterface, int i) {
		// what we want to do
	}
});
AlertDialog alert = alertDialog.create(); // we create alert for show
alert.setTitle("Alert!");
alert.show(); // display alert

// alertDialog, your_activity, Alert_text, setCancelable(), yes, no, alert, Alert_title

/**
* Alert 3
* Custom Alert with custom xml file
*/
AlertDialog.Builder alertBulder = new AlertDialog.Builder(your_activity.this);
View nView = getLayoutInflater().inflate(R.layout.custom_xml_file,null);

// write what want to do ----->
	//cast
	xml_view view1 = (xml_view) nView.findViewById(R.id.view1_id);
// <----- write what want to do

alertBulder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
	@Override
	public void onClick(DialogInterface dialogInterface, int i) {
		// what we want to do
	}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
	@Override
	public void onClick(DialogInterface dialogInterface, int i) {
		// what we want to do
	}
});
alertBulder.setCancelable(false);
alertBulder.setView(nView);
AlertDialog dialog = alertBulder.create();
dialog.show();

// alertBulder, your_activity, nView, custom_xml_file, xml_view, view1, view1_id, yes, no, setCancelable(), alert, Alert_title