Dialog boxes

Showing dialog boxes from an android application can be usefull.

This article will be using a layout like this – 4 buttons with their own function (complete code id listed last in this article):

Info boxes

An info box is called a Toast on the Android OS. A toast message is a small window that appear in the button half on the device screen. It should only be used as an information service to the user. The window disappears by itself, so as a developer you can not be sure that the user actually sees the message displayed. If you want to user to take action on the popup window, you should use an alert dialog instead – this is covered later on.

The Toast message is very easy to create. The most simple way to display a toast is by calling the maketext()-method like this:

...
Toast.makeText(this, "This is the Toast message", Toast.LENGTH_LONG).show();
...

This will display a box like this:

Alert boxes

The Alert box should be use when you want to make sure, that the user reads and takes action on the information window. To display the alert window, can be done like this:

...
            // prepare the alert box                   
            AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
            
            // set the message to display
            alertbox.setMessage("This is the alertbox!");
            
            // add a neutral button to the alert box and assign a click listener
            alertbox.setNeutralButton("Ok", new DialogInterface.OnClickListener() {
                
                // click listener on the alert box
                public void onClick(DialogInterface arg0, int arg1) {
                    // the button was clicked
                    Toast.makeText(getApplicationContext(), "OK button clicked", Toast.LENGTH_LONG).show();
                }
            });
            
            // show it
            alertbox.show();
...

This will popup a window like this:

When is OK button is clicked, it will – in this example – show a toast message like this:

Yes/no boxes

If one button on the alert dialog isn’t enough we can use the setPositiveButton() and setNegativeButton() on the AlertDialog Builder like this:

...
            // prepare the alert box                   
            AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
            
            // set the message to display
            alertbox.setMessage("This is the alertbox!");
                    
            // set a positive/yes button and create a listener                    
            alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                
                // do something when the button is clicked
                public void onClick(DialogInterface arg0, int arg1) {
                    Toast.makeText(getApplicationContext(), "'Yes' button clicked", Toast.LENGTH_SHORT).show();
                }
            });
            
            // set a negative/no button and create a listener 
            alertbox.setNegativeButton("No", new DialogInterface.OnClickListener() {

                // do something when the button is clicked                
                public void onClick(DialogInterface arg0, int arg1) {
                    Toast.makeText(getApplicationContext(), "'No' button clicked", Toast.LENGTH_SHORT).show();
                }
            });
            
            // display box
            alertbox.show();
...

This will show a window like this:

When either of the buttons is clicked it will run the assigned listener. Here we have clicked the yes button:

Loading box

If you want to display a loading window or some kind of progress alert it can be done with the ProgressDialog like this:

...
            // prepare the dialog box
            ProgressDialog dialog = new ProgressDialog(this);
            
            // make the progress bar cancelable
            dialog.setCancelable(true);
            
            // set a message text
            dialog.setMessage("Loading...");
            
            // show it
            dialog.show();
...

This will popup a progress window like this:

This window will not close by itself. You have to make it complete, by running a code that increment the internal counter on the ProgressDialog, so that the progressdialog can calculate the percentage by itself. For this we should use a thread-based application, that runs some code in the background and from there set the progress bar at the given value. This is not covered in this article though.

Complete code

The small code samples above are shown here in the complete formation, including the main.xml layout.

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show Toast" android:id="@+id/toastbtn"></Button>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show Alert" android:id="@+id/alertbtn"></Button>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show Yes/No" android:id="@+id/yesnobtn"></Button>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show Progress" android:id="@+id/progressbtn"></Button>
</LinearLayout>

dialogboxes.java

package huuah.dialogboxes;

import android.app.Activity;
import android.os.Bundle;
import android.view.View.OnClickListener;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.app.ProgressDialog;

public class dialogboxes extends Activity implements OnClickListener {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // set a click listener on the toast button
        Button toast = (Button) findViewById(R.id.toastbtn);
        toast.setOnClickListener(this);
            
        // set a click listener on the alert button
        Button alert = (Button) findViewById(R.id.alertbtn);
        alert.setOnClickListener(this);
        
        // set a click listener on the yesno button
        Button yesno = (Button) findViewById(R.id.yesnobtn);
        yesno.setOnClickListener(this);
        
        // set a click listener on the progress button
        Button progress = (Button) findViewById(R.id.progressbtn);
        progress.setOnClickListener(this);        
    }
    
       
    public void onClick(View view) {
        // which button is clicked?
        
        // the Toast button
        if (view == findViewById(R.id.toastbtn)) {
            // display the toast popup window
            Toast.makeText(this, "This is the Toast message", Toast.LENGTH_LONG).show();
        }

        // the Alert button the activated
        if (view == findViewById(R.id.alertbtn)) {
        
            // prepare the alert box                   
            AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
            
            // set the message to display
            alertbox.setMessage("This is the alertbox!");
            
            // add a neutral button to the alert box and assign a click listener
            alertbox.setNeutralButton("Ok", new DialogInterface.OnClickListener() {
                
                // click listener on the alert box
                public void onClick(DialogInterface arg0, int arg1) {
                    // the button was clicked
                    Toast.makeText(getApplicationContext(), "OK button clicked", Toast.LENGTH_LONG).show();
                }
            });
            
            // show it
            alertbox.show();
        }
        
        // the yesno button is clicked
        if (view == findViewById(R.id.yesnobtn)) {        
            // prepare the alert box                   
            AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
            
            // set the message to display
            alertbox.setMessage("This is the alertbox!");
                    
            // set a positive/yes button and create a listener                    
            alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                
                // do something when the button is clicked
                public void onClick(DialogInterface arg0, int arg1) {
                    Toast.makeText(getApplicationContext(), "'Yes' button clicked", Toast.LENGTH_SHORT).show();
                }
            });
            
            // set a negative/no button and create a listener 
            alertbox.setNegativeButton("No", new DialogInterface.OnClickListener() {

                // do something when the button is clicked                
                public void onClick(DialogInterface arg0, int arg1) {
                    Toast.makeText(getApplicationContext(), "'No' button clicked", Toast.LENGTH_SHORT).show();
                }
            });
            
            // display box
            alertbox.show();
        }
 
        // progress button clicked
        if (view == findViewById(R.id.progressbtn)) {
            // prepare the dialog box
            ProgressDialog dialog = new ProgressDialog(this);
            
            // make the progress bar cancelable
            dialog.setCancelable(true);
            
            // set a message text
            dialog.setMessage("Loading...");
            
            // show it
            dialog.show();
        }
        
    }
}

I hope this will the useful. If you want to read more on this subject, then take a look at some of the Android books out there