Intent

Intent

Introduction

An intent is used to send a message from one Activity to another. For instance an Intent can be used by one Activity to start the Activity within another app. We have two kinds of Intents, implicit Intents and explicit Intents.

Implicit Intents send out a message an rely on the underlying system to determine which app responds to the message.

Explicit Intents as the name suggest, specify the Activity that will respond to the message.

Implicit Intents

The following snippet shows an implicit Intent in action. The system will open the registered email client to respond when this Intent is invoked.

{lang=”java”}

//>> emailintent
                // Create the text message with a string
                Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
                emailIntent.setData(Uri.parse("mailto:developer@example.com"));

                // Verify that the intent will resolve to an activity
                if (emailIntent.resolveActivity(getPackageManager()) != null) {
                    startActivity(emailIntent);
                }
                //<<

Code Listing 14 is a full code listing of the MainActivity.java file. It demonstrates how to implement an implicit intent in our Netflix clone app.

{lang=”java”}

//>> emailintent
                // Create the text message with a string
                Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
                emailIntent.setData(Uri.parse("mailto:developer@example.com"));

                // Verify that the intent will resolve to an activity
                if (emailIntent.resolveActivity(getPackageManager()) != null) {
                    startActivity(emailIntent);
                }
                //<<

Explicit Intents

When you create an explicit Intent you specify that class that you want to respond to the Intent. In the following code snippet we specify the Main2Activity class to handle our message.

//>> emailintent
                // Create the text message with a string
                Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
                emailIntent.setData(Uri.parse("mailto:developer@example.com"));

                // Verify that the intent will resolve to an activity
                if (emailIntent.resolveActivity(getPackageManager()) != null) {
                    startActivity(emailIntent);
                }
                //<<

The following code listing shows the MainActivity.java file that calls the second activity that holds our search functionality.

{lang=”java”}

//>> emailintent
                // Create the text message with a string
                Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
                emailIntent.setData(Uri.parse("mailto:developer@example.com"));

                // Verify that the intent will resolve to an activity
                if (emailIntent.resolveActivity(getPackageManager()) != null) {
                    startActivity(emailIntent);
                }
                //<<

The following code listing shows the MainActivity2.java file that is called by MainActivity.java.

//>> emailintent
                // Create the text message with a string
                Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
                emailIntent.setData(Uri.parse("mailto:developer@example.com"));

                // Verify that the intent will resolve to an activity
                if (emailIntent.resolveActivity(getPackageManager()) != null) {
                    startActivity(emailIntent);
                }
                //<<