Implementing share functionality in an Android app allows users to easily share content from your app with other apps or contacts. This feature is useful for sharing text, images, links, or any other type of content with various social media platforms, messaging apps, or email. To enable sharing in your Android app, you need to create an intent, specify the content to share, and start the activity chooser. The intent represents the action of sharing and contains the content you want to share. The activity chooser is a system dialog that presents the user with a list of apps capable of handling the share intent.

Here's a step-by-step guide on how to implement the share functionality in an Android app: Create an Intent: Intents are used to communicate between different components of an Android app. In this case, you'll create an intent to share data.

Intent shareIntent = new Intent(Intent.ACTION_SEND);
shareIntent.setType("text/plain");
shareIntent.putExtra(Intent.EXTRA_TEXT, "Hello, this is the content to share!");

Start the Activity Chooser: The Activity Chooser allows the user to select an app to share the content with. You can start the chooser using Intent.createChooser().

String title = "Share via";
startActivity(Intent.createChooser(shareIntent, title));

Handle the Share Intent: When the user selects an app from the activity chooser, you can handle the share intent in your app's activity. Add the following code in the onCreate() method of your activity.

Intent receivedIntent = getIntent();
String receivedAction = receivedIntent.getAction();
String receivedType = receivedIntent.getType();

if (receivedAction != null && receivedAction.equals(Intent.ACTION_SEND)) {
    if (receivedType != null && receivedType.equals("text/plain")) {
        String sharedText = receivedIntent.getStringExtra(Intent.EXTRA_TEXT);
        if (sharedText != null) {
            // Handle the shared text here
        }
    }
}

Directly share to WhatsApp:

 Intent whatsappIntent = new Intent(Intent.ACTION_SEND);
                whatsappIntent.setType("text/plain");
                whatsappIntent.setPackage("com.whatsapp");
                whatsappIntent.putExtra(Intent.EXTRA_TEXT, "The text you wanted to share");
                try {
                    startActivity(whatsappIntent);
                } catch (android.content.ActivityNotFoundException ex) {
                    Toast.makeText(getApplicationContext(),"Whatsapp have not been installed.",Toast.LENGTH_LONG).show();
                }

By implementing these steps, you'll have the share functionality in your Android app. When the user selects the share option, they'll be able to choose from a list of apps installed on their device to share the content with.