Tools: The Hidden Magic Behind Android’s Share Button

Step 1: Understanding the Intent ## Step 2: Breaking Down the Implicit Intent ## Step 3: The Journey of an Intent ## Step 4: A Real Example — Sharing an Image ## Step 5: How Receiving Apps Register ## Step 6: Why It Matters for Developers ## Step 7: The Takeaway ## Developer Challenge Have you ever hit the Share button in your app — maybe to send a funny meme, a link, or a photo — and seen that neat list of apps pop up? As a mobile developer, I always thought it was just… magic. Call an Intent, Android shows a list, job done. But one day, while debugging a crash on ActivityNotFoundException, I paused and asked myself: “Wait… how does Android actually know which apps to show? How does it know WhatsApp, Gmail, or Drive can handle my data?” That question sent me down a rabbit hole that changed how I think about app interactions forever. I started with the basics. An Intent is like a messenger in Android. It carries a message from one part of the system — or even one app — to another. There are two types of Intents: I wrote a tiny snippet in my app: At first glance, it seems simple. But internally, it’s a beautifully orchestrated dance. Here’s what I realized: An Implicit Intent has three main parts: These three pieces of info act like a search query to find the right apps. I wanted to visualize the flow. When I tap Share, this is what happens behind the scenes: At this moment, it hit me: the share sheet is not a UI trick. It’s AMS + PMS doing intelligent matching under the hood. Mind blown. I tested sharing a photo: The resolve list might include WhatsApp, Gmail, Drive, etc. Android doesn’t hardcode these — it calculates dynamically based on my device’s installed apps and their intent-filters. For apps to show in the share sheet, they declare intent-filters: Android matches my Intent against this, adds it to the resolve list, and the app appears as an option. Simple in theory, elegant in execution. This little deep dive changed how I design apps: It also taught me to think like Android. Every tap, every Intent, every share sheet is a tiny example of Android’s architecture at work. Next time you tap Share, imagine the journey: Your Intent → AMS → PMS → Resolve List → Share Sheet → Chosen App Understanding this makes you not just a developer who “makes things work,” but a developer who understands why things work. And that perspective is invaluable. Open your favorite app and tap Share. Ask yourself: Curiosity leads to mastery. Start small, like I did with ACTION_SEND, and you’ll soon be exploring more complex flows like ACTION_VIEW, ACTION_PICK, and custom deep links. Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well For further actions, you may consider blocking this person and/or reporting abuse CODE_BLOCK: val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_TEXT, "Check out this cool blog!") type = "text/plain" } startActivity(Intent.createChooser(shareIntent, "Share via")) Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_TEXT, "Check out this cool blog!") type = "text/plain" } startActivity(Intent.createChooser(shareIntent, "Share via")) CODE_BLOCK: val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_TEXT, "Check out this cool blog!") type = "text/plain" } startActivity(Intent.createChooser(shareIntent, "Share via")) CODE_BLOCK: val imageUri: Uri = getImageUri() val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_STREAM, imageUri) type = "image/jpeg" } startActivity(Intent.createChooser(shareIntent, "Share Image via")) Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: val imageUri: Uri = getImageUri() val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_STREAM, imageUri) type = "image/jpeg" } startActivity(Intent.createChooser(shareIntent, "Share Image via")) CODE_BLOCK: val imageUri: Uri = getImageUri() val shareIntent = Intent().apply { action = Intent.ACTION_SEND putExtra(Intent.EXTRA_STREAM, imageUri) type = "image/jpeg" } startActivity(Intent.createChooser(shareIntent, "Share Image via")) CODE_BLOCK: <intent-filter> <action android:name="android.intent.action.SEND" /> <category android:name="android.intent.category.DEFAULT" /> <data android:mimeType="image/*" /> </intent-filter> Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: <intent-filter> <action android:name="android.intent.action.SEND" /> <category android:name="android.intent.category.DEFAULT" /> <data android:mimeType="image/*" /> </intent-filter> CODE_BLOCK: <intent-filter> <action android:name="android.intent.action.SEND" /> <category android:name="android.intent.category.DEFAULT" /> <data android:mimeType="image/*" /> </intent-filter> - Explicit Intents: You know exactly which component should handle your request. Example: opening your own ProfileActivity. - Implicit Intents: You only describe what you want done, not who should do it. Example: sharing an image, sending an email, or opening a PDF. Android figures out the rest. - Action: What you want to do (ACTION_SEND = send something). - Category: The general type of action (CATEGORY_DEFAULT = standard). - MIME Type: What type of data you’re sending (text/plain, image/jpeg, etc.). - The Intent hits the Activity Manager Service (AMS): Think of AMS as Android’s traffic controller. It decides: “Where should this message go?” - AMS asks the Package Manager Service (PMS) for matches: PMS is a database of all installed apps and their capabilities (declared via <intent-filter> in AndroidManifest.xml). - PMS matches the Intent to apps: It checks the action, category, and MIME type against every app’s intent filters. All matching apps go into a resolve list. - AMS decides what to do next: No matches? Throws ActivityNotFoundException. One match? Launches it directly. Multiple matches? Shows a chooser dialog (the familiar share sheet). - ACTION_SEND → I want to send something. - EXTRA_STREAM → My image URI. - type = "image/jpeg" → Only apps that can handle JPEG images appear. - Action → Can handle SEND - Category → Default - Data → Any image - Better UX: I can control which apps appear by tweaking MIME types. - Graceful error handling: I now check for ActivityNotFoundException. - Powerful cross-app features: I can build apps that communicate seamlessly without hardcoding app dependencies. - How is Android deciding which apps to show? - What happens if no app can handle my Intent? - How could I design my app to only show relevant options?