Top 5 Android Studio Features You Must Know to Boost Your App Development

📘 Chapter 3: Logcat, Breakpoints, and Debugging Tools

🧭 What You’ll Learn

This chapter teaches you how to:

• Read and filter Logcat logs for debugging
• Set breakpoints and inspect variables at runtime
• Use step-by-step debugging effectively
• Evaluate expressions and modify variables during execution
• Handle exceptions and crash reports
• Understand Watch, Evaluate, and Call Stack windows
• Utilize debugging tools for performance bottlenecks and logic bugs

🚦 Why Debugging Tools Matter

Bugs can hide in the most unexpected places. Without strong debugging skills, you can spend hours chasing problems that could be diagnosed in seconds with the right tools.

With Android Studio’s suite of debugging features, you can:

• Diagnose crashes, UI glitches, and data errors
• Pinpoint root causes instead of just symptoms
• Test conditions, branches, and variable states
• Gain deep insights into your app's runtime behavior

🔍 What Is Logcat?

Logcat is the system log for Android. It provides real-time logging for everything happening on the device or emulator:

• System messages
• Exceptions and stack traces
• Log.d, Log.i, Log.w, Log.e outputs from your code
• Garbage collection and memory info
• App lifecycle callbacks

✅ How to Access Logcat

• Open Android Studio
• Run your app
• Navigate to View > Tool Windows > Logcat
• Filter by app package or PID (process ID)

🧪 Logcat Usage Example

kotlin

Log.d("MainActivity", "Button clicked!")

Log.i("UserService", "User loaded: $userId")

Log.w("Login", "Login took too long")

Log.e("API", "Network error: ${e.message}")

🎛️ Logcat Filters and Options

🔎 Breakpoints: Your First Line of Defense

Breakpoints pause your app at a specific line during execution. This allows you to inspect:

• Current variable values
• The path of execution
• Conditions that triggered a bug

✅ How to Add a Breakpoint

• Click in the gutter (left of the line number)
• Run the app in Debug Mode
• When execution hits the breakpoint, it pauses

📌 Example: Debugging a Button Click

kotlin

button.setOnClickListener {

    val user = userService.getUser()

    Log.d("User", "User ID: ${user.id}") // <- Add breakpoint here

}

🧠 Breakpoint Types

⚙️ Runtime Debugging Tools

Once paused at a breakpoint, Android Studio unlocks a full debugging interface:

🔍 Sample Debug Session Flow

1. Set a breakpoint on a login button
2. Run in debug mode
3. App pauses when the user taps the button
4. Use Variables tab to check user input
5. Use Evaluate Expression to test logic
6. Fix bug, then Resume execution

🧪 Evaluating Expressions in Debug Mode

• Open Evaluate Expression window (Alt + F8)
• Type any expression: user.email.contains("@")
• Supports method calls, mathematical ops, and Kotlin/Java syntax

🧩 Example: Change Variable During Debug

kotlin

user.name = "Test User"

This modifies the variable in real-time, letting you test outcomes without rebuilding the app.

⚠️ Debugging Common Runtime Issues

🔁 Exception Breakpoints

You can configure Android Studio to break on exceptions, even if they aren’t handled.

1. Open Run > View Breakpoints (Ctrl+Shift+F8)
2. Enable Any Exception
3. Now, every unhandled or thrown exception will pause execution

🧠 Advanced Debugging with Conditional Breakpoints

Right-click a breakpoint → "More"

🔍 Example:

text

Condition: user.id == 42

This ensures the breakpoint only triggers for that specific user.

💡 Pro Debugging Tips

• Use Log.d tags consistently across your app ("LoginActivity", "NetworkManager")
• Group log output using log levels
• Don’t leave debug logs in production builds
• Use assertions in dev to enforce invariants
• Always test on both emulator and real devices for behavioral consistency

✅ Summary Table: Debugging Tools in Android Studio