Debugging with Breakpoints
Debugging with Breakpoints
About
- Breakpoints pause code execution for inspection.
- Supported in IDEs (VSCode, Android Studio) and DevTools.
- Allows examining variables, call stack, and control flow.
- Essential for diagnosing runtime issues.
Main Topics
-
Setting Breakpoints
- Definition: How to add breakpoints in IDEs.
- Example:
void calculate() { int x = 5; // Set breakpoint on this line print(x * 2); }
-
Breakpoint Types
- Definition: Line vs conditional vs exception breakpoints.
- Example:
// Conditional breakpoint (VSCode): // Right-click → Add Conditional Breakpoint // Condition: `x > 10`
-
Execution Control
- Definition: Step Over/Into/Out commands.
- Example:
void main() { print('Start'); // Step Over calculate(); // Step Into }
-
Inspecting State
- Definition: Viewing variables and call stack.
- Example:
// During breakpoint pause: // - Hover variables for values // - View Call Stack panel
-
Logging Breakpoints
- Definition: Breakpoints that log without pausing.
- Example:
// In VSCode: // Right-click → Add Logpoint // Message: 'x value: {x}'
How to Use
- Set: Click gutter in IDE or use
debugger()
statement - Manage: Enable/disable in “Breakpoints” view
- Navigate: F8 (Step Over), F7 (Step Into) in VSCode
- Inspect: Watch expressions for complex variables
How It Works
- Compilation: Debug info embedded in Dart bytecode
- Pausing: VM suspends at breakpoint locations
- State Capture: Snapshots variable values when paused
- Resume: VM continues execution on command
Example Debug Session:
void main() {
debugger(); // Programmatic breakpoint
for (var i = 0; i < 5; i++) {
print(i); // Set line breakpoint here
}
}
Conclusion
Dart DevTools is an indispensable suite for debugging and optimizing Dart applications. It provides real-time insights into app performance, memory usage, and widget hierarchies, making it essential for developing production-quality applications with efficient data handling and smooth execution.