Feature/structured logging support

timber-sample/src/main/java/com/example/timber/ExampleApp.java

@@ -3,6 +3,9 @@
 import android.app.Application;
 import android.support.annotation.NonNull;
 import android.util.Log;
+
+import java.util.Map;
+
 import timber.log.Timber;
 
 import static timber.log.Timber.DebugTree;
@@ -15,6 +18,7 @@ public class ExampleApp extends Application {
       Timber.plant(new DebugTree());
     } else {
       Timber.plant(new CrashReportingTree());
+      Timber.plant(new StructuredLoggingTree());
     }
   }
 
@@ -36,4 +40,20 @@ private static class CrashReportingTree extends Timber.Tree {
       }
     }
   }
+
+  /** A tree which logs important events in a structured format. */
+  private static class StructuredLoggingTree extends Timber.Tree {
+    @Override protected void log(int priority, String tag, @NonNull String message, Throwable t) {
+      log(priority, tag, message, t, null);
+    }
+
+    @Override protected void log(int priority, String tag, @NonNull String message, Throwable t,
+                                 Map<String, Object> metadata) {
+      if (priority == Log.VERBOSE || priority == Log.DEBUG) {
+        return;
+      }
+
+      FakeCrashLibrary.log(priority, message, metadata);
+    }
+  }
 }

timber-sample/src/main/java/com/example/timber/FakeCrashLibrary.java

@@ -1,11 +1,17 @@
 package com.example.timber;
 
+import java.util.Map;
+
 /** Not a real crash reporting library! */
 public final class FakeCrashLibrary {
   public static void log(int priority, String tag, String message) {
     // TODO add log entry to circular buffer.
   }
 
+  public static void log(int priority, String message, Map<String, Object> metadata) {
+    // TODO add log entry with metadata
+  }
+
   public static void logWarning(Throwable t) {
     // TODO report non-fatal warning.
   }

timber-sample/src/main/java/com/example/timber/ui/DemoActivity.java

@@ -5,6 +5,9 @@
 import android.widget.Button;
 import android.widget.Toast;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import butterknife.ButterKnife;
 import butterknife.OnClick;
 import com.example.timber.R;
@@ -24,6 +27,10 @@ public class DemoActivity extends Activity {
   @OnClick({ R.id.hello, R.id.hey, R.id.hi })
   public void greetingClicked(Button button) {
     Timber.i("A button with ID %s was clicked to say '%s'.", button.getId(), button.getText());
+    Map<String, Object> eventMetadata = new HashMap<>();
+    eventMetadata.put("event-type", "button-pressed");
+    eventMetadata.put("button-id", String.valueOf(button.getId()));
+    Timber.v(eventMetadata, "This is an example of a structured log");
     Toast.makeText(this, "Check logcat for a greeting!", LENGTH_SHORT).show();
   }
 }