fix(android): keep scanning mCurrentFocus across every display

devices/android.go

@@ -1069,20 +1069,30 @@ func (d *AndroidDevice) getForegroundComponent() (string, string, error) {
 		return "", "", fmt.Errorf("failed to get window displays: %w", err)
 	}
 
-	// parse package name from mCurrentFocus line
-	// format: mCurrentFocus=Window{... u0 com.package.name/com.package.name.MainActivity}
-	lines := strings.Split(string(output), "\n")
-	for _, line := range lines {
-		if strings.Contains(line, "mCurrentFocus") {
-			parts := strings.Fields(line)
-			if len(parts) >= 3 {
-				focusPart := strings.TrimSuffix(parts[2], "}")
-				// split into package name (before the '/') and activity (after)
-				if idx := strings.Index(focusPart, "/"); idx != -1 {
-					return focusPart[:idx], focusPart[idx+1:], nil
-				}
-			}
-			break
+	return parseForegroundComponent(string(output))
+}
+
+// parseForegroundComponent extracts the focused package and activity from
+// `dumpsys window displays` lines of the form:
+//
+//	mCurrentFocus=Window{... u0 com.package.name/com.package.name.MainActivity}
+//
+// A multi-display device prints one such line per display and the unfocused ones read
+// "mCurrentFocus=null", so a line that does not parse means "not this display" rather
+// than "no foreground app".
+func parseForegroundComponent(output string) (string, string, error) {
+	for _, line := range strings.Split(output, "\n") {
+		if !strings.Contains(line, "mCurrentFocus") {
+			continue
+		}
+		parts := strings.Fields(line)
+		if len(parts) < 3 {
+			continue
+		}
+		focusPart := strings.TrimSuffix(parts[2], "}")
+		// split into package name (before the '/') and activity (after)
+		if idx := strings.Index(focusPart, "/"); idx != -1 {
+			return focusPart[:idx], focusPart[idx+1:], nil
 		}
 	}
 

devices/android_foreground_test.go

@@ -0,0 +1,56 @@
+package devices
+
+import "testing"
+
+func Test_parseForegroundComponent(t *testing.T) { //nolint:funlen
+	tests := []struct {
+		name         string
+		input        string
+		wantPackage  string
+		wantActivity string
+		wantErr      bool
+	}{
+		{
+			name:         "single display",
+			input:        "  mCurrentFocus=Window{9c8e10c u0 com.example.app/com.example.app.MainActivity}",
+			wantPackage:  "com.example.app",
+			wantActivity: "com.example.app.MainActivity",
+		},
+		{
+			name: "multi display with a null before the focused one",
+			input: "  mCurrentFocus=null\n" +
+				"  mCurrentFocus=Window{d0ebdc2 u0 com.example.app/com.example.app.MainActivity}",
+			wantPackage:  "com.example.app",
+			wantActivity: "com.example.app.MainActivity",
+		},
+		{
+			name:    "every display unfocused",
+			input:   "  mCurrentFocus=null\n  mCurrentFocus=null",
+			wantErr: true,
+		},
+		{
+			name:    "no mCurrentFocus line at all",
+			input:   "Display: mDisplayId=0\n  mBaseDisplayWidth=1080",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			pkg, activity, err := parseForegroundComponent(tt.input)
+			if tt.wantErr {
+				if err == nil {
+					t.Fatalf("parseForegroundComponent() expected an error, got %q/%q", pkg, activity)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("parseForegroundComponent() error = %v", err)
+			}
+			if pkg != tt.wantPackage || activity != tt.wantActivity {
+				t.Errorf("parseForegroundComponent() = %q/%q, want %q/%q",
+					pkg, activity, tt.wantPackage, tt.wantActivity)
+			}
+		})
+	}
+}