C# 呼叫 Google Earth COM API 開發（四）：圖層讀取與顯示控制

實作從 Google Earth 讀取圖層資料庫，並在工具面板的 TreeView 中遞迴顯示，支援勾選控制圖層可見性。

核心程式碼

protected void ShowLayers() {
    Thread.Sleep(500);
    FeatureCollectionGE layers = GeApp.GetLayersDatabases();
    GEToolPad toolPad = GetToolPad();
    toolPad.ShowLayers(layers);
}

public void ShowLayers(FeatureCollectionGE layers) {
    if (this.InvokeRequired) {
        this.Invoke(new Action(() => InternalShowLayers(layers)));
    } else InternalShowLayers(layers);
}

protected void InternalShowLayers(FeatureCollectionGE layers) {
    tvLayers.Nodes.Clear();
    if (layers == null || layers.Count <= 0) return;
    foreach (FeatureGE layer in layers) {
        TreeNode node = new TreeNode(layer.Name) { Checked = layer.Visibility > 0, Tag = layer };
        ShowChildrenLayers(layer, node);
        node.Expand();
        tvLayers.Nodes.Add(node);
    }
}

protected void ShowChildrenLayers(FeatureGE layer, TreeNode node) {
    foreach (FeatureGE child in layer.GetChildren()) {
        TreeNode tn = new TreeNode(child.Name) { Checked = child.Visibility > 0, Tag = child };
        ShowChildrenLayers(child, tn);
        node.Nodes.Add(tn);
    }
}

使用 Invoke 確保跨執行緒 UI 更新安全。