Layers (Optional Content)

PDF layers (optional content groups, OCG) organize page content so users can control visibility, printing, and export per layer. Foxit PDF SDK for Android provides layer APIs through the Core SDK to read the layer tree, manage nodes, and control graphics objects in layers.

Core Classes

Class	Description
LayerTree	Layer tree from PDFDoc; root node and global state
LayerNode	Layer node; children, name, visibility, usage
LayerPrintData	Print usage
LayerZoomData	Zoom usage

Check Whether Document Has Layers

if (doc.hasLayer()) {
    LayerTree layerTree = new LayerTree(doc);
    // ...
}

Get Layer Tree

LayerTree layerTree = new LayerTree(doc);

LayerNode root = layerTree.getRootNode();

int count = root.getChildrenCount();
for (int i = 0; i < count; i++) {
    LayerNode child = root.getChild(i);
    String name = child.getName();
    boolean hasLayer = child.hasLayer();
}

Set Global Base State

layerTree.setBaseState(LayerTree.e_StateON);

Constant	Description
e_StateON	All layers visible by default
e_StateOFF	All layers hidden by default
e_StateUnchanged	Unchanged
e_StateUndefined	Undefined

Manage Layer Nodes

Add Child Node

LayerNode newNode = parentNode.addChild(0, "新图层", true);

addChild() parameters:

Parameter	Type	Description
index	int	Insert index
name	String	Layer name
has_Layer	boolean	true = layer; false = group only

Remove and Move Nodes

parentNode.removeChild(0);
node.moveTo(newParent, 2);

Set Layer Properties

node.setName("Background Layer");
node.setDefaultVisible(true);

Control Layer Usage

View and Export

node.setViewUsage(LayerTree.e_StateON);
node.setExportUsage(LayerTree.e_StateOFF);

Print Usage

LayerPrintData printData = node.getPrintUsage();
node.setPrintUsage(printData);

Zoom Usage

LayerZoomData zoomData = node.getZoomUsage();
node.setZoomUsage(zoomData);

Remove Usage

node.removeUsage(usageType);

Layer Queries

boolean isLayer = node.hasLayer();
boolean locked = node.isLocked();
boolean inPage = node.isInPage(page);
boolean hasIntent = node.hasIntent("View");

Graphics Objects in Layers

GraphicsObjectArray objects = node.getGraphicsObjects(page);
node.addGraphicsObject(page, graphicsObject);
node.removeGraphicsObject(graphicsObject);

Example: Traverse Layer Tree

PDFDoc doc = new PDFDoc(filePath);
doc.load(null);

if (!doc.hasLayer()) return;

LayerTree layerTree = new LayerTree(doc);
LayerNode root = layerTree.getRootNode();
printLayerNode(root, 0);

private void printLayerNode(LayerNode node, int depth) throws PDFException {
    String indent = new String(new char[depth * 2]).replace('\0', ' ');
    String name = node.getName();
    boolean isLayer = node.hasLayer();

    Log.d("Layer", indent + name + (isLayer ? " [Layer]" : " [Group]"));

    int count = node.getChildrenCount();
    for (int i = 0; i < count; i++) {
        printLayerNode(node.getChild(i), depth + 1);
    }
}

API Reference

See the API Reference for full LayerTree and LayerNode documentation.