> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/android/get-started/samples/logicalstructuretest.md).

# LogicalStructure

Sample Java, Kotlin code for using Apryse Android SDK to explore the logical structure and content of a tagged PDF file, then dumps the information to the console window. In tagged PDF files, StructTr

Sample Java, Kotlin code for using Apryse Android SDK to explore the logical structure and content of a tagged PDF file, then dumps the information to the console window. In tagged PDF files, StructTree acts as a central repository for information related to a PDF document's logical structure. The tree consists of StructElement-s and ContentItem-s which are leaf nodes of the structure tree.

Learn more about our full [PDF Data Extraction SDK Capabilities](https://apryse.com/capabilities/extraction).

To start your free trial, [get started with Android SDK](/android/get-started/get-started.md).

{% tabs %}
{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------
package com.pdftron.android.pdfnetsdksamples.samples

import com.pdftron.android.pdfnetsdksamples.OutputListener
import com.pdftron.android.pdfnetsdksamples.PDFNetSample
import com.pdftron.android.pdfnetsdksamples.R
import com.pdftron.android.pdfnetsdksamples.util.Utils
import com.pdftron.common.PDFNetException
import com.pdftron.pdf.PDFDoc
import com.pdftron.pdf.PageIterator
import com.pdftron.pdf.struct.ContentItem
import com.pdftron.pdf.struct.SElement
import com.pdftron.pdf.struct.STree
import com.pdftron.sdf.SDFDoc

class LogicalStructureTest : PDFNetSample() {
    override fun run(outputListener: OutputListener?) {
        super.run(outputListener)
        mOutputListener = outputListener
        mFileList.clear()
        printHeader(outputListener!!)
        try  // Extract logical structure from a PDF document
        {
            PDFDoc(Utils.getAssetTempFile(INPUT_PATH.toString() + "tagged.pdf")!!.getAbsolutePath()).use { doc ->
                doc.initSecurityHandler()
                mOutputListener!!.println("____________________________________________________________")
                mOutputListener!!.println("Sample 1 - Traverse logical structure tree...")
                run({
                    val tree: STree = doc.getStructTree()
                    if (tree.isValid()) {
                        mOutputListener!!.println("Document has a StructTree root.")
                        for (i in 0 until tree.getNumKids()) {
                            // Recursively get structure  info for all all child elements.
                            ProcessStructElement(tree.getKid(i), 0)
                        }
                    } else {
                        mOutputListener!!.println("This document does not contain any logical structure.")
                    }
                })
                mOutputListener!!.println("\nDone 1.")
                mOutputListener!!.println("____________________________________________________________")
                mOutputListener!!.println("Sample 2 - Get parent logical structure elements from")
                mOutputListener!!.println("layout elements.")
                run({
                    val reader: com.pdftron.pdf.ElementReader = com.pdftron.pdf.ElementReader()
                    val itr: PageIterator = doc.getPageIterator()
                    while (itr.hasNext()) {
                        reader.begin(itr.next())
                        ProcessElements(reader)
                        reader.end()
                    }
                })
                mOutputListener!!.println("\nDone 2.")
                mOutputListener!!.println("____________________________________________________________")
                mOutputListener!!.println("Sample 3 - 'XML style' extraction of PDF logical structure and page content.")
                run({

                    //A map which maps page numbers(as Integers)
                    //to page Maps(which map from struct mcid(as Integers) to
                    //text Strings)
                    val mcid_doc_map: MutableMap<Int, Map<Int, String>> = java.util.TreeMap<Int, Map<Int, String>>()
                    val reader: com.pdftron.pdf.ElementReader = com.pdftron.pdf.ElementReader()
                    val itr: PageIterator = doc.getPageIterator()
                    while (itr.hasNext()) {
                        val current: com.pdftron.pdf.Page? = itr.next()
                        reader.begin(current)
                        val page_mcid_map: MutableMap<Int, String> = java.util.TreeMap<Int, String>()
                        mcid_doc_map.put(current!!.getIndex(), page_mcid_map)
                        ProcessElements2(reader, page_mcid_map)
                        reader.end()
                    }
                    val tree: STree = doc.getStructTree()
                    if (tree.isValid()) {
                        for (i in 0 until tree.getNumKids()) {
                            ProcessStructElement2(tree.getKid(i), mcid_doc_map, 0)
                        }
                    }
                })
                mOutputListener!!.println("\nDone 3.")
                doc.save(Utils.createExternalFile("LogicalStructure.pdf", mFileList).getAbsolutePath(), SDFDoc.SaveMode.LINEARIZED, null)
            }
        } catch (e: java.lang.Exception) {
            mOutputListener!!.printError(e.getStackTrace())
        }
        for (file in mFileList) {
            addToFileList(file)
        }
        printFooter(outputListener)
    }

    companion object {
        private var mOutputListener: OutputListener? = null
        private val mFileList: java.util.ArrayList<String> = java.util.ArrayList<String>()
        fun PrintIndent(indent: Int) {
            mOutputListener!!.println()
            for (i in 0 until indent) mOutputListener!!.print("  ")
        }

        // Used in code snippet 1.
        @Throws(PDFNetException::class)
        fun ProcessStructElement(element: SElement, indent: Int) {
            var indent = indent
            if (!element.isValid()) {
                return
            }

            // Print out the type and title info, if any.
            PrintIndent(indent++)
            mOutputListener!!.print("Type: " + element.getType())
            if (element.hasTitle()) {
                mOutputListener!!.print(". Title: " + element.getTitle())
            }
            val num: Int = element.getNumKids()
            for (i in 0 until num) {
                // Check is the kid is a leaf node (i.e. it is a ContentItem).
                if (element.isContentItem(i)) {
                    val cont: ContentItem = element.getAsContentItem(i)
                    val type: Int = cont.getType()
                    val page: com.pdftron.pdf.Page = cont.getPage()
                    PrintIndent(indent)
                    mOutputListener!!.print("Content Item. Part of page #" + page.getIndex())
                    PrintIndent(indent)
                    when (type) {
                        ContentItem.e_MCID, ContentItem.e_MCR -> mOutputListener!!.print("MCID: " + cont.getMCID())
                        ContentItem.e_OBJR -> {
                            mOutputListener!!.print("OBJR ")
                            val ref_obj: com.pdftron.sdf.Obj = cont.getRefObj()
                            if (ref_obj != null) mOutputListener!!.print("- Referenced Object#: " + ref_obj.getObjNum())
                        }
                        else -> {
                        }
                    }
                } else {  // the kid is another StructElement node.
                    ProcessStructElement(element.getAsStructElem(i), indent)
                }
            }
        }

        // Used in code snippet 2.
        @Throws(PDFNetException::class)
        fun ProcessElements(reader: com.pdftron.pdf.ElementReader) {
            var element: com.pdftron.pdf.Element?
            // Read page contents
            while (true) {
                element = reader.next()
                if (element == null) {
                    break
                }
                // In this sample we process only paths & text, but the code can be
                // extended to handle any element type.
                val type: Int = element.getType()
                if (type == com.pdftron.pdf.Element.e_path || type == com.pdftron.pdf.Element.e_text || type == com.pdftron.pdf.Element.e_path) {
                    when (type) {
                        com.pdftron.pdf.Element.e_path -> mOutputListener!!.print("\nPATH: ")
                        com.pdftron.pdf.Element.e_text -> mOutputListener!!.print("""
    
    TEXT: ${element.getTextString()}
    
    """.trimIndent())
                        com.pdftron.pdf.Element.e_form -> mOutputListener!!.print("\nFORM XObject: ")
                    }

                    // Check if the element is associated with any structural element.
                    // Content items are leaf nodes of the structure tree.
                    val struct_parent: SElement = element.getParentStructElement()
                    if (struct_parent.isValid()) {
                        // Print out the parent structural element's type, title, and object number.
                        mOutputListener!!.print(" Type: " + struct_parent.getType()
                                + ", MCID: " + element.getStructMCID())
                        if (struct_parent.hasTitle()) {
                            mOutputListener!!.print(". Title: " + struct_parent.getTitle())
                        }
                        mOutputListener!!.print(", Obj#: " + struct_parent.getSDFObj().getObjNum())
                    }
                }
            }
        }

        // Used in code snippet 3.
        //typedef map<int, string> MCIDPageMap;
        //typedef map<int, MCIDPageMap> MCIDDocMap;
        // Used in code snippet 3.
        @Throws(PDFNetException::class)
        fun ProcessElements2(reader: com.pdftron.pdf.ElementReader, mcid_page_map: MutableMap<Int, String>) {
            var element: com.pdftron.pdf.Element?
            // Read page contents
            while (true) {
                element = reader.next()
                if (element == null) {
                    break
                }
                // In this sample we process only text, but the code can be extended
                // to handle paths, images, or any other Element type.
                val mcid: Int = element.getStructMCID()
                if (mcid >= 0 && element.getType() == com.pdftron.pdf.Element.e_text) {
                    val `val`: String = element.getTextString()
                    if (mcid_page_map.containsKey(mcid)) mcid_page_map.put(mcid, mcid_page_map[mcid] + `val`) else mcid_page_map.put(mcid, `val`)
                }
            }
        }

        // Used in code snippet 3.
        @Throws(PDFNetException::class)
        fun ProcessStructElement2(element: SElement, mcid_doc_map: Map<Int, Map<Int, String>>, indent: Int) {
            if (!element.isValid()) {
                return
            }

            // Print out the type and title info, if any.
            PrintIndent(indent)
            mOutputListener!!.print("<" + element.getType())
            if (element.hasTitle()) {
                mOutputListener!!.print(" title=\"" + element.getTitle() + "\"")
            }
            mOutputListener!!.print(">")
            val num: Int = element.getNumKids()
            for (i in 0 until num) {
                if (element.isContentItem(i)) {
                    val cont: ContentItem = element.getAsContentItem(i)
                    if (cont.getType() == ContentItem.e_MCID) {
                        val page_num: Int = cont.getPage().getIndex()
                        if (mcid_doc_map.containsKey(page_num)) {
                            val mcid_page_map = mcid_doc_map[page_num]!!
                            val mcid_key: Int = cont.getMCID()
                            if (mcid_page_map.containsKey(mcid_key)) {
                                mOutputListener!!.print(mcid_page_map[mcid_key])
                            }
                        }
                    }
                } else {  // the kid is another StructElement node.
                    ProcessStructElement2(element.getAsStructElem(i), mcid_doc_map, indent + 1)
                }
            }
            PrintIndent(indent)
            mOutputListener!!.print("</" + element.getType() + ">")
        }
        /**
         * @param args
         */
    }

    init {
        setTitle(R.string.sample_logicalstructure_title)
        setDescription(R.string.sample_logicalstructure_description)
    }
}
```

{% endcode %}
{% endtab %}

{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

package com.pdftron.android.pdfnetsdksamples.samples;

import com.pdftron.android.pdfnetsdksamples.OutputListener;
import com.pdftron.android.pdfnetsdksamples.PDFNetSample;
import com.pdftron.android.pdfnetsdksamples.R;
import com.pdftron.android.pdfnetsdksamples.util.Utils;
import com.pdftron.common.PDFNetException;
import com.pdftron.pdf.Element;
import com.pdftron.pdf.ElementReader;
import com.pdftron.pdf.PDFDoc;
import com.pdftron.pdf.Page;
import com.pdftron.pdf.PageIterator;
import com.pdftron.pdf.struct.ContentItem;
import com.pdftron.pdf.struct.SElement;
import com.pdftron.pdf.struct.STree;
import com.pdftron.sdf.Obj;
import com.pdftron.sdf.SDFDoc;

import java.util.ArrayList;
import java.util.Map;
import java.util.TreeMap;

public class LogicalStructureTest extends PDFNetSample {

	private static OutputListener mOutputListener;

	private static ArrayList<String> mFileList = new ArrayList<>();

    public LogicalStructureTest() {
        setTitle(R.string.sample_logicalstructure_title);
        setDescription(R.string.sample_logicalstructure_description);
    }

	@Override
	public void run(OutputListener outputListener) {
		super.run(outputListener);
		mOutputListener = outputListener;
		mFileList.clear();
		printHeader(outputListener);

        try (PDFDoc doc = new PDFDoc((Utils.getAssetTempFile(INPUT_PATH + "tagged.pdf").getAbsolutePath())))    // Extract logical structure from a PDF document
        {
            doc.initSecurityHandler();

            mOutputListener.println("____________________________________________________________");
            mOutputListener.println("Sample 1 - Traverse logical structure tree...");
            {
                STree tree = doc.getStructTree();
                if (tree.isValid()) {
                    mOutputListener.println("Document has a StructTree root.");

                    for (int i = 0; i < tree.getNumKids(); ++i) {
                        // Recursively get structure  info for all all child elements.
                        ProcessStructElement(tree.getKid(i), 0);
                    }
                } else {
                    mOutputListener.println("This document does not contain any logical structure.");
                }
            }
            mOutputListener.println("\nDone 1.");

            mOutputListener.println("____________________________________________________________");
            mOutputListener.println("Sample 2 - Get parent logical structure elements from");
            mOutputListener.println("layout elements.");
            {
                ElementReader reader = new ElementReader();
                for (PageIterator itr = doc.getPageIterator(); itr.hasNext(); ) {
                    reader.begin(itr.next());
                    ProcessElements(reader);
                    reader.end();
                }
            }
            mOutputListener.println("\nDone 2.");

            mOutputListener.println("____________________________________________________________");
            mOutputListener.println("Sample 3 - 'XML style' extraction of PDF logical structure and page content.");
            {
                //A map which maps page numbers(as Integers)
                //to page Maps(which map from struct mcid(as Integers) to
                //text Strings)
                Map<Integer, Map<Integer, String>> mcid_doc_map = new TreeMap<Integer, Map<Integer, String>>();
                ElementReader reader = new ElementReader();
                for (PageIterator itr = doc.getPageIterator(); itr.hasNext(); ) {
                    Page current = itr.next();
                    reader.begin(current);
                    Map<Integer, String> page_mcid_map = new TreeMap<Integer, String>();
                    mcid_doc_map.put(new Integer(current.getIndex()), page_mcid_map);
                    ProcessElements2(reader, page_mcid_map);
                    reader.end();
                }

                STree tree = doc.getStructTree();
                if (tree.isValid()) {
                    for (int i = 0; i < tree.getNumKids(); ++i) {
                        ProcessStructElement2(tree.getKid(i), mcid_doc_map, 0);
                    }
                }
            }
            mOutputListener.println("\nDone 3.");
            doc.save((Utils.createExternalFile("LogicalStructure.pdf", mFileList).getAbsolutePath()), SDFDoc.SaveMode.LINEARIZED, null);
        } catch (Exception e) {
            mOutputListener.printError(e.getStackTrace());
        }

		for (String file : mFileList) {
			addToFileList(file);
		}
		printFooter(outputListener);
	}
    static void PrintIndent(int indent) {
        mOutputListener.println();
        for (int i = 0; i < indent; ++i) mOutputListener.print("  ");
    }

    // Used in code snippet 1.
    static void ProcessStructElement(SElement element, int indent) throws PDFNetException {
        if (!element.isValid()) {
            return;
        }

        // Print out the type and title info, if any.
        PrintIndent(indent++);
        mOutputListener.print("Type: " + element.getType());
        if (element.hasTitle()) {
            mOutputListener.print(". Title: " + element.getTitle());
        }

        int num = element.getNumKids();
        for (int i = 0; i < num; ++i) {
            // Check is the kid is a leaf node (i.e. it is a ContentItem).
            if (element.isContentItem(i)) {
                ContentItem cont = element.getAsContentItem(i);
                int type = cont.getType();

                Page page = cont.getPage();

                PrintIndent(indent);
                mOutputListener.print("Content Item. Part of page #" + page.getIndex());

                PrintIndent(indent);
                switch (type) {
                    case ContentItem.e_MCID:
                    case ContentItem.e_MCR:
                        mOutputListener.print("MCID: " + cont.getMCID());
                        break;
                    case ContentItem.e_OBJR: {
                        mOutputListener.print("OBJR ");
                        Obj ref_obj = cont.getRefObj();
                        if (ref_obj != null)
                            mOutputListener.print("- Referenced Object#: " + ref_obj.getObjNum());
                    }
                    break;
                    default:
                        break;
                }
            } else {  // the kid is another StructElement node.
                ProcessStructElement(element.getAsStructElem(i), indent);
            }
        }
    }

    // Used in code snippet 2.
    static void ProcessElements(ElementReader reader) throws PDFNetException {
        Element element;
        while ((element = reader.next()) != null)    // Read page contents
        {
            // In this sample we process only paths & text, but the code can be
            // extended to handle any element type.
            int type = element.getType();
            if (type == Element.e_path || type == Element.e_text || type == Element.e_path) {
                switch (type) {
                    case Element.e_path:                // Process path ...
                        mOutputListener.print("\nPATH: ");
                        break;
                    case Element.e_text:                // Process text ...
                        mOutputListener.print("\nTEXT: " + element.getTextString() + "\n");
                        break;
                    case Element.e_form:                // Process form XObjects
                        mOutputListener.print("\nFORM XObject: ");
                        //reader.FormBegin();
                        //ProcessElements(reader);
                        //reader.End();
                        break;
                }

                // Check if the element is associated with any structural element.
                // Content items are leaf nodes of the structure tree.
                SElement struct_parent = element.getParentStructElement();
                if (struct_parent.isValid()) {
                    // Print out the parent structural element's type, title, and object number.
                    mOutputListener.print(" Type: " + struct_parent.getType()
                            + ", MCID: " + element.getStructMCID());
                    if (struct_parent.hasTitle()) {
                        mOutputListener.print(". Title: " + struct_parent.getTitle());
                    }
                    mOutputListener.print(", Obj#: " + struct_parent.getSDFObj().getObjNum());
                }
            }
        }
    }

    // Used in code snippet 3.
    //typedef map<int, string> MCIDPageMap;
    //typedef map<int, MCIDPageMap> MCIDDocMap;

    // Used in code snippet 3.
    static void ProcessElements2(ElementReader reader, Map<Integer, String> mcid_page_map) throws PDFNetException {
        Element element;
        while ((element = reader.next()) != null) // Read page contents
        {
            // In this sample we process only text, but the code can be extended
            // to handle paths, images, or any other Element type.
            int mcid = element.getStructMCID();
            Integer key_mcid = new Integer(mcid);
            if (mcid >= 0 && element.getType() == Element.e_text) {
                String val = element.getTextString();
                if (mcid_page_map.containsKey(key_mcid))
                    mcid_page_map.put(key_mcid, ((String) (mcid_page_map.get(key_mcid)) + val));
                else mcid_page_map.put(key_mcid, val);
            }
        }
    }

    // Used in code snippet 3.
    static void ProcessStructElement2(SElement element, Map<Integer, Map<Integer, String>> mcid_doc_map, int indent) throws PDFNetException {
        if (!element.isValid()) {
            return;
        }

        // Print out the type and title info, if any.
        PrintIndent(indent);
        mOutputListener.print("<" + element.getType());
        if (element.hasTitle()) {
            mOutputListener.print(" title=\"" + element.getTitle() + "\"");
        }
        mOutputListener.print(">");

        int num = element.getNumKids();
        for (int i = 0; i < num; ++i) {
            if (element.isContentItem(i)) {
                ContentItem cont = element.getAsContentItem(i);
                if (cont.getType() == ContentItem.e_MCID) {
                    int page_num = cont.getPage().getIndex();
                    Integer page_num_key = new Integer(page_num);
                    if (mcid_doc_map.containsKey(page_num_key)) {
                        Map<Integer, String> mcid_page_map = mcid_doc_map.get(page_num_key);
                        Integer mcid_key = new Integer(cont.getMCID());
                        if (mcid_page_map.containsKey(mcid_key)) {
                            mOutputListener.print(mcid_page_map.get(mcid_key));
                        }
                    }
                }
            } else {  // the kid is another StructElement node.
                ProcessStructElement2(element.getAsStructElem(i), mcid_doc_map, indent + 1);
            }
        }

        PrintIndent(indent);
        mOutputListener.print("</" + element.getType() + ">");
    }

    /**
     * @param args
     */

}
```

{% endcode %}
{% endtab %}
{% endtabs %}


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