Guides

How to Make an Android PDF Viewer in Java

This section will help you to quickly get started with ComPDF SDK to make an Android app in Java with step-by-step instructions. Through the following steps, you will get a simple application that can display the contents of a specified PDF file.

Create a New Project

Use Android Studio to create a Phone & Tablet project. Here we create a No Activity project.

Add the ComPDF SDK Package

The first step we need to take is to import the ComPDF SDK. You can integrate it in two ways: using Integrate With Gradle or Integrate Manually.

Integrate With Gradle

Open the settings.gradle file located in your project's root directory and add the mavenCentral repository:

diff

dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
+       mavenCentral()
    }
}

Open the build.gradle file in the application module directory:

Edit it and add the complete ComPDF SDK dependency:

groovy

dependencies {
  implementation 'com.compdf:compdfkit:3.0.1'
  implementation 'com.compdf:compdfkit-ui:3.0.1'
}

Apply for read and write permissions in AndroidManifest.xml:

xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Note: On your apps that target Android 6.0 or higher, make sure to check for and request read and write permissions to external storage at runtime.

If you use an online license, please add network access permissions in AndroidManifest.xml:

xml

<uses-permission android:name="android.permission.INTERNET"/>

Integrate Manually

Copy "ComPDFKit.aar" and "ComPDFKit-UI.aar" to the "libs" directory of the app.

Add the following code into the app dictionary’s "build.gradle" file:

groovy

...
dependencies {
    /*ComPDF SDK*/
    implementation(fileTree('libs'))
    ...
}
...

Add ComPDF SDK for Android as a dependency to the project. Inside the app dictionary’s "build.gradle", add "ComPDFKit.aar", "ComPDFKit-UI.aar", and the related support libraries to the dependencies. For simplicity, update the dependencies as follows:

groovy

dependencies {
    ...
    //glide
    implementation 'com.github.bumptech.glide:glide:4.12.0'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.12.0'

    implementation 'androidx.documentfile:documentfile:1.0.1'
}

Apply for read and write permissions in AndroidManifest.xml:

xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Note: On your apps that target Android 6.0 or higher, make sure to check for and request read and write permissions to external storage at runtime.

If you use an online license, please add network access permissions in AndroidManifest.xml:

xml

<uses-permission android:name="android.permission.INTERNET"/>

Apply the License Key

For detailed steps, please refer to Apply the License Key.

Add Proguard Rules

In the proguard-rules.pro file, please add the obfuscation configuration information for compdfkit as follows:

properties

-keep class com.compdfkit.ui.** {*;}
-keep class com.compdfkit.core.** {*;}

Display a PDF Document

Copy a PDF document into the assets directory of your Android project. For example, import the file "Quick Start Guide.pdf" to the path src/main/assets.

Create a new Empty Activity under your package, and set the activity name to MainActivity.

Android Studio will automatically generate a source file called "MainActivity.java" and a layout file called "activity_main.xml".

The source file:

The layout file:

Create a CPDFReaderView in your "activity_main.xml" to display the contents of the PDF document:

xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <!-- Create a CPDFReaderView -->
    <com.compdfkit.ui.reader.CPDFReaderView
        android:id="@+id/readerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Get the CPDFReaderView from the layout or create a CPDFReaderView directly in the code in the corresponding MainActivity.java file:

Javakotlin

Java

// Your MainActivity.java file

package com.compdfkit.pdfviewer;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import com.compdfkit.ui.reader.CPDFReaderView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get CPDFReaderView from xml.
        CPDFReaderView readerView = findViewById(R.id.readerview);
        // Code to create CPDFReaderView.
        // CPDFDocument readerView = new CPDFReaderView(content);
    }
}

kotlin

// Your MainActivity.kt file
package com.compdfkit.pdfviewer

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle
import com.compdfkit.ui.reader.CPDFReaderView

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Get CPDFReaderView from xml.
        val readerView = findViewById<CPDFReaderView>(R.id.readerview)
        // Code to create CPDFReaderView.
        // CPDFDocument readerView = new CPDFReaderView(content);
    }
}

Open the document. This is a time-consuming process, so it needs to be executed in a sub-thread. After the document is opened successfully, the UI that renders the PDF is initiated:

Javakotlin

Java

// Your MainActivity.java file

... //imports

public class MainActivity extends AppCompatActivity {

    // Copy the PDF file from the assets folder to the cache folder.
    private void copyPdfFromAssetsToCache(String fileName) {
        try {
            InputStream inputStream = getAssets().open(fileName);
            File outputFile = new File(getCacheDir(), fileName);
            FileOutputStream outputStream = new FileOutputStream(outputFile);

            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }

            inputStream.close();
            outputStream.flush();
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        CPDFReaderView readerView = findViewById(R.id.readerview);
        // Code to create CPDFReaderView.
        // CPDFDocument readerView = new CPDFReaderView(content);

        //Create a document object.
        CPDFDocument document = new CPDFDocument(this);
  

        new Thread(() -> {
            String fileName = "Quick Start Guide.pdf";
            copyPdfFromAssetsToCache(fileName);

            File file = new File(getCacheDir(), fileName);
            String filePath = file.getAbsolutePath();

            //Open document.
            CPDFDocument.PDFDocumentError error = document.open(filePath);
            if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorPassword) {
                //The document is encrypted and requires a password to open.
                error = document.open(filePath, "password");
            }

            if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorSuccess) {
                //The document is opened successfully and data can be parsed and manipulated.
            } else {
                //The PDF file failed to open. You can refer to the API file for specific error
            }
        }).start();
    }
}

kotlin

// Your MainActivity.kt file

... //imports

class MainActivity : AppCompatActivity() {

  // Copy the PDF file from the assets folder to the cache folder.
  private fun copyPdfFromAssetsToCache(fileName: String) {
    try {
      val inputStream = assets.open(fileName)
      val outputFile = File(cacheDir, fileName)
      val outputStream = FileOutputStream(outputFile)

      val buffer = ByteArray(1024)
      var bytesRead: Int
      while (inputStream.read(buffer).also { bytesRead = it } != -1) {
        outputStream.write(buffer, 0, bytesRead)
      }
      inputStream.close()
      outputStream.flush()
      outputStream.close()
    } catch (e: IOException) {
      e.printStackTrace()
    }
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val readerView = findViewById<CPDFReaderView>(R.id.readerview)
    // Code to create CPDFReaderView.
    // CPDFDocument readerView = new CPDFReaderView(content);

    //Create a document object.
    val document = CPDFDocument(this)

    Thread {
      val fileName = "Quick Start Guide.pdf"
      copyPdfFromAssetsToCache(fileName)

      val file = File(cacheDir, fileName)
      val filePath = file.absolutePath

      //Open document.
      var error = document.open(filePath)
      if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorPassword) {
        //The document is encrypted and requires a password to open.
        error = document.open(filePath, "password")
      }
      if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorSuccess) {
        //The document is opened successfully and data can be parsed and manipulated.
      } else {
        //The PDF file failed to open. You can refer to the API file for specific error
      }
    }.start()
  }
}

Set the basic properties of CPDFReaderView :

Javakotlin

Java

// Your MainActivity.java file

... // imports

public class MainActivity extends AppCompatActivity {
    // Create a handler to run the code on the main thread.
    private Handler mainThreadHandler = new Handler(Looper.getMainLooper());
...
    if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorSuccess) {
        // The document is opened successfully and data can be parsed and manipulated.
        mainThreadHandler.post(() -> {
            // Set the document content for UI.
            readerView.setPDFDocument(document);
        });
    } else {
        // The PDF file failed to open. You can refer to the API file for specific error
    }
...
}

kotlin

// Your MainActivity.kt file

... // imports

public class MainActivity : AppCompatActivity() {
    // Create a handler to run the code on the main thread.
    private var mainThreadHandler =  Handler(Looper.getMainLooper());
    ...
    if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorSuccess) {
        // The document is opened successfully and data can be parsed and manipulated.
        mainThreadHandler.post {
            // Set the document content for UI.
            readerView.setPDFDocument(document);
        }
    } else {
        // The PDF file failed to open. You can refer to the API file for specific error
    }
    ...
}

Your code may resemble the following at this stage:

Javakotlin

Java

// Your MainActivity.java file

... // imports

public class MainActivity extends AppCompatActivity {
    // Create a handler to run the code on the main thread.
    private Handler mainThreadHandler = new Handler(Looper.getMainLooper());
    // Copy the PDF file from the assets folder to the cache folder.
    private void copyPdfFromAssetsToCache(String fileName) {
        try {
            InputStream inputStream = getAssets().open(fileName);
            File outputFile = new File(getCacheDir(), fileName);
            FileOutputStream outputStream = new FileOutputStream(outputFile);

            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }

            inputStream.close();
            outputStream.flush();
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        CPDFReaderView readerView = findViewById(R.id.readerview);

        //Create a document object.
        CPDFDocument document = new CPDFDocument(this);

        new Thread(() -> {
            String fileName = "Quick Start Guide.pdf";
            copyPdfFromAssetsToCache(fileName);

            File file = new File(getCacheDir(), fileName);
            String filePath = file.getAbsolutePath();

            //Open document.
            CPDFDocument.PDFDocumentError error = document.open(filePath);
            if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorPassword) {
                //The document is encrypted and requires a password to open.
                error = document.open(filePath, "password");
            }

            if (error == CPDFDocument.PDFDocumentError.PDFDocumentErrorSuccess) {
                //The document is opened successfully and data can be parsed and manipulated.
                mainThreadHandler.post(() -> {
                    //Set the document to the reader view.
                    readerView.setPDFDocument(document);
                });
            } else {
                //The PDF file failed to open. You can refer to the API file for specific error
            }
        }).start();
    }
}

kotlin

// Your MainActivity.kt file

... // imports

class MainActivity : AppCompatActivity() {
    // Create a handler to run the code on the main thread.
    private val mainThreadHandler = Handler(Looper.getMainLooper())

    // Copy the PDF file from the assets folder to the cache folder.
    private fun copyPdfFromAssetsToCache(fileName: String) {
        try {
            val inputStream = assets.open(fileName)
            val outputFile = File(cacheDir, fileName)
            val outputStream = FileOutputStream(outputFile)
            val buffer = ByteArray(1024)
            var bytesRead: Int
            while (inputStream.read(buffer).also { bytesRead = it } != -1) {
                outputStream.write(buffer, 0, bytesRead)
            }
            inputStream.close()
            outputStream.flush()
            outputStream.close()
        } catch (e: IOException) {
            e.printStackTrace()
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val readerView = findViewById<CPDFReaderView>(R.id.readerview)

        //Create a document object.
        val document = CPDFDocument(this)
        Thread {
            val fileName = "Quick Start Guide.pdf"
            copyPdfFromAssetsToCache(fileName)
            val file = File(cacheDir, fileName)
            val filePath = file.absolutePath

            //Open document.
            var error = document.open(filePath)
            if (error == PDFDocumentError.PDFDocumentErrorPassword) {
                //The document is encrypted and requires a password to open.
                error = document.open(filePath, "password")
            }
            if (error == PDFDocumentError.PDFDocumentErrorSuccess) {
                //The document is opened successfully and data can be parsed and manipulated.
                mainThreadHandler.post {
                    //Set the document to the reader view.
                    readerView.pdfDocument = document
                }
            } else {
                //The PDF file failed to open. You can refer to the API file for specific error
            }
        }.start()
    }
}

xml

<!-- Your activity_main.xml file -->
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.compdfkit.ui.reader.CPDFReaderView
        android:id="@+id/readerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Run the application.

Now, with the help of ComPDF, you can get a simple application to display a PDF file.

Troubleshooting

Unable to Open the PDF Files
The license we provide to you is tied to your application ID, so ensure that the license acquired matches your application ID.
Other Problems
If you meet some other problems when integrating our ComPDF SDK for Android, feel free to contact ComPDF team.

PDF Generation Template Editor

Overview and Integration

Basic Reading

Document Navigation

Text Interaction

Interaction Enhancements

Advanced Customization

Accessibility

How to Make an Android PDF Viewer in Java

Create a New Project

Add the ComPDF SDK Package

Integrate With Gradle

Integrate Manually

Apply the License Key

Add Proguard Rules

Display a PDF Document

Troubleshooting

How to Make an Android PDF Viewer in Java ​

Create a New Project ​

Add the ComPDF SDK Package ​

Integrate With Gradle ​

Integrate Manually ​

Apply the License Key ​

Add Proguard Rules ​

Display a PDF Document ​

Troubleshooting ​

How to Make an Android PDF Viewer in Java

Create a New Project

Add the ComPDF SDK Package

Integrate With Gradle

Integrate Manually

Apply the License Key

Add Proguard Rules

Display a PDF Document

Troubleshooting