Null Context when Generating PDF

Question

I’m starting my studies on Android programming and I’m having a hard time understanding how to fix the error presented when debugging the app to generate PDF.

E/Androidruntime: FATAL EXCEPTION: main Process: br.com.Belov.novomenu, PID: 9371 java.lang.Illegalstateexception: Could not execute method for android:onClick at android.support.v7.app.Appcompatviewinflater$Declaredonclicklistener.onClick(Appcompatviewinflater.java:293)

This error is shown when going through the method.

public void viewPDF(){
    Intent intent = new Intent(context, ViewPDFActivity.class);
    intent.putExtra("Path",pdfFile.getAbsolutePath());
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    context.startActivity(intent);
}

Specifically when trying to cross the line

Intent intent = new Intent(context, ViewPDFActivity.class);

of the Templatepdf class (below).

public class TemplatePDF {
private Context context;
private File pdfFile;
private Document document;
private PdfWriter pdfWriter;
private Paragraph paragraph;
private Font fTitle=new Font(Font.FontFamily.TIMES_ROMAN, 20, Font.BOLD);
private Font fSubTitle=new Font(Font.FontFamily.TIMES_ROMAN, 18, Font.BOLD);
private Font fText=new Font(Font.FontFamily.TIMES_ROMAN, 12, Font.BOLD);
private Font fHighText=new Font(Font.FontFamily.TIMES_ROMAN, 15, Font.BOLD, BaseColor.RED);

public TemplatePDF(Context applicationContext) {
    this.context=context;
}

public void openDocument() {
    createFile();
    try {
        document = new Document(PageSize.A4);
        pdfWriter = PdfWriter.getInstance(document, new FileOutputStream(pdfFile));
        document.open();
    } catch (Exception e) {
        Log.e("openDocument", e.toString());
    }
}

private void createFile(){
    File folder=new File(Environment.getExternalStorageDirectory().toString(),"PDF");
    if (!folder.exists())
        folder.mkdir();
    pdfFile=new File(folder, "templatepdf.pdf");

}

public void closeDocument(){
    document.close();
}

public void addMetaData(String title, String subject, String author){
    document.addAuthor(author);
    document.addTitle(title);
    document.addSubject(subject);
}

public void addTitles(String title, String subTitle, String date){
    try {
    paragraph=new Paragraph();
    addChildP(new Paragraph(title,fTitle));
    addChildP(new Paragraph(subTitle,fSubTitle));
    addChildP(new Paragraph("Gerado"+date,fHighText));
    paragraph.setSpacingAfter(30);
    document.add(paragraph);
    } catch (Exception e) {
        Log.e("addTitle", e.toString());
    }

}
private void addChildP(Paragraph childParagraph) {
    childParagraph.setAlignment(Element.ALIGN_CENTER);
    paragraph.add(childParagraph);
}

public void addParagraph(String text){
    try {
    paragraph=new Paragraph(text, fText);
    paragraph.setSpacingAfter(5);
    paragraph.setSpacingBefore(5);
    document.add(paragraph);
    } catch (Exception e) {
        Log.e("addParagraph", e.toString());
    }
}

public void createTable(String[]header, ArrayList<String[]>clients){
    try {
    paragraph=new Paragraph();
    paragraph.setFont(fText);
    PdfPTable pdfPTable=new PdfPTable(header.length);
    pdfPTable.setWidthPercentage(100);
    PdfPCell pdfPCell;
    int indexC=0;
    while (indexC<header.length){
        pdfPCell=new PdfPCell(new Phrase(header[indexC++],fSubTitle));
        pdfPCell.setHorizontalAlignment(Element.ALIGN_CENTER);
        pdfPCell.setBackgroundColor(BaseColor.GREEN);
        pdfPTable.addCell(pdfPCell);
    }
    for (int indexR=0;indexR<clients.size();indexR++){
        String[]row=clients.get(indexR);
        for ( indexC=0;indexC<header.length;indexC++){
            pdfPCell=new PdfPCell(new Phrase(row[indexC]));
            pdfPCell.setHorizontalAlignment(Element.ALIGN_CENTER);
            pdfPCell.setFixedHeight(40);
            pdfPTable.addCell(pdfPCell);
        }
    }
    paragraph.add(pdfPTable);
    document.add(paragraph);
    } catch (Exception e) {
        Log.e("createTable", e.toString());
    }
}

public void viewPDF(){
    Intent intent = new Intent(context, ViewPDFActivity.class);
    intent.putExtra("Path",pdfFile.getAbsolutePath());
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    context.startActivity(intent);
}

which you should call Activity

public class ViewPDFActivity extends AppCompatActivity {

private PDFView pdfView;
private File file;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_pdf);
    pdfView=(PDFView)findViewById(R.id.pdfView);

    Bundle bundle = getIntent().getExtras();
    if(bundle!=null){
        file= new File(bundle.getString("Path",""));
    }

    pdfView.fromFile(file)
            .enableSwipe(true)
            .swipeHorizontal(false)
            .enableDoubletap(true)
            .enableAntialiasing(true)
            .load();
}

Follow the Debugger information when arriving on the line.

Here is the main activity and its respective XML

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import java.util.ArrayList;


public class Sup_Print_HTML extends AppCompatActivity {

    private String[]header={"Id", "Nome","Apelido"};
    private String shortText="Olá";
    private String longText="Testando impressão em PDF, teste";
    private TemplatePDF templatePDF;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sup_print_act_html);
        templatePDF = new TemplatePDF(getApplicationContext());
        templatePDF.openDocument();
        templatePDF.addMetaData("Clientes", "Vendas", "Felipi");
        templatePDF.addTitles("teste de PDF", "Clientes", "02/01/2018" );
        templatePDF.addParagraph(shortText);
        templatePDF.addParagraph(longText);
        templatePDF.createTable(header,getClients());
        templatePDF.closeDocument();

    }
    public void pdfView (View view){
        templatePDF.viewPDF();

    }

    private ArrayList<String[]>getClients(){
        ArrayList<String[]>rows=new ArrayList<>();

        rows.add(new String[]{"1", "Pedro", "Novo"});
        rows.add(new String[]{"2", "Alexandre", "Neves"});
        rows.add(new String[]{"3", "Amanda", "Alencar"});
        rows.add(new String[]{"4", "Polyana", "Santos"});
        rows.add(new String[]{"5", "Gero", "test"});
        return rows;

    }

XML

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="br.com.belov.novomenu.Sup_Print_HTML">

    <Button
        android:id="@+id/btn_criarPDF"
        android:layout_marginTop="30dp"
        android:clickable="true"
        android:onClick="pdfView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:text="Criar PDF" />

</LinearLayout>

Answer 1

After some researches I managed to find the problem.

replaces the line

public TemplatePDF(Context applicationContext) {
this.context=context;
}

by the line

 public TemplatePDF(Context context) {
    this.context=context;
}

That’s why it was presenting null context.