Question

我是android的新用户，我尝试使用itext jar文件查看pdf文件。我的代码是：

package com.example.pdfone;

public class MainActivity {

    public static final String RESULT = "Workspace/one.pdf";

    public static void main(String[] args) throws DocumentException, IOException {
        Document document = new Document();
        PdfWriter.getInstance(document, new FileOutputStream(RESULT));
        document.open();
        document.add(new Paragraph("Hello World!"));
        document.close();
    }

}

但是当我运行这个程序时，它在控制台

中出现Error: Could not find or load main class com.example.pdfone.MainActivity错误

我该怎么办？请帮我。提前谢谢

Answer 1

您需要先学习Android。

您的类需要扩展Activity类。

iText只能创建pdf文件，无法查看。阅读是可能的。在Android中使用Adobe Acrobat或任何其他PDF工具进行查看。

示例解决方案如下所示，适用于Android中的PDF读写

100％工作代码截图如下，

enter image description here

activity_main.xml中

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_gravity="center"
    tools:context=".MainActivity" >
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textAlignment="center"
        android:text="Android Read/Write File" />

    <EditText
        android:id="@+id/fname"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="File Name"
        android:text="sample_pdf_file" />

    <EditText
        android:id="@+id/ftext"
        android:layout_width="fill_parent"
        android:layout_height="100px"
        android:hint="File Text"
        android:text="Hello World" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btnwrite"
        android:text="Write File" />

    <EditText
        android:id="@+id/fnameread"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="File Name"
        android:text="sample_pdf_file" />

       <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btnread"
        android:text="Read File" />
       <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/filecon" />
</LinearLayout>

FileOperations.java

package com.example.readwrite;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.StringWriter;

import android.util.Log;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.pdf.parser.PdfReaderContentParser;
import com.itextpdf.text.pdf.parser.SimpleTextExtractionStrategy;
import com.itextpdf.text.pdf.parser.TextExtractionStrategy;

public class FileOperations {
    public FileOperations() {
    }

    public Boolean write(String fname, String fcontent) {
        try {
            String fpath = "/sdcard/" + fname + ".pdf";
            File file = new File(fpath);
            // If file does not exists, then create it
            if (!file.exists()) {
                file.createNewFile();
            }

            // step 1
            Document document = new Document();
            // step 2
            PdfWriter.getInstance(document,
                    new FileOutputStream(file.getAbsoluteFile()));
            // step 3
            document.open();
            // step 4
            document.add(new Paragraph("Hello World!"));
            document.add(new Paragraph("Hello World2!"));
            // step 5
            document.close();

            Log.d("Suceess", "Sucess");
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        } catch (DocumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        }
    }

    public String read(String fname) {
        BufferedReader br = null;
        String response = null;
        try {
            StringBuffer output = new StringBuffer();
            String fpath = "/sdcard/" + fname + ".pdf";

            PdfReader reader = new PdfReader(new FileInputStream(fpath));
            PdfReaderContentParser parser = new PdfReaderContentParser(reader);

            StringWriter strW = new StringWriter();

            TextExtractionStrategy strategy;
            for (int i = 1; i <= reader.getNumberOfPages(); i++) {
                strategy = parser.processContent(i,
                        new SimpleTextExtractionStrategy());

                strW.write(strategy.getResultantText());

            }

            response = strW.toString();

        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
        return response;
    }
}

MainActivity.java

package com.example.readwrite;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
    EditText fname, fcontent, fnameread;
    Button write, read;
    TextView filecon;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fname = (EditText) findViewById(R.id.fname);
        fcontent = (EditText) findViewById(R.id.ftext);
        fnameread = (EditText) findViewById(R.id.fnameread);
        write = (Button) findViewById(R.id.btnwrite);
        read = (Button) findViewById(R.id.btnread);
        filecon = (TextView) findViewById(R.id.filecon);
        write.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                String filename = fname.getText().toString();
                String filecontent = fcontent.getText().toString();
                FileOperations fop = new FileOperations();
                fop.write(filename, filecontent);
                if (fop.write(filename, filecontent)) {
                    Toast.makeText(getApplicationContext(),
                            filename + ".pdf created", Toast.LENGTH_SHORT)
                            .show();
                } else {
                    Toast.makeText(getApplicationContext(), "I/O error",
                            Toast.LENGTH_SHORT).show();
                }
            }
        });
        read.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                String readfilename = fnameread.getText().toString();
                FileOperations fop = new FileOperations();
                String text = fop.read(readfilename);
                if (text != null) {
                    filecon.setText(text);
                } else {
                    Toast.makeText(getApplicationContext(), "File not Found",
                            Toast.LENGTH_SHORT).show();
                    filecon.setText(null);
                }
            }
        });
    }
}

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.readwrite"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="18" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.readwrite.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

确保将itextpdf-5.5.1.jar放在正确的位置，如下所示

enter image description here

错误：无法找到或加载主类com.example.pdfone.MainActivity

1 个答案: