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1. Requirements description

The browsing experience of browsing e-books on mobile phones is similar to that of reading paper books. The visual effects of paper flipping are still present during the page-turning process, which makes readers look pleasing to the eye. To sum up, mobile phone reading is nothing more than two major functions: one is bookshelf management, which is mainly for adding, deleting, modifying and checking books, and the other is browsing operations, which is mainly for handling the page-turning process.

2. Functional Analysis

There are several problems with e-books. On the one hand, there are various formats of e-books. On the other hand, Android does not have ready-made controls to display these e-books in a unified way. It is very difficult to display e-books in different formats on the screen of a mobile phone.

For the previous question. E-books can be unified into a few public formats to reduce the difficulty of coding. For the latter problem, each page of the e-book can be converted into an image file, and then the e-book can be browsed using the image view.

In the next practical project, only two formats of e-books are supported for the time being, namely PDF, a platform-independent electronic file and DJVU.

Next, analyze some technologies used in e-book readers

Asset Manager AssetManager initial five demo eBooks

Database framework Room The book title and author pages of each e-book are uniformly saved in the database

PDF file renderer parses PDF files into a set of images

The Bezier curve is used to realize the special effect of page turning in the process of browsing the pages of e-books

JNI interface

Image file processing

input dialog

The following briefly introduces the relationship between the main code modules

EbookReaderActivity The book list page of the e-book reader

PdfRenderActivity PDF e-book reading page

PdfSlideActivity PDF e-book smooth page turning

PdfCurveActivity Bezier curve page turning

PdfOpenglActivity curl page

DvjuRenderActivity DJVU e-book reading page

ImageFragment Display fragments of e-book pictures on each page

3. Effect display

The effect is shown as follows. There are both ordinary smooth page turning and Bezier curve and curly page turning. It looks more realistic and pleasing to the eye.

The demonstration video is as follows

Android e-book App

The renderings are as follows

4. Code

Ebook class

package com.example.ebook;

import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import com.example.ebook.adapter.BookListAdapter;
import com.example.ebook.dao.BookDao;
import com.example.ebook.entity.BookInfo;
import com.example.ebook.util.AssetsUtil;
import com.example.ebook.widget.InputDialog;

import java.util.ArrayList;
import java.util.List;

public class EbookReaderActivity extends AppCompatActivity implements
        AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener {
    private static final String TAG = "EbookReaderActivity";
    private ListView lv_ebook; // 声明一个用于展示书籍列表的列表视图对象
    private String[] mFileNameArray = {"tangshi.pdf", "android.pdf", "zhugeliang.djvu", "dufu.djvu", "luyou.djvu"};
    private List<BookInfo> mBookList = new ArrayList<>(); // 书籍信息列表
    private BookListAdapter mAdapter; // 声明一个书籍列表的适配器对象
    private BookDao bookDao; // 声明一个书籍的持久化对象

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ebook_reader);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); // 保持屏幕常亮
        initView(); // 初始化视图
        new Thread(() -> copyPdfFile()).start(); // 启动演示文件的复制线程
    }

    // 初始化视图
    private void initView() {
        Toolbar tl_head = findViewById(R.id.tl_head);
        tl_head.setTitle("电子书架");
        setSupportActionBar(tl_head); // 替换系统自带的ActionBar
        // 设置工具栏左侧导航图标的点击监听器
        tl_head.setNavigationOnClickListener(view -> finish());
        lv_ebook = findViewById(R.id.lv_ebook);
    }

    // 把assets目录下的演示文件复制到存储卡
    private void copyPdfFile() {
        // 从App实例中获取唯一的书籍持久化对象
        bookDao = MainApplication.getInstance().getBookDB().bookDao();
        mBookList = bookDao.queryAllBook(); // 获取所有书籍记录
        if (mBookList!=null && mBookList.size()>0) {
            runOnUiThread(() -> initBookList()); // 初始化书籍列表
            return;
        }
        List<BookInfo> bookList = new ArrayList<>();
        for (String file_name : mFileNameArray) {
            String dir = String.format("%s/%s/",
                    getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS).toString(),
                    file_name.substring(file_name.lastIndexOf(".")+1)
            );
            String fileName = file_name.substring(file_name.lastIndexOf("/") + 1);
            // 把资产目录下的电子书复制到存储卡
            AssetsUtil.Assets2Sd(this, fileName, dir + fileName);
            bookList.add(new BookInfo(file_name));
        }
        bookDao.insertBookList(bookList); // 把演示用的电子书信息添加到数据库
        runOnUiThread(() -> initBookList()); // 初始化书籍列表
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        initBookList(); // 初始化书籍列表
    }

    // 初始化书籍列表
    private void initBookList() {
        mBookList = bookDao.queryAllBook(); // 获取所有书籍记录
        // 下面把书籍列表通过ListView展现出来
        mAdapter = new BookListAdapter(this, mBookList);
        lv_ebook.setAdapter(mAdapter);
        lv_ebook.setOnItemClickListener(this);
        lv_ebook.setOnItemLongClickListener(this);
    }

    // 在点击书籍记录时触发
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        String file_name = mBookList.get(position).getFileName();
        String title = mBookList.get(position).getTitle();
        Log.d(TAG, "file_name="+file_name+", title="+title);
        if (file_name.endsWith(".pdf")) { // PDF格式
            // 跳转到PDF阅读界面
            startReader(file_name, title, PdfRenderActivity.class);
        } else if (file_name.endsWith(".djvu")) { // DJVU格式
            // 跳转到第三方Vudroid提供的阅读界面
            startReader(file_name, title, DjvuRenderActivity.class);
        } else {
            Toast.makeText(this, "暂不支持该格式的电子书", Toast.LENGTH_SHORT).show();
        }
    }

    // 在长按书籍记录时触发
    @Override
    public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
        // 以下创建并弹出标题填写对话框
        InputDialog dialog = new InputDialog(this, mBookList.get(position).getFileName(),
                position, "请输入书籍名称", (idt, content, seq) -> {
            BookInfo book = mBookList.get(seq);
            book.setTitle(content);
            bookDao.updateBook(book); // 更新数据库中该书籍记录的标题
        });
        dialog.show();
        return true;
    }

    // 启动指定的电子书阅读界面
    private void startReader(String file_name, String title, Class<?> cls) {
        Intent intent = new Intent(this, cls);
        intent.putExtra("file_name", file_name);
        intent.putExtra("title", title);
        startActivity(intent);
    }

}

PDF class

package com.example.ebook;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.text.TextUtils;
import android.util.Log;
import android.view.ViewGroup;

import com.example.ebook.util.AssetsUtil;
import com.example.ebook.util.Utils;
import com.example.ebook.widget.CurveView;

import java.util.ArrayList;
import java.util.List;

public class PdfCurveActivity extends AppCompatActivity {
    private final static String TAG = "PdfCurveActivity";
    private CurveView cv_book; // 声明一个卷曲视图对象
    private List<String> mPathList = new ArrayList<>(); // 图片路径列表
    private String mFileName = "tangshi.pdf"; // 演示文件的名称

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_curve);
        initView(); // 初始化视图
        // 加载pdf会花一点点时间，这里先让整个界面出来，再慢慢渲染pdf
        new Handler(Looper.myLooper()).post(() -> renderPDF());
    }

    // 初始化视图
    private void initView() {
        String title = "";
        // 从前个页面传来的数据中获取书籍的标题和文件名称
        if (getIntent().getExtras()!=null && !getIntent().getExtras().isEmpty()) {
            title = getIntent().getStringExtra("title");
            mFileName = getIntent().getStringExtra("file_name");
        }
        Toolbar tl_head = findViewById(R.id.tl_head);
        tl_head.setTitle(!TextUtils.isEmpty(title) ? title : mFileName);

        // 设置工具栏左侧导航图标的点击监听器
        tl_head.setNavigationOnClickListener(view -> finish());
        cv_book = findViewById(R.id.cv_book);
        findViewById(R.id.btn_resume).setOnClickListener(v -> cv_book.reset());
    }

    // 开始渲染PDF文件
    private void renderPDF() {
        // 把资产文件转换为图片路径列表
        mPathList = AssetsUtil.getPathListFromPdf(this, mFileName);
        Log.d(TAG, "mPathList.size="+mPathList.size());
        Bitmap first = BitmapFactory.decodeFile(mPathList.get(0));
        int height = (int)(1.0*first.getHeight()/first.getWidth() * Utils.getScreenWidth(this));
        Log.d(TAG, "height="+height);
        ViewGroup.LayoutParams params = cv_book.getLayoutParams();
        params.height = height; // 根据书页图片的尺寸调整卷曲视图的高度
        cv_book.setLayoutParams(params); // 设置卷曲视图的布局参数
        cv_book.setFilePath(mPathList); // 设置卷曲视图的文件路径
    }

}

Curly page turning class

package com.example.ebook;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.pdf.PdfRenderer;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.os.ParcelFileDescriptor;
import android.text.TextUtils;
import android.util.Log;
import android.view.ViewGroup.LayoutParams;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import com.example.ebook.util.AssetsUtil;
import com.example.ebook.util.BitmapUtil;
import com.example.ebook.util.Utils;

import java.io.File;
import java.util.ArrayList;

import fi.harism.curl.CurlPage;
import fi.harism.curl.CurlView;

public class PdfOpenglActivity extends AppCompatActivity {
    private final static String TAG = "PdfOpenglActivity";
    private CurlView cv_content; // 声明一个卷曲视图对象
    private ArrayList<String> mImgList = new ArrayList<>(); // 图片路径列表
    private String mFileName = "tangshi.pdf"; // 演示文件的名称

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_opengl);
        initView(); // 初始化视图
        // 加载pdf会花一点点时间，这里先让整个界面出来，再慢慢渲染pdf
        new Handler(Looper.myLooper()).post(() -> renderPDF());
    }

    // 初始化视图
    private void initView() {
        String title = "";
        // 从前个页面传来的数据中获取书籍的标题和文件名称
        if (getIntent().getExtras()!=null && !getIntent().getExtras().isEmpty()) {
            title = getIntent().getStringExtra("title");
            mFileName = getIntent().getStringExtra("file_name");
        }
        Toolbar tl_head = findViewById(R.id.tl_head);
        tl_head.setTitle(!TextUtils.isEmpty(title) ? title : mFileName);

        // 设置工具栏左侧导航图标的点击监听器
        tl_head.setNavigationOnClickListener(view -> finish());
        cv_content = findViewById(R.id.cv_content);
    }

    // 开始渲染PDF文件
    private void renderPDF() {
        String dir = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS).toString() + "/pdf/";
        String filePath = dir + mFileName;
        // 无法直接从asset目录读取PDF文件，只能先把PDF文件复制到存储卡，再从存储卡读取PDF
        AssetsUtil.Assets2Sd(this, mFileName, filePath);
        try {
            // 打开存储卡里指定路径的PDF文件
            ParcelFileDescriptor pfd = ParcelFileDescriptor.open(
                    new File(filePath), ParcelFileDescriptor.MODE_READ_ONLY);
            // 创建一个PDF渲染器
            PdfRenderer pdfRenderer = new PdfRenderer(pfd);
            Log.d(TAG, "page count=" + pdfRenderer.getPageCount());
            // 依次处理PDF文件的每个页面
            for (int i = 0; i < pdfRenderer.getPageCount(); i++) {
                // 生成该页图片的保存路径
                String imgPath = String.format("%s/%03d.jpg", dir, i);
                mImgList.add(imgPath);
                // 打开序号为i的页面
                PdfRenderer.Page page = pdfRenderer.openPage(i);
                // 创建该页面的临时位图
                Bitmap bitmap = Bitmap.createBitmap(page.getWidth(), page.getHeight(),
                        Bitmap.Config.ARGB_8888);
                bitmap.eraseColor(Color.WHITE); // 将临时位图洗白
                // 渲染该PDF页面并写入到临时位图
                page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
                BitmapUtil.saveImage(imgPath, bitmap); // 把位图对象保存为图片文件
                page.close(); // 关闭该PDF页面
            }
            pdfRenderer.close(); // 处理完毕，关闭PDF渲染器
        } catch (Exception e1) {
            e1.printStackTrace();
        }
        // 从指定路径的图片文件中获取位图数据
        Bitmap bitmap = BitmapFactory.decodeFile(mImgList.get(0));
        int iv_height = (int)(1.0*bitmap.getHeight()/bitmap.getWidth() * Utils.getScreenWidth(this));
        showImage(iv_height); // 在卷曲视图上显示位图图像
        bitmap.recycle(); // 回收位图对象
    }

    // 在卷曲视图上显示位图图像
    private void showImage(int height) {
        LayoutParams params = cv_content.getLayoutParams();
        params.height = height;
        // 设置卷曲视图的布局参数
        cv_content.setLayoutParams(params);
        // 设置卷曲视图的书页提供器
        cv_content.setPageProvider(new PageProvider(mImgList));
        // 设置卷曲视图的尺寸变更观察器
        cv_content.setSizeChangedObserver(new SizeChangedObserver());
        // 设置卷曲视图默认显示第一页
        cv_content.setCurrentIndex(0);
        // 设置卷曲视图的背景颜色
        cv_content.setBackgroundColor(Color.LTGRAY);
    }

    // 定义一个加载图片页面的提供器
    private class PageProvider implements CurlView.PageProvider {
        private ArrayList<String> mPathArray = new ArrayList<>();

        public PageProvider(ArrayList<String> pathArray) {
            mPathArray = pathArray;
        }

        @Override
        public int getPageCount() {
            return mPathArray.size();
        }

        // 在页面更新时触发
        public void updatePage(CurlPage page, int width, int height, int index) {
            // 加载指定页面的位图
            Bitmap front = BitmapFactory.decodeFile(mPathArray.get(index));
            // 设置书页的纹理
            page.setTexture(front, CurlPage.SIDE_BOTH);
        }
    }

    // 定义一个监听卷曲视图发生尺寸变更的观察器
    private class SizeChangedObserver implements CurlView.SizeChangedObserver {
        @Override
        public void onSizeChanged(int w, int h) {
            // 设置卷曲视图的观看模式
            cv_content.setViewMode(CurlView.SHOW_ONE_PAGE);
            // 设置卷曲视图的四周边缘
            cv_content.setMargins(0f, 0f, 0f, 0f);
        }
    }

}

XML file

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/book_bg3"
    android:orientation="vertical">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/tl_head"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="@color/blue_light"
        app:navigationIcon="@drawable/icon_back" />

    <ListView
        android:id="@+id/lv_ebook"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>

It's not easy to create and find it helpful, please like, follow and collect~~~

The realization of the electronic bookshelf App of Android App development practical project (with source code and demonstration video, it is easy to understand and can be used directly)

1. Requirements description

2. Functional Analysis

3. Effect display

4. Code

XML file

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