Qt在Android平台上实现html转PDF的功能，

来源：开发者投稿于 2019-11-25 被查看 24717 次评论：237

Qt在Android平台上实现html转PDF的功能，

Qt for Android

Qt for Android enables you to run Qt 5 applications Android devices. All Qt modules (essential and add-on) are supported except Qt WebEngine, Qt Serial Port, and the platform-specific ones (Qt Mac Extras, Qt Windows Extras, and Qt X11 Extras).

在Windows或者Linux平台上可以用QtWebEngine模块实现网页预览和打印成PDF文档，用起来很方便，生成的文档质量也比较好，但在Android平台上QtWebEngine模块不能用，想要显示网页可以用QtWebView模块，不支持打印成PDF。尝试用QTextDocument和QPrinter将html转为PDF，发现QTextDocument不支持CSS样式，生成的PDF文档排版是错的。

查看QtWebView在Android平台上的实现，可以发现其用的就是Android的WebView控件实现的网页显示。尝试在Android平台上实现html生成PDF，找到了这篇文章https://www.jianshu.com/p/d82bd61b11a4，验证后可行。需要依赖第三方库DexMaker，可以用谷歌实现的 implementation 'com.google.dexmaker:dexmaker:1.2'，库文件名为dexmaker-1.2.jar。

修改QT源码，在Android平台上实现html转PDF的功能

修改$QtSrc/qtwebview/src/jar/src/org/qtproject/qt5/android/view/QtAndroidWebViewController.java文件

/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtWebView module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL3$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPLv3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or later as published by the Free
** Software Foundation and appearing in the file LICENSE.GPL included in
** the packaging of this file. Please review the following information to
** ensure the GNU General Public License version 2.0 requirements will be
** met: http://www.gnu.org/licenses/gpl-2.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

package org.qtproject.qt5.android.view;

import android.content.pm.PackageManager;
import android.view.View;
import android.webkit.GeolocationPermissions;
import android.webkit.URLUtil;
import android.webkit.ValueCallback;
import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Bundle;
import android.os.CancellationSignal;
import android.os.ParcelFileDescriptor;
import android.print.PageRange;
import android.print.PrintAttributes;
import android.print.PrintDocumentAdapter;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.webkit.WebChromeClient;

import java.lang.Runnable;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;

import java.lang.String;

import android.webkit.WebSettings;
import android.webkit.WebSettings.PluginState;
import android.graphics.Bitmap;

import java.util.concurrent.Semaphore;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

import android.os.Build;

import java.util.concurrent.TimeUnit;

import com.google.dexmaker.stock.ProxyBuilder;

public class QtAndroidWebViewController
{
    private final Activity m_activity;
    private final long m_id;
    private boolean busy;
    private boolean m_hasLocationPermission;
    private WebView m_webView = null;
    private static final String TAG = "QtAndroidWebViewController";
    private final int INIT_STATE = 0;
    private final int STARTED_STATE = 1;
    private final int LOADING_STATE = 2;
    private final int FINISHED_STATE = 3;

    private volatile int m_loadingState = INIT_STATE;
    private volatile int m_progress = 0;
    private volatile int m_frameCount = 0;

    // API 11 methods
    private Method m_webViewOnResume = null;
    private Method m_webViewOnPause = null;
    private Method m_webSettingsSetDisplayZoomControls = null;

    // API 19 methods
    private Method m_webViewEvaluateJavascript = null;

    // Native callbacks
    private native void c_onPageFinished(long id, String url);
    private native void c_onPageStarted(long id, String url, Bitmap icon);
    private native void c_onProgressChanged(long id, int newProgress);
    private native void c_onReceivedIcon(long id, Bitmap icon);
    private native void c_onReceivedTitle(long id, String title);
    private native void c_onRunJavaScriptResult(long id, long callbackId, String result);
    private native void c_onReceivedError(long id, int errorCode, String description, String url);
    private native void c_onpdfPrintingFinished(long id, boolean succeed);

    // We need to block the UI thread in some cases, if it takes to long we should timeout before
    // ANR kicks in... Usually the hard limit is set to 10s and if exceed that then we're in trouble.
    // In general we should not let input events be delayed for more then 500ms (If we're spending more
    // then 200ms somethings off...).
    private final long BLOCKING_TIMEOUT = 250;

    private void resetLoadingState(final int state)
    {
        m_progress = 0;
        m_frameCount = 0;
        m_loadingState = state;
    }

    private class Html2Pdf {
        private File file;
        private File dexCacheFile;
        private PrintDocumentAdapter printAdapter;
        private PageRange[] ranges;
        private ParcelFileDescriptor descriptor;
    
        private void printToPdf(WebView webView, String fileName) {
            if (webView != null) {
                file = new File(fileName);
                dexCacheFile = webView.getContext().getDir("dex", 0);
                if (!dexCacheFile.exists()) {
                    dexCacheFile.mkdir();
                }
                try {
                    if (file.exists()) {
                        file.delete();
                    }
                    file.createNewFile();
                    descriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_WRITE);
                    PrintAttributes attributes = new PrintAttributes.Builder()
                            .setMediaSize(PrintAttributes.MediaSize.ISO_A4)
                            .setResolution(new PrintAttributes.Resolution("id", Context.PRINT_SERVICE, 300, 300))
                            .setColorMode(PrintAttributes.COLOR_MODE_COLOR)
                            .setMinMargins(PrintAttributes.Margins.NO_MARGINS)
                            .build();
                    ranges = new PageRange[]{PageRange.ALL_PAGES};
    
                    printAdapter = webView.createPrintDocumentAdapter();
                    printAdapter.onStart();
                    printAdapter.onLayout(attributes, attributes, new CancellationSignal(), getLayoutResultCallback(new InvocationHandler() {
                        @Override
                        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                            if (method.getName().equals("onLayoutFinished")) {
                                onLayoutSuccess();
                            } else {
                                descriptor.close();
                                c_onpdfPrintingFinished(m_id, false);
                                busy = false;
                            }
                            return null;
                        }
                    }, dexCacheFile.getAbsoluteFile()), new Bundle());
                } catch (IOException e) {
                    if (descriptor != null) {
                        try {
                            descriptor.close();
                        } catch (IOException ex) {
                            ex.printStackTrace();
                        }
                    }
                    c_onpdfPrintingFinished(m_id, false);
                    e.printStackTrace();
                    busy = false;
                }
            }
        }
    
        private void onLayoutSuccess() throws IOException {
            PrintDocumentAdapter.WriteResultCallback callback = getWriteResultCallback(new InvocationHandler() {
                @Override
                public Object invoke(Object o, Method method, Object[] objects) throws Throwable {
                    if (method.getName().equals("onWriteFinished")) {
                        c_onpdfPrintingFinished(m_id, true);
                    } else {
                        c_onpdfPrintingFinished(m_id, false);
                    }
                    busy = false;
                    if (descriptor != null) {
                        try {
                            descriptor.close();
                        } catch (IOException ex) {
                            ex.printStackTrace();
                        }
                    }
                    return null;
                }
            }, dexCacheFile.getAbsoluteFile());
            printAdapter.onWrite(ranges, descriptor, new CancellationSignal(), callback);
        }
    
        @SuppressLint("NewApi")
        private  PrintDocumentAdapter.LayoutResultCallback getLayoutResultCallback(InvocationHandler invocationHandler, File dexCacheDir) throws IOException {
            return ProxyBuilder.forClass(PrintDocumentAdapter.LayoutResultCallback.class)
                    .dexCache(dexCacheDir)
                    .handler(invocationHandler)
                    .build();
        }
    
        @SuppressLint("NewApi")
        private  PrintDocumentAdapter.WriteResultCallback getWriteResultCallback(InvocationHandler invocationHandler, File dexCacheDir) throws IOException {
            return ProxyBuilder.forClass(PrintDocumentAdapter.WriteResultCallback.class)
                    .dexCache(dexCacheDir)
                    .handler(invocationHandler)
                    .build();
        }    
    }

    private class QtAndroidWebViewClient extends WebViewClient
    {
        QtAndroidWebViewClient() { super(); }

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url)
        {
            // handle http: and http:, etc., as usual
            if (URLUtil.isValidUrl(url))
                return false;

            // try to handle geo:, tel:, mailto: and other schemes
            try {
                Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
                view.getContext().startActivity(intent);
                return true;
            } catch (Exception e) {
                e.printStackTrace();
            }

            return false;
        }

        @Override
        public void onLoadResource(WebView view, String url)
        {
            super.onLoadResource(view, url);
        }

        @Override
        public void onPageFinished(WebView view, String url)
        {
            super.onPageFinished(view, url);
            m_loadingState = FINISHED_STATE;
            if (m_progress != 100) // onProgressChanged() will notify Qt if we didn't finish here.
                return;

             m_frameCount = 0;
             c_onPageFinished(m_id, url);
        }

        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon)
        {
            super.onPageStarted(view, url, favicon);
            if (++m_frameCount == 1) { // Only call onPageStarted for the first frame.
                m_loadingState = LOADING_STATE;
                c_onPageStarted(m_id, url, favicon);
            }
        }

        @Override
        public void onReceivedError(WebView view,
                                    int errorCode,
                                    String description,
                                    String url)
        {
            super.onReceivedError(view, errorCode, description, url);
            resetLoadingState(INIT_STATE);
            c_onReceivedError(m_id, errorCode, description, url);
        }
    }

    private class QtAndroidWebChromeClient extends WebChromeClient
    {
        QtAndroidWebChromeClient() { super(); }
        @Override
        public void onProgressChanged(WebView view, int newProgress)
        {
            super.onProgressChanged(view, newProgress);
            m_progress = newProgress;
            c_onProgressChanged(m_id, newProgress);
            if (m_loadingState == FINISHED_STATE && m_progress == 100) { // Did we finish?
                m_frameCount = 0;
                c_onPageFinished(m_id, view.getUrl());
            }
        }

        @Override
        public void onReceivedIcon(WebView view, Bitmap icon)
        {
            super.onReceivedIcon(view, icon);
            c_onReceivedIcon(m_id, icon);
        }

        @Override
        public void onReceivedTitle(WebView view, String title)
        {
            super.onReceivedTitle(view, title);
            c_onReceivedTitle(m_id, title);
        }

        @Override
        public void onGeolocationPermissionsShowPrompt(String origin, GeolocationPermissions.Callback callback)
        {
            callback.invoke(origin, m_hasLocationPermission, false);
        }
    }

    public QtAndroidWebViewController(final Activity activity, final long id)
    {
        m_activity = activity;
        m_id = id;
        final Semaphore sem = new Semaphore(0);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                m_webView = new WebView(m_activity);
                m_hasLocationPermission = hasLocationPermission(m_webView);
                WebSettings webSettings = m_webView.getSettings();

                if (Build.VERSION.SDK_INT > 10) {
                    try {
                        m_webViewOnResume = m_webView.getClass().getMethod("onResume");
                        m_webViewOnPause = m_webView.getClass().getMethod("onPause");
                        m_webSettingsSetDisplayZoomControls = webSettings.getClass().getMethod("setDisplayZoomControls", boolean.class);
                        if (Build.VERSION.SDK_INT > 18) {
                            m_webViewEvaluateJavascript = m_webView.getClass().getMethod("evaluateJavascript",
                                                                                         String.class,
                                                                                         ValueCallback.class);
                        }
                    } catch (Exception e) { /* Do nothing */ e.printStackTrace(); }
                }

                //allowing access to location without actual ACCESS_FINE_LOCATION may throw security exception
                webSettings.setGeolocationEnabled(m_hasLocationPermission);

                webSettings.setJavaScriptEnabled(true);
                if (m_webSettingsSetDisplayZoomControls != null) {
                    try { m_webSettingsSetDisplayZoomControls.invoke(webSettings, false); } catch (Exception e) { e.printStackTrace(); }
                }
                webSettings.setBuiltInZoomControls(true);
                webSettings.setPluginState(PluginState.ON);
                m_webView.setWebViewClient((WebViewClient)new QtAndroidWebViewClient());
                m_webView.setWebChromeClient((WebChromeClient)new QtAndroidWebChromeClient());
                sem.release();
            }
        });

        try {
            sem.acquire();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void loadUrl(final String url)
    {
        if (url == null) {
            return;
        }

        resetLoadingState(STARTED_STATE);
        c_onPageStarted(m_id, url, null);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.loadUrl(url); }
        });
    }

    public void loadData(final String data, final String mimeType, final String encoding)
    {
        if (data == null)
            return;

        resetLoadingState(STARTED_STATE);
        c_onPageStarted(m_id, null, null);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.loadData(data, mimeType, encoding); }
        });
    }

    public void loadDataWithBaseURL(final String baseUrl,
                                    final String data,
                                    final String mimeType,
                                    final String encoding,
                                    final String historyUrl)
    {
        if (data == null)
            return;

        resetLoadingState(STARTED_STATE);
        c_onPageStarted(m_id, null, null);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.loadDataWithBaseURL(baseUrl, data, mimeType, encoding, historyUrl); }
        });
    }

    public void goBack()
    {
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.goBack(); }
        });
    }

    public boolean canGoBack()
    {
        final boolean[] back = {false};
        final Semaphore sem = new Semaphore(0);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { back[0] = m_webView.canGoBack(); sem.release(); }
        });

        try {
            sem.tryAcquire(BLOCKING_TIMEOUT, TimeUnit.MILLISECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return back[0];
    }

    public void goForward()
    {
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.goForward(); }
        });
    }

    public boolean canGoForward()
    {
        final boolean[] forward = {false};
        final Semaphore sem = new Semaphore(0);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { forward[0] = m_webView.canGoForward(); sem.release(); }
        });

        try {
            sem.tryAcquire(BLOCKING_TIMEOUT, TimeUnit.MILLISECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return forward[0];
    }

    public void stopLoading()
    {
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.stopLoading(); }
        });
    }

    public void reload()
    {
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { m_webView.reload(); }
        });
    }

    public String getTitle()
    {
        final String[] title = {""};
        final Semaphore sem = new Semaphore(0);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { title[0] = m_webView.getTitle(); sem.release(); }
        });

        try {
            sem.tryAcquire(BLOCKING_TIMEOUT, TimeUnit.MILLISECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return title[0];
    }

    public int getProgress()
    {
        return m_progress;
    }

    public boolean isLoading()
    {
        return m_loadingState == LOADING_STATE || m_loadingState == STARTED_STATE || (m_progress > 0 && m_progress < 100);
    }

    public void runJavaScript(final String script, final long callbackId)
    {
        if (script == null)
            return;

        if (Build.VERSION.SDK_INT < 19 || m_webViewEvaluateJavascript == null)
            return;

        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                try {
                    m_webViewEvaluateJavascript.invoke(m_webView, script, callbackId == -1 ? null :
                        new ValueCallback<String>() {
                            @Override
                            public void onReceiveValue(String result) {
                                c_onRunJavaScriptResult(m_id, callbackId, result);
                            }
                        });
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public String getUrl()
    {
        final String[] url = {""};
        final Semaphore sem = new Semaphore(0);
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { url[0] = m_webView.getUrl(); sem.release(); }
        });

        try {
            sem.tryAcquire(BLOCKING_TIMEOUT, TimeUnit.MILLISECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return url[0];
    }

    public WebView getWebView()
    {
       return m_webView;
    }

    public void onPause()
    {
        if (m_webViewOnPause == null)
            return;

        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { try { m_webViewOnPause.invoke(m_webView); } catch (Exception e) { e.printStackTrace(); } }
        });
    }

    public void onResume()
    {
        if (m_webViewOnResume == null)
            return;

        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() { try { m_webViewOnResume.invoke(m_webView); } catch (Exception e) { e.printStackTrace(); } }
        });
    }

    private static boolean hasLocationPermission(View view)
    {
        final String name = view.getContext().getPackageName();
        final PackageManager pm = view.getContext().getPackageManager();
        return pm.checkPermission("android.permission.ACCESS_FINE_LOCATION", name) == PackageManager.PERMISSION_GRANTED;
    }

    public void destroy()
    {
        m_activity.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                m_webView.destroy();
            }
        });
    }

    public void printToPdf(final String fileName){
        if(!busy){
            busy = true;
            m_activity.runOnUiThread(new Runnable() {
                @Override
                public void run() { 
                    Html2Pdf html2Pdf = new Html2Pdf();
                    html2Pdf.printToPdf(m_webView, fileName);
                }
            });
        }else{
            c_onpdfPrintingFinished(m_id,false); 
        }
    }

}

修改$QtSrc/qtwebview/src/plugins/android/qandroidwebview_p.h

修改$QtSrc/qtwebview/src/plugins/android/qandroidwebview.cpp

修改$QtSrc/qtwebview/src/webview/qabstractwebview_p.h（以下增加的所有的C++代码、函数、信号等都用#if ANDROID宏条件编译）

修改$QtSrc/qtwebview/src/webview/qquickwebview_p.h

修改$QtSrc/qtwebview/src/webview/qquickwebview.cpp

修改$QtSrc/qtwebview/src/webview/qwebviewinterface_p.h

修改$QtSrc/qtwebview/src/webview/qwebviewfactory.cpp

修改$QtSrc/qtwebview/src/webview/qwebview_p.h

修改$QtSrc/qtwebview/src/webview/qwebview.cpp

在$QtSrc/qtwebview/src/jar目录下新建lib目录，将dexmaker-1.2.jar文件拷贝到该目录下

修改$QtSrc/qtwebview/src/jar/jar.pro

TARGET = QtAndroidWebView

load(qt_build_paths)
CONFIG += java
DESTDIR = $$MODULE_BASE_OUTDIR/jar

JAVACLASSPATH += $$PWD/src \
    $$PWD/lib/dexmaker-1.2.jar

JAVASOURCES += $$PWD/src/org/qtproject/qt5/android/view/QtAndroidWebViewController.java

# install
target.path = $$[QT_INSTALL_PREFIX]/jar
target.files += $$PWD/lib/dexmaker-1.2.jar
INSTALLS += target

修改$QtSrc/qtwebview/src/webview/webview.pro

……

QMAKE_DOCS = \
             $$PWD/doc/qtwebview.qdocconf

ANDROID_BUNDLED_JAR_DEPENDENCIES = \
    jar/QtAndroidWebView.jar \
    jar/dexmaker-1.2.jar
ANDROID_PERMISSIONS = \
    android.permission.ACCESS_FINE_LOCATION
ANDROID_LIB_DEPENDENCIES = \
    plugins/webview/libqtwebview_android.so

HEADERS += $$PUBLIC_HEADERS $$PRIVATE_HEADERS

load(qt_module)

修改$QtSrc/qtwebview/src/imports/plugins.qmltypes

配置和编译

上述软件版本

使用示例

import QtQuick 2.12
import QtQuick.Window 2.12
import QtWebView 1.1
import QtQuick.Controls 2.12

Window {
    id: window
    visible: true
    width: 1080
    height: 1920
    title: qsTr("Hello World")
    WebView{
        id:webView
        anchors.bottom: printBtn.top
        anchors.right: parent.right
        anchors.left: parent.left
        anchors.top: parent.top
        anchors.bottomMargin: 0
        url:"http://www.qq.com"
        onPdfPrintingFinished: {
            printBtn.text = "打印" + (succeed?"成功":"失败")
            printBtn.enabled = true
        }
    }

    Button {
        id:printBtn
        text: "打印"
        anchors.bottom: parent.bottom
        anchors.bottomMargin: 0
        onClicked: {
            printBtn.enabled = false
            webView.printToPdf("/sdcard/aaa.pdf")
        }
    }
}

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