Qt在Android平台上实现html转PDF的功能

程序员文章站 2022-07-04 23:37:26

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 WebE ......

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，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.
**
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** licensees holding valid commercial qt licenses may use this file in
** accordance with the commercial license agreement provided with the
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** and conditions see http://www.qt.io/terms-conditions. for further
** information use the contact form at http://www.qt.io/contact-us.
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** 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
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****************************************************************************/

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); 
        }
    }

}

主要修改：
1. 增加了 void printtopdf(final string filename)打印接口
2. 增加了 native void c_onpdfprintingfinished(long id, boolean succeed)作为打印完成的回调
3. 增加了内部类html2pdf实现打印成pdf

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

增加槽函数 void printtopdf(const qstring &filename) q_decl_override;

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

实现槽函数

void qandroidwebviewprivate::printtopdf(const qstring &filename)
{
    const qjniobjectprivate &filenamestring = qjniobjectprivate::fromstring(filename);
    m_viewcontroller.callmethod<void>("printtopdf","(ljava/lang/string;)v",filenamestring.object());
}

实现java代码中打印完成的回调

static void c_onpdfprintingfinished(jnienv *env,
                              jobject thiz,
                              jlong id,
                              jboolean succeed)
{
    q_unused(env)
    q_unused(thiz)
    const webviews &wv = (*g_webviews);
    qandroidwebviewprivate *wc = wv[id];
    if (!wc)
        return;
    q_emit wc->pdfprintingfinished(succeed);
}

修改jniexport jint jni_onload(javavm* vm, void* /*reserved*/)，注册c_onpdfprintingfinished回调函数。

jninativemethod methods[]数组里增加一项
{"c_onpdfprintingfinished","(jz)v",reinterpret_cast<void *>(c_onpdfprintingfinished)}

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）

增加信号void pdfprintingfinished(bool succeed);

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

增加公开槽函数 void printtopdf(const qstring &filename) q_decl_override;
增加信号 void pdfprintingfinished(bool succeed);
增加私有槽函数 void onpdfprintingfinished(bool succeed);

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

构造函数里关联槽函数和信号

#if android
connect(m_webview, &qwebview::pdfprintingfinished, this, &qquickwebview::onpdfprintingfinished);
#endif

实现槽函数printtopdf

#if android
void qquickwebview::printtopdf(const qstring &filename)
{
    m_webview->printtopdf(filename);
}
#endif

实现槽函数onpdfprintingfinished

#if android
void qquickwebview::onpdfprintingfinished(bool succeed)
{
    q_emit pdfprintingfinished(succeed);
}
#endif

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

增加纯虚函数 virtual void printtopdf(const qstring &filename) = 0;

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

qnullwebview类增加

void printtopdf(const qstring &filename) override
    {q_unused(filename); }

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

增加公开槽函数 void printtopdf(const qstring &filename) q_decl_override;
增加信号 void pdfprintingfinished(bool succeed);
增加私有槽函数 void onpdfprintingfinished(bool succeed);

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

构造函数里关联槽函数和信号

#if android
connect(d, &qabstractwebview::pdfprintingfinished, this, &qwebview::onpdfprintingfinished);
#endif

实现槽函数printtopdf

#if android
void qwebview::printtopdf(const qstring &filename)
{
    d->printtopdf(filename);
}
#endif

实现槽函数onpdfprintingfinished

#if android
void qwebview::onpdfprintingfinished(bool succeed)
{
    q_emit pdfprintingfinished(succeed);
}
#endif

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

增加信号

signal {
            name: "pdfprintingfinished"
            revision: 1
            parameter { name: "succeed"; type: "bool" }
        }

增加方法

method {
            name: "printtopdf"
            revision: 1
            parameter { name: "filename"; type: "string" }
        }

配置和编译

./configure -extprefix $qtinstall/android_arm64_v8a -xplatform android-clang -release -nomake tests -nomake examples -opensource -confirm-license -recheck-all -android-ndk $ndkpath -android-sdk $androidsdkpath -android-ndk-host linux-x86_64 -android-arch arm64-v8a

-android-arch支持armeabi, armeabi-v7a, arm64-v8a, x86, x86_64，一次只能编译一个架构，注意不同架构要修改安装目录

make -j8
make install

上述软件版本

qt：5.13.2
ndk：r20b(20.1.5948944)
android-buildtoolsversion：29.0.2

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")
        }
    }
}

下期预告：在android平台上实现串口读写的功能

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