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QT实测经验教训

C/C++
2022-04-07
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摘要

Qt调用自己的 Activity获得返回值

Qt播放视频报错 DirectShowPlayerService::doRender: Unresolved error code 0x80040266

qt android动态权限申请

QT调用自己的Activity得到返回值

activity在AndroidManifest.xml中定义

<intent-filter>

</intent-filter>

</activity>

XNActivity布局代码

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:background="#ff0000ff"

<Button

android:layout_width="match_parent"

android:text="@string/click"

android:layout_height="wrap_content"

android:id="@+id/mybt"

</LinearLayout>

XNActivity.Java代码

package org.qtproject.example.HelloWindow;

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import org.qtproject.qt5.android.bindings.QtActivity;

public class XNActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_xn);

findViewById(R.id.mybt).setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

Intent intent =new Intent(XNActivity.this, QtActivity.class);

intent.putExtra("select","123中华民族");

setResult(Activity.RESULT_OK,intent);

finish();//结束当前Activity，返回上一个activity

}

});

}

QT端调用代码

ActivityResult *m_ActivityResult;

QAndroidJniEnvironment env;

if(m_ActivityResult!=NULL)

{

delete m_ActivityResult;

}

m_ActivityResult = new ActivityResult(0);

connect(m_ActivityResult,SIGNAL(sendData(QString)),this,SLOT(sendData(QString)));

QtAndroid::runOnAndroidThread([=](){

QAndroidJniObject action = QAndroidJniObject::fromString("org.qtproject.example.HelloWindow.XNActivity");

QAndroidJniObject intent("android/content/Intent","(Ljava/lang/String;)V", action.object<jstring>());

QtAndroid::startActivity(intent, 0, m_ActivityResult);

});

ActivityResult .h

#ifndef ACTIVITYRESULT_H

#define ACTIVITYRESULT_H

#include <QAndroidActivityResultReceiver>

class ActivityResult : public QObject,public QAndroidActivityResultReceiver

{

Q_OBJECT

signals:

void sendData(QString);

public:

int requestId;

ActivityResult(int id, QObject *parent = nullptr) : QObject(parent), requestId(id) {}

void handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data);

};

#endif // ACTIVITYRESULT_H

ActivityResult .cpp

#include <QDebug>

void ActivityResult::handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data)

{

QString myStr=QString("receiverRequestCode %1 resultCode %2").arg(receiverRequestCode).arg(resultCode);

emit sendData(myStr);

return;

if(receiverRequestCode == requestId)

{

if(resultCode ==-1)// RESULT_OK)

{

QAndroidJniObject name=QAndroidJniObject::fromString("select");

QAndroidJniObject str = data.callObjectMethod("getStringExtra", "(Ljava/lang/String;)Ljava/lang/String;",name.object<jstring>());

if(str==NULL)

{

emit sendData(tr("返回为空"));

return;

}

str.toString();

emit sendData(str.toString());

return;

}

else

{

//some code here

}

QT调用JAVA代码及数据类型对照

数据类型签名对照表:

jobject

Ljava/lang/Object;

jclass

Ljava/lang/Class;

jstring

Ljava/lang/String;

jthrowable

Ljava/lang/Throwable;

jobjectArray

[Ljava/lang/Object;

jarray

[<type>

jbooleanArray

jbyteArray

jcharArray

jshortArray

jintArray

jlongArray

jfloatArray

jdoubleArray

Primitive Types

jboolean

jbyte

jchar

jshort

jint

jlong

jfloat

jdouble

void

Custom type

L<fully-qualified-name>;

函数描述如:

(输入参数1;输入参数2;)返回类型;是传的要加;

（I）V

(Ljava/lang/String;)Ljava/lang/Object;

(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;

MyJavaClass.java

package com;

import java.io.OutputStream;

import java.util.Iterator;

import java.util.List;

import android.app.Activity;

import android.content.ContentValues;

import android.content.res.Configuration;

import android.hardware.Camera;

import android.net.Uri;

import android.os.Bundle;

import android.provider.MediaStore;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

import android.view.View;

import android.widget.LinearLayout;

public class MyJavaClass

{

public static int mystatic(int n) //静态函数；

{

return n+1;

}

public int getNum() //没有参数；

{

return 12345678;

}

public int setNum( int n ) //有参调用

{

return n;

}

public String getStr(String perfix) //返回对象

{

String teststr = new String("hello " + perfix);

return teststr;

}

boolean boolTest() //返回bool类型

{

return true;

}

QT调用

int n=5;

jint A=QAndroidJniObject::callStaticMethod<jint>

("com/MyJavaClass" // class name

, "mystatic" // method name

, "(I)I" // signature

, n);

QString s = QString::number(A);

QMessageBox::information(NULL, tr("提示"), s,QMessageBox::Yes | QMessageBox::No, QMessageBox::Yes);

QAndroidJniObject QAndroidJniObject_MyJavaClass_obj("com/MyJavaClass");

jint B = QAndroidJniObject_MyJavaClass_obj.callMethod<jint>("getNum");

QString ss = QString::number(B);

QMessageBox::information(NULL, tr("提示"), ss,QMessageBox::Yes | QMessageBox::No, QMessageBox::Yes);

return;

Java调用QT

** Java QtActivity 代码**

package org.qtproject.qt5.android.bindings;

public class QtActivity extends Activity

{

public static native int sendVideoData(long unused, byte[] data, int len, long timestamp);

public static native int sendCh340xData(byte[] data, int len);

}

c++ 导出函数

qt 会生成 so 文件直接导出只要导出函数签名一致 java 就能调用不需要调用 System.loadLibrary("")

#if defined(Q_OS_ANDROID)

#include <jni.h>

#ifdef __cplusplus

extern "C" {

#endif

JNIEXPORT jint JNICALL

Java_org_qtproject_qt5_android_bindings_QtActivity_sendCh340xData(

JNIEnv *env, jclass type,

jbyteArray data_, jint len)

{

jbyte *data = env->GetByteArrayElements(data_, NULL);

QByteArray buff;

buff.resize(len);

memcpy(buff.data(), (uint8_t *)data, len);

QMetaObject::invokeMethod(g_cH34xWidget, "onData", Qt::QueuedConnection, Q_ARG(QByteArray, buff));

env->ReleaseByteArrayElements(data_, data, 0);

return 0;

}

#ifdef __cplusplus

}

#endif

#if defined(Q_OS_ANDROID)

#include <jni.h>

#ifdef __cplusplus

extern "C" {

#endif

JNIEXPORT jint JNICALL

Java_org_qtproject_qt5_android_bindings_QtActivity_sendVideoData(

JNIEnv *env, jclass type, jlong cptr,

jbyteArray data_, jint len, jlong timestamp)

{

jbyte *data = env->GetByteArrayElements(data_, NULL);

uint8_t *buf = (uint8_t *)data;

TcpClient::instance()->sendVideo((uint8_t *)buf, len);

env->ReleaseByteArrayElements(data_, data, 0);

return 0;

}

#ifdef __cplusplus

}

#endif

JAVA代码

package com.qdian.testmyapp;

public class MainActivity extends AppCompatActivity {

{

public native String stringFromJNI();

}

C++代码

#include <jni.h>

#include <string>

extern "C" JNIEXPORT jstring JNICALL

Java_com_qdian_testmyapp_MainActivity_stringFromJNI(

JNIEnv* env,

jobject /* this */) {

std::string hello = "Hello from C++";

return env->NewStringUTF(hello.c_str());

}

java jni c++ 工作过程中常用的一些东西，在这里总结一下

获取field

env->getFieldID(class,"name",field类型);

获取method

env->getMethodID(class,"方法名"，(参数)返回类型 );

还有三个特殊的string object arraylist

string---Ljava/lang/String

object---Ljava/lang/Object

array---Ljava/util/ArrayList

char *转jstring

JNIEnv* env,

std::string hello = "Hello from C++";

jstring str=env->NewStringUTF(hello.c_str());

jstring转char *

JNIEnv* env,

jboolean isCopy;

//evn:JNI 接口指针,data:Java 字符串对象,isCopy:指向布尔值的指针

char *startData = (*evn)->GetStringUTFChars(evn, data, &isCopy);

//使用了GetStringUTFChars一定要调用ReleaseStringChars函数释放资源

//env:JNI 接口指针,data:Java 字符串对象,指向UTF-8 字符串的指针

(*evn)->ReleaseStringUTFChars(evn,data,startData);

JNIEnv的使用在C和C++中的区别

2人收藏此文章, 我要收藏发表于1个月前(2012-10-09 18:59) , 已有 121次阅读，共 0个评论

对于JNIEnv *env来说，在C中调用：

(*env)->NewStringUTF(env, "Hello from JNI!");

而在C++中如果按照上述调用则会发生'base operand of '->' has non-pointer type '_JNIEnv''错误，需要如下调用：

env->NewStringUTF("Hello from JNI!");

JNIEXPORT jstring JNICALL getString(JNIEnv *evn, jobject jobject1, jstring data) {

jboolean isCopy;

//evn:JNI 接口指针,data:Java 字符串对象,isCopy:指向布尔值的指针

char *startData = (*evn)->GetStringUTFChars(evn, data, &isCopy);

char *endData="Hello";

int size1=strlen(startData);

int size2= strlen(endData);

char resultData[256];

int index=-1;

for(int k=0;k<size1;k++){

resultData[++index]=startData[k];

}

for(int k=0;k<size2;k++){

resultData[++index]=endData[k];

}

jstring result=(*evn)->NewStringUTF(evn,resultData);

//使用了GetStringUTFChars一定要调用ReleaseStringChars函数释放资源

//env:JNI 接口指针,data:Java 字符串对象,指向UTF-8 字符串的指针

(*evn)->ReleaseStringUTFChars(evn,data,startData);

return result;

}

jni 方法签名： {"getString","(Ljava/lang/String;)Ljava/lang/String;",(void*)getString},

java调用 getString("jni-") 返回：jni-hello

使用JNIEnv全局变量调用FindClass()等函数发生crash

jclass remotedesktopclass = sJniEnv->FindClass("com/xxx/xxx/xxx/xxx");

sJniEnv是一个全局变量,但其实不应该全局保存JNIEnv。

这是一个和thread紧密关联的变量，在其他线程中使用就会crash。

【解决方式】

JNIEXPORT void JNICALL Java_xx_xx_xx_xx_xxx(JNIEnv * jniEnv, jobject object, jstring jflowNum, jstring judid){

jniEnv->GetJavaVM(&javaVm);

jclass tmp = jniEnv->FindClass("com/nationsky/rc/util/RemoteDesktopUtil");

remotedesktopclass = (jclass)jniEnv->NewGlobalRef(tmp);

.............

static void keyPress(int keyCode){

JavaVMAttachArgs args = { JNI_VERSION_1_6, __FUNCTION__, __null };

JNIEnv* jniEvn = __null;

int res = javaVm->AttachCurrentThread(&jniEvn, &args);

method = jniEvn->GetStaticMethodID(remotedesktopclass,

"pressHome", "()V");

使用JNIEnv全局变量调用FindClass()等函数发生crash

jclass remotedesktopclass = sJniEnv->FindClass("com/xxx/xxx/xxx/xxx");

sJniEnv是一个全局变量,但其实不应该全局保存JNIEnv。

这是一个和thread紧密关联的变量，在其他线程中使用就会crash。

【解决方式】

JNIEXPORT void JNICALL Java_xx_xx_xx_xx_xxx(JNIEnv * jniEnv, jobject object, jstring jflowNum, jstring judid){

jniEnv->GetJavaVM(&javaVm);

jclass tmp = jniEnv->FindClass("com/nationsky/rc/util/RemoteDesktopUtil");

remotedesktopclass = (jclass)jniEnv->NewGlobalRef(tmp);

.............

static void keyPress(int keyCode){

JavaVMAttachArgs args = { JNI_VERSION_1_6, __FUNCTION__, __null };

JNIEnv* jniEvn = __null;

int res = javaVm->AttachCurrentThread(&jniEvn, &args);

method = jniEvn->GetStaticMethodID(remotedesktopclass,

"pressHome", "()V");

Qt控件内加控件

Qt5增强了很多安全性验证，如果出现setGeometry: Unable to set geometry，请将该控件的可见移到加入布局之后。

可以将控件A添加到布局，然后控件B设置该布局，这种灵活性大大提高了控件的组合度，比如可以在文本框左侧右侧增加一个搜索按钮，按钮设置图标即可。

QPushButton *btn = new QPushButton;

btn->resize(30, ui->lineEdit->height());

QHBoxLayout *layout = new QHBoxLayout(ui->lineEdit);

layout->setMargin(0);

layout->addStretch();

layout->addWidget(btn);

Qml控件占据剩余空间

Label {

id: titleLabel

text: listView.currentItem ? listView.currentItem.text : "Gallery"

font.pixelSize: 20

elide: Label.ElideRight

horizontalAlignment: Qt.AlignHCenter

verticalAlignment: Qt.AlignVCenter

Layout.fillWidth: true

}

ToolButton

工具栏

ToolBar { //工具栏

RowLayout{ //横向

ToolButton{} //工具按钮

ToolButton{}

}

发布QML程序

windeployqt g:\HelloPlayer\HelloPlayer.exe --qmldir F:\QtAll\5.12.3\mingw73_32\qml

Qt播放视频报错 DirectShowPlayerService::doRender: Unresolved error code 0x80040266

下载并安装 LAVFilters：https://github.com/Nevcairiel/LAVFilters/releases

installer方式直接按步骤安装

压缩包方式解压右键以管理员运行 install_video.bat 文件

切记：需要重启电脑

完美，没毛病

播放器代码

QT += quick multimedia

CONFIG += c++11

#include <QGuiApplication>

#include <QQmlApplicationEngine>

int main(int argc, char *argv[])

{

QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

QGuiApplication app(argc, argv);

QQmlApplicationEngine engine;

const QUrl url(QStringLiteral("qrc:/main.qml"));

QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,

&app, [url](QObject *obj, const QUrl &objUrl) {

if (!obj && url == objUrl)

QCoreApplication::exit(-1);

}, Qt::QueuedConnection);

engine.load(url);

return app.exec();

}

import QtQuick 2.12

import QtMultimedia 5.0

import QtQuick.Window 2.12

import QtQuick.Controls 2.12

//运行报错：Warning: "No decoder available for type 'video/x-h264, stream-format=(string)avc...

//sudo apt-get install gstreamer1.0-libav 即可解决 Qt在linux下使用gstreamer，Windows下使用directshow

ApplicationWindow {

width: 800

height: 600

title: "视频"

visible: true

property var date: new Date()

function parseTotalDuration(time) {

date.setTime(time)

if (time / 3600000 >= 1) {

//大于1小时

return Math.floor(time / 3600000) + ":" + Qt.formatDateTime(date,

"mm:ss")

} else {

return Qt.formatTime(date, "mm:ss")

}

Rectangle {

id: video

width: parent.width

height: 450

MediaPlayer {

id: mediaPlayer

source: "http://www.1xn1.com/upfiles/files/201912/2d67b6b5758c4098b8b8bd9534532b7c.mp4"

autoPlay: true

onError: {

console.log(errorString)

}

//position 属性单位是毫秒，onPositionChanged 信号处理器，实时显示进度

onPositionChanged: {

progress.text = parseTotalDuration(

position) + progress.time

}

//duration 单位是毫秒，onDurationChanged 信号处理器，可以取到时长

onDurationChanged: {

progress.time = " / " + parseTotalDuration(duration)

}

onPlaybackStateChanged: {

switch (playbackState) {

case MediaPlayer.PlayingState:

state.text = "播放中"

break

case MediaPlayer.PausedState:

state.text = "已暂停"

break

case MediaPlayer.StoppedState:

state.text = "已结束"

break

}

//多媒体元信息

onStatusChanged: {

switch (status) {

case MediaPlayer.Loaded:

console.log(metaData.albumArtist, metaData.albumTitle,

metaData.author, metaData.channelCount)

break

}

VideoOutput {

anchors.fill: parent

source: mediaPlayer

}

MouseArea {

anchors.fill: parent

onDoubleClicked: {

if (mediaPlayer.playbackState === 2) {

mediaPlayer.play()

} else if (mediaPlayer.playbackState === 1) {

mediaPlayer.pause()

} else {

mediaPlayer.play()

}

Connections {

target: mediaPlayer

onStopped: {

}

Text {

id: progress

anchors.left: video.left

anchors.top: video.bottom

anchors.topMargin: 10

color: "#000000"

font.pointSize: 12

property string time

}

Text {

id: state

anchors {

verticalCenter: progress.verticalCenter

horizontalCenter: parent.horizontalCenter

}

color: "#000000"

font.pointSize: 12

}

Rectangle {

id: progressBar

anchors.left: parent.left

anchors.right: parent.right

anchors.top: progress.bottom

anchors.topMargin: 6

height: 6

radius: 3

color: "darkgray"

Rectangle {

anchors.left: parent.left

anchors.top: parent.top

anchors.bottom: parent.bottom

radius: 3

width: mediaPlayer.duration > 0 ? parent.width * mediaPlayer.position

/ mediaPlayer.duration : 0

color: "#4A6DBC"

}

MouseArea {

property int pos

anchors.fill: parent

onClicked: {

//seekable 属性指示媒体是否支持 seek,为true时，用seek(pos)方法来定位播放

if (mediaPlayer.seekable)

pos = mediaPlayer.duration * mouse.x / width

mediaPlayer.seek(pos)

}

qt android动态权限申请

前端时间要用qt开发一个android程序，结果发现在真机运行的时候莫名其妙无法加载写入文件，导致项目被搁置，今天重新研究了一下，终于搞定了，特此记录一下

工程中引入模块 androidextras

接下来项目中加入如下代码

bool MainWindow::requestPermission()

{

QtAndroid::PermissionResult r = QtAndroid::checkPermission("android.permission.WRITE_EXTERNAL_STORAGE");

if(r == QtAndroid::PermissionResult::Denied) {

QtAndroid::requestPermissionsSync(QStringList()<<"android.permission.WRITE_EXTERNAL_STORAGE");

r = QtAndroid::checkPermission("android.permission.CAMERA");

if(r == QtAndroid::PermissionResult::Denied) {

return false;

}

return true;

}

使用权限前调用函数requestPermission();就可以了

但是里面要修改成相应权限

android.permission.WRITE_EXTERNAL_STORAGE

android.permission.READ_EXTERNAL_STORAGE

android.permission.CAMERA

另外手机内存卡的根目录就是/storage/emulated/0/

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