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Eskil Abrahamsen Blomfeldt 在他的博客上发表了一篇文章,展示了如何在此处从 C++ 调用 QtActivity/(HangmanActivity) 静态 Java 方法。

他提到他只使用静态方法,因为这更容易(确实)并且在他的示例中不需要更多。引用:

在我的游戏中,Activity 是一个单例,所以我在构造函数中存储了对该对象的静态引用。(我的 C++ Data 类具有相同的逻辑。我这样做是为了方便使用静态方法在 Java 和 C++ 代码之间进行通信。对于更复杂的示例,还可以在每个 C++ 中存储引用和指针和 Java 对象,将其映射到其他语言中的等价物,但这在这个游戏中不是必需的。)

调用静态方法有效。调用非静态方法不起作用(从未输入函数)。如果我在 onCreate() 中调用非静态方法 connectBluetooth() 它可以工作。有没有办法可以调用并且在 onCreate() 中没有非静态方法?

编辑:

我想我会添加一些代码。我扩展了 QtActivity 类:

package org.qtproject.qt5.android.bindings;

import org.qtproject.qt5.android.bindings.QtApplication;
import org.qtproject.qt5.android.bindings.QtActivity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import java.lang.String;

public class MyActivity extends QtActivity
{
    private BluetoothAdapter bluetoothAdapter;
    private static final int ENABLE_BLUETOOTH_REQUEST = 1;

        public MyActivity()
        {
            Log.d(QtApplication.QtTAG, "MyActivity constructor called");
        }

        @Override
        public void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
        }

        @Override
        public void onDestroy()
        {
            super.onDestroy();
        }

    @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data)
    {
                Log.d(QtApplication.QtTAG, "onActivityResult entered");
        if(requestCode == 1)
        {
            if(requestCode == 1)
            {
                if(resultCode == RESULT_OK)
                {
                                        Log.d(QtApplication.QtTAG, "User accepted to enable Bluetooth");
                }
                else if(resultCode == RESULT_CANCELED)
                {
                                        Log.d(QtApplication.QtTAG, "User declined to enable Bluetooth");
                }
            }
        }
    }

        public void connectBluetooth()
        {
            Log.d(QtApplication.QtTAG, "connectBluetooth() entered");
            bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
            if(bluetoothAdapter == null)
            {
                Log.d(QtApplication.QtTAG, "Bluetooth adapter is not found");
                return;
            }

            if(!bluetoothAdapter.isEnabled())
            {
                Log.d(QtApplication.QtTAG, "Bluetooth is off");
                Intent enableBluetoothIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBluetoothIntent, ENABLE_BLUETOOTH_REQUEST);
            }
        }

        public static void test()
        {
            Log.d(QtApplication.QtTAG, "Static Test OK!");
        }
}

我尝试从这个 C++ 类中调用这些方法:

#include "bluetooth.h"
#include <QtAndroidExtras>
#include <QDebug>

Bluetooth::Bluetooth(QObject *parent) :
    QObject(parent)
{
}

void Bluetooth::connect()
{
    //Test static call
    QAndroidJniObject::callStaticMethod<void>("org/qtproject/qt5/android/bindings/MyActivity", "test");


    //Test non-static call
    //Line below creates a new object and is a subclass of QtActivity.
    bluetooth = new QAndroidJniObject("org/qtproject/qt5/android/bindings/MyActivity");

    if(!bluetooth->isValid())
    {
        qDebug() << "bluetooth is an invalid java object";
        return;
    }

    bluetooth->callMethod<void>("connectBluetooth");
}

编辑: 我最不确定的程序部分是 AndroidManifest.xml。也许这里有一些东西可以解释这种行为?

<?xml version='1.0' encoding='utf-8'?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" package="org.qtproject.example.AndroidTest" android:versionName="1.0" android:installLocation="auto">
    <application android:label="@string/app_name" android:name="org.qtproject.qt5.android.bindings.QtApplication">
        <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|locale|fontScale|keyboard|keyboardHidden|navigation" android:label="@string/app_name" android:name="org.qtproject.qt5.android.bindings.MyActivity" android:screenOrientation="unspecified">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
            <meta-data android:value="AndroidTest" android:name="android.app.lib_name"/>
            <meta-data android:resource="@array/qt_sources" android:name="android.app.qt_sources_resource_id"/>
            <meta-data android:value="default" android:name="android.app.repository"/>
            <meta-data android:resource="@array/qt_libs" android:name="android.app.qt_libs_resource_id"/>
            <meta-data android:resource="@array/bundled_libs" android:name="android.app.bundled_libs_resource_id"/>
            <!-- Deploy Qt libs as part of package -->
            <meta-data android:value="1" android:name="android.app.bundle_local_qt_libs"/>
            <meta-data android:resource="@array/bundled_in_lib" android:name="android.app.bundled_in_lib_resource_id"/>
            <meta-data android:resource="@array/bundled_in_assets" android:name="android.app.bundled_in_assets_resource_id"/>
            <!-- Run with local libs -->
            <meta-data android:value="1" android:name="android.app.use_local_qt_libs"/>
            <meta-data android:value="/data/local/tmp/qt/" android:name="android.app.libs_prefix"/>
            <meta-data android:value="plugins/platforms/android/libqtforandroidGL.so:lib/libQt5QuickParticles.so" android:name="android.app.load_local_libs"/>
            <meta-data android:value="jar/QtAndroid.jar:jar/QtAndroidAccessibility.jar:jar/QtAndroid-bundled.jar:jar/QtAndroidAccessibility-bundled.jar" android:name="android.app.load_local_jars"/>
            <meta-data android:value="" android:name="android.app.static_init_classes"/>
            <!--  Messages maps -->
            <meta-data android:value="@string/ministro_not_found_msg" android:name="android.app.ministro_not_found_msg"/>
            <meta-data android:value="@string/ministro_needed_msg" android:name="android.app.ministro_needed_msg"/>
            <meta-data android:value="@string/fatal_error_msg" android:name="android.app.fatal_error_msg"/>
            <!--  Messages maps -->
            <!-- Splash screen -->
            <meta-data android:resource="@layout/splash" android:name="android.app.splash_screen"/>
            <!-- Splash screen -->
        </activity>
    </application>
    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19"/>
    <supports-screens android:smallScreens="true" android:anyDensity="true" android:largeScreens="true" android:normalScreens="true"/>
    <uses-permission android:name="android.permission.BLUETOOTH"/>
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>
4

1 回答 1

0

我仍然不能调用非静态函数,但是一种解决方法是使用单例模式,它将类的实例化限制为一个对象并调用能够调用非静态方法的静态函数。

这是通过在构造函数中添加对自身的类/对象引用来完成的:

private static MyActivity m_instance;

public MyActivity()
{
    m_instance = this;
}

现在可以在静态函数中调用非静态函数。例如,上面的非静态函数 bluetoothConnect() 现在可以重写为:

public static void connectBluetooth()
{
    Log.d(QtApplication.QtTAG, "connectBluetooth() entered");
    m_instance.bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if(m_instance.bluetoothAdapter == null)
    {
        Log.d(QtApplication.QtTAG, "Bluetooth adapter is not found");
        return;
    }

    if(!m_instance.bluetoothAdapter.isEnabled())
    {
        Log.d(QtApplication.QtTAG, "Bluetooth is off");
        Intent enableBluetoothIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        m_instance.startActivityForResult(enableBluetoothIntent, ENABLE_BLUETOOTH_REQUEST);
    }
    else
    {
        Log.d(QtApplication.QtTAG, "Bluetooth is on");
        m_instance.startDiscovery();
    }
}

这里唯一的区别是在方法中添加了 static 关键字并添加了“m_instance”。在每个非静态方法调用之前。

现在可以从 C++ 调用此函数作为静态函数:

QAndroidJniObject::callStaticMethod<void>("org/qtproject/qt5/android/bindings/MyActivity", "connectBluetooth");

我想这是一个单例的缺点是只能制作这个类的一个对象,但据我所知,它不会限制太多..

这只是一种解决方法,我仍然对如何调用非静态函数非常感兴趣。此答案不会被接受为已接受的答案。

于 2014-01-04T19:07:24.500 回答