Cocos2d-x-3.6 用户交互原理---------如何通过JNI连接Java和C++

cocos2d-xc++JavaJNI

            用户交互这里指的就是用户在手机上的点击，滑动以及晃动手机等行为，从而得到相应的反馈。今天学习Cocos2dx，遇到交互问题，所以就写出来和大家分享一下。我这里是以Android连接为例的，因为目前我只会Android相关的开发。好了，不多说，看下面步骤：

第一步：在Android中，交互操作的入口在SurfaceView或是GLSurfaceView中的onTouchEvent时间中。本例代码所在位置org.cocos2dx.lib---->Cocos2dxGLSurfaceView.java

public boolean onTouchEvent(final MotionEvent pMotionEvent) {
        // these data are used in ACTION_MOVE and ACTION_CANCEL
        final int pointerNumber = pMotionEvent.getPointerCount();
        final int[] ids = new int[pointerNumber];
        final float[] xs = new float[pointerNumber];
        final float[] ys = new float[pointerNumber];

        for (int i = 0; i < pointerNumber; i++) {
            ids[i] = pMotionEvent.getPointerId(i);
            xs[i] = pMotionEvent.getX(i);
            ys[i] = pMotionEvent.getY(i);
        }

        switch (pMotionEvent.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_POINTER_DOWN:
                final int indexPointerDown = pMotionEvent.getAction() >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int idPointerDown = pMotionEvent.getPointerId(indexPointerDown);
                final float xPointerDown = pMotionEvent.getX(indexPointerDown);
                final float yPointerDown = pMotionEvent.getY(indexPointerDown);

                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionDown(idPointerDown, xPointerDown, yPointerDown);
                    }
                });
                break;

            case MotionEvent.ACTION_DOWN:
                // there are only one finger on the screen
                final int idDown = pMotionEvent.getPointerId(0);
                final float xDown = xs[0];
                final float yDown = ys[0];

                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionDown(idDown, xDown, yDown);
                    }
                });
                break;

            case MotionEvent.ACTION_MOVE:
                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionMove(ids, xs, ys);
                    }
                });
                break;

            case MotionEvent.ACTION_POINTER_UP:
                final int indexPointUp = pMotionEvent.getAction() >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int idPointerUp = pMotionEvent.getPointerId(indexPointUp);
                final float xPointerUp = pMotionEvent.getX(indexPointUp);
                final float yPointerUp = pMotionEvent.getY(indexPointUp);

                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionUp(idPointerUp, xPointerUp, yPointerUp);
                    }
                });
                break;

            case MotionEvent.ACTION_UP:
                // there are only one finger on the screen
                final int idUp = pMotionEvent.getPointerId(0);
                final float xUp = xs[0];
                final float yUp = ys[0];

                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionUp(idUp, xUp, yUp);
                    }
                });
                break;

            case MotionEvent.ACTION_CANCEL:
                this.queueEvent(new Runnable() {
                    @Override
                    public void run() {
                        Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionCancel(ids, xs, ys);
                    }
                });
                break;
        }

            return true;
    }

第二步： Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleActionDown(idDown, xDown, yDown)等相关语句的方法在org.cocos2dx.lib------>Cocos2dxRender.java，代码如下：

private static native void nativeTouchesBegin(final int id, final float x, final float y);
private static native void nativeTouchesEnd(final int id, final float x, final float y);
private static native void nativeTouchesMove(final int[] ids, final float[] xs, final float[] ys);
private static native void nativeTouchesCancel(final int[] ids, final float[] xs, final float[] ys);

public void handleActionDown(final int id, final float x, final float y) {
    Cocos2dxRenderer.nativeTouchesBegin(id, x, y);
}

public void handleActionUp(final int id, final float x, final float y) {
    Cocos2dxRenderer.nativeTouchesEnd(id, x, y);
}

public void handleActionCancel(final int[] ids, final float[] xs, final float[] ys) {
    Cocos2dxRenderer.nativeTouchesCancel(ids, xs, ys);
}

public void handleActionMove(final int[] ids, final float[] xs, final float[] ys) {
    Cocos2dxRenderer.nativeTouchesMove(ids, xs, ys);
}

第三步：  private static native void nativeTouchesBegin(final int id, final float x, final float y)这是本地方法，调用c++内容的语句。而这些内容被打包在Android工程中的libs/armeabi/cocos2dcpp.so文件中。所以我们在使用这些方法时一定要加载这个.so文件。代码位置在org.cocos2dx.lib--->Cocos2dxActivity.java，内容如下：

protected void onLoadNativeLibraries() {
       try {
           ApplicationInfo ai = getPackageManager().getApplicationInfo(getPackageName(), PackageManager.GET_META_DATA);
           Bundle bundle = ai.metaData;
           String libName = bundle.getString("android.app.lib_name");
           System.loadLibrary(libName);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }

bundle.getString("android.app.lib_name")文件是找出.so文件。和它相关内容在Android工程中AndroidManifest.xml里，内容如下：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="org.cocos.CocosProject4"
      android:versionCode="1"
      android:versionName="1.0"
      android:installLocation="auto">

    <uses-sdk android:minSdkVersion="9"/>
    <uses-feature android:glEsVersion="0x00020000" />

    <application android:label="@string/app_name"
                 android:icon="@drawable/icon">

        <!-- Tell Cocos2dxActivity the name of our .so -->
        <meta-data android:name="android.app.lib_name"
                  android:value="cocos2dcpp" />

        <activity android:name="org.cocos2dx.cpp.AppActivity"
                  android:label="@string/app_name"
                  android:screenOrientation="landscape"
                  android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
                  android:configChanges="orientation">

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

    <supports-screens android:anyDensity="true"
                      android:smallScreens="true"
                      android:normalScreens="true"
                      android:largeScreens="true"
                      android:xlargeScreens="true"/>

    <uses-permission android:name="android.permission.INTERNET"/>
</manifest>

第四步：cocos2dcpp.so文件的生成，因为native 方法都在这里面。它的生成在Android工程中的jni文件里么的Android.mk文件（相关内容参考链接）。native方法所在文件路径cocos2d-x-3.6/cocos/platform/android/jni/TouchesJni.cpp,内容如下：

#include "base/CCDirector.h"
#include "base/CCEventKeyboard.h"
#include "base/CCEventDispatcher.h"
#include "platform/android/CCGLViewImpl-android.h"

#include <android/log.h>
#include <jni.h>

using namespace cocos2d;

extern "C" {
    JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeTouchesBegin(JNIEnv * env, jobject thiz, jint id, jfloat x, jfloat y) {
        intptr_t idlong = id;
        cocos2d::Director::getInstance()->getOpenGLView()->handleTouchesBegin(1, &idlong, &x, &y);
    }

    JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeTouchesEnd(JNIEnv * env, jobject thiz, jint id, jfloat x, jfloat y) {
        intptr_t idlong = id;
        cocos2d::Director::getInstance()->getOpenGLView()->handleTouchesEnd(1, &idlong, &x, &y);
    }

    JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeTouchesMove(JNIEnv * env, jobject thiz, jintArray ids, jfloatArray xs, jfloatArray ys) {
        int size = env->GetArrayLength(ids);
        jint id[size];
        jfloat x[size];
        jfloat y[size];

        env->GetIntArrayRegion(ids, 0, size, id);
        env->GetFloatArrayRegion(xs, 0, size, x);
        env->GetFloatArrayRegion(ys, 0, size, y);

        intptr_t idlong[size];
        for(int i = 0; i < size; i++)
            idlong[i] = id[i];

        cocos2d::Director::getInstance()->getOpenGLView()->handleTouchesMove(size, idlong, x, y);
    }

    JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeTouchesCancel(JNIEnv * env, jobject thiz, jintArray ids, jfloatArray xs, jfloatArray ys) {
        int size = env->GetArrayLength(ids);
        jint id[size];
        jfloat x[size];
        jfloat y[size];

        env->GetIntArrayRegion(ids, 0, size, id);
        env->GetFloatArrayRegion(xs, 0, size, x);
        env->GetFloatArrayRegion(ys, 0, size, y);

        intptr_t idlong[size];
        for(int i = 0; i < size; i++)
            idlong[i] = id[i];

        cocos2d::Director::getInstance()->getOpenGLView()->handleTouchesCancel(size, idlong, x, y);
    }

    }

第五步：cocos2d::Director::getInstance()->getOpenGLView()->handleTouchesBegin(1, &idlong, &x, &y)这个方法是如何起作用的呢，文件位置在cocos2d-x-3.6/cocos/platform/CCGLView.cpp，内如如下：

void GLView::handleTouchesBegin(int num, intptr_t ids[], float xs[], float ys[])
{
    intptr_t id = 0;
    float x = 0.0f;
    float y = 0.0f;
    int unusedIndex = 0;
    EventTouch touchEvent;

    for (int i = 0; i < num; ++i)
    {
        id = ids[i];
        x = xs[i];
        y = ys[i];

        auto iter = g_touchIdReorderMap.find(id);

        // it is a new touch
        if (iter == g_touchIdReorderMap.end())
        {
            unusedIndex = getUnUsedIndex();

            // The touches is more than MAX_TOUCHES ?
            if (unusedIndex == -1) {
                CCLOG("The touches is more than MAX_TOUCHES, unusedIndex = %d", unusedIndex);
                continue;
            }

            Touch* touch = g_touches[unusedIndex] = new (std::nothrow) Touch();
            touch->setTouchInfo(unusedIndex, (x - _viewPortRect.origin.x) / _scaleX,
                                     (y - _viewPortRect.origin.y) / _scaleY);

            CCLOGINFO("x = %f y = %f", touch->getLocationInView().x, touch->getLocationInView().y);

            g_touchIdReorderMap.insert(std::make_pair(id, unusedIndex));
            touchEvent._touches.push_back(touch);
        }
    }

    if (touchEvent._touches.size() == 0)
    {
        CCLOG("touchesBegan: size = 0");
        return;
    }

    touchEvent._eventCode = EventTouch::EventCode::BEGAN;
    auto dispatcher = Director::getInstance()->getEventDispatcher();
    dispatcher->dispatchEvent(&touchEvent);
}

第六步：使用。首先要给_eventDispathcer(在CCNote.cpp文件中)添加listener,示例如下：

auto listener = EventListenerTouchAllAtOnce::create();
   listener->onTouchesBegan = CC_CALLBACK_2(ParticleDemo::onTouchesBegan, this);
   listener->onTouchesMoved = CC_CALLBACK_2(ParticleDemo::onTouchesMoved, this);
   listener->onTouchesEnded = CC_CALLBACK_2(ParticleDemo::onTouchesEnded, this);
   _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);

其次就是我们实际操作，使交互产生什么样的变化，代码如下：

void ParticleDemo::onTouchesBegan(const std::vector<Touch*>& touches, Event  *event)
{
    onTouchesEnded(touches, event);
}

void ParticleDemo::onTouchesMoved(const std::vector<Touch*>& touches, Event  *event)
{
    return onTouchesEnded(touches, event);
}

void ParticleDemo::onTouchesEnded(const std::vector<Touch*>& touches, Event  *event)
{
    auto touch = touches[0];

    auto location = touch->getLocation();

    auto pos = Vec2::ZERO;
    if (_background)
    {
        pos = _background->convertToWorldSpace(Vec2::ZERO);
    }

    if (_emitter != nullptr)
    {
        _emitter->setPosition(location -pos);
    }
}

上面代码是ParticleTest中的内容，通过dispathcer将参数最终传递给要变化的_mitter，就是粒子发射器的移动。