環境:Cocos2dx v3.5
經網上搜索資料知道有兩種方法可以實現Android返回鍵的退出功能,下面分別說明。
1、修改java代碼
首先,在Cocos2dx的源文件中找到Cocos2dxGLSurfaceView.java文件,它的路徑是:cocos2d\cocos\platform\android\java\src\org\cocos2dx\lib\Cocos2dxGLSurfaceView.java。注意要在自己的工程文件裏面找這個文件。
打開Cocos2dxGLSurfaceView.java,找到其中的onKeyDown函數:
@Override
public boolean onKeyDown(final int pKeyCode, final KeyEvent pKeyEvent) {
switch (pKeyCode) {
case KeyEvent.KEYCODE_BACK:
Cocos2dxVideoHelper.mVideoHandler.sendEmptyMessage(Cocos2dxVideoHelper.KeyEventBack);
case KeyEvent.KEYCODE_MENU:
case KeyEvent.KEYCODE_DPAD_LEFT:
case KeyEvent.KEYCODE_DPAD_RIGHT:
case KeyEvent.KEYCODE_DPAD_UP:
case KeyEvent.KEYCODE_DPAD_DOWN:
case KeyEvent.KEYCODE_ENTER:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
case KeyEvent.KEYCODE_DPAD_CENTER:
this.queueEvent(new Runnable() {
@Override
public void run() {
Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleKeyDown(pKeyCode);
}
});
return true;
default:
return super.onKeyDown(pKeyCode, pKeyEvent);
}
}
修改爲如下代碼(在case KeyEvent.KEYCODE_BACK分支中添加返回false的語句,表示不處理按鍵消息):
@Override
public boolean onKeyDown(final int pKeyCode, final KeyEvent pKeyEvent) {
switch (pKeyCode) {
case KeyEvent.KEYCODE_BACK:
Cocos2dxVideoHelper.mVideoHandler.sendEmptyMessage(Cocos2dxVideoHelper.KeyEventBack);
return false;
case KeyEvent.KEYCODE_MENU:
case KeyEvent.KEYCODE_DPAD_LEFT:
case KeyEvent.KEYCODE_DPAD_RIGHT:
case KeyEvent.KEYCODE_DPAD_UP:
case KeyEvent.KEYCODE_DPAD_DOWN:
case KeyEvent.KEYCODE_ENTER:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
case KeyEvent.KEYCODE_DPAD_CENTER:
this.queueEvent(new Runnable() {
@Override
public void run() {
Cocos2dxGLSurfaceView.this.mCocos2dxRenderer.handleKeyDown(pKeyCode);
}
});
return true;
default:
return super.onKeyDown(pKeyCode, pKeyEvent);
}
}
其次,找到AppActivity.java文件,其路徑爲:proj.android\src\org\cocos2dx\cpp\AppActivity.java。它的代碼如下:
package org.cocos2dx.cpp;
import org.cocos2dx.lib.Cocos2dxActivity;
public class AppActivity extends Cocos2dxActivity {
}
修改爲(添加onKeyDown方法,處理返回鍵按下事件):
package org.cocos2dx.cpp;
import org.cocos2dx.lib.Cocos2dxActivity;
import org.cocos2dx.lib.Cocos2dxGLSurfaceView;
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.widget.Toast;
public class AppActivity extends Cocos2dxActivity {
private long mKeyTime = 0;
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (KeyEvent.KEYCODE_BACK == keyCode && KeyEvent.ACTION_DOWN == keyCode) {
if ((System.currentTimeMillis() - mKeyTime) > 2000) {
mKeyTime = System.currentTimeMillis();
Toast.makeText(getApplicationContext(), "要離開遊戲嗎?", Toast.LENGTH_SHORT).show();
} else {
finish();
System.exit(0);
}
return true;
}
return super.onKeyDown(keyCode, event);
}
}
最終,重新編譯生成apk文件,按下Android手機的返回鍵,就能實現退出遊戲了。但是經測試,遊戲會直接退出,而不會出現提示,以後再探索。
2、在Cocos2dx中添加代碼
第一步,在Cocos2dx的場景類中添加虛方法:
virtual void onKeyReleased(cocos2d::EventKeyboard::KeyCode keyCode, cocos2d::Event* event);
第二步,實現該虛方法:
void HelloWorld::onKeyReleased(EventKeyboard::KeyCode keyCode, Event* event)
{
switch (keyCode)
{
case EventKeyboard::KeyCode::KEY_BACK: //返回鍵
//退出遊戲
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WP8) || (CC_TARGET_PLATFORM == CC_PLATFORM_WINRT)
MessageBox("You pressed the close button. Windows Store Apps do not implement a close button.","Alert");
return;
#endif
Director::getInstance()->end();
#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
exit(0);
#endif
break;
default:
break;
}
}
第三步,在場景類的init方法中添加按鍵事件監聽:
//Android按鍵監聽
auto keyboardListener = EventListenerKeyboard::create();
keyboardListener->onKeyReleased = CC_CALLBACK_2(HelloWorld::onKeyReleased, this);
this->getEventDispatcher()->addEventListenerWithSceneGraphPriority(keyboardListener, this);
最後,重新編譯,同樣能夠實現退出的效果。
結論:java代碼對Android系統有直接的操作,因此它比Cocos2dx的退出更直接,兩種方法再次啓動遊戲的時候會從頭加載資源。另外,官方demo中指出,第2種方法“Only avaliable on Desktop and Android”,即僅僅對WIndows平臺和Android平臺有效,並且需要在onKeyReleased事件中處理消息才能正確響應。