小编Jos*_*ury的帖子

我正在尝试使用以下代码将相机预览绘制到SurfaceHolder上:

    @Override
    public void onCreate(SurfaceHolder surfaceHolder) {
        super.onCreate(surfaceHolder);

        Log.d(TAG, "Releasing camera first, just to make sure");
        releaseCamera();

        Log.d(TAG, "Opening Camera object.");
        mCamera = Camera.open();

        if (mCamera == null) {
            Log.d(TAG, "Camera is null.");
        }
    }

    @Override
    public void onSurfaceCreated(SurfaceHolder holder) {
        super.onSurfaceCreated(holder);
        Log.d(TAG, "Surface created.");

        try {
            if (holder == null) {
                Log.d(TAG, "SurfaceHolder is empty.");
            }

            Log.d(TAG, "Setting preview display.");
            mCamera.setPreviewDisplay(holder);

        } catch (IOException e) {
            Log.d(TAG, "IOException on setPreviewDisplay.");

            releaseCamera();
        }
    }


  @Override
    public void onSurfaceChanged(SurfaceHolder holder, int …

我在App Engine(Python)中使用ReferencePropertys时遇到了一些麻烦.

为了一点乐趣,我正在尝试建模文件夹/文件系统,但无法获取文件夹引用文件夹.

我的第一次尝试是这样的:

class Folder(db.Model):
    id = db.StringProperty()
    name = db.StringProperty()
    created = db.DateTimeProperty(auto_now_add=True)
    folder = db.ReferenceProperty(Folder, collection_name="folders")

但是,当尝试定义"文件夹"时,未定义"文件夹",因此失败.

我也尝试在"文件夹"的主声明之外定义"文件夹",如下所示:

class Folder(db.Model):
    id = db.StringProperty()
    name = db.StringProperty()
    created = db.DateTimeProperty(auto_now_add=True)

Folder.folder = db.ReferenceProperty(Folder, collection_name="folders")

但是失败了:AttributeError:'Folder'对象没有属性'folders'

我有点难过.有没有人有这方面的经验,或解决这个问题？

提前致谢.

我有以下代码

#include <iostream>
#include <vector>

class Entity {
public:
    virtual void func() = 0;
};

class Monster : public Entity {
public:
    void func();
};

void Monster::func() {
std::cout << "I AM A MONSTER" << std::endl;
} 

class Buddha : public Entity {
public:
    void func();
};

void Buddha::func() {
std::cout << "OHMM" << std::endl;
}

int main() {
const int num = 5;  // How many of each to make
std::vector<Entity*> t;

for(int i = 0; i < num; …

嘿 - 我写的一个小玩具程序有一个奇怪的问题,试试线程.
这是我的代码:

#include <pthread.h>
#include <iostream>

using std::cout;
using std::endl;

void *threadFunc(void *arg) {
    cout << "I am a thread. Hear me roar." << endl;

    pthread_exit(NULL);
}

int main() {
    cout << "Hello there." << endl;
    int returnValue;
    pthread_t myThread;

    returnValue = pthread_create(&myThread, NULL, threadFunc, NULL);

    if (returnValue != 0) {
        cout << "Couldn't create thread! Whoops." << endl;
        return -1;
    }

    return 0;
}

主要的第一个cout没有注释掉,线程打印很好.
但是,没有它,线程根本不会打印任何东西.

有帮助吗？

我正在尝试在类中实例化一个类,以便外部类包含内部类.

这是我的代码:

#include <iostream>
#include <string>

class Inner {
    private: 
        std::string message;

    public:
        Inner(std::string m);
        void print() const;
};

Inner::Inner(std::string m) {
    message = m;
}

void Inner::print() const {
    std::cout << message << std::endl;
    std::cout << message << std::endl;
}

class Outer {
    private:
        std::string message;
        Inner in;

    public:
        Outer(std::string m);
        void print() const;
};

Outer::Outer(std::string m) {
    message = m;
}

void Outer::print() const {
    std::cout << message << std::endl;
}

int main() {
    Outer out("Hello world.");
    out.print(); …