Question

我从Mario Zechner的书＃34; Beginning Android Games，2nd Edition开始构思这个游戏＆＃34;所以归功于他！

现在，我想在屏幕上创建和动画很多对象，比如＆＃34;敌人或块＃34;。我想创建一个单独的类，并在这个类中创建一个数组或链接的实例列表，这样我就不必为每个＆＃34;敌人＆＃34;编写代码。我想在那里定义那里的运动。我试过......

Enemy e = new Enemy(canvas);

但它不起作用。我是Android的初学者，拼命想学习！我想出了运动，碰撞等，但是卡在这里。请给我一些想法。

public class MyGFXSur extends SurfaceView implements Runnable{

    SurfaceHolder holder;
    Thread thread = null;
    boolean isRunning = false;

    public MyGFXSur(Context context) {
        super(context);
        holder = getHolder();

    }

    public void pause(){
        isRunning = false;
        while (true){
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            break;
        }
        thread = null;
    }

    public void resume(){
        isRunning = true;
        thread = new Thread(this);
        thread.start();
    }

    @Override
    public void run() {
        while(isRunning){
            if(!holder.getSurface().isValid()){
                continue;
            }
            Canvas canvas = holder.lockCanvas();
            canvas.drawRGB(02, 02, 150);
            if(x != 0 && y != 0){
                Bitmap test = BitmapFactory.decodeResource(getResources(), R.drawable.greenball);
            canvas.drawBitmap(test, x-(test.getWidth()/2), y-(test.getWidth()/2), null);
            }
            holder.unlockCanvasAndPost(canvas);
        }
    }
}

另一类......

public class GFXSur extends Activity implements View.OnTouchListener{

    MyGFXSur mygfxsur;
    float x, y;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mygfxsur = new MyGFXSur(this);
        mygfxsur.setOnTouchListener(this);
        x = 0;
        y = 0;
        setContentView(mygfxsur);


    }

    @Override
    protected void onResume() {
        super.onResume();
        mygfxsur.resume();
    }

    @Override
    protected void onPause() {
        super.onPause();
        mygfxsur.pause();
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {

        x = event.getX();
        y = event.getY();

        return true;
    }
}

我尝试了以下操作，但是我收到了这个错误：＆＃34;无法解析方法getResources（）＆＃34;

public class Enemy {
    public Enemy(Canvas canvas) {
        Bitmap test = BitmapFactory.decodeResource(getResources(), R.drawable.greenball);
        canvas.drawBitmap(test, 100, 100, null);
    }
}

Answer 1

在这里，您应该给出一个如何处理自绘图对象的提示：

定义DrawingObject应该做什么的SuperClass

public abstract class DrawinObject{ 
    public abstract void draw(Canvas canvas);
    public abstract void updatePhysics();
}

实现Class，例如绘制一个Rect，但你可以绘制任何东西

public class MyRect extends DrawinObject{

    Paint paint;
    Context context;

    public MyRect(Context context){
        //do some init
        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
    }

    public void updatePhysics(){

    }

    public void draw(Canvas canvas){
        //if you need some resources eg drawables just call
        //context.getResources().getDrawables(R.drawable.ic_launcher);
        canvas.drawRect(30, 30, 80, 80, paint);
    }
}

另一个实现

public class MyCircle extends DrawinObject{

    Paint paint;
    int x, y;

    public MyRect(){
        //do some init
        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.WHITE);

        x= 10;
        y = 30;
    }   

    public void updatePhysics(){
        x++;
        y++;
    }


    public void draw(Canvas canvas){
         canvas.drawCircle(x / 2, y / 2, radius, paint);
    }
}

现在，只需将它们添加到List并循环遍历游戏循环中的列表

即可

//MAIN
private ArrayList<DrawinObject> myDrawingObjects;
    public MyGFXSur(Context context){
        myDrawingObjects = new ArrayList<DrawinObject>();
        myDrawingObjects.add(new MyCircle());
        myDrawingObjects.add(new MyRect(MainActivity.this)); 
    }


     @Override
    public void run() {
        while(isRunning){
            if(!holder.getSurface().isValid()){
                continue;
            }
            updatePhysics();
            Canvas canvas = holder.lockCanvas();
            drawObjects(canvas);    
            holder.unlockCanvasAndPost(canvas);
        }
    }

    private void updatePhysics(){
        for(DrawinObject drawObject : myDrawingObjects){
            drawObject.updatePhysics();
        }   
    }

    private void drawObjects(Canvas canvas){
        for(DrawinObject drawObject : myDrawingObjects){
            drawObject.draw(canvas);
        }
    }

Answer 2

您必须处理从活动到Enemy Class的上下文，在该类中您拥有了decodeBitmap方法。否则为NULLPointer异常

在Canvas中绘制多个对象

2 个答案: