Question

我做了一个程序来画一个球在屏幕上弹跳。它昨天工作正常，但我只是加载它，现在它不会在正确的X位置绘制，它只是停留在0. Y仍然很好但是..

class GameThreadView extends SurfaceView implements Runnable {


// for thread
 Thread renderThread = null;
 // volatile equals keep order of execution
 volatile boolean running = false; 
 // for canvas, also used to synchronize
 SurfaceHolder holder;
 GameThreadAndroid gta;
 Paint bg;
 Paint fg;
 // game stuff
 int frameCount = 0;
 int count = 0;
 float aDeltaTime = 0f;
 float accumTime = 0f;

 int touchX = -50;
 int touchY = -50;

 float ballX, ballY = 0.5f;

 float moveX, moveY = 0.2f;

 Random r = new Random();

 public GameThreadView(Context context) {
  super(context);  
  gta = (GameThreadAndroid)context;

  holder = getHolder();   

  fg = new Paint(Paint.ANTI_ALIAS_FLAG);
  fg.setTextSize(36);
  fg.setTextAlign(Paint.Align.CENTER);
  fg.setColor(getResources().getColor(R.color.text));

  bg = new Paint();
  bg.setColor(getResources().getColor(R.color.background));
  Log.d("GAME","GameThreadView");

  // 
  moveY = r.nextFloat() * 0.5f;
 }

 /*
  * Actually always starts a new thread
  */
 public void resume() {          
  running = true;
  renderThread = new Thread(this);
  renderThread.start();         
 }
 /*
  * Actually kills thread
  */
 public void pause() {        
  running = false;

  while(true) {
   try {
    renderThread.join();
    break;
   } catch (InterruptedException e) {
    // retry
   }
  }
  renderThread = null;        
 }

 public void run() {
  long startTime = System.nanoTime();

  while(running) {  
   if(!holder.getSurface().isValid())
    continue;

   float deltaTime = (System.nanoTime()-startTime)/1000000000.0f;
   startTime = System.nanoTime();

   updateGame(deltaTime);

   Canvas canvas = holder.lockCanvas();            
   drawSurface(canvas);                                           
   holder.unlockCanvasAndPost(canvas);            
  }
 } 
 // All game logic
 private void updateGame(float deltaTime) {
  accumTime += deltaTime;
  count++;        

  if (accumTime > 1f) {
   aDeltaTime = deltaTime;
   frameCount = count;
   count = 0;
   accumTime = 0;
   Log.d("GAME", String.format("frame count = %d", frameCount));
  }

  // move the ball
  ballX += moveX * deltaTime;
  ballY += moveY * deltaTime;

  // hit walls
  if(ballX > 1.0f){
   ballX = 1.0f;
   moveX = -moveX;
  }
  if(ballY > 1.0f){
   ballY = 1.0f;
   moveY = -moveY;
  }
  if(ballX < 0.0f){
   ballX = 0.0f;
   moveX = -moveX;
  }
  if(ballY < 0.0f){
   ballY = 0.0f;
   moveY = -moveY;
  }
 }

 private void drawSurface(Canvas canvas) {    
  canvas.drawPaint(bg);

  int w = canvas.getWidth() / 2;
  canvas.drawText(Integer.toString(frameCount), w, canvas.getHeight() * 1/3, fg);          
  canvas.drawText(Float.toString(aDeltaTime), w, canvas.getHeight() * 2/3, fg);   

  canvas.drawCircle(ballX * canvas.getWidth(), ballY * canvas.getHeight(), 20, fg);
 }


 /*
  * Called from outside this object so must be synchronized
  * @see android.view.View#onTouchEvent(android.view.MotionEvent)
  */
 public boolean onTouchEvent(MotionEvent event) {
  synchronized (this) {
   switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
   case MotionEvent.ACTION_MOVE:
   case MotionEvent.ACTION_UP:
    touchX = (int) event.getX();
    touchY = (int) event.getY();
    break;
   }
   return true;
  }
 }

Answer 1

我认为问题在于你永远不会在这里初始化moveX（用零初始化）：

float moveX, moveY = 0.2f;

并在下一个方法中再次设置moveY，但moveX的值仍为零：

public GameThreadView(Context context) {
    super(context);  
    gta = (GameThreadAndroid)context;

    holder = getHolder();   

    fg = new Paint(Paint.ANTI_ALIAS_FLAG);
    fg.setTextSize(36);
    fg.setTextAlign(Paint.Align.CENTER);
    fg.setColor(getResources().getColor(R.color.text));

    bg = new Paint();
    bg.setColor(getResources().getColor(R.color.background));
    Log.d("GAME","GameThreadView");

   // Here you set moveY 
   moveY = r.nextFloat() * 0.5f;

   // You need to add somthing similar to moveX, like this
   moveX = r.nextFloat() * 0.5f;


 }

通过该更改，它应该按预期运行。

希望它可以帮助你：）

Eclipse，drawCircle函数没有绘制到正确的位置

1 个答案: