while 循环导致 UI 变为空白
While loop causes UI to go blank
我正在编写一个简单的 Whack a Mole 克隆，并且我在 layout.xml 的 GridLayout 中声明了我的 UI 元素，然后以编程方式分配给数组中的 ImageView 变量。我有一个 startGame() 方法，它只需要一个 运行dom int，将其从数组中拉出并使其显示一秒钟，然后重复。出于某种原因，当我将此代码放入 while() 循环时，它会导致我的 UI 在启动后立即变为空白。
我知道这是 while() 循环，因为我尝试将代码从 while() 循环中取出，并且它 运行 正确（一次），但是当放在 while 循环中时一切都变白了。
这是导致问题的方法：
public void startGame() {
gameStarted = true;
while(gameStarted) {
randomInt = rand.nextInt(11);
mole[randomInt].setVisibility(View.VISIBLE);
handler.postDelayed(new Runnable() {
@Override
public void run() {
mole[randomInt].setVisibility(View.INVISIBLE);
}
}, 5000);
}
}
所有其他相关代码都在 onCreate 中，否则它只是骨架 Activity 子类。
public class WAM_Activity extends Activity {
private ImageView[] mole = new ImageView[11];
private int[] moleId = {R.id.mole1, R.id.mole3, R.id.mole4, R.id.mole5, R.id.mole6, R.id.mole7, R.id.mole8, R.id.mole9, R.id.mole10, R.id.mole11, R.id.mole12};
private boolean gameStarted;
private int randomInt = 0;
private Random rand = new Random();
Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.wam_view_layout);
for (int i = 0; i < 11; i++) {
mole[i] = (ImageView) findViewById(moleId[i]);
mole[i].setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//do stuff eventually
}
});
}
gameStarted = true;
startGame();
}
知道为什么这不起作用吗？我已经盯着它看了几个小时了，我很困惑。
Android 不能那样工作，当 onCreate 被调用时，它需要完成才能让应用程序继续响应，我很惊讶你没有得到任何 "App not respopnding"错误。
如果您想创建一个 "game loop"，您只需创建一个新的 Thread 并将 while 放在那里即可。
Activity 的生命周期必须在不阻塞它们的情况下执行，应用程序才能正常运行，有关更多信息，请查看 here.
你知道线程吗？如果您愿意，我可以 post 一个如何使用线程执行此操作的示例，但它可能很长，如果您不知道 Thread 是什么，它会让您感到困惑。
编辑：好的，我将举一个 Thread
的例子
当我创建我的游戏时，我通常只有一个 Activity，它唯一做的就是创建自定义 SurfaceView，没有别的。
public class GameActivity extends Activity
{
//This is a custom class that extends SurfaceView - I will write it below
private GameSurface game;
@Override
protected void onCreate(Bundle bundle)
{
super.onCreate(bundle);
//Create a new instance of the game
game = new GameSurface(this);
//Set the View of the game to the activity
setContentView(game);
}
}
您还可以添加额外的东西，例如 onSaveInstanceState 来保存游戏数据并稍后恢复它们，但我现在不想添加它们，所以代码看起来很简单。
这个class很简单，让我们继续我们的SurfaceView。我选择 SurfaceView 的原因是因为它允许在其上绘制自定义图形——这正是我们在视频游戏中想要的。我会尽量使 class 尽可能简单：
/*SurfaceHolder.Callback will run some functions in our class when
our surface is completed - at that point we can initialize data
that have to do with the View's width/height.
I don't know if you've noticed that on a View's onCreate()
when you call getWidth() or getHeight() you get 0, that's because
the surface is not initialized yet, this is a way to fix that.
Also we need a Runnable to run the Thread inside this class,
no need to make more classes and make it more complicated*/
public class GameSurface extends SurfaceView
implements SurfaceHolder.Callback, Runnable
{
//This is our thread - we need the "running" variable to be
//able to stop the Thread manually, this will go inside our "while" loop
private Thread thread;
private boolean running;
//Right here you can add more variables that draw graphics
//For example you can create a new class that has a function that
//takes Canvas as a parameter and draws stuff into it, I will add
//a Rect in this case which is a class already made by android
//but you can create your own class that draws images or more
//complicated stuff
private Rect myRect;
//Rect needs a paint to give it color
private Paint myPaint;
//Constructor
public GameSurface(Context context)
{
super(context);
//This is the callback to let us know when surface is completed
getHolder().addCallback(this);
}
//When a class implements SurfaceHolder.Callback you are forced to
//create three functions "surfaceCreated", "surfaceChanged" and
//"surfaceDestroyed" these are called when the surface is created,
//when some settings are changed (like the orientation) and when
//it is about to be destroyed
@Override
public void surfaceCreated(Surface holder)
{
//Let's initialize our Rect, lets assume we want it to have 40
//pixels height and fill the screen's width
myRect = new Rect(0, 0, getWidth(), 40);
//Give color to the rect
myPaint = new Paint();
myPaint.setARGB(0, 255, 0, 0);
//In case you are not familiar with the Rect class, as
//parameters it gets Rect(left, top, right, bottom)
//Time to start our Thread - nothing much to explain here if
//you know how threads work, remember this class implements
//Runnable so the Thread's constructor gets "this" as parameter
running = true;
thread = new Thread(this);
thread.start();
}
//We won't use this one for now, but we are forced to type it
//Even if we leave it empty
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
//When the surface is destroyed we just want the Thread to
//terminate - we don't want threads running when our app is not visible!
@Override
public void surfaceDestroyed(SurfaceHolder holder)
//We will type this function later
{destroyThread();}
//Time for the interesting stuff! let's start with input
@Override
public boolean onTouchEvent(MotionEvent event)
{
//The logic is as follows: when our Rect is touched, we want
//it to become smaller
if (event.getAction() == MotionEvent.ACTION_DOWN)
{
if (myRect.contains((int) event.getX(), (int) event.getY())
{
myRect.right -= 5;
//Return true - we did something with the input
return true;
}
}
return super.onTouchEvent(event);
}
//This is our update, it will run once per frame
private void update()
{
//Let's assume we want our rect to move 1 pixel downwards
//on every frame
myRect.offset(0, 1);
}
//Now for our draw function
public void draw(Canvas canvas)
{
//Here we want to draw a background and our rect
canvas.drawARGB(0, 0, 0, 255);
canvas.drawRect(myRect, myPaint);
}
//The only thing left is our run() function for the Thread
@Override
public void run()
{
//Screen
Canvas canvas;
//Our game cycle (the famous while)
while(running)
{
//Count start time so we can calculate frames
int startTime = System.currentTimeMillis();
//Update our game
update();
//Empty screen so it can obtain new instance
canvas = null;
//Try locking the canvas for pixel editing on surface
try
{
//Try getting screen
canvas = getHolder().lockCanvas();
//Succeeded
if (canvas != null) synchronized (getHolder())
{
//Actual drawing - our draw function
draw(canvas);
}
} finally
{
//Draw changes
if (canvas != null) getHolder().unlockCanvasAndPost(canvas);
}
//End Frame - 1000/30 means 30 frames per second
int frameTime = System.currentTimeMillis() -startTime;
if (frameTime < 1000/30)
try { Thread.sleep(1000/30 -frameTime); } catch (InterruptedException e){}
}
}
//Last but not least, our function for closing the thread
private void destroyThread()
{
//Stop thread's loop
running = false;
//Try to join thread with UI thread
boolean retry = true;
while (retry)
{
try {thread.join(); retry = false;}
catch (InterruptedException e) {}
}
}
}
我可能犯了一些小错误（可能是区分大小写的字母），所以请随时更正这些错误，我立即编写了代码，所以我没有时间测试它，但它应该可以完美运行。
如果您还有其他问题，需要更多解释或有什么不对，请告诉我！
我正在编写一个简单的 Whack a Mole 克隆，并且我在 layout.xml 的 GridLayout 中声明了我的 UI 元素，然后以编程方式分配给数组中的 ImageView 变量。我有一个 startGame() 方法，它只需要一个 运行dom int，将其从数组中拉出并使其显示一秒钟，然后重复。出于某种原因，当我将此代码放入 while() 循环时，它会导致我的 UI 在启动后立即变为空白。
我知道这是 while() 循环，因为我尝试将代码从 while() 循环中取出，并且它 运行 正确（一次），但是当放在 while 循环中时一切都变白了。
这是导致问题的方法：
public void startGame() {
gameStarted = true;
while(gameStarted) {
randomInt = rand.nextInt(11);
mole[randomInt].setVisibility(View.VISIBLE);
handler.postDelayed(new Runnable() {
@Override
public void run() {
mole[randomInt].setVisibility(View.INVISIBLE);
}
}, 5000);
}
}
所有其他相关代码都在 onCreate 中，否则它只是骨架 Activity 子类。
public class WAM_Activity extends Activity {
private ImageView[] mole = new ImageView[11];
private int[] moleId = {R.id.mole1, R.id.mole3, R.id.mole4, R.id.mole5, R.id.mole6, R.id.mole7, R.id.mole8, R.id.mole9, R.id.mole10, R.id.mole11, R.id.mole12};
private boolean gameStarted;
private int randomInt = 0;
private Random rand = new Random();
Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.wam_view_layout);
for (int i = 0; i < 11; i++) {
mole[i] = (ImageView) findViewById(moleId[i]);
mole[i].setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//do stuff eventually
}
});
}
gameStarted = true;
startGame();
}
知道为什么这不起作用吗？我已经盯着它看了几个小时了，我很困惑。
Android 不能那样工作，当 onCreate 被调用时，它需要完成才能让应用程序继续响应，我很惊讶你没有得到任何 "App not respopnding"错误。
如果您想创建一个 "game loop"，您只需创建一个新的 Thread 并将 while 放在那里即可。
Activity 的生命周期必须在不阻塞它们的情况下执行，应用程序才能正常运行，有关更多信息，请查看 here.
你知道线程吗？如果您愿意，我可以 post 一个如何使用线程执行此操作的示例，但它可能很长，如果您不知道 Thread 是什么，它会让您感到困惑。
编辑：好的，我将举一个 Thread
当我创建我的游戏时，我通常只有一个 Activity，它唯一做的就是创建自定义 SurfaceView，没有别的。
public class GameActivity extends Activity
{
//This is a custom class that extends SurfaceView - I will write it below
private GameSurface game;
@Override
protected void onCreate(Bundle bundle)
{
super.onCreate(bundle);
//Create a new instance of the game
game = new GameSurface(this);
//Set the View of the game to the activity
setContentView(game);
}
}
您还可以添加额外的东西，例如 onSaveInstanceState 来保存游戏数据并稍后恢复它们，但我现在不想添加它们，所以代码看起来很简单。
这个class很简单，让我们继续我们的SurfaceView。我选择 SurfaceView 的原因是因为它允许在其上绘制自定义图形——这正是我们在视频游戏中想要的。我会尽量使 class 尽可能简单：
/*SurfaceHolder.Callback will run some functions in our class when
our surface is completed - at that point we can initialize data
that have to do with the View's width/height.
I don't know if you've noticed that on a View's onCreate()
when you call getWidth() or getHeight() you get 0, that's because
the surface is not initialized yet, this is a way to fix that.
Also we need a Runnable to run the Thread inside this class,
no need to make more classes and make it more complicated*/
public class GameSurface extends SurfaceView
implements SurfaceHolder.Callback, Runnable
{
//This is our thread - we need the "running" variable to be
//able to stop the Thread manually, this will go inside our "while" loop
private Thread thread;
private boolean running;
//Right here you can add more variables that draw graphics
//For example you can create a new class that has a function that
//takes Canvas as a parameter and draws stuff into it, I will add
//a Rect in this case which is a class already made by android
//but you can create your own class that draws images or more
//complicated stuff
private Rect myRect;
//Rect needs a paint to give it color
private Paint myPaint;
//Constructor
public GameSurface(Context context)
{
super(context);
//This is the callback to let us know when surface is completed
getHolder().addCallback(this);
}
//When a class implements SurfaceHolder.Callback you are forced to
//create three functions "surfaceCreated", "surfaceChanged" and
//"surfaceDestroyed" these are called when the surface is created,
//when some settings are changed (like the orientation) and when
//it is about to be destroyed
@Override
public void surfaceCreated(Surface holder)
{
//Let's initialize our Rect, lets assume we want it to have 40
//pixels height and fill the screen's width
myRect = new Rect(0, 0, getWidth(), 40);
//Give color to the rect
myPaint = new Paint();
myPaint.setARGB(0, 255, 0, 0);
//In case you are not familiar with the Rect class, as
//parameters it gets Rect(left, top, right, bottom)
//Time to start our Thread - nothing much to explain here if
//you know how threads work, remember this class implements
//Runnable so the Thread's constructor gets "this" as parameter
running = true;
thread = new Thread(this);
thread.start();
}
//We won't use this one for now, but we are forced to type it
//Even if we leave it empty
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
//When the surface is destroyed we just want the Thread to
//terminate - we don't want threads running when our app is not visible!
@Override
public void surfaceDestroyed(SurfaceHolder holder)
//We will type this function later
{destroyThread();}
//Time for the interesting stuff! let's start with input
@Override
public boolean onTouchEvent(MotionEvent event)
{
//The logic is as follows: when our Rect is touched, we want
//it to become smaller
if (event.getAction() == MotionEvent.ACTION_DOWN)
{
if (myRect.contains((int) event.getX(), (int) event.getY())
{
myRect.right -= 5;
//Return true - we did something with the input
return true;
}
}
return super.onTouchEvent(event);
}
//This is our update, it will run once per frame
private void update()
{
//Let's assume we want our rect to move 1 pixel downwards
//on every frame
myRect.offset(0, 1);
}
//Now for our draw function
public void draw(Canvas canvas)
{
//Here we want to draw a background and our rect
canvas.drawARGB(0, 0, 0, 255);
canvas.drawRect(myRect, myPaint);
}
//The only thing left is our run() function for the Thread
@Override
public void run()
{
//Screen
Canvas canvas;
//Our game cycle (the famous while)
while(running)
{
//Count start time so we can calculate frames
int startTime = System.currentTimeMillis();
//Update our game
update();
//Empty screen so it can obtain new instance
canvas = null;
//Try locking the canvas for pixel editing on surface
try
{
//Try getting screen
canvas = getHolder().lockCanvas();
//Succeeded
if (canvas != null) synchronized (getHolder())
{
//Actual drawing - our draw function
draw(canvas);
}
} finally
{
//Draw changes
if (canvas != null) getHolder().unlockCanvasAndPost(canvas);
}
//End Frame - 1000/30 means 30 frames per second
int frameTime = System.currentTimeMillis() -startTime;
if (frameTime < 1000/30)
try { Thread.sleep(1000/30 -frameTime); } catch (InterruptedException e){}
}
}
//Last but not least, our function for closing the thread
private void destroyThread()
{
//Stop thread's loop
running = false;
//Try to join thread with UI thread
boolean retry = true;
while (retry)
{
try {thread.join(); retry = false;}
catch (InterruptedException e) {}
}
}
}
我可能犯了一些小错误（可能是区分大小写的字母），所以请随时更正这些错误，我立即编写了代码，所以我没有时间测试它，但它应该可以完美运行。
如果您还有其他问题，需要更多解释或有什么不对，请告诉我！