每秒更改按钮的背景

Question

我有一个带有8个按钮的活动。 我希望所有按钮的背景在活动运行的每一秒之间随机地变化。 为此，我使用以下代码：

 public class CoinFrenzy extends Activity { private int draw1 = R.drawable.buttonshape1; private int draw2 = R.drawable.buttonshape2; private int draw3 = R.drawable.buttonshape3; private int draw4 = R.drawable.buttonshape4; private int draw5 = R.drawable.buttonshape5; private int draw6 = R.drawable.buttonshape6; private int draw7 = R.drawable.buttonshape7; private int draw8 = R.drawable.buttonshape8; private ArrayList<Integer> selector = new ArrayList<>(); private ArrayList<Button> buttonlist = new ArrayList<>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_coin_frenzy); Button btn1 = (Button) findViewById(R.id.angry_btn); Button btn2 = (Button) findViewById(R.id.angry_btn2); Button btn3 = (Button) findViewById(R.id.angry_btn3); Button btn4 = (Button) findViewById(R.id.angry_btn4); Button btn5 = (Button) findViewById(R.id.angry_btn5); Button btn6 = (Button) findViewById(R.id.angry_btn6); Button btn7 = (Button) findViewById(R.id.angry_btn7); Button btn8 = (Button) findViewById(R.id.angry_btn8); buttonlist.add(btn1); buttonlist.add(btn2); buttonlist.add(btn3); buttonlist.add(btn4); buttonlist.add(btn5); buttonlist.add(btn6); buttonlist.add(btn7); buttonlist.add(btn8); selector.add(draw1); selector.add(draw2); selector.add(draw3); selector.add(draw4); selector.add(draw5); selector.add(draw6); selector.add(draw7); selector.add(draw8); h.postDelayed(myRunnable, 1000); } public static int randInt(int min, int max) { // NOTE: Usually this should be a field rather than a method // variable so that it is not re-seeded every call. Random rand = new Random(); // nextInt is normally exclusive of the top value, // so add 1 to make it inclusive int randomNum = rand.nextInt((max - min) + 1) + min; return randomNum; } private Handler h = new Handler(Looper.getMainLooper()); private Runnable myRunnable = new Runnable() { public void run() { for (Integer x : selector) { int randomInt = randInt(0, 7); int back = selector.get(randomInt); Button currbtn = buttonlist.get(randomInt); currbtn.setBackgroundResource(back); } //run again in one second h.postDelayed(myRunnable, 1000); }}; 

但是，一秒钟过后，我的应用程序崩溃了，没有任何logcat错误。

Answer 1

首先执行以下两件事：

1. 您必须从线程中删除更改按钮代码的背景。 这是崩溃的主要原因。 在下面，您可以找到两种方法来解决如何在android的main / UI线程上运行代码的问题：

2. runOnUIThread活动的方法

    runOnUiThread(new Runnable() { public void run() { // change background color here } }); 

3. 处理程序

    Handler handler = new Handler(Looper.getMainLooper()); handler.post(new Runnable() { public void run() { // UI code goes here } }); 

每当您要更新UI（例如更新视图或其他与UI相关的东西的颜色）时，您可能都想使用两种方法之一。 否则，应用程序可能会崩溃，因为Android上的UI类不是线程安全的。

这会帮助你！

Answer 2

更换您的

private Handler h = new Handler();

至

private Handler h = new Handler(Looper.getMainLooper());

否则，您的代码将在UI线程外运行

Answer 3

您必须将动态索引传递到

int randomInt = randInt(0, 7);

您总是传递相同的值，因为min为0，max为7，因此不会更改任何背景。

使用选择器随机ID将7替换为动态循环值x。

private Runnable myRunnable = new Runnable() {
        public void run() {
            for (Integer x : selector) {
                int randomInt = randInt(0, x);
                int back = selector.get(randomInt);
                Button currbtn = buttonlist.get(randomInt);
                currbtn.setBackgroundResource(back);

            }

            //run again in one second
                h.postDelayed(myRunnable, 1000);

        }};

这将对您有所帮助。