java - 在开始时为 ImageView 设置随机位置

Question

我的RelativeLayout 上有8 个ImageView。当 Activity onCreate 时，它​​启动方法 init:

 private void init() {
        gameFieldView = (RelativeLayout) getGameFieldView();
        mainView = (LinearLayout) getMainView();
        topOffset = mainView.getHeight() - gameFieldView.getHeight() - 6;
        // THERE ARE 0 height and width of gameFieldView, and mainView 
        for (int i = 0; i < LETTERS_NUMBER; i++) {
            ImageView letter = (ImageView) findViewById(R.id.e1_letter + i);
            generateRandomPosition(random, letter); // When i comment this line it is ok (What kind of sorcery is this?), but i want to set random position to ImageView "letter"
        }
    }

现在generateRandomPosition看起来像

private void generateRandomPosition(Random random, ImageView letter) {
        int height = letter.getHeight();
        int width = letter.getWidth();
        int top = random.nextInt(gameFieldView.getMeasuredHeight() - height - topOffset); // It obviously crashes because of IllegalArgumentException - parameter < 0 because of gameFieldView height = 0 
        int left = random.nextInt(gameFieldView.getMeasuredWidth() - width);
        letter.layout(left, top, left + width, top + height);
    }

我做错了什么？提前致谢。

更新。顺便说一下，我尝试在 onWindowFocusChanged 中调用 init() ，它解决了 IllegalArgumentException 的问题，以正确的方式进行顶部和左侧计数，但即使在 letter.layout() 之后，imageview 仍保持在左上角

Answer 1

如果您下次能发布您的 LogCat/StackTrace，将会很有帮助。无论如何，问题出在下面一行: findViewById(R.id.e1_letter + i); 您正在获取资源的引用 id 并向其添加一个整数。这可能并不能说明什么。在空对象上设置某些内容是行不通的。循环遍历Rel​​ativeLayout的子级会更容易，如下所示:

ViewGroup v = (ViewGroup) gameFieldView;
for(int i = 0; i < v.getChildCount(); ++i) {
    ImageView letter = (ImageView) v.getChildAt(i);
    generateRandomPosition(random, letter); 
}

这样你就不需要所有 ImageView 的 id