有没有办法检索TextView的可见行数或范围？

Question

我有一个全屏TextView持有一个需要滚动的长跨度.TextView的getLineCount()为我提供了整个文本块使用的总行数,但我想知道屏幕上当前可以看到多少行文本.

或者,更好的是,有没有办法找出屏幕上当前可见的线条范围？例如,当视图滚动时,我可以告诉20-60行当前是否可见？

Answer 1

我想出了答案:

int height    = myTextView.getHeight();
int scrollY   = myTextView.getScrollY();
Layout layout = myTextView.getLayout();

int firstVisibleLineNumber = layout.getLineForVertical(scrollY);
int lastVisibleLineNumber  = layout.getLineForVertical(scrollY+height);

Answer 2

为了使它们工作,您应该以这种方式编写@Robert发布​​的代码:

ViewTreeObserver vto = txtViewEx.getViewTreeObserver();
        vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                ViewTreeObserver obs = txtViewEx.getViewTreeObserver();
                obs.removeOnGlobalLayoutListener(this);
                height = txtViewEx.getHeight();
                scrollY = txtViewEx.getScrollY();
                Layout layout = txtViewEx.getLayout();

                firstVisibleLineNumber = layout.getLineForVertical(scrollY);
                lastVisibleLineNumber = layout.getLineForVertical(height+scrollY);

            }
        });