Question

我想在TextView上进行分页，就像有网页编号的网站一样。我能够对下面给出的代码进行分页。但不知道如何显示页码。这是我将文本分成页面的代码：

      public class PaginationController {

            private static final String TAG = PaginationController.class.getSimpleName();

            private final TextView mTextView;

            private int mPageIndex;
            private String mText;
            private HashMap<Integer, Boundary> mBoundaries;
            private int mLastPageIndex;

            public PaginationController(@NonNull TextView textView) {
                mTextView = textView;
                mBoundaries = new HashMap<>();
                mLastPageIndex = -1;
            }

            public void onTextLoaded(@NonNull String text, @NonNull final OnInitializedListener listener) {
                mPageIndex = 0;
                mText = text;

                if (mTextView.getLayout() == null) {
                    mTextView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
                        @Override
                        public void onGlobalLayout() {
                            ViewTreeObserver obs = mTextView.getViewTreeObserver();
                            obs.removeOnGlobalLayoutListener(this);
                            setTextWithCaching(mPageIndex, 0);
                            listener.onInitialized();
                        }

                    });

                } else {
                    setTextWithCaching(mPageIndex, 0);
                    listener.onInitialized();
                }
            }

            /**
             * Assume, that page index can be only next or previous. For other cases
             *
             * @param pageIndex index of selected page
             */
            private void selectPage(int pageIndex) {
                Log.v(TAG, "selectPage=" + pageIndex);

                String displayedText;
                if (mBoundaries.containsKey(pageIndex)) {
                    // use existing boundaries
                    Boundary boundary = mBoundaries.get(pageIndex);
                    displayedText = mText.substring(boundary.start, boundary.end);
                    mTextView.setText(displayedText);
                    Log.v(TAG, "Existing[" + pageIndex + "]: " + displayedText);
                } else if (mBoundaries.containsKey(pageIndex - 1)) {
                    //calculate boundaries for new page (previous exists)
                    Boundary previous = mBoundaries.get(pageIndex - 1);
                    setTextWithCaching(pageIndex, previous.end);
                } else {
                    Log.v(TAG, "selectPage(" + pageIndex + "), values=[" + mBoundaries.keySet());
                    // TODO implement selectPage(n), n - random int
                }
            }

            private void setTextWithCaching(int pageIndex, int pageStartSymbol) {
                String restText = mText.substring(pageStartSymbol);

                mTextView.setText(restText);

                int height = mTextView.getHeight();
                int scrollY = mTextView.getScrollY();
                Layout layout = mTextView.getLayout();
                int firstVisibleLineNumber = layout.getLineForVertical(scrollY);
                int lastVisibleLineNumber = layout.getLineForVertical(height + scrollY);

                //check is latest line fully visible
                if (mTextView.getHeight() < layout.getLineBottom(lastVisibleLineNumber)) {
                    lastVisibleLineNumber--;
                }

                int start = pageStartSymbol + mTextView.getLayout().getLineStart(firstVisibleLineNumber);
                int end = pageStartSymbol + mTextView.getLayout().getLineEnd(lastVisibleLineNumber);

                if (end == mText.length()) {
                    mLastPageIndex = pageIndex;
                }
                String displayedText = mText.substring(start, end);
                Log.v(TAG, "Added to Cache[" + pageIndex + "](symbols={" + start + "," + end + "}): " + displayedText);

                //correct visible text
                mTextView.setText(displayedText);

                mBoundaries.put(pageIndex, new Boundary(start, end));
            }

            public boolean next() {
                throwIfNotInitialized();
                if (isNextEnabled()) {
                    selectPage(++mPageIndex);
                    return true;
                }
                return false;
            }

            public boolean previous() {
                throwIfNotInitialized();
                if (isPreviousEnabled()) {
                    selectPage(--mPageIndex);
                    return true;
                }
                return false;
            }

            public boolean isNextEnabled() {
                throwIfNotInitialized();
                return mPageIndex < mLastPageIndex || mLastPageIndex < 0;
            }

            public boolean isPreviousEnabled() {
                throwIfNotInitialized();
                return mPageIndex > 0;
            }

            void throwIfNotInitialized() {
                if (mText == null) {
                    throw new IllegalStateException("Call onTextLoaded(String) first");
                }
            }

            private class Boundary {

                final int start;
                final int end;

                private Boundary(int start, int end) {
                    this.start = start;
                    this.end = end;
                }
            }

            public interface OnInitializedListener {
                void onInitialized();
            }
        }

        This code is my code to set text to textview:

          mController = new PaginationController(tvContent);

                        if(history!=null)
                        onTextLoaded(history);

Answer 1

有两个容易做pagination的文字。

RecylerView，横向为LinearLayoutManager。
或者您可以将ViewPager与PagerAdapter一起使用。

如何对TextView进行分页

1 个答案: