Android中如何實現文字分頁？

Android中的分頁文字

確定可見文字

要確定螢幕上的可見文本，請等待文字佈局完成，然後使用:

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);

            }
        });

演算法摘要

目標：當最後一條可見線完全適合視圖的高度時打破新頁面。

實作細節

Pagination 類別實作必要的邏輯：

public class Pagination {
    // Configuration parameters
    private boolean mIncludePad;
    private int mWidth;
    private int mHeight;
    private float mSpacingMult;
    private float mSpacingAdd;
    private CharSequence mText;
    private TextPaint mPaint;
    private List<CharSequence> mPages;

    public Pagination(CharSequence text, int pageW, int pageH, TextPaint paint, float spacingMult, float spacingAdd, boolean inclidePad) {
        // ... initialization ...
        layout();
    }

    private void layout() {
        // ... perform layout and pagination ...
    }
}

演算法Flow

1. 遍歷文字行。
2. 檢查行的底部是否超過視圖的高度。
3. 如果是，則打破一個新頁面並調整累積高度計算.

範例用法

下面的範例將分頁套用到混合HTML 和Spanned 字串：

public class PaginationActivity extends Activity {
    // ... code ...
    private Pagination mPagination;
    private CharSequence mText;
    private int mCurrentIndex = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // ... code ...
        mText = TextUtils.concat(htmlString, spanString);

        mTextView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            // ... code ...
            mPagination = new Pagination(mText,
                    mTextView.getWidth(),
                    mTextView.getHeight(),
                    mTextView.getPaint(),
                    mTextView.getLineSpacingMultiplier(),
                    mTextView.getLineSpacingExtra(),
                    mTextView.getIncludeFontPadding());
            update();
        });
    }

    private void update() {
        final CharSequence text = mPagination.get(mCurrentIndex);
        if(text != null) mTextView.setText(text);
    }
}

PagedTextView 函式庫

考慮使用PagedTextView庫以更輕鬆地整合：

dependencies {
    implementation 'com.github.onikx:pagedtextview:0.1.3'
}

<com.onik.pagedtextview.PagedTextView
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

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