android - SlidingTabLayout 当前项集在首次加载 Activity 时未显示

Question

我正在使用带有 View 寻呼机的滑动标签布局。我的滑动标签布局条显示了很多项目，数字从 10 到 200。

下面的图片完整地描述了我的问题:首先是它是如何工作的，第二张图片显示了我遇到的问题。

1. 第一张图片(我的标签如何工作):

2. 第二张图片(我遇到的问题和要实现的目标):

我的 SlidingTabLayoutClass:

public class SlidingTabLayout extends HorizontalScrollView {

/**
 * Allows complete control over the colors drawn in the tab layout. Set with
 * {@link #setCustomTabColorizer(TabColorizer)}.
 */
public interface TabColorizer {

    /**
     * @return return the color of the indicator used when {@code position} is selected.
     */
    int getIndicatorColor(int position);

    /**
     * @return return the color of the divider drawn to the right of {@code position}.
     */
    int getDividerColor(int position);

}

private static final int TITLE_OFFSET_DIPS = 24;
private static final int TAB_VIEW_PADDING_DIPS = 16;
private static final int TAB_VIEW_TEXT_SIZE_SP = 12;

private int mTitleOffset;

private int mTabViewLayoutId;
private int mTabViewTextViewId;

private ViewPager mViewPager;
private ViewPager.OnPageChangeListener mViewPagerPageChangeListener;

private final SlidingTabStrip mTabStrip;

public SlidingTabLayout(Context context) {
    this(context, null);
}

public SlidingTabLayout(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public SlidingTabLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    // Disable the Scroll Bar
    setHorizontalScrollBarEnabled(false);
    // Make sure that the Tab Strips fills this View
    setFillViewport(true);

    mTitleOffset = (int) (TITLE_OFFSET_DIPS * getResources().getDisplayMetrics().density);

    mTabStrip = new SlidingTabStrip(context);
    addView(mTabStrip, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
}

/**
 * Set the custom {@link TabColorizer} to be used.
 *
 * If you only require simple custmisation then you can use
 * {@link #setSelectedIndicatorColors(int...)} and {@link #setDividerColors(int...)} to achieve
 * similar effects.
 */
public void setCustomTabColorizer(TabColorizer tabColorizer) {
    mTabStrip.setCustomTabColorizer(tabColorizer);
}

/**
 * Sets the colors to be used for indicating the selected tab. These colors are treated as a
 * circular array. Providing one color will mean that all tabs are indicated with the same color.
 */
public void setSelectedIndicatorColors(int... colors) {
    mTabStrip.setSelectedIndicatorColors(colors);
}

/**
 * Sets the colors to be used for tab dividers. These colors are treated as a circular array.
 * Providing one color will mean that all tabs are indicated with the same color.
 */
public void setDividerColors(int... colors) {
    mTabStrip.setDividerColors(colors);
}

/**
 * Set the {@link ViewPager.OnPageChangeListener}. When using {@link SlidingTabLayout} you are
 * required to set any {@link ViewPager.OnPageChangeListener} through this method. This is so
 * that the layout can update it's scroll position correctly.
 *
 * @see ViewPager#setOnPageChangeListener(ViewPager.OnPageChangeListener)
 */
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
    mViewPagerPageChangeListener = listener;
}

/**
 * Set the custom layout to be inflated for the tab views.
 *
 * @param layoutResId Layout id to be inflated
 * @param textViewId id of the {@link TextView} in the inflated view
 */
public void setCustomTabView(int layoutResId, int textViewId) {
    mTabViewLayoutId = layoutResId;
    mTabViewTextViewId = textViewId;
}

/**
 * Sets the associated view pager. Note that the assumption here is that the pager content
 * (number of tabs and tab titles) does not change after this call has been made.
 */
public void setViewPager(ViewPager viewPager) {
    mTabStrip.removeAllViews();

    mViewPager = viewPager;
    if (viewPager != null) {
        viewPager.setOnPageChangeListener(new InternalViewPagerListener());
        populateTabStrip();
    }
}

/**
 * Create a default view to be used for tabs. This is called if a custom tab view is not set via
 * {@link #setCustomTabView(int, int)}.
 */
protected TextView createDefaultTabView(Context context) {
    TextView textView = new TextView(context);
    textView.setGravity(Gravity.CENTER);
    textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, TAB_VIEW_TEXT_SIZE_SP);
    textView.setTypeface(Typeface.DEFAULT_BOLD);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        // If we're running on Honeycomb or newer, then we can use the Theme's
        // selectableItemBackground to ensure that the View has a pressed state
        TypedValue outValue = new TypedValue();
        getContext().getTheme().resolveAttribute(android.R.attr.selectableItemBackground,
                outValue, true);
        textView.setBackgroundResource(outValue.resourceId);
    }

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        // If we're running on ICS or newer, enable all-caps to match the Action Bar tab style
        textView.setAllCaps(true);
    }

    int padding = (int) (TAB_VIEW_PADDING_DIPS * getResources().getDisplayMetrics().density);
    textView.setPadding(padding, padding, padding, padding);

    return textView;
}

private void populateTabStrip() {
    final PagerAdapter adapter = mViewPager.getAdapter();
    final View.OnClickListener tabClickListener = new TabClickListener();

    for (int i = 0; i < adapter.getCount(); i++) {
        View tabView = null;
        TextView tabTitleView = null;

        if (mTabViewLayoutId != 0) {
            // If there is a custom tab view layout id set, try and inflate it
            tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip,
                    false);
            tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
        }

        if (tabView == null) {
            tabView = createDefaultTabView(getContext());
        }

        if (tabTitleView == null && TextView.class.isInstance(tabView)) {
            tabTitleView = (TextView) tabView;
        }

        tabTitleView.setText(adapter.getPageTitle(i));
        tabView.setOnClickListener(tabClickListener);

        mTabStrip.addView(tabView);
    }
}

@Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();

    if (mViewPager != null) {
        scrollToTab(mViewPager.getCurrentItem(), 0);
    }
}

private void scrollToTab(int tabIndex, int positionOffset) {
    final int tabStripChildCount = mTabStrip.getChildCount();
    if (tabStripChildCount == 0 || tabIndex < 0 || tabIndex >= tabStripChildCount) {
        return;
    }

    View selectedChild = mTabStrip.getChildAt(tabIndex);
    if (selectedChild != null) {
        int targetScrollX = selectedChild.getLeft() + positionOffset;

        if (tabIndex > 0 || positionOffset > 0) {
            // If we're not at the first child and are mid-scroll, make sure we obey the offset
            targetScrollX -= mTitleOffset;
        }

        scrollTo(targetScrollX, 0);
    }
}

private class InternalViewPagerListener implements ViewPager.OnPageChangeListener {
    private int mScrollState;

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        int tabStripChildCount = mTabStrip.getChildCount();
        if ((tabStripChildCount == 0) || (position < 0) || (position >= tabStripChildCount)) {
            return;
        }

        mTabStrip.onViewPagerPageChanged(position, positionOffset);

        View selectedTitle = mTabStrip.getChildAt(position);
        int extraOffset = (selectedTitle != null)
                ? (int) (positionOffset * selectedTitle.getWidth())
                : 0;
        scrollToTab(position, extraOffset);

        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageScrolled(position, positionOffset,
                    positionOffsetPixels);
        }
    }

    @Override
    public void onPageScrollStateChanged(int state) {
        mScrollState = state;

        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageScrollStateChanged(state);
        }
    }

    @Override
    public void onPageSelected(int position) {
        if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
            mTabStrip.onViewPagerPageChanged(position, 0f);
            scrollToTab(position, 0);
        }

        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageSelected(position);
        }
    }

}

private class TabClickListener implements View.OnClickListener {
    @Override
    public void onClick(View v) {
        for (int i = 0; i < mTabStrip.getChildCount(); i++) {
            if (v == mTabStrip.getChildAt(i)) {
                mViewPager.setCurrentItem(i);
                return;
              }
          }
      }
  }

}

请帮忙解决我的问题

我尝试过的方法:

1.)我尝试调用 scrollToTab(mViewPager.getCurrentItem(), 0);在 SlidingTabLayout 类的 setViewPager 方法中，但在首次加载 Activity 时无法显示第 6 个项目。

2.)代替scrollToTab(mViewPager.getCurrentItem(), 0);在 SlidingTabLayout 类的 setViewPager 方法中，我尝试调用 scrollTo(500,0)，它在 Activity 首次加载时向我显示了滚动的滑动标签条，这种方式效率不高，因为我们不知道要放置什么值500 为不同的设备。

我创建的这个滑动选项卡布局类似于下面显示的布局，唯一的区别是我的选项卡显示带有圆形背景的数字，而下图只描绘了三个选项卡，我的选项卡布局包含许多编号从 10 到 200 的选项卡。

Answer 1

我已经通过使用 android 的 Gallery Control 而不是带有 View Pager 的 SlidingTabLayout 解决了上述问题，有了 gallery，我能够将 6 个项目显示为默认选择，并且在第一次加载 Activity 时它也可见。代码:mGallery.setSelection(6);