来自Google I/O SlidingTabStrip.java的R.attr.colorForeground错误

Question

我正在尝试将选项卡添加到我的应用程序中，并已添加了来自Google的SlidingTabLayout.java和SlidingTabStrip.java。 我还确保在SlidingTabLayout类中添加了setDistributeEvenly方法。

我的问题出现在R.attr.colorForeground上。 我收到错误消息“无法解析符号'colorForeground'。”

以下是这些类用于选项卡的两个类。

class SlidingTabStrip extends LinearLayout {


private static final int DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS = 0;
private static final byte DEFAULT_BOTTOM_BORDER_COLOR_ALPHA = 0x26;
private static final int SELECTED_INDICATOR_THICKNESS_DIPS = 3;
private static final int DEFAULT_SELECTED_INDICATOR_COLOR = 0xFF33B5E5;


private final int mBottomBorderThickness;
private final Paint mBottomBorderPaint;


private final int mSelectedIndicatorThickness;
private final Paint mSelectedIndicatorPaint;


private final int mDefaultBottomBorderColor;
private final SimpleTabColorizer mDefaultTabColorizer;
private int mSelectedPosition;
private float mSelectionOffset;
private SlidingTabLayout.TabColorizer mCustomTabColorizer;


SlidingTabStrip(Context context) {
    this(context, null);
}


SlidingTabStrip(Context context, AttributeSet attrs) {
    super(context, attrs);
    setWillNotDraw(false);


    final float density = getResources().getDisplayMetrics().density;


    TypedValue outValue = new TypedValue();
    context.getTheme().resolveAttribute(R.attr.colorForeground, outValue, true);
    final int themeForegroundColor = outValue.data;


    mDefaultBottomBorderColor = setColorAlpha(themeForegroundColor,
            DEFAULT_BOTTOM_BORDER_COLOR_ALPHA);


    mDefaultTabColorizer = new SimpleTabColorizer();
    mDefaultTabColorizer.setIndicatorColors(DEFAULT_SELECTED_INDICATOR_COLOR);


    mBottomBorderThickness = (int) (DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS * density);
    mBottomBorderPaint = new Paint();
    mBottomBorderPaint.setColor(mDefaultBottomBorderColor);


    mSelectedIndicatorThickness = (int) (SELECTED_INDICATOR_THICKNESS_DIPS * density);
    mSelectedIndicatorPaint = new Paint();
}

/**
 * Set the alpha value of the {@code color} to be the given {@code alpha} value.
 */
private static int setColorAlpha(int color, byte alpha) {
    return Color.argb(alpha, Color.red(color), Color.green(color), Color.blue(color));
}

/**
 * Blend {@code color1} and {@code color2} using the given ratio.
 *
 * @param ratio of which to blend. 1.0 will return {@code color1}, 0.5 will give an even blend,
 *              0.0 will return {@code color2}.
 */
private static int blendColors(int color1, int color2, float ratio) {
    final float inverseRation = 1f - ratio;
    float r = (Color.red(color1) * ratio) + (Color.red(color2) * inverseRation);
    float g = (Color.green(color1) * ratio) + (Color.green(color2) * inverseRation);
    float b = (Color.blue(color1) * ratio) + (Color.blue(color2) * inverseRation);
    return Color.rgb((int) r, (int) g, (int) b);
}

void setCustomTabColorizer(SlidingTabLayout.TabColorizer customTabColorizer) {
    mCustomTabColorizer = customTabColorizer;
    invalidate();
}

void setSelectedIndicatorColors(int... colors) {
    // Make sure that the custom colorizer is removed
    mCustomTabColorizer = null;
    mDefaultTabColorizer.setIndicatorColors(colors);
    invalidate();
}

void onViewPagerPageChanged(int position, float positionOffset) {
    mSelectedPosition = position;
    mSelectionOffset = positionOffset;
    invalidate();
}

@Override
protected void onDraw(Canvas canvas) {
    final int height = getHeight();
    final int childCount = getChildCount();
    final SlidingTabLayout.TabColorizer tabColorizer = mCustomTabColorizer != null
            ? mCustomTabColorizer
            : mDefaultTabColorizer;


    // Thick colored underline below the current selection
    if (childCount > 0) {
        View selectedTitle = getChildAt(mSelectedPosition);
        int left = selectedTitle.getLeft();
        int right = selectedTitle.getRight();
        int color = tabColorizer.getIndicatorColor(mSelectedPosition);


        if (mSelectionOffset > 0f && mSelectedPosition < (getChildCount() - 1)) {
            int nextColor = tabColorizer.getIndicatorColor(mSelectedPosition + 1);
            if (color != nextColor) {
                color = blendColors(nextColor, color, mSelectionOffset);
            }


            // Draw the selection partway between the tabs
            View nextTitle = getChildAt(mSelectedPosition + 1);
            left = (int) (mSelectionOffset * nextTitle.getLeft() +
                    (1.0f - mSelectionOffset) * left);
            right = (int) (mSelectionOffset * nextTitle.getRight() +
                    (1.0f - mSelectionOffset) * right);
        }


        mSelectedIndicatorPaint.setColor(color);


        canvas.drawRect(left, height - mSelectedIndicatorThickness, right,
                height, mSelectedIndicatorPaint);
    }


    // Thin underline along the entire bottom edge
    canvas.drawRect(0, height - mBottomBorderThickness, getWidth(), height, mBottomBorderPaint);
}

private static class SimpleTabColorizer implements SlidingTabLayout.TabColorizer {
    private int[] mIndicatorColors;


    @Override
    public final int getIndicatorColor(int position) {
        return mIndicatorColors[position % mIndicatorColors.length];
    }


    void setIndicatorColors(int... colors) {
        mIndicatorColors = colors;
    }
}

}

public class SlidingTabLayout extends HorizontalScrollView {
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 final SlidingTabStrip mTabStrip;
private int mTitleOffset;

private int mTabViewLayoutId;
private int mTabViewTextViewId;
private boolean mDistributeEvenly;

private ViewPager mViewPager;
private SparseArray<String> mContentDescriptions = new SparseArray<String>();
private ViewPager.OnPageChangeListener mViewPagerPageChangeListener;

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.
 * <p/>
 * If you only require simple custmisation then you can use
 * {@link #setSelectedIndicatorColors(int...)} to achieve
 * similar effects.
 */
public void setCustomTabColorizer(TabColorizer tabColorizer) {
    mTabStrip.setCustomTabColorizer(tabColorizer);
}

public void setDistributeEvenly(boolean distributeEvenly) {
    mDistributeEvenly = distributeEvenly;
}

/**
 * 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);
}

/**
 * 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);
    textView.setLayoutParams(new LinearLayout.LayoutParams(
            ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));

    TypedValue outValue = new TypedValue();
    getContext().getTheme().resolveAttribute(android.R.attr.selectableItemBackground,
            outValue, true);
    textView.setBackgroundResource(outValue.resourceId);
    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;
        }

        if (mDistributeEvenly) {
            LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) tabView.getLayoutParams();
            lp.width = 0;
            lp.weight = 1;
        }

        tabTitleView.setText(adapter.getPageTitle(i));
        tabView.setOnClickListener(tabClickListener);
        String desc = mContentDescriptions.get(i, null);
        if (desc != null) {
            tabView.setContentDescription(desc);
        }

        mTabStrip.addView(tabView);
        if (i == mViewPager.getCurrentItem()) {
            tabView.setSelected(true);
        }
    }
}

public void setContentDescription(int i, String desc) {
    mContentDescriptions.put(i, desc);
}

@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);
    }
}

/**
 * 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);

}

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);
        }
        for (int i = 0; i < mTabStrip.getChildCount(); i++) {
            mTabStrip.getChildAt(i).setSelected(position == i);
        }
        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;
            }
        }
    }
}

在谷歌的这两个类中，它们都没有声明colorForeground，所以我假设这是设置在Android中的？如果能帮助解决colorForeground问题，将不胜感激。

- Adam Gardner

Answer 1

这是因为Android无法找到R.attr.colorForeground，由于您（就像我曾经做过的一样）将自己的R导入到SlidingTabStrip中。更好的方法是导入import android.R; （虽然Android Studio会发出警告）或直接使用android.R.attr.colorForeground。

- guness

Answer 2

移除你自己的包例如：com.yourpackage.R。 使用android.R.attr.colorForeground代替R.attr.colorForeground

- Sai's Stack

Answer 3

这里有一个区别：

android.R;
is used for accessing public standard android SDK resources.

并且

com.yourpackage.R;
is used for accessing YOUR resources in your application.

你可以同时使用两者，但如果你正在使用你的 R 引用，你必须根据你需要的位置/内容明确解决其中之一。

- JoxTraex