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PagerTitleStrip.javaAPI DocAndroid 5.1 API18813Thu Mar 12 22:22:56 GMT 2015android.support.v4.view

PagerTitleStrip

public class PagerTitleStrip extends android.view.ViewGroup implements ViewPager.Decor
PagerTitleStrip is a non-interactive indicator of the current, next, and previous pages of a {@link ViewPager}. It is intended to be used as a child view of a ViewPager widget in your XML layout. Add it as a child of a ViewPager in your layout file and set its android:layout_gravity to TOP or BOTTOM to pin it to the top or bottom of the ViewPager. The title from each page is supplied by the method {@link PagerAdapter#getPageTitle(int)} in the adapter supplied to the ViewPager.

For an interactive indicator, see {@link PagerTabStrip}.

Fields Summary
private static final String
TAG
ViewPager
mPager
android.widget.TextView
mPrevText
android.widget.TextView
mCurrText
android.widget.TextView
mNextText
private int
mLastKnownCurrentPage
private float
mLastKnownPositionOffset
private int
mScaledTextSpacing
private int
mGravity
private boolean
mUpdatingText
private boolean
mUpdatingPositions
private final PageListener
mPageListener
private WeakReference
mWatchingAdapter
private static final int[]
ATTRS
private static final int[]
TEXT_ATTRS
private static final float
SIDE_ALPHA
private static final int
TEXT_SPACING
private int
mNonPrimaryAlpha
int
mTextColor
private static final PagerTitleStripImpl
IMPL
Constructors Summary
public PagerTitleStrip(android.content.Context context)

        this(context, null);
public PagerTitleStrip(android.content.Context context, android.util.AttributeSet attrs)

        super(context, attrs);

        addView(mPrevText = new TextView(context));
        addView(mCurrText = new TextView(context));
        addView(mNextText = new TextView(context));

        final TypedArray a = context.obtainStyledAttributes(attrs, ATTRS);
        final int textAppearance = a.getResourceId(0, 0);
        if (textAppearance != 0) {
            mPrevText.setTextAppearance(context, textAppearance);
            mCurrText.setTextAppearance(context, textAppearance);
            mNextText.setTextAppearance(context, textAppearance);
        }
        final int textSize = a.getDimensionPixelSize(1, 0);
        if (textSize != 0) {
            setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
        }
        if (a.hasValue(2)) {
            final int textColor = a.getColor(2, 0);
            mPrevText.setTextColor(textColor);
            mCurrText.setTextColor(textColor);
            mNextText.setTextColor(textColor);
        }
        mGravity = a.getInteger(3, Gravity.BOTTOM);
        a.recycle();

        mTextColor = mCurrText.getTextColors().getDefaultColor();
        setNonPrimaryAlpha(SIDE_ALPHA);

        mPrevText.setEllipsize(TruncateAt.END);
        mCurrText.setEllipsize(TruncateAt.END);
        mNextText.setEllipsize(TruncateAt.END);

        boolean allCaps = false;
        if (textAppearance != 0) {
            final TypedArray ta = context.obtainStyledAttributes(textAppearance, TEXT_ATTRS);
            allCaps = ta.getBoolean(0, false);
            ta.recycle();
        }

        if (allCaps) {
            setSingleLineAllCaps(mPrevText);
            setSingleLineAllCaps(mCurrText);
            setSingleLineAllCaps(mNextText);
        } else {
            mPrevText.setSingleLine();
            mCurrText.setSingleLine();
            mNextText.setSingleLine();
        }

        final float density = context.getResources().getDisplayMetrics().density;
        mScaledTextSpacing = (int) (TEXT_SPACING * density);
Methods Summary
intgetMinHeight()

        int minHeight = 0;
        final Drawable bg = getBackground();
        if (bg != null) {
            minHeight = bg.getIntrinsicHeight();
        }
        return minHeight;
public intgetTextSpacing()

return
The required spacing between title segments in pixels

        return mScaledTextSpacing;
protected voidonAttachedToWindow()

        super.onAttachedToWindow();

        final ViewParent parent = getParent();
        if (!(parent instanceof ViewPager)) {
            throw new IllegalStateException(
                    "PagerTitleStrip must be a direct child of a ViewPager.");
        }

        final ViewPager pager = (ViewPager) parent;
        final PagerAdapter adapter = pager.getAdapter();

        pager.setInternalPageChangeListener(mPageListener);
        pager.setOnAdapterChangeListener(mPageListener);
        mPager = pager;
        updateAdapter(mWatchingAdapter != null ? mWatchingAdapter.get() : null, adapter);
protected voidonDetachedFromWindow()

        super.onDetachedFromWindow();
        if (mPager != null) {
            updateAdapter(mPager.getAdapter(), null);
            mPager.setInternalPageChangeListener(null);
            mPager.setOnAdapterChangeListener(null);
            mPager = null;
        }
protected voidonLayout(boolean changed, int l, int t, int r, int b)

        if (mPager != null) {
            final float offset = mLastKnownPositionOffset >= 0 ? mLastKnownPositionOffset : 0;
            updateTextPositions(mLastKnownCurrentPage, offset, true);
        }
protected voidonMeasure(int widthMeasureSpec, int heightMeasureSpec)

        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        final int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        final int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("Must measure with an exact width");
        }

        int childHeight = heightSize;
        int minHeight = getMinHeight();
        int padding = 0;
        padding = getPaddingTop() + getPaddingBottom();
        childHeight -= padding;

        final int childWidthSpec = MeasureSpec.makeMeasureSpec((int) (widthSize * 0.8f),
                MeasureSpec.AT_MOST);
        final int childHeightSpec = MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.AT_MOST);

        mPrevText.measure(childWidthSpec, childHeightSpec);
        mCurrText.measure(childWidthSpec, childHeightSpec);
        mNextText.measure(childWidthSpec, childHeightSpec);

        if (heightMode == MeasureSpec.EXACTLY) {
            setMeasuredDimension(widthSize, heightSize);
        } else {
            int textHeight = mCurrText.getMeasuredHeight();
            setMeasuredDimension(widthSize, Math.max(minHeight, textHeight + padding));
        }
public voidrequestLayout()

        if (!mUpdatingText) {
            super.requestLayout();
        }
public voidsetGravity(int gravity)
Set the {@link Gravity} used to position text within the title strip. Only the vertical gravity component is used.

param
gravity {@link Gravity} constant for positioning title text

        mGravity = gravity;
        requestLayout();
public voidsetNonPrimaryAlpha(float alpha)
Set the alpha value used for non-primary page titles.

param
alpha Opacity value in the range 0-1f

        mNonPrimaryAlpha = (int) (alpha * 255) & 0xFF;
        final int transparentColor = (mNonPrimaryAlpha << 24) | (mTextColor & 0xFFFFFF);
        mPrevText.setTextColor(transparentColor);
        mNextText.setTextColor(transparentColor);
private static voidsetSingleLineAllCaps(android.widget.TextView text)

        if (android.os.Build.VERSION.SDK_INT >= 14) {
            IMPL = new PagerTitleStripImplIcs();
        } else {
            IMPL = new PagerTitleStripImplBase();
        }
    
        IMPL.setSingleLineAllCaps(text);
public voidsetTextColor(int color)
Set the color value used as the base color for all displayed page titles. Alpha will be ignored for non-primary page titles. See {@link #setNonPrimaryAlpha(float)}.

param
color Color hex code in 0xAARRGGBB format

        mTextColor = color;
        mCurrText.setTextColor(color);
        final int transparentColor = (mNonPrimaryAlpha << 24) | (mTextColor & 0xFFFFFF);
        mPrevText.setTextColor(transparentColor);
        mNextText.setTextColor(transparentColor);
public voidsetTextSize(int unit, float size)
Set the default text size to a given unit and value. See {@link TypedValue} for the possible dimension units.

Example: to set the text size to 14px, use setTextSize(TypedValue.COMPLEX_UNIT_PX, 14);

param
unit The desired dimension unit
param
size The desired size in the given units

        mPrevText.setTextSize(unit, size);
        mCurrText.setTextSize(unit, size);
        mNextText.setTextSize(unit, size);
public voidsetTextSpacing(int spacingPixels)
Set the required spacing between title segments.

param
spacingPixels Spacing between each title displayed in pixels

        mScaledTextSpacing = spacingPixels;
        requestLayout();
voidupdateAdapter(PagerAdapter oldAdapter, PagerAdapter newAdapter)

        if (oldAdapter != null) {
            oldAdapter.unregisterDataSetObserver(mPageListener);
            mWatchingAdapter = null;
        }
        if (newAdapter != null) {
            newAdapter.registerDataSetObserver(mPageListener);
            mWatchingAdapter = new WeakReference<PagerAdapter>(newAdapter);
        }
        if (mPager != null) {
            mLastKnownCurrentPage = -1;
            mLastKnownPositionOffset = -1;
            updateText(mPager.getCurrentItem(), newAdapter);
            requestLayout();
        }
voidupdateText(int currentItem, PagerAdapter adapter)

        final int itemCount = adapter != null ? adapter.getCount() : 0;
        mUpdatingText = true;

        CharSequence text = null;
        if (currentItem >= 1 && adapter != null) {
            text = adapter.getPageTitle(currentItem - 1);
        }
        mPrevText.setText(text);

        mCurrText.setText(adapter != null && currentItem < itemCount ?
                adapter.getPageTitle(currentItem) : null);

        text = null;
        if (currentItem + 1 < itemCount && adapter != null) {
            text = adapter.getPageTitle(currentItem + 1);
        }
        mNextText.setText(text);

        // Measure everything
        final int width = getWidth() - getPaddingLeft() - getPaddingRight();
        final int childHeight = getHeight() - getPaddingTop() - getPaddingBottom();
        final int childWidthSpec = MeasureSpec.makeMeasureSpec((int) (width * 0.8f),
                MeasureSpec.AT_MOST);
        final int childHeightSpec = MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.AT_MOST);
        mPrevText.measure(childWidthSpec, childHeightSpec);
        mCurrText.measure(childWidthSpec, childHeightSpec);
        mNextText.measure(childWidthSpec, childHeightSpec);

        mLastKnownCurrentPage = currentItem;

        if (!mUpdatingPositions) {
            updateTextPositions(currentItem, mLastKnownPositionOffset, false);
        }

        mUpdatingText = false;
voidupdateTextPositions(int position, float positionOffset, boolean force)

        if (position != mLastKnownCurrentPage) {
            updateText(position, mPager.getAdapter());
        } else if (!force && positionOffset == mLastKnownPositionOffset) {
            return;
        }

        mUpdatingPositions = true;

        final int prevWidth = mPrevText.getMeasuredWidth();
        final int currWidth = mCurrText.getMeasuredWidth();
        final int nextWidth = mNextText.getMeasuredWidth();
        final int halfCurrWidth = currWidth / 2;

        final int stripWidth = getWidth();
        final int stripHeight = getHeight();
        final int paddingLeft = getPaddingLeft();
        final int paddingRight = getPaddingRight();
        final int paddingTop = getPaddingTop();
        final int paddingBottom = getPaddingBottom();
        final int textPaddedLeft = paddingLeft + halfCurrWidth;
        final int textPaddedRight = paddingRight + halfCurrWidth;
        final int contentWidth = stripWidth - textPaddedLeft - textPaddedRight;

        float currOffset = positionOffset + 0.5f;
        if (currOffset > 1.f) {
            currOffset -= 1.f;
        }
        final int currCenter = stripWidth - textPaddedRight - (int) (contentWidth * currOffset);
        final int currLeft = currCenter - currWidth / 2;
        final int currRight = currLeft + currWidth;

        final int prevBaseline = mPrevText.getBaseline();
        final int currBaseline = mCurrText.getBaseline();
        final int nextBaseline = mNextText.getBaseline();
        final int maxBaseline = Math.max(Math.max(prevBaseline, currBaseline), nextBaseline);
        final int prevTopOffset = maxBaseline - prevBaseline;
        final int currTopOffset = maxBaseline - currBaseline;
        final int nextTopOffset = maxBaseline - nextBaseline;
        final int alignedPrevHeight = prevTopOffset + mPrevText.getMeasuredHeight();
        final int alignedCurrHeight = currTopOffset + mCurrText.getMeasuredHeight();
        final int alignedNextHeight = nextTopOffset + mNextText.getMeasuredHeight();
        final int maxTextHeight = Math.max(Math.max(alignedPrevHeight, alignedCurrHeight),
                alignedNextHeight);

        final int vgrav = mGravity & Gravity.VERTICAL_GRAVITY_MASK;

        int prevTop;
        int currTop;
        int nextTop;
        switch (vgrav) {
            default:
            case Gravity.TOP:
                prevTop = paddingTop + prevTopOffset;
                currTop = paddingTop + currTopOffset;
                nextTop = paddingTop + nextTopOffset;
                break;
            case Gravity.CENTER_VERTICAL:
                final int paddedHeight = stripHeight - paddingTop - paddingBottom;
                final int centeredTop = (paddedHeight - maxTextHeight) / 2;
                prevTop = centeredTop + prevTopOffset;
                currTop = centeredTop + currTopOffset;
                nextTop = centeredTop + nextTopOffset;
                break;
            case Gravity.BOTTOM:
                final int bottomGravTop = stripHeight - paddingBottom - maxTextHeight;
                prevTop = bottomGravTop + prevTopOffset;
                currTop = bottomGravTop + currTopOffset;
                nextTop = bottomGravTop + nextTopOffset;
                break;
        }

        mCurrText.layout(currLeft, currTop, currRight,
                currTop + mCurrText.getMeasuredHeight());

        final int prevLeft = Math.min(paddingLeft, currLeft - mScaledTextSpacing - prevWidth);
        mPrevText.layout(prevLeft, prevTop, prevLeft + prevWidth,
                prevTop + mPrevText.getMeasuredHeight());

        final int nextLeft = Math.max(stripWidth - paddingRight - nextWidth,
                currRight + mScaledTextSpacing);
        mNextText.layout(nextLeft, nextTop, nextLeft + nextWidth,
                nextTop + mNextText.getMeasuredHeight());

        mLastKnownPositionOffset = positionOffset;
        mUpdatingPositions = false;