/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.support.v4.view;
import android.content.Context;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.graphics.drawable.Drawable;
import android.text.TextUtils.TruncateAt;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.widget.TextView;
/**
* 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.
*/
public class PagerTitleStrip extends ViewGroup implements ViewPager.Decor {
private static final String TAG = "PagerTitleStrip";
ViewPager mPager;
private TextView mPrevText;
private TextView mCurrText;
private TextView mNextText;
private int mLastKnownCurrentPage = -1;
private float mLastKnownPositionOffset = -1;
private int mScaledTextSpacing;
private boolean mUpdatingText;
private boolean mUpdatingPositions;
private final PageListener mPageListener = new PageListener();
private static final int[] ATTRS = new int[] {
android.R.attr.textAppearance,
android.R.attr.textColor,
android.R.attr.textSize
};
private static final int SIDE_ALPHA = 0x99; // single-byte alpha, 0 = invisible, FF = opaque
private static final int TEXT_SPACING = 16; // dip
public PagerTitleStrip(Context context) {
this(context, null);
}
public PagerTitleStrip(Context context, 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);
}
if (a.hasValue(1)) {
final int textColor = a.getColor(1, 0);
mPrevText.setTextColor(textColor);
mCurrText.setTextColor(textColor);
mNextText.setTextColor(textColor);
}
final int textSize = a.getDimensionPixelSize(2, 0);
if (textSize != 0) {
mPrevText.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
mCurrText.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
mNextText.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
}
a.recycle();
final int defaultColor = mPrevText.getTextColors().getDefaultColor();
final int transparentColor = (SIDE_ALPHA << 24) | (defaultColor & 0xFFFFFF);
mPrevText.setTextColor(transparentColor);
mNextText.setTextColor(transparentColor);
mPrevText.setEllipsize(TruncateAt.END);
mCurrText.setEllipsize(TruncateAt.END);
mNextText.setEllipsize(TruncateAt.END);
mPrevText.setSingleLine();
mCurrText.setSingleLine();
mNextText.setSingleLine();
final float density = context.getResources().getDisplayMetrics().density;
mScaledTextSpacing = (int) (TEXT_SPACING * density);
}
@Override
protected void onAttachedToWindow() {
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(null, adapter);
}
@Override
protected void onDetachedFromWindow() {
updateAdapter(mPager.getAdapter(), null);
mPager.setInternalPageChangeListener(null);
mPager.setOnAdapterChangeListener(null);
mPager = null;
}
void updateText(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 ? 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.EXACTLY);
mPrevText.measure(childWidthSpec, childHeightSpec);
mCurrText.measure(childWidthSpec, childHeightSpec);
mNextText.measure(childWidthSpec, childHeightSpec);
mLastKnownCurrentPage = currentItem;
if (!mUpdatingPositions) {
updateTextPositions(currentItem, mLastKnownPositionOffset);
}
mUpdatingText = false;
}
@Override
public void requestLayout() {
if (!mUpdatingText) {
super.requestLayout();
}
}
void updateAdapter(PagerAdapter oldAdapter, PagerAdapter newAdapter) {
if (oldAdapter != null) {
oldAdapter.unregisterDataSetObserver(mPageListener);
}
if (newAdapter != null) {
newAdapter.registerDataSetObserver(mPageListener);
}
if (mPager != null) {
mLastKnownCurrentPage = -1;
mLastKnownPositionOffset = -1;
updateText(mPager.getCurrentItem(), newAdapter);
requestLayout();
}
}
void updateTextPositions(int position, float positionOffset) {
if (position != mLastKnownCurrentPage) {
updateText(position, mPager.getAdapter());
} else if (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 paddingLeft = getPaddingLeft();
final int paddingRight = getPaddingRight();
final int paddingTop = getPaddingTop();
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;
mCurrText.layout(currLeft, paddingTop, currRight,
paddingTop + mCurrText.getMeasuredHeight());
final int prevLeft = Math.min(paddingLeft, currLeft - mScaledTextSpacing - prevWidth);
mPrevText.layout(prevLeft, paddingTop, prevLeft + prevWidth,
paddingTop + mPrevText.getMeasuredHeight());
final int nextLeft = Math.max(stripWidth - paddingRight - nextWidth,
currRight + mScaledTextSpacing);
mNextText.layout(nextLeft, paddingTop, nextLeft + nextWidth,
paddingTop + mNextText.getMeasuredHeight());
mLastKnownPositionOffset = positionOffset;
mUpdatingPositions = false;
}
@Override
protected void onMeasure(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 = 0;
int padding = 0;
final Drawable bg = getBackground();
if (bg != null) {
minHeight = bg.getIntrinsicHeight();
}
padding = getPaddingTop() + getPaddingBottom();
childHeight -= padding;
final int childWidthSpec = MeasureSpec.makeMeasureSpec((int) (widthSize * 0.8f),
MeasureSpec.AT_MOST);
final int childHeightSpec = MeasureSpec.makeMeasureSpec(childHeight, heightMode);
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));
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (mPager != null) {
updateTextPositions(mPager.getCurrentItem(), 0.f);
}
}
private class PageListener extends DataSetObserver implements ViewPager.OnPageChangeListener,
ViewPager.OnAdapterChangeListener {
private int mScrollState;
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if (positionOffset > 0.5f) {
// Consider ourselves to be on the next page when we're 50% of the way there.
position++;
}
updateTextPositions(position, positionOffset);
}
@Override
public void onPageSelected(int position) {
if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
// Only update the text here if we're not dragging or settling.
updateText(mPager.getCurrentItem(), mPager.getAdapter());
}
}
@Override
public void onPageScrollStateChanged(int state) {
mScrollState = state;
}
@Override
public void onAdapterChanged(PagerAdapter oldAdapter, PagerAdapter newAdapter) {
updateAdapter(oldAdapter, newAdapter);
}
@Override
public void onChanged() {
updateText(mPager.getCurrentItem(), mPager.getAdapter());
}
}
}