Java tutorial
/* * Copyright (C) 2012 Jake Wharton * * 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 co.paulburke.android.textviewpager; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.drawable.Drawable; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.view.DirectionalViewPager; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; /** * Customized UnderlinePageIndicator from the ViewPageIndicator library that * emulates a scroll bar based on the orientation of the * {@link DirectionalViewPager} it's connected to. * * @author Jake Wharton * @author paulburke (ipaulpro) Modified to support {@link DirectionalViewPager} * and better resemble a scroll bar. */ public class TextViewPagerIndicator extends View implements ViewPager.OnPageChangeListener { private static final String TAG = "TextViewPagerIndicator"; private static final int FADE_FRAME_MS = 30; private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); private boolean mFades; private int mFadeDelay; private int mFadeLength; private int mFadeBy; private DirectionalViewPager mViewPager; private DirectionalViewPager.OnPageChangeListener mListener; private int mScrollState; private int mCurrentPage; private float mPositionOffset; private final Runnable mFadeRunnable = new Runnable() { @Override public void run() { if (!mFades) return; final int alpha = Math.max(mPaint.getAlpha() - mFadeBy, 0); mPaint.setAlpha(alpha); setBackgroundAlpha(alpha); invalidate(); if (alpha > 0) { postDelayed(this, FADE_FRAME_MS); } } }; public TextViewPagerIndicator(Context context) { this(context, null); } public TextViewPagerIndicator(Context context, AttributeSet attrs) { this(context, attrs, R.attr.scrollPageIndicatorStyle); } public TextViewPagerIndicator(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); if (isInEditMode()) return; final Resources res = getResources(); // Load defaults from resources final boolean defaultFades = res.getBoolean(R.bool.scroll_indicator_fades); final int defaultFadeDelay = res.getInteger(R.integer.scroll_indicator_fade_delay); final int defaultFadeLength = res.getInteger(R.integer.scroll_indicator_fade_length); final int defaultSelectedColor = res.getColor(R.color.scroll_indicator_selected_color); // Retrieve styles attributes TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.TextViewPagerIndicator, defStyle, 0); setFades(a.getBoolean(R.styleable.TextViewPagerIndicator_fades, defaultFades)); setSelectedColor(a.getColor(R.styleable.TextViewPagerIndicator_selectedColor, defaultSelectedColor)); setFadeDelay(a.getInteger(R.styleable.TextViewPagerIndicator_fadeDelay, defaultFadeDelay)); setFadeLength(a.getInteger(R.styleable.TextViewPagerIndicator_fadeLength, defaultFadeLength)); Drawable background = a.getDrawable(R.styleable.TextViewPagerIndicator_android_background); if (background != null) setBackgroundDrawable(background); a.recycle(); } public boolean getFades() { return mFades; } public void setFades(boolean fades) { if (fades != mFades) { mFades = fades; if (fades) { post(mFadeRunnable); } else { removeCallbacks(mFadeRunnable); mPaint.setAlpha(0xFF); setBackgroundAlpha(0xFF); invalidate(); } } } public int getFadeDelay() { return mFadeDelay; } public void setFadeDelay(int fadeDelay) { mFadeDelay = fadeDelay; } public int getFadeLength() { return mFadeLength; } public void setFadeLength(int fadeLength) { mFadeLength = fadeLength; mFadeBy = 0xFF / (mFadeLength / FADE_FRAME_MS); } public int getSelectedColor() { return mPaint.getColor(); } public void setSelectedColor(int selectedColor) { mPaint.setColor(selectedColor); invalidate(); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); if (mViewPager == null) return; final int count = mViewPager.getAdapter().getCount(); if (count == 0) return; if (mCurrentPage >= count) { setCurrentItem(count - 1); return; } float left = 0f, top = 0f, right = 0f, bottom = 0f; final int paddingTop = getPaddingTop(); final int paddingBottom = getPaddingBottom(); final int paddingRight = getPaddingRight(); final int paddingLeft = getPaddingLeft(); if (isHorizontal()) { final float pageWidth = (getWidth() - paddingLeft - paddingRight) / (1f * count); left = paddingLeft + pageWidth * (mCurrentPage + mPositionOffset); right = left + pageWidth; top = 0f; bottom = getHeight(); } else if (isVertical()) { final float pageHeight = (getHeight() - paddingTop - paddingBottom) / (1f * count); top = paddingTop + pageHeight * (mCurrentPage + mPositionOffset); bottom = top + pageHeight; left = 0f; right = getWidth(); } canvas.drawRect(left, top, right, bottom, mPaint); } private boolean isHorizontal() { return mViewPager.getOrientation() == DirectionalViewPager.HORIZONTAL; } private boolean isVertical() { return mViewPager.getOrientation() == DirectionalViewPager.VERTICAL; } public void setViewPager(ViewPager viewPager) { if (mViewPager == viewPager) { return; } if (mViewPager != null) { // Clear us from the old pager. mViewPager.setOnPageChangeListener(null); } if (viewPager.getAdapter() == null) { throw new IllegalStateException("ViewPager does not have adapter instance."); } mViewPager = (DirectionalViewPager) viewPager; mViewPager.setOnPageChangeListener(this); mViewPager.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN) { show(); } return false; } }); invalidate(); post(new Runnable() { @Override public void run() { if (mFades) { post(mFadeRunnable); } } }); } public void show() { removeCallbacks(mFadeRunnable); mPaint.setAlpha(0xFF); setBackgroundAlpha(0xFF); postDelayed(mFadeRunnable, mFadeDelay); } public void hide() { removeCallbacks(mFadeRunnable); post(mFadeRunnable); } public void setViewPager(ViewPager view, int initialPosition) { setViewPager(view); setCurrentItem(initialPosition); } public void setCurrentItem(int item) { if (mViewPager == null) { throw new IllegalStateException("ViewPager has not been bound."); } mViewPager.setCurrentItem(item); mCurrentPage = item; invalidate(); } public void notifyDataSetChanged() { invalidate(); } @Override public void onPageScrollStateChanged(int state) { mScrollState = state; if (mListener != null) { mListener.onPageScrollStateChanged(state); } } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { mCurrentPage = position; mPositionOffset = positionOffset; if (mFades) { if (positionOffsetPixels > 0) { removeCallbacks(mFadeRunnable); mPaint.setAlpha(0xFF); setBackgroundAlpha(0xFF); } else if (mScrollState != ViewPager.SCROLL_STATE_DRAGGING) { postDelayed(mFadeRunnable, mFadeDelay); } } invalidate(); if (mListener != null) { mListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } } @Override public void onPageSelected(int position) { if (mScrollState == ViewPager.SCROLL_STATE_IDLE) { mCurrentPage = position; mPositionOffset = 0; invalidate(); mFadeRunnable.run(); } if (mListener != null) { mListener.onPageSelected(position); } } public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) { mListener = listener; } private void setBackgroundAlpha(int alpha) { Drawable background = getBackground(); if (background != null) background.setAlpha(alpha); } @Override public void onRestoreInstanceState(Parcelable state) { SavedState savedState = (SavedState) state; super.onRestoreInstanceState(savedState.getSuperState()); mCurrentPage = savedState.currentPage; requestLayout(); } @Override public Parcelable onSaveInstanceState() { Parcelable superState = super.onSaveInstanceState(); SavedState savedState = new SavedState(superState); savedState.currentPage = mCurrentPage; return savedState; } static class SavedState extends BaseSavedState { int currentPage; public SavedState(Parcelable superState) { super(superState); } private SavedState(Parcel in) { super(in); currentPage = in.readInt(); } @Override public void writeToParcel(Parcel dest, int flags) { super.writeToParcel(dest, flags); dest.writeInt(currentPage); } public static final Creator<SavedState> CREATOR = new Creator<SavedState>() { @Override public SavedState createFromParcel(Parcel in) { return new SavedState(in); } @Override public SavedState[] newArray(int size) { return new SavedState[size]; } }; } }