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 com.tweetlanes.android.core.widget.viewpagerindicator; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Paint; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.ViewConfigurationCompat; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import com.tweetlanes.android.core.R; /** * Draws a line for each page. The current page line is colored differently than * the unselected page lines. */ public class UnderlinePageIndicator extends View implements PageIndicator { private static final int INVALID_POINTER = -1; 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 ViewPager mViewPager; private ViewPager.OnPageChangeListener mListener; private int mScrollState; private int mCurrentPage; private float mPositionOffset; private int mTouchSlop; private float mLastMotionX = -1; private int mActivePointerId = INVALID_POINTER; private boolean mIsDragging; private final Runnable mFadeRunnable = new Runnable() { @Override public void run() { final int alpha = Math.max(mPaint.getAlpha() - mFadeBy, 0); mPaint.setAlpha(alpha); invalidate(); if (alpha > 0) { postDelayed(this, FADE_FRAME_MS); } } }; public UnderlinePageIndicator(Context context) { this(context, null); } public UnderlinePageIndicator(Context context, AttributeSet attrs) { this(context, attrs, R.attr.vpiUnderlinePageIndicatorStyle); } public UnderlinePageIndicator(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.default_underline_indicator_fades); final int defaultFadeDelay = res.getInteger(R.integer.default_underline_indicator_fade_delay); final int defaultFadeLength = res.getInteger(R.integer.default_underline_indicator_fade_length); final int defaultSelectedColor = res.getColor(R.color.default_underline_indicator_selected_color); // Retrieve styles attributes TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.UnderlinePageIndicator, defStyle, 0); setFades(a.getBoolean(R.styleable.UnderlinePageIndicator_fades, defaultFades)); setSelectedColor(a.getColor(R.styleable.UnderlinePageIndicator_selectedColor, defaultSelectedColor)); setFadeDelay(a.getInteger(R.styleable.UnderlinePageIndicator_fadeDelay, defaultFadeDelay)); setFadeLength(a.getInteger(R.styleable.UnderlinePageIndicator_fadeLength, defaultFadeLength)); a.recycle(); final ViewConfiguration configuration = ViewConfiguration.get(context); mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration); } public void setFades(boolean fades) { if (fades != mFades) { mFades = fades; if (fades) { post(mFadeRunnable); } else { removeCallbacks(mFadeRunnable); mPaint.setAlpha(0xFF); invalidate(); } } } void setFadeDelay(int fadeDelay) { mFadeDelay = fadeDelay; } void setFadeLength(int fadeLength) { mFadeLength = fadeLength; mFadeBy = 0xFF / (mFadeLength / FADE_FRAME_MS); } 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; } final int paddingLeft = getPaddingLeft(); final float pageWidth = (getWidth() - paddingLeft - getPaddingRight()) / (1f * count); final float left = paddingLeft + pageWidth * (mCurrentPage + mPositionOffset); final float right = left + pageWidth; final float top = getPaddingTop(); final float bottom = getHeight() - getPaddingBottom(); canvas.drawRect(left, top, right, bottom, mPaint); } public boolean onTouchEvent(MotionEvent ev) { if (super.onTouchEvent(ev)) { return true; } if ((mViewPager == null) || (mViewPager.getAdapter().getCount() == 0)) { return false; } final int action = ev.getAction(); switch (action & MotionEventCompat.ACTION_MASK) { case MotionEvent.ACTION_DOWN: mActivePointerId = MotionEventCompat.getPointerId(ev, 0); mLastMotionX = ev.getX(); break; case MotionEvent.ACTION_MOVE: { final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId); final float x = MotionEventCompat.getX(ev, activePointerIndex); final float deltaX = x - mLastMotionX; if (!mIsDragging) { if (Math.abs(deltaX) > mTouchSlop) { mIsDragging = true; } } if (mIsDragging) { mLastMotionX = x; if (mViewPager.isFakeDragging() || mViewPager.beginFakeDrag()) { mViewPager.fakeDragBy(deltaX); } } break; } case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: if (!mIsDragging) { final int count = mViewPager.getAdapter().getCount(); final int width = getWidth(); final float halfWidth = width / 2f; final float sixthWidth = width / 6f; if ((mCurrentPage > 0) && (ev.getX() < halfWidth - sixthWidth)) { mViewPager.setCurrentItem(mCurrentPage - 1); return true; } else if ((mCurrentPage < count - 1) && (ev.getX() > halfWidth + sixthWidth)) { mViewPager.setCurrentItem(mCurrentPage + 1); return true; } } mIsDragging = false; mActivePointerId = INVALID_POINTER; if (mViewPager.isFakeDragging()) mViewPager.endFakeDrag(); break; case MotionEventCompat.ACTION_POINTER_DOWN: { final int index = MotionEventCompat.getActionIndex(ev); mLastMotionX = MotionEventCompat.getX(ev, index); mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } case MotionEventCompat.ACTION_POINTER_UP: final int pointerIndex = MotionEventCompat.getActionIndex(ev); final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex); if (pointerId == mActivePointerId) { final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex); } mLastMotionX = MotionEventCompat.getX(ev, MotionEventCompat.findPointerIndex(ev, mActivePointerId)); break; } return true; } @Override 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 = viewPager; mViewPager.setOnPageChangeListener(this); invalidate(); post(new Runnable() { @Override public void run() { if (mFades) { post(mFadeRunnable); } } }); } @Override public void setViewPager(ViewPager view, int initialPosition) { setViewPager(view); setCurrentItem(initialPosition); } @Override public void setCurrentItem(int item) { if (mViewPager == null) { throw new IllegalStateException("ViewPager has not been bound."); } mViewPager.setCurrentItem(item); mCurrentPage = item; invalidate(); } @Override 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); } 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); } } @Override public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) { mListener = listener; } @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]; } }; } }