Java tutorial
/* * Copyright (C) 2011 Patrik Akerfeldt * Copyright (C) 2011 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.jakewharton.android.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.graphics.Paint.Style; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; /** * Draws circles (one for each view). The current view position is filled and * others are only stroked. */ public class CirclePageIndicator extends View implements PageIndicator { private float mRadius; private final Paint mPaintStroke; private final Paint mPaintFill; private ViewPager mViewPager; private ViewPager.OnPageChangeListener mListener; private int mCurrentPage; private int mSnapPage; private int mCurrentOffset; private int mPageWidth; private boolean mCentered; private boolean mSnap; public CirclePageIndicator(Context context) { this(context, null); } public CirclePageIndicator(Context context, AttributeSet attrs) { this(context, attrs, R.attr.circlePageIndicatorStyle); } public CirclePageIndicator(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); //Load defaults from resources final Resources res = getResources(); final int defaultFillColor = res.getColor(R.color.default_circle_indicator_fill_color); final int defaultStrokeColor = res.getColor(R.color.default_circle_indicator_stroke_color); final float defaultStrokeWidth = res.getDimension(R.dimen.default_circle_indicator_stroke_width); final float defaultRadius = res.getDimension(R.dimen.default_circle_indicator_radius); final boolean defaultCentered = res.getBoolean(R.bool.default_circle_indicator_centered); final boolean defaultSnap = res.getBoolean(R.bool.default_circle_indicator_snap); //Retrieve styles attributes TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CirclePageIndicator, defStyle, R.style.Widget_CirclePageIndicator); mCentered = a.getBoolean(R.styleable.CirclePageIndicator_centered, defaultCentered); mPaintStroke = new Paint(Paint.ANTI_ALIAS_FLAG); mPaintStroke.setStyle(Style.STROKE); mPaintStroke.setColor(a.getColor(R.styleable.CirclePageIndicator_strokeColor, defaultStrokeColor)); mPaintStroke .setStrokeWidth(a.getDimension(R.styleable.CirclePageIndicator_strokeWidth, defaultStrokeWidth)); mPaintFill = new Paint(Paint.ANTI_ALIAS_FLAG); mPaintFill.setStyle(Style.FILL); mPaintFill.setColor(a.getColor(R.styleable.CirclePageIndicator_fillColor, defaultFillColor)); mRadius = a.getDimension(R.styleable.CirclePageIndicator_radius, defaultRadius); mSnap = a.getBoolean(R.styleable.CirclePageIndicator_snap, defaultSnap); a.recycle(); } public void setCentered(boolean centered) { mCentered = centered; invalidate(); } public boolean isCentered() { return mCentered; } public void setFillColor(int fillColor) { mPaintFill.setColor(fillColor); invalidate(); } public int getFillColor() { return mPaintFill.getColor(); } public void setStrokeColor(int strokeColor) { mPaintStroke.setColor(strokeColor); invalidate(); } public int getStrokeColor() { return mPaintStroke.getColor(); } public void setStrokeWidth(float strokeWidth) { mPaintStroke.setStrokeWidth(strokeWidth); invalidate(); } public float getStrokeWidth() { return mPaintStroke.getStrokeWidth(); } public void setRadius(float radius) { mRadius = radius; invalidate(); } public float getRadius() { return mRadius; } public void setSnap(boolean snap) { mSnap = snap; invalidate(); } public boolean isSnap() { return mSnap; } /* * (non-Javadoc) * * @see android.view.View#onDraw(android.graphics.Canvas) */ @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); final int count = mViewPager.getAdapter().getCount(); final float threeRadius = mRadius * 3; final float topOffset = getPaddingTop() + mRadius; final int paddingLeft = getPaddingLeft(); float leftOffset = paddingLeft + mRadius; if (mCentered) { leftOffset += ((getWidth() - paddingLeft - getPaddingRight()) / 2.0f) - ((count * threeRadius) / 2.0f); } //Draw stroked circles for (int iLoop = 0; iLoop < count; iLoop++) { canvas.drawCircle(leftOffset + (iLoop * threeRadius), topOffset, mRadius, mPaintStroke); } //Draw the filled circle according to the current scroll float cx = (mSnap ? mSnapPage : mCurrentPage) * threeRadius; if (!mSnap && (mPageWidth != 0)) { cx += (mCurrentOffset * 1.0f / mPageWidth) * threeRadius; } canvas.drawCircle(leftOffset + cx, topOffset, mRadius, mPaintFill); } @Override public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN) { final int count = mViewPager.getAdapter().getCount(); final float halfWidth = getWidth() / 2; final float halfCircleWidth = (count * 3 * mRadius) / 2; if ((mCurrentPage > 0) && (event.getX() < halfWidth - halfCircleWidth)) { setCurrentItem(mCurrentPage - 1); return true; } else if ((mCurrentPage < count - 1) && (event.getX() > halfWidth + halfCircleWidth)) { setCurrentItem(mCurrentPage + 1); return true; } } return super.onTouchEvent(event); } @Override public void setViewPager(ViewPager view) { if (view.getAdapter() == null) { throw new IllegalStateException("ViewPager does not have adapter instance."); } mViewPager = view; mViewPager.setOnPageChangeListener(this); mPageWidth = mViewPager.getWidth(); invalidate(); } @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 onPageScrollStateChanged(int state) { if (mListener != null) { mListener.onPageScrollStateChanged(state); } } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { mCurrentPage = position; mCurrentOffset = positionOffsetPixels; mPageWidth = mViewPager.getWidth(); invalidate(); if (mListener != null) { mListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } } @Override public void onPageSelected(int position) { mCurrentPage = position; mSnapPage = position; invalidate(); if (mListener != null) { mListener.onPageSelected(position); } } @Override public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) { mListener = listener; } /* * (non-Javadoc) * * @see android.view.View#onMeasure(int, int) */ @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(measureWidth(widthMeasureSpec), measureHeight(heightMeasureSpec)); } /** * Determines the width of this view * * @param measureSpec * A measureSpec packed into an int * @return The width of the view, honoring constraints from measureSpec */ private int measureWidth(int measureSpec) { int result = 0; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY) { //We were told how big to be result = specSize; } else { //Calculate the width according the views count final int count = mViewPager.getAdapter().getCount(); result = (int) (getPaddingLeft() + getPaddingRight() + (count * 2 * mRadius) + (count - 1) * mRadius + 1); //Respect AT_MOST value if that was what is called for by measureSpec if (specMode == MeasureSpec.AT_MOST) { result = Math.min(result, specSize); } } return result; } /** * Determines the height of this view * * @param measureSpec * A measureSpec packed into an int * @return The height of the view, honoring constraints from measureSpec */ private int measureHeight(int measureSpec) { int result = 0; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); //We were told how big to be if (specMode == MeasureSpec.EXACTLY) { result = specSize; } //Measure the height else { result = (int) (2 * mRadius + getPaddingTop() + getPaddingBottom() + 1); //Respect AT_MOST value if that was what is called for by measureSpec if (specMode == MeasureSpec.AT_MOST) { result = Math.min(result, specSize); } } return result; } @Override public void onRestoreInstanceState(Parcelable state) { SavedState savedState = (SavedState) state; super.onRestoreInstanceState(savedState.getSuperState()); mCurrentPage = savedState.currentPage; mSnapPage = 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 Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { @Override public SavedState createFromParcel(Parcel in) { return new SavedState(in); } @Override public SavedState[] newArray(int size) { return new SavedState[size]; } }; } }