Java tutorial
package com.breadwallet.tools.adapter; import android.annotation.SuppressLint; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.Drawable; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.util.Log; import com.breadwallet.BreadWalletApp; import com.breadwallet.presenter.activities.MainActivity; import com.breadwallet.tools.animation.BRAnimator; /** * BreadWallet * <p> * Created by Mihail Gutan <mihail@breadwallet.com> on 6/29/15. * Copyright (c) 2016 breadwallet LLC * <p> * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * <p> * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * <p> * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ @SuppressLint("NewApi") public class ParallaxViewPager extends ViewPager { public static final String TAG = ParallaxViewPager.class.getName(); private static final int FIT_WIDTH = 0; private static final int FIT_HEIGHT = 1; public static final float OVERLAP_FULL = 1f; private static final float OVERLAP_HALF = 0.5f; public static final float OVERLAP_QUARTER = 0.25f; private static final float CORRECTION_PERCENTAGE = 0.01f; private Bitmap bitmap; private Rect source, destination; private int scaleType; private int chunkWidth; private int projectedWidth; private float overlap; private OnPageChangeListener secondOnPageChangeListener; public ParallaxViewPager(Context context) { super(context); init(); } public ParallaxViewPager(Context context, AttributeSet attrs) { super(context, attrs); init(); } private void init() { source = new Rect(); destination = new Rect(); scaleType = FIT_HEIGHT; overlap = OVERLAP_HALF; //noinspection deprecation setOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { if (bitmap != null) { source.left = (int) Math .floor((position + positionOffset - CORRECTION_PERCENTAGE) * chunkWidth); source.right = (int) Math.ceil( (position + positionOffset + CORRECTION_PERCENTAGE) * chunkWidth + projectedWidth); destination.left = (int) Math .floor((position + positionOffset - CORRECTION_PERCENTAGE) * getWidth()); destination.right = (int) Math .ceil((position + positionOffset + 1 + CORRECTION_PERCENTAGE) * getWidth()); invalidate(); } if (secondOnPageChangeListener != null) { secondOnPageChangeListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } } @Override public void onPageSelected(final int position) { if (secondOnPageChangeListener != null && BRAnimator.level == 0) { secondOnPageChangeListener.onPageSelected(position); } MainActivity app = MainActivity.app; if (app != null && BRAnimator.level == 0) { ((BreadWalletApp) app.getApplication()).cancelToast(); ((BreadWalletApp) app.getApplication()).hideKeyboard(app); app.hideAllBubbles(); app.setPagerIndicator(position); } } @Override public void onPageScrollStateChanged(int state) { if (secondOnPageChangeListener != null) { secondOnPageChangeListener.onPageScrollStateChanged(state); } } }); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); destination.top = 0; destination.bottom = h; if (getAdapter() != null && bitmap != null) calculateParallaxParameters(); } private void calculateParallaxParameters() { if (bitmap.getWidth() < getWidth() && bitmap.getWidth() < bitmap.getHeight() && scaleType == FIT_HEIGHT) { Log.w(ParallaxViewPager.class.getName(), "Invalid bitmap bounds for the current device, parallax effect will not work."); } final float ratio = (float) getHeight() / bitmap.getHeight(); if (ratio != 1) { switch (scaleType) { case FIT_WIDTH: source.top = (int) ((bitmap.getHeight() - bitmap.getHeight() / ratio) / 2); source.bottom = bitmap.getHeight() - source.top; chunkWidth = (int) Math.ceil((float) bitmap.getWidth() / (float) getAdapter().getCount()); projectedWidth = chunkWidth; break; case FIT_HEIGHT: default: source.top = 0; source.bottom = bitmap.getHeight(); projectedWidth = (int) Math.ceil(getWidth() / ratio); chunkWidth = (int) Math .ceil((bitmap.getWidth() - projectedWidth) / (float) getAdapter().getCount() * overlap); break; } } } /** * Sets the background from a resource file. * * @param resid */ @Override public void setBackgroundResource(int resid) { BitmapFactory.Options options = new BitmapFactory.Options(); options.inScaled = true; options.inTargetDensity = 100; bitmap = BitmapFactory.decodeResource(getResources(), resid, options); } /** * Sets the background from a Drawable. * * @param background */ @Override public void setBackground(Drawable background) { bitmap = ((BitmapDrawable) background).getBitmap(); } /** * Deprecated. * Sets the background from a Drawable. * * @param background */ @SuppressWarnings("deprecation") @Override public void setBackgroundDrawable(Drawable background) { bitmap = ((BitmapDrawable) background).getBitmap(); } /** * Sets the background from a bitmap. * * @param bitmap * @return The ParallaxViewPager object itself. */ public ParallaxViewPager setBackground(Bitmap bitmap) { this.bitmap = bitmap; return this; } /** * Sets how the view should scale the background. The available choices are: * <ul> * <li>FIT_HEIGHT - the height of the image is resized to matched the height of the View, also stretching the width to keep the aspect ratio. The non-visible part of the bitmap is divided into equal parts, each of them sliding in at the proper position.</li> * <li>FIT_WIDTH - the width of the background image is divided into equal chunks, each taking up the whole width of the screen.</li> * </ul> * * @param scaleType * @return */ public ParallaxViewPager setScaleType(final int scaleType) { if (scaleType != FIT_WIDTH && scaleType != FIT_HEIGHT) throw new IllegalArgumentException("Illegal argument: scaleType must be FIT_WIDTH or FIT_HEIGHT"); this.scaleType = scaleType; return this; } /** * Sets the amount of overlapping with the setOverlapPercentage(final float percentage) method. This is a number between 0 and 1, the smaller it is, the slower is the background scrolling. * * @param percentage * @return The ParallaxViewPager object itself. */ public ParallaxViewPager setOverlapPercentage(final float percentage) { if (percentage <= 0 || percentage >= 1) throw new IllegalArgumentException("Illegal argument: percentage must be between 0 and 1"); overlap = percentage; return this; } /** * Recalculates the parameters of the parallax effect, useful after changes in runtime. * * @return The ParallaxViewPager object itself. */ public ParallaxViewPager invalidateParallaxParameters() { calculateParallaxParameters(); return this; } @Override protected void onDraw(Canvas canvas) { if (bitmap != null) canvas.drawBitmap(bitmap, source, destination, null); } public void addOnPageChangeListener(OnPageChangeListener listener) { secondOnPageChangeListener = listener; } }