Java tutorial
/* * Copyright 2015 Scott Weeden-Moody * * 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.lillicoder.demo.carouselview.widget; import android.annotation.TargetApi; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.os.Build; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.Checkable; import android.widget.LinearLayout; import com.lillicoder.demo.carouselview.R; import junit.framework.Assert; import java.util.List; /** * View that displays a carousel of arbitrary views in a {@link ViewPager}. */ public class CarouselView extends LinearLayout { private ViewPager mViewPager; private ViewGroup mIndicatorContainer; private int mIndicatorDrawableResourceId; private int mIndicatorPadding; public CarouselView(Context context) { this(context, null); } public CarouselView(Context context, AttributeSet attrs) { super(context, attrs); initialize(context, attrs, 0); } @TargetApi(Build.VERSION_CODES.HONEYCOMB) public CarouselView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initialize(context, attrs, defStyle); } /** * Adds indicators to this carousels indicator container. All previously added * indicators will be removed. * @param amount Number of indicators to add. */ private void addIndicators(int amount) { mIndicatorContainer.removeAllViews(); for (int position = 0; position < amount; position++) { CheckedImageView indicator = new CheckedImageView(getContext()); indicator.setImageResource(mIndicatorDrawableResourceId); indicator.setPadding(mIndicatorPadding, mIndicatorPadding, mIndicatorPadding, mIndicatorPadding); indicator.setChecked(position == 0); // Ensure first item is activated by default mIndicatorContainer.addView(indicator); } } /** * Inflates and initializes this view. * @param context {@link Context} for this view. * @param attrs {@link AttributeSet} for this view. * @param defStyle Optional default style for this view. */ private void initialize(Context context, AttributeSet attrs, int defStyle) { setOrientation(LinearLayout.VERTICAL); LayoutInflater inflater = LayoutInflater.from(context); inflater.inflate(R.layout.view_carousel, this); mViewPager = (ViewPager) findViewById(R.id.CarouselView_viewPager); mIndicatorContainer = (ViewGroup) findViewById(R.id.CarouselView_indicatorContainer); if (attrs != null) { TypedArray attributes = context.obtainStyledAttributes(attrs, R.styleable.CarouselView, defStyle, 0); Resources resources = getResources(); mIndicatorDrawableResourceId = attributes.getResourceId(R.styleable.CarouselView_indicator, R.drawable.carousel_indicator); mIndicatorPadding = (int) attributes.getDimension(R.styleable.CarouselView_indicatorPadding, resources.getDimension(R.dimen.indicator_padding)); } mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageScrollStateChanged(int state) { } @Override public void onPageScrolled(int position, float floatOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { int childCount = mIndicatorContainer.getChildCount(); for (int childPosition = 0; childPosition < childCount; childPosition++) { Checkable child = (Checkable) mIndicatorContainer.getChildAt(childPosition); if (child != null) { child.setChecked(childPosition == position); } } } }); } /** * Sets the {@link Adapter} for this view. * @param adapter Adapter to set. */ public void setAdapter(Adapter adapter) { addIndicators(adapter.getCount()); mViewPager.setAdapter(adapter); } /** * <p> * Adapter that backs a {@link CarouselView}. * </p> * <p> * Since instantiating adapter items can return any kind of object, * it is left to implementers to implement the following methods: * * <ul> * <li>{@link PagerAdapter#destroyItem(ViewGroup, int, Object)}</li> * <li>{@link PagerAdapter#instantiateItem(ViewGroup, int)}</li> * <li>{@link PagerAdapter#isViewFromObject(View, Object)}</li> * </ul> * </p> */ public abstract static class Adapter<T> extends PagerAdapter { private static final String PRECONDITION_NULL_OR_EMPTY_ITEMS = "Cannot instantiate a carousel adapter with a null or empty list of items."; private List<T> mItems; public Adapter(List<T> items) { Assert.assertTrue(PRECONDITION_NULL_OR_EMPTY_ITEMS, items != null && !items.isEmpty()); mItems = items; } @Override public void destroyItem(ViewGroup container, int position, Object object) { onDestroyItem(container, position, object); } @Override public int getCount() { return mItems.size(); } @Override public Object instantiateItem(ViewGroup container, int position) { return onInstantiateItem(container, position); } /** * Gets the object for the adapter at the given position. * @param position Position of the object to get. * @return Object for this adapter at the given position. * @throws IndexOutOfBoundsException Thrown if the given position is out of the bounds of * the list of items backing this adapter. */ public T getItem(int position) { return mItems.get(position); } /** * Callback fired to remove a carousel page for the given position. * The adapter is responsible for removing the view from its container. * @param container The containing View from which the page will be removed. * @param position The page position to be removed. * @param object The same object that was returned by {@link #onInstantiateItem(ViewGroup, int)}. */ public abstract void onDestroyItem(ViewGroup container, int position, Object object); /** * Callback fired to create the carousel page for the given position. * The adapter is responsible for adding the view to the container given here. * @param container The containing View in which the page will be shown. * @param position The page position to be instantiated. * @return Object representing the new page. This does not need to be a View, * but can be some other container of the page. */ public abstract Object onInstantiateItem(ViewGroup container, int position); } }