今天我所要作的笔记是：
可切换式的卡片CardView。
Java代码部分
1、我们要根据自己的当前版本号添加相对应的一个依赖：
implementation 'com.android.support:cardview-v7:28.0.0'
2、编写Fragment，在自己需要Activity中添加Fragment，在该Fragment编写如下代码。我的Fragment是DiscoveryFragment。
public class DiscoveryFragment extends Fragment {
private ViewPager mViewPager;
private CardPagerAdapter mCardAdapter;
private ShadowTransformer mCardShadowTransformer;
private CardView mCardView;
public DiscoveryFragment() {
// Required empty public constructor
}
View view;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
if(view == null) {
view = inflater.inflate(R.layout.fragment_discovery, container, false);
mCardView = view.findViewById(R.id.cardView);
mCardView.setMaxCardElevation(mCardView.getCardElevation()
* CardAdapter.MAX_ELEVATION_FACTOR);
initCard();
}
return view;
}
private void initCard() {
mViewPager = view.findViewById(R.id.viewPager);
mCardAdapter = new CardPagerAdapter();
mCardAdapter.addCardItem(new CardItem(R.string.title_1, R.string.text_1));
mCardAdapter.addCardItem(new CardItem(R.string.title_2, R.string.text_1));
mCardAdapter.addCardItem(new CardItem(R.string.title_3, R.string.text_1));
mCardAdapter.addCardItem(new CardItem(R.string.title_4, R.string.text_1));
mCardShadowTransformer = new ShadowTransformer(mViewPager, mCardAdapter);
mCardShadowTransformer.enableScaling(true);
mViewPager.setAdapter(mCardAdapter);
mViewPager.setPageTransformer(false, mCardShadowTransformer);
mViewPager.setOffscreenPageLimit(3);
}
public CardView getCardView() {
return mCardView;
}
}
3、CardFragmentPagerAdapter
public class CardFragmentPagerAdapter extends FragmentStatePagerAdapter implements CardAdapter {
private List mFragments;
private float mBaseElevation;
public CardFragmentPagerAdapter(FragmentManager fm, float baseElevation) {
super(fm);
mFragments = new ArrayList<>();
mBaseElevation = baseElevation;
for(int i = 0; i< 5; i++){
addCardFragment(new DiscoveryFragment());
}
}
@Override
public float getBaseElevation() {
return mBaseElevation;
}
@Override
public CardView getCardViewAt(int position) {
return mFragments.get(position).getCardView();
}
@Override
public int getCount() {
return mFragments.size();
}
@Override
public Fragment getItem(int position) {
return mFragments.get(position);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Object fragment = super.instantiateItem(container, position);
mFragments.set(position, (DiscoveryFragment) fragment);
return fragment;
}
public void addCardFragment(DiscoveryFragment fragment) {
mFragments.add(fragment);
}
}
4、CardPagerAdapter
public class CardPagerAdapter extends PagerAdapter implements CardAdapter {
private List mViews;
private List mData;
private float mBaseElevation;
public CardPagerAdapter() {
mData = new ArrayList<>();
mViews = new ArrayList<>();
}
public void addCardItem(CardItem item) {
mViews.add(null);
mData.add(item);
}
public float getBaseElevation() {
return mBaseElevation;
}
@Override
public CardView getCardViewAt(int position) {
return mViews.get(position);
}
@Override
public int getCount() {
return mData.size();
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
View view = LayoutInflater.from(container.getContext())
.inflate(R.layout.adapter, container, false);
container.addView(view);
bind(mData.get(position), view);
CardView cardView = view.findViewById(R.id.cardView);
if (mBaseElevation == 0) {
mBaseElevation = cardView.getCardElevation();
}
cardView.setMaxCardElevation(mBaseElevation * MAX_ELEVATION_FACTOR);
mViews.set(position, cardView);
return view;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
mViews.set(position, null);
}
private void bind(CardItem item, View view) {
TextView titleTextView = (TextView) view.findViewById(R.id.titleTextView);
TextView contentTextView = (TextView) view.findViewById(R.id.contentTextView);
titleTextView.setText(item.getTitle());
contentTextView.setText(item.getText());
}
}
5、CardItem
public class CardItem {
private int mTextResource;
private int mTitleResource;
public CardItem(int title, int text) {
mTitleResource = title;
mTextResource = text;
}
public int getText() {
return mTextResource;
}
public int getTitle() {
return mTitleResource;
}
}
6、ShadowTransformer
public class ShadowTransformer implements ViewPager.OnPageChangeListener, ViewPager.PageTransformer {
private ViewPager mViewPager;
private CardAdapter mAdapter;
private float mLastOffset;
private boolean mScalingEnabled;
public ShadowTransformer(ViewPager viewPager, CardAdapter adapter) {
mViewPager = viewPager;
viewPager.addOnPageChangeListener(this);
mAdapter = adapter;
}
public void enableScaling(boolean enable) {
if (mScalingEnabled && !enable) {
// shrink main card
CardView currentCard = mAdapter.getCardViewAt(mViewPager.getCurrentItem());
if (currentCard != null) {
currentCard.animate().scaleY(1);
currentCard.animate().scaleX(1);
}
}else if(!mScalingEnabled && enable){
// grow main card
CardView currentCard = mAdapter.getCardViewAt(mViewPager.getCurrentItem());
if (currentCard != null) {
currentCard.animate().scaleY(1.1f);
currentCard.animate().scaleX(1.1f);
}
}
mScalingEnabled = enable;
}
@Override
public void transformPage(View page, float position) {
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
int realCurrentPosition;
int nextPosition;
float baseElevation = mAdapter.getBaseElevation();
float realOffset;
boolean goingLeft = mLastOffset > positionOffset;
// If we're going backwards, onPageScrolled receives the last position
// instead of the current one
if (goingLeft) {
realCurrentPosition = position + 1;
nextPosition = position;
realOffset = 1 - positionOffset;
} else {
nextPosition = position + 1;
realCurrentPosition = position;
realOffset = positionOffset;
}
// Avoid crash on overscroll
if (nextPosition > mAdapter.getCount() - 1
|| realCurrentPosition > mAdapter.getCount() - 1) {
return;
}
CardView currentCard = mAdapter.getCardViewAt(realCurrentPosition);
// This might be null if a fragment is being used
// and the views weren't created yet
if (currentCard != null) {
if (mScalingEnabled) {
currentCard.setScaleX((float) (1 + 0.1 * (1 - realOffset)));
currentCard.setScaleY((float) (1 + 0.1 * (1 - realOffset)));
}
currentCard.setCardElevation((baseElevation + baseElevation
* (CardAdapter.MAX_ELEVATION_FACTOR - 1) * (1 - realOffset)));
}
CardView nextCard = mAdapter.getCardViewAt(nextPosition);
// We might be scrolling fast enough so that the next (or previous) card
// was already destroyed or a fragment might not have been created yet
if (nextCard != null) {
if (mScalingEnabled) {
nextCard.setScaleX((float) (1 + 0.1 * (realOffset)));
nextCard.setScaleY((float) (1 + 0.1 * (realOffset)));
}
nextCard.setCardElevation((baseElevation + baseElevation
* (CardAdapter.MAX_ELEVATION_FACTOR - 1) * (realOffset)));
}
mLastOffset = positionOffset;
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
}
}
7、CardAdapter
public interface CardAdapter {
int MAX_ELEVATION_FACTOR = 8;
float getBaseElevation();
CardView getCardViewAt(int position);
int getCount();
}
XML文件
1、CardPagerAdapter的布局文件adapter
2、fragment_discovery
以上。
代码来自：（致谢）
https://blog.csdn.net/chenzheng8975/article/details/76976122