Android仿知乎广告

最近在我三星手机上看到了很有意思的图片广告，听说是模仿知乎创意广告。来回看了看，觉得挺有意思，就开始动手写写这个小效果。很简单，一点也不难实现。不多说，先上图：

直接贴代码，不懂看注释:

1、重写ImageView

/*** Created by csc on 2018/1/24.* explain：*/public class AdsImagView extends ImageView {public AdsImagView(Context context, @Nullable AttributeSet attrs) {super(context, attrs);}//广告位的高度private int imgvHeight;//显示比率private float rate=1;@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);//设置广告位的高度imgvHeight=h;}@Overrideprotected void onDraw(Canvas canvas) {//获得画板Drawable drawable=getDrawable();//getIntrinsicWidth()和getIntrinsicHeight()，顾名思义他们是用来取得Drawable的固有的宽度和高度// w/getIntrinsicWidth()=y/getIntrinsicHeight()int w=getWidth();int h= (int) (w*1.0f/drawable.getIntrinsicWidth()*drawable.getIntrinsicHeight());//设置图片的显示范围 drawable.setBounds(0,0,w,h);//表示图片可移动的的最大范围int maxDy=h-imgvHeight;canvas.save();//图片的纵向位移canvas.translate(0,-maxDy*rate); super.onDraw(canvas);//这里注意:为什么super写在这里，因为如果先画再super就会把我们画的给挡住。canvas.restore();}//设置图片的位移(条目距离顶部的距离，rv的高度)public void setDy(int distanceTop,int rvHeight){//广告位有效滚动的距离int canHeight=rvHeight-distanceTop;//求出滚动的比率rate=distanceTop*1.0f/canHeight;if (rate<=0){rate=0;}if (rate>=1){rate=1;}invalidate();}
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><com.youyu.zhihuads.AdsImagViewandroid:src="@drawable/beautiful"android:id="@+id/imgv"android:layout_width="match_parent"android:layout_height="150dp"android:scaleType="matrix" /><TextViewandroid:id="@+id/tv"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/imgv"android:gravity="center"android:text="条目"android:textSize="20sp" /></RelativeLayout>

public class MainActivity extends AppCompatActivity {private RecyclerView mRv;private List<String> lists=new ArrayList<>();private RvAdapter mAdapter;private LinearLayoutManager lineatLayoutManager;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);lineatLayoutManager=new LinearLayoutManager(this);for (int i = 0; i < 50; i++) {lists.add("我是新闻第:"+i+"条");}mRv = (RecyclerView) findViewById(R.id.rv);mRv.setLayoutManager(lineatLayoutManager);mAdapter=new RvAdapter(lists);mRv.setAdapter(mAdapter);//设置Rv的滚动监听mRv.addOnScrollListener(new RecyclerView.OnScrollListener() {@Overridepublic void onScrolled(RecyclerView recyclerView, int dx, int dy) {super.onScrolled(recyclerView, dx, dy);//第一个显示的条目int fistVisible=lineatLayoutManager.findFirstVisibleItemPosition();//最后一个显示的条目int lastVisible=lineatLayoutManager.findLastVisibleItemPosition();//从第一个显示条目 遍历到 最后一个显示的条目for (int i = fistVisible; i <= lastVisible; i++) {//根据位置找到控件View view = lineatLayoutManager.findViewByPosition(i);AdsImagView imgv=view.findViewById(R.id.imgv);if (imgv.getVisibility()==View.VISIBLE){//获取广告位的位置与Rv顶部的距离int top=view.getTop();//获取Rv的高度int rvHeight=mRv.getHeight();//设置广告的位移imgv.setDy(top,rvHeight);}}}});}}