compile 'com.bartoszlipinski.recyclerviewheader:library:1.2.1'
compile 'com.android.support:recyclerview-v7:25.3.1'

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:tools="http://schemas.android.com/tools"
       android:background="#f2f2f2"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
  <android.support.v7.widget.RecyclerView
    android:id="@+id/recycler"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>
  <TextView
    android:background="#ffffff"
    android:paddingTop="5dp"
    android:paddingBottom="5dp"
    android:gravity="center_horizontal"
    tools:visibility="visible"
    android:textColor="#000000"
    android:textSize="20sp"
    android:id="@+id/home_text"
    android:visibility="invisible"
    android:text="首頁(yè)"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>
</FrameLayout>

public class MainActivity extends AppCompatActivity {
  private TextView mTextView;
  private int mTextViewHeight;
  private RecyclerView mRecyclerView;
  private RecyclerViewHeader mRecyclerViewHeader;
  //頭部圖片(輪播圖的高度)
  private int mRecyclerHeaderBannerHeight;
  //頭部的高度
  private int mRecyclerHeaderHeight;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mTextView = (TextView) findViewById(R.id.home_text);
    //recyclerView填充數(shù)據(jù)(忽略不計(jì))
    initData();
    mRecyclerView = (RecyclerView) findViewById(R.id.recycler);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mRecyclerView.setAdapter(mAdapter);
    //獲取到文本的高度
    mTextViewHeight = mTextView.getHeight();
    //輪播圖片的高度--和xml圖片的高度是一樣的
    mRecyclerHeaderBannerHeight = (int) getResources().getDimension(R.dimen.home_page_banner_height);
    //RecyclerView每個(gè)Item之間的距離,和Adapter中設(shè)置的距離一樣
    final int recyclerItemHeight = (int) getResources().getDimension(R.dimen.home_page_list_item_margin_top);
    //添加頭部視圖,其布局文件就忽略
    mRecyclerViewHeader = RecyclerViewHeader.fromXml(this, R.layout.list_item_prime_product_header);

    //設(shè)置其滑動(dòng)事件
    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
      @Override
      public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        //設(shè)置其透明度
        float alpha = 0;
        int scollYHeight = getScollYHeight(true, mRecyclerHeaderHeight);
        //起始截止變化高度,如可以變化高度為mRecyclerHeaderHeight
        int baseHeight = mRecyclerHeaderBannerHeight - recyclerItemHeight - mTextViewHeight;
        if(scollYHeight >= baseHeight) {
          //完全不透明
          alpha = 1;
        }else {
        //產(chǎn)生漸變效果
          alpha = scollYHeight / (baseHeight*1.0f);
        }
        mTextView.setAlpha(alpha);
        super.onScrolled(recyclerView, dx, dy);
      }
    });
    //將頭部視圖添加到RecyclerView中
    mRecyclerViewHeader.attachTo(mRecyclerView);
    //第一次進(jìn)來其狀態(tài)顯示
    mRecyclerViewHeader.post(new Runnable() {
      @Override
      public void run() {
        mRecyclerHeaderHeight = mRecyclerViewHeader.getHeight();
        mTextViewHeight = mTextView.getHeight();
        mTextView.setVisibility(View.VISIBLE);
        mTextView.setAlpha(0);
      }
    });
  }

/**
   * 計(jì)算RecyclerView滑動(dòng)的距離
   * @param hasHead 是否有頭部
   * @param headerHeight RecyclerView的頭部高度
   * @return 滑動(dòng)的距離
   */
  private int getScollYHeight(boolean hasHead, int headerHeight) {
    LinearLayoutManager layoutManager = (LinearLayoutManager) mRecyclerView.getLayoutManager();
    //獲取到第一個(gè)可見的position,其添加的頭部不算其position當(dāng)中
    int position = layoutManager.findFirstVisibleItemPosition();
    //通過position獲取其管理器中的視圖
    View firstVisiableChildView = layoutManager.findViewByPosition(position);
    //獲取自身的高度
    int itemHeight = firstVisiableChildView.getHeight();
    //有頭部
    if(hasHead) {
      return headerHeight + itemHeight*position - firstVisiableChildView.getTop();
    }else {
      return itemHeight*position - firstVisiableChildView.getTop();
    }
  }