Android可折叠式菜单栏

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBar"
        android:layout_width="match_parent"
        android:layout_height="250dp"
        >
        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:contentScrim="?attr/colorPrimary"
            >
<!--定义标题栏的具体内容-->
            <ImageView
                android:id="@+id/fruit_image_view"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"/><!--折叠过程中产生一定的错位偏移00-->
            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"/><!--折叠过程中位置始终不变-->

        </android.support.design.widget.CollapsingToolbarLayout>

    </android.support.design.widget.AppBarLayout>
<!--定义主体内容-->
    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <android.support.v7.widget.CardView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginBottom="15dp"
                android:layout_marginLeft="15dp"
                android:layout_marginRight="15dp"
                android:layout_marginTop="35dp"
                app:cardCornerRadius="4dp">
                <TextView
                    android:id="@+id/fruit_content_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"/>
            </android.support.v7.widget.CardView>



        </LinearLayout>
    </android.support.v4.widget.NestedScrollView><!--NestedScrollView在ScrollView基础上加入了嵌套响应滚动事件-->

    <!--浮动按钮-->
    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/a"
        app:layout_anchor="@id/appBar"
        app:layout_anchorGravity="bottom|end"/><!--layout_anchor设置出现位置layout_anchorGravity出现在右下角-->
</android.support.design.widget.CoordinatorLayout>

package com.example.myapplication;

import android.content.Intent;
import android.support.design.widget.CollapsingToolbarLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;

public class activity_fruit extends AppCompatActivity {
    public static final String FRUIT_NAME = "fruit_name";
    public static final String FRUIT_IMAGE_ID = "fruit_image_id";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fruit);
        Intent intent = getIntent();
        String fruitName = intent.getStringExtra(FRUIT_NAME);
        int fruitImageId = intent.getIntExtra(FRUIT_IMAGE_ID, 0);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        CollapsingToolbarLayout collapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.collapsing_toolbar);
        ImageView fruitImageView = (ImageView) findViewById(R.id.fruit_image_view);
        TextView fruitContentText = (TextView) findViewById(R.id.fruit_content_text);
        setSupportActionBar(toolbar);
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.setDisplayHomeAsUpEnabled(true)  ;//返回箭头
            Log.e("MainActivity.class", "onCreate");
        }else{
            Log.e("MainActivity.class", "onCreate: null");
        }
        collapsingToolbarLayout.setTitle(fruitName);//设置标题
        Glide.with(this).load(fruitImageId).into(fruitImageView);//传入水果图片
        String fruitContent = generateFruitContent(fruitName);
        fruitContentText.setText(fruitContent);
    }

    private String generateFruitContent(String fruitName) {
        StringBuilder fruitContent = new StringBuilder();
        for (int i = 0; i < 500; i++) {
            fruitContent.append(fruitName);
        }
        return fruitContent.toString();
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

  @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if(mContext==null){
            mContext=parent.getContext();
        }
        View view= LayoutInflater.from(mContext).inflate(R.layout.fruit_item,parent,false);
        final ViewHolder holder=new ViewHolder(view);
        holder.cardView.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                int position=holder.getAdapterPosition();


                Fruit fruit=mFruitList.get(position);
                Intent intent=new Intent(mContext,  activity_fruit.class);
                intent.putExtra(activity_fruit.FRUIT_IMAGE_ID,fruit.getImageId());
                intent.putExtra(activity_fruit.FRUIT_NAME,fruit.getName());
                mContext.startActivity(intent);
            }
        });
        return holder;
    }