ListView上滑和下滑,显示和隐藏Toolbar的实现方法

android:theme="@style/Theme.AppCompat.Light.NoActionBar">

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/activity_main"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context="com.example.listview_unit4_1.MainActivity">
 <ListView
  android:id="@+id/list_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent"/>
 <android.support.v7.widget.Toolbar
  android:id="@+id/toolbar"
  android:layout_width="match_parent"
  android:layout_height="?attr/actionBarSize"
  android:background="@color/colorPrimary"/>
</RelativeLayout>

package com.example.listview_unit4_1;
import android.animation.ObjectAnimator;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
 private ListView listView;
 private List<String> listViewData;//数据源
 private ArrayAdapter<String> adapter;
 private Toolbar toolbar;
 private int mTouchSlop;//系统认为的最小滑动距离
 private float mFirstY;//用户首次触摸的Y坐标
 private float mLastY;//用户滑动结束时Y坐标
 private ObjectAnimator mAnimator;//将控件与动画联系起来的类（可以使指定的控件，实现指定的动画效果）
 private boolean mShow;//toolbar是否显示
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  toolbar = (Toolbar) findViewById(R.id.toolbar);
  setSupportActionBar(toolbar);
  //初始化数据源
  initData();
  listView = (ListView) findViewById(R.id.list_view);
  //为ListView增加一个HeadView(避免第一个Item被toolbar遮挡)
  //abc_action_bar_default_height_material属性获取系统actionBar的高度
  View headView = new View(this);
  headView.setLayoutParams(new ListView.LayoutParams(ListView.LayoutParams.MATCH_PARENT,
    (int)getResources().getDimension(R.dimen.abc_action_bar_default_height_material)));
  listView.addHeaderView(headView);
  //获取系统定义的最低滑动距离
  mTouchSlop = ViewConfiguration.get(this).getScaledTouchSlop();
  adapter = new ArrayAdapter<String>(this, R.layout.support_simple_spinner_dropdown_item, listViewData);
  listView.setAdapter(adapter);
  //为ListView设置触摸事件监听
  listView.setOnTouchListener(new View.OnTouchListener() {
   @Override
   public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction()){
     case MotionEvent.ACTION_DOWN:
      mFirstY = event.getY();//getY获取的是相对于View的坐标，getRawY获取的是相对于屏幕的坐标
      break;
     case MotionEvent.ACTION_MOVE:
      mLastY = event.getY();
      if(mLastY - mFirstY > mTouchSlop){//手指向下滑动，显示toolbar
       if(!mShow){
        Log.i("tag", "mLastY_手指下滑="+mLastY);
        toolbarAnim(0);//显示
        mShow = !mShow;
       }
      }else if(mFirstY - mLastY > mTouchSlop){//手指向上滑动，隐藏toolbar
       if(mShow){
        Log.i("tag", "mLastY_手指上滑="+mLastY);
        toolbarAnim(1);//隐藏
        mShow = !mShow;
       }
      }
      break;
     default:break;
    }
    return false;//一般返回false，提交给上级
   }
  });
 }
 public void toolbarAnim(int flag){
  if(mAnimator != null && mAnimator.isRunning()){
   mAnimator.cancel();
  }
  if(flag == 0){
   Log.i("tag", "手指下滑,》》》》》》》显示");
   mAnimator = ObjectAnimator.ofFloat(toolbar, "translationY", toolbar.getTranslationY(), 0);
  }else if(flag == 1){
   Log.i("tag", "手指上滑，》》》》》》》隐藏");
   mAnimator = ObjectAnimator.ofFloat(toolbar, "translationY", toolbar.getTranslationY(),
     -toolbar.getHeight());
  }
  mAnimator.start();//开始动画
 }
 /**
  * 初始化ListView的数据源
  */
 public void initData(){
  listViewData = new ArrayList<>();
  String s;
  for(int i = 0; i < 20; i ++){
   s = ""+i;
   listViewData.add(s);
  }
 }
}

//第一个参数用于指定这个动画要操作的是哪个控件
//第二个参数用于指定这个动画要操作这个控件的哪个属性
//第三个参数是可变长参数,指这个属性值是从多少变到多少
mAnimator = ObjectAnimator.ofFloat(toolbar, "translationY", toolbar.getTranslationY(), 0);
mAnimator = ObjectAnimator.ofFloat(toolbar, "translationY", toolbar.getTranslationY(),
     -toolbar.getHeight());