滑动渐变

本文章是我通过参考一篇文章改写的，很久之前了，所以忘记参考谁的了，感谢那位大神。

全部JAVA代码

import android.graphics.Color;import android.os.Bundle;import android.os.Handler;import android.support.v7.app.ActionBarActivity;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.AbsListView;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.ListView;import android.widget.TextView;import com.senzhi.mysupertest.R;/** * Created by zz on 2017/2/1. */public class ActionBarShadeActivity extends ActionBarActivity {    private ListView lv;//listview的header    private ImageView headerView;    private ImageView iv_search;    float alpha;    int height;    View atView;//需要跟随listview滑动渐变的ActionBar    private View alphaTitleBar;    private TextView tv_title;    private TextView tv_alpha;    private CommentListAdapter commentAdapter;    private Handler handler = new Handler();    Runnable runnable = new Runnable() {        @Override        public void run() {            tv_alpha.setText(atView.getTop()+"   "+height+"   "+alpha);        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_actionbar_shade);        alphaTitleBar = findViewById(R.id.title_bar);        tv_title = (TextView) findViewById(R.id.tv_title);        tv_alpha = (TextView) findViewById(R.id.tv_alpha);        iv_search = (ImageView) findViewById(R.id.iv_search);        lv = (ListView) findViewById(R.id.lv);//        commentList = new ArrayList<>();        commentAdapter = new CommentListAdapter();        headerView = new ImageView(this);        headerView.setBackgroundColor(Color.BLACK);        headerView.setLayoutParams(new AbsListView.LayoutParams(                AbsListView.LayoutParams.MATCH_PARENT,                600));        lv.addHeaderView(headerView);        lv.setAdapter(commentAdapter);//设置listview的监听滑动的事件        lv.setOnScrollListener((AbsListView.OnScrollListener) new AlphaListener());    }    private class AlphaListener implements AbsListView.OnScrollListener {        @Override        public void onScrollStateChanged(AbsListView view, int scrollState) {        }        @Override        public void onScroll(AbsListView view, int firstVisibleItem,                             int visibleItemCount, int totalItemCount) {            if(view.getChildCount() == 0)                return;            if(firstVisibleItem == 0){                atView = view.getChildAt(0);                height = atView.getHeight();                if(-atView.getTop() < height){                    alpha = ( Math.abs(atView.getTop())) / (alphaTitleBar.getHeight() * 4f);                    alphaTitleBar.setBackgroundColor(Color.rgb(0,0,0));//                    }                    if(Math.abs(atView.getTop()) >height/2){                        alphaTitleBar.setBackgroundColor(Color.rgb(255,255,255));                        alphaTitleBar.setAlpha(Math.abs((float) (alpha-0.4)*2));                        tv_title.setTextColor(Color.BLACK);                        iv_search.setImageResource(R.drawable.searchblack);                    }else{                        alphaTitleBar.setAlpha(Math.abs(1-(float) (alpha-0.1)*2));                        tv_title.setTextColor(Color.WHITE);//                        alphaTitleBar.setBackgroundColor(Color.rgb(0,0,0));                        iv_search.setImageResource(R.drawable.searchwhite);                    }                }                new Thread(){                    @Override                    public void run() {                        try{                            handler.postDelayed(runnable,20);                        }catch (Exception e){                        }                    }                }.start();            }            if(firstVisibleItem == 1)                alphaTitleBar.setAlpha(1);        }    }    public class CommentListAdapter extends BaseAdapter {        CommentViewHolder holder;        @Override        public int getCount() {            return 20;        }        @Override        public Object getItem(int i) {            return 20;        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(int position, View convertView, ViewGroup viewGroup) {            if(convertView == null){                holder = new CommentViewHolder();                convertView = LayoutInflater.from(ActionBarShadeActivity.this).inflate(R.layout.person_mycomment_comment_adapter,null);                holder.user_head = (ImageView) convertView.findViewById(R.id.user_head);                holder.tv_name = (TextView) convertView.findViewById(R.id.tv_name);                holder.tv_content = (TextView) convertView.findViewById(R.id.tv_content);                holder.tv_source = (TextView) convertView.findViewById(R.id.tv_source);                holder.tv_time = (TextView) convertView.findViewById(R.id.tv_time);                holder.tv_trumbup = (TextView) convertView.findViewById(R.id.tv_trumbup);                holder.tv_comment = (TextView) convertView.findViewById(R.id.tv_comment);                convertView.setTag(holder);            }else{                holder = (CommentViewHolder) convertView.getTag();            }            return convertView;        }    }    public class CommentViewHolder{        ImageView user_head;        TextView tv_name;        TextView tv_content;        TextView tv_source;        TextView tv_time;        TextView tv_trumbup;        TextView tv_comment;    }}

页面布局xml代码

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/container_view"    android:layout_width="match_parent"    android:layout_height="match_parent" >    <ListView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:background="#3000"        android:id="@+id/lv"></ListView>    <RelativeLayout        android:id="@+id/title_bar"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="#000000">        <TextView            android:id="@+id/tv_title"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:textColor="#FFFFFF"            android:text="TITLE"            android:layout_centerInParent="true"            android:textSize="20sp"/>        <ImageView            android:id="@+id/iv_search"            android:layout_width="50dp"            android:layout_height="50dp"            android:src="@drawable/searchwhite"            android:padding="10dp"            android:layout_alignParentRight="true"            />    </RelativeLayout>    <TextView        android:id="@+id/tv_alpha"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="alpha"        android:layout_centerInParent="true"        /></RelativeLayout>

listView的适配器布局代码就不贴了，listView可以自定义，随便定义一个简单的就行了，愿谅解。

实现原理：

通过监听listView的滑动事件获取到每次滑动listView时，titlebar所在页面的高度，计算出渐变值并给titlebar设置透明度实现滑动渐变。

很简单的一个东西，发挥自己的想象，可以实现很厉害的效果。