Android 实现ToolBar滑动渐变

title.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

android:id="@+id/top_bg"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="@color/white"

android:orientation="vertical">

<View

android:id="@+id/viewTop"

android:layout_width="match_parent"

android:layout_height="25dp" />

<RelativeLayout

android:layout_width="match_parent"

android:layout_height="45dp">

<ImageView

android:id="@+id/toolbar_iv_back"

android:layout_width="45dp"

android:layout_height="match_parent"

android:layout_gravity="center"

android:padding="14dp"

android:src="@drawable/img_back" />

<TextView

android:id="@+id/toolbar_tv_title"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_centerInParent="true"

android:layout_marginLeft="45dp"

android:layout_marginRight="60dp"

android:ellipsize="end"

android:gravity="center"

android:lines="1"

android:text="我是标题"

android:textSize="17sp"

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:layout_alignParentRight="true"

android:layout_centerVertical="true">

<TextView

android:id="@+id/toolbar_tv_menu"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:gravity="center"

android:lines="1"

android:paddingLeft="10dp"

android:paddingRight="10dp"

android:textSize="14sp"

<ImageView

android:id="@+id/toolbar_iv_menu"

android:layout_width="45dp"

android:layout_height="match_parent"

android:padding="14dp"

android:visibility="gone" />

</LinearLayout>

</RelativeLayout>

<View

android:id="@+id/view_line"

android:layout_width="match_parent"

android:layout_height="0.5dp"

android:background="@color/background"

</LinearLayout>

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent">

<com.cy.myapplication.MyScrollView

android:id="@+id/scroller"

android:layout_width="match_parent"

android:layout_height="match_parent">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="2000dp"

android:background="@color/colorAccent" />

</LinearLayout>

</com.cy.myapplication.MyScrollView>

<include

layout="@layout/title" />

</RelativeLayout>

MyScrollView 自定义滚动View

package com.cy.myapplication;

import android.content.Context;

import android.os.Build;

import android.os.Handler;

import android.util.AttributeSet;

import android.view.MotionEvent;

import android.widget.ScrollView;

import androidx.annotation.RequiresApi;

/**

* Created by ShinnyYang on 2020/8/18.

public class MyScrollView extends ScrollView {

private OnScrollListener onScrollListener;

/**

* 主要是用在用户手指离开MyScrollView，MyScrollView还在继续滑动，我们用来保存Y的距离，然后做比较

private int lastScrollY;

public MyScrollView(Context context) {

super(context);

}

public MyScrollView(Context context, AttributeSet attrs) {

super(context, attrs);

}

public MyScrollView(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

}

@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)

public MyScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {

super(context, attrs, defStyleAttr, defStyleRes);

}

/**

* 设置滚动接口

* @param onScrollListener

public void setScrolListener(OnScrollListener onScrollListener){

this.onScrollListener = onScrollListener;

}

/**

* 用于用户手指离开MyScrollView的时候获取MyScrollView滚动的Y距离，然后回调给onScroll方法中

private Handler handler = new Handler() {

public void handleMessage(android.os.Message msg) {

int scrollY = MyScrollView.this.getScrollY();

if(onScrollListener != null){

onScrollListener.onScroll(scrollY);

}

//此时的距离和记录下的距离不相等，在隔5毫秒给handler发送消息

if(lastScrollY != scrollY){

lastScrollY = scrollY;

handler.sendMessageDelayed(handler.obtainMessage(), 5);

}

};

/**

* 重写onTouchEvent，当用户的手在MyScrollView上面的时候，

* 直接将MyScrollView滑动的Y方向距离回调给onScroll方法中，当用户抬起手的时候，

* MyScrollView可能还在滑动，所以当用户抬起手我们隔20毫秒给handler发送消息，在handler处理

* MyScrollView滑动的距离

@Override

public boolean onTouchEvent(MotionEvent ev) {

if(onScrollListener != null){

onScrollListener.onScroll(lastScrollY = this.getScrollY());

}

if(ev.getAction() == MotionEvent.ACTION_UP){

handler.sendMessageDelayed(handler.obtainMessage(), 20);

}

return super.onTouchEvent(ev);

}

public interface OnScrollListener{

/**

* 回调方法，返回MyScrollView滑动的Y方向距离

* @param scrollY

* 、

public void onScroll(int scrollY);

}

Main里面实现

private LinearLayout top_bg;

private MyScrollView scroller;

private void initView() {

top_bg = (LinearLayout) findViewById(R.id.top_bg);

scroller = (MyScrollView) findViewById(R.id.scroller);

top_bg.getBackground().setAlpha(0);

scroller.setScrolListener(this);

}

@Override

public void onScroll(int scrollY) {

if (scrollY < 100) {

top_bg.getBackground().setAlpha(0);

} else if (scrollY >= 100 && scrollY < 860) {

top_bg.getBackground().setAlpha((scrollY - 100) / 3);

} else {

top_bg.getBackground().setAlpha(255);

}

<color name="white">#ffffff</color>