Android 滑动Scrollview标题栏渐变效果(仿京东toolbar)

scrollview标题栏滑动渐变

仿京东样式(上滑显示下滑渐变消失)

/**
 * @classname myscrollview
 * @author rex
 * @date 2021/1/27 17:38
 */
public class myscrollview extends scrollview {
 private translucentlistener mtranslucentlistener;

 public void settranslucentlistener(translucentlistener translucentlistener) {
  this.mtranslucentlistener = translucentlistener;
 }
 public myscrollview(context context) {
  this(context, null);
 }

 public myscrollview(context context, attributeset attrs) {
  this(context, attrs, 0);
 }

 public myscrollview(context context, attributeset attrs, int defstyleattr) {
  this(context, attrs, defstyleattr, 0);
 }

 public myscrollview(context context, attributeset attrs, int defstyleattr, int defstyleres) {
  super(context, attrs, defstyleattr, defstyleres);
 }

 @override
 protected void onscrollchanged(int l, int t, int oldl, int oldt) {
  super.onscrollchanged(l, t, oldl, oldt);
  if (mtranslucentlistener != null) {
   //scrollview滑出高度
   int scrolly = getscrolly();
   //屏幕高度
   int screenheight = getcontext().getresources().getdisplaymetrics().heightpixels;
   //有效滑动距离为屏幕2分之一
   // alpha = 滑动高度/（screenheight/3f）
   if (scrolly <= screenheight / 2f) {
    log.d(">>>>>>>>>", "scrollview划出高度：" + scrolly);
    log.d(">>>>>>>>>", "屏幕高度：" + screenheight);
    log.d(">>>>>>>>>", "渐变值：" + (0 + scrolly / (screenheight / 4f)));
    // 渐变的过程 1~0
    mtranslucentlistener.ontranslucent(0 + scrolly / (screenheight /4f));
   }
  }
 }
}

activity 设置

public class toolbaractivity extends appcompatactivity implements translucentlistener {
 private toolbar mtoolbar;
 private myscrollview mscrollview;

 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_toobar);
  mtoolbar = findviewbyid(r.id.id_toolbar);
  mscrollview = findviewbyid(r.id.id_scrollview);
  //初始化渐变为0
  mtoolbar.setalpha(0);
  //设置渐变回调
  mscrollview.settranslucentlistener(this);
 }

 @override
 public void ontranslucent(float alpha) {
  mtoolbar.setalpha(alpha);
 }
}

渐变回调接口

/**
 * @classname translucentlistener
 * @author rex
 * @date 2021/1/27 17:38
 */
public interface translucentlistener {
 /**
  * 透明度的回调监听
  *
  * @param alpha 0~1 透明度
  */
 public void ontranslucent(float alpha);
}

布局文件

<relativelayout 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">

 <com.rex.rxhttpdemo.myscrollview
  android:id="@+id/id_scrollview"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:clipchildren="false"
  android:cliptopadding="false"
  >

  <linearlayout
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical">

   <button
    android:id="@+id/button1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button0" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button1" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button2" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button3" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button4" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button5" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />

   <button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="button" />
  </linearlayout>
 </com.rex.rxhttpdemo.myscrollview>

 <androidx.appcompat.widget.toolbar
  android:id="@+id/id_toolbar"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:background="@color/coloraccent"
  app:title="title"
  />

</relativelayout>

下滑显示上滑渐变消失

/**
 * @classname myscrollview
 * @author rex
 * @date 2021/1/27 17:38
 */
public class myscrollview extends scrollview {
 private translucentlistener mtranslucentlistener;

 public void settranslucentlistener(translucentlistener translucentlistener) {
  this.mtranslucentlistener = translucentlistener;
 }
 public myscrollview(context context) {
  this(context, null);
 }

 public myscrollview(context context, attributeset attrs) {
  this(context, attrs, 0);
 }

 public myscrollview(context context, attributeset attrs, int defstyleattr) {
  this(context, attrs, defstyleattr, 0);
 }

 public myscrollview(context context, attributeset attrs, int defstyleattr, int defstyleres) {
  super(context, attrs, defstyleattr, defstyleres);
 }

 @override
 protected void onscrollchanged(int l, int t, int oldl, int oldt) {
  super.onscrollchanged(l, t, oldl, oldt);
  if (mtranslucentlistener != null) {
   //scrollview滑出高度
   int scrolly = getscrolly();
   //屏幕高度
   int screenheight = getcontext().getresources().getdisplaymetrics().heightpixels;
   //有效滑动距离为屏幕2分之一
   // alpha = 滑动高度/（screenheight/3f）
   if (scrolly <= screenheight / 2f) {
    log.d(">>>>>>>>>", "scrollview划出高度：" + scrolly);
    log.d(">>>>>>>>>", "屏幕高度：" + screenheight);
    log.d(">>>>>>>>>", "渐变值：" + (1 - scrolly / (screenheight / 4f)));
    // 渐变的过程 1~0
    mtranslucentlistener.ontranslucent(1 - scrolly / (screenheight /4f));
   }
  }
 }
}

注意: 这里只是更改了 mtranslucentlistener.ontranslucent 里的 渐变值

activty 里 把初始化 mtoolbar.setalpha(0); 去掉

xml

 <com.rex.rxhttpdemo.myscrollview
  android:id="@+id/id_scrollview"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:clipchildren="false"
  android:cliptopadding="false"
  android:paddingtop="?attr/actionbarsize"
  >
 </com.rex.rxhttpdemo.myscrollview>

xml 加入 paddingtop .

注意:
android:clipchildren=“false”
android:cliptopadding="false"
这俩个属性 如果不加会有留白

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