Android之scrollview滑动使标题栏渐变背景色的实例代码

之前也是在网上看到这种效果，不过是滚动listview来改变标题栏的颜色，感觉那个应用的比较少，比如我要滚动scrollview来实现呢，那么问题就来了，废话少说，看一下要实现的效果先(这是在项目应用的效果)。

直接上源代码：

一、核心类(ObservableScrollView.java)

package com.jukopro.titlebarcolor;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.ScrollView;
/**
* 带滚动监听的scrollview
*
*/
public class ObservableScrollView extends ScrollView {
public interface ScrollViewListener {
 void onScrollChanged(ObservableScrollView scrollView, int x, int y,
   int oldx, int oldy);
}
private ScrollViewListener scrollViewListener = null;
public ObservableScrollView(Context context) {
 super(context);
}
public ObservableScrollView(Context context, AttributeSet attrs,
  int defStyle) {
 super(context, attrs, defStyle);
}
public ObservableScrollView(Context context, AttributeSet attrs) {
 super(context, attrs);
}
public void setScrollViewListener(ScrollViewListener scrollViewListener) {
 this.scrollViewListener = scrollViewListener;
}
@Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
 super.onScrollChanged(x, y, oldx, oldy);
 if (scrollViewListener != null) {
  scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);
 }
}
}

二、具体使用(MainActivity.java)

package com.jukopro.titlebarcolor;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.ViewTreeObserver;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import com.jukopro.titlebarcolor.ObservableScrollView.ScrollViewListener;
public class MainActivity extends Activity implements ScrollViewListener{
private ObservableScrollView scrollView;
private ListView listView;
private ImageView imageView;
private TextView textView;
private int imageHeight;
@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 scrollView = (ObservableScrollView) findViewById(R.id.scrollview);
 listView = (ListView) findViewById(R.id.listview);
 imageView = (ImageView) findViewById(R.id.imageview);
 textView = (TextView) findViewById(R.id.textview);
 initListeners();
 initData();
}
private void initListeners() {
 // 获取顶部图片高度后，设置滚动监听
 ViewTreeObserver vto = imageView.getViewTreeObserver();
 vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
  @Override
  public void onGlobalLayout() {
   imageView.getViewTreeObserver().removeGlobalOnLayoutListener(
     this);
   imageHeight = imageView.getHeight();
   scrollView.setScrollViewListener(MainActivity.this);
  }
 });
}
private void initData() {
 ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.data));
 listView.setAdapter(adapter);
}
@Override
public void onScrollChanged(ObservableScrollView scrollView, int x, int y,
  int oldx, int oldy) {
 // TODO Auto-generated method stub
 // Log.i("TAG", "y--->" + y + " height-->" + height);
 if (y <= 0) {
  textView.setBackgroundColor(Color.argb((int) 0, 227, 29, 26));//AGB由相关工具获得，或者美工提供
 } else if (y > 0 && y <= imageHeight) {
  float scale = (float) y / imageHeight;
  float alpha = (255 * scale);
  // 只是layout背景透明(仿知乎滑动效果)
  textView.setBackgroundColor(Color.argb((int) alpha, 227, 29, 26));
 } else {
  textView.setBackgroundColor(Color.argb((int) 255, 227, 29, 26));
 }
}
}

三、XML(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"  tools:context="${relativePackage}.${activityClass}" >  <com.jukopro.titlebarcolor.ObservableScrollView   android:id="@+id/scrollview"   android:layout_width="match_parent"   android:layout_height="match_parent"   android:scrollbars="none" >   <LinearLayout    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:orientation="vertical" >    <ImageView     android:id="@+id/imageview"     android:layout_width="match_parent"     android:layout_height="200dp"     android:background="@drawable/zuqiu" />    <com.jukopro.titlebarcolor.MyListview     android:id="@+id/listview"     android:layout_width="match_parent"     android:layout_height="wrap_content" >    </com.jukopro.titlebarcolor.MyListview>   </LinearLayout>  </com.jukopro.titlebarcolor.ObservableScrollView>  <TextView   android:id="@+id/textview"   android:layout_width="match_parent"   android:layout_height="48dp"   android:gravity="center"   android:text="我是标题"   android:textSize="18sp"   android:textColor="@android:color/white"   android:background="#00000000" /> </RelativeLayout> 

还不懂的童鞋可以下载源代码.

来源：https://blog.csdn.net/sinat_21283073/article/details/51315926