Android中自定义ScrollView的滑动监听事件，并在滑动时渐变标题栏背景颜色

ObservableScrollView

package com.jukopro.titlebarcolor;import android.content.Context;import android.util.AttributeSet;import android.widget.ScrollView;/*** 自定义带滚动监听的scrollview**/public class ObservableScrollView extends ScrollView {/*** 接口回调*/private ScrollViewListener scrollViewListener = null;public interface ScrollViewListener {void onScrollChanged(ObservableScrollView scrollView, int x, int y,int oldx, int oldy);}public void setScrollViewListener(ScrollViewListener scrollViewListener) {this.scrollViewListener = scrollViewListener;}/*** 重写的onScrollChanged方法监听坐标* 这个监听在源码中没有写成回调的样子，* 只是写成了方法的样子，由于修饰这个方法的修饰符是protected，*（protected只能在本类，子类，同一包中调用），* 所以拿到ScrollView对象后在无法activity中调用此方法，* 所以只能重写后，子类中自动调用，* 所以要想在activity调用，* 就要写回调，* 上面就是我写的回调* 在Android源码中这种写法很多，在很多控件中都有*/@Overrideprotected 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);}}/***构造方法（在这里没用）*/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);}}

<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.ObservableScrollViewandroid:id="@+id/scrollview"android:layout_width="match_parent"android:layout_height="match_parent"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="vertical"><ImageViewandroid:id="@+id/imageview"android:layout_width="match_parent"android:layout_height="200dp"android:background="@drawable/zuqiu" /><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/><TextViewandroid:layout_width="match_parent"android:layout_height="50dp"android:text="我是翟浩浩"android:gravity="center"/></LinearLayout></com.jukopro.titlebarcolor.ObservableScrollView><TextViewandroid: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="#ffffff"android:background="#00000000" /></RelativeLayout>

package com.jukopro.titlebarcolor;import android.app.Activity;import android.graphics.Color;import android.os.Bundle;import android.util.Log;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 {private ObservableScrollView scrollView;private ImageView imageView;private TextView textView;private int imageHeight;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);scrollView = (ObservableScrollView) findViewById(R.id.scrollview);imageView = (ImageView) findViewById(R.id.imageview);textView = (TextView) findViewById(R.id.textview);initListeners();}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() {@Overridepublic void onGlobalLayout() {imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);imageHeight = imageView.getHeight();scrollView.setScrollViewListener(new ScrollViewListener() {@Overridepublic 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) {//                          设置文字背景颜色，白色textView.setBackgroundColor(Color.argb((int) 0, 255, 255, 255));//AGB由相关工具获得，或者美工提供//                          设置文字颜色，黑色textView.setTextColor(Color.argb((int) 0, 255, 255, 255));Log.e("111","y <= 0");} 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)白色透明textView.setBackgroundColor(Color.argb((int) alpha, 255, 255, 255));//                          设置文字颜色，黑色，加透明度textView.setTextColor(Color.argb((int) alpha, 0, 0, 0));Log.e("111","y > 0 && y <= imageHeight");} else {//							白色不透明textView.setBackgroundColor(Color.argb((int) 255, 255, 255, 255));//                          设置文字颜色//黑色textView.setTextColor(Color.argb((int) 255, 0, 0, 0));Log.e("111","else");}}});}});}}