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)

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									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)

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									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)

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									<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>