Android之scrollview滑动使标题栏渐变背景色的实例代码

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); 
  } 
 } 
} 

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 adapter = new ArrayAdapter(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)); 
  } 
 } 
}