ScrllViewを解析する--疑似QQ空間タイトルバーのグラデーション
まず効果図を見ます。
<?xml version="1.0" encoding="utf-8"?>
<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="com.hankkin.gradationtitlebar.QQSpeakActivity">
<com.hankkin.gradationscroll.GradationScrollView
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/iv_banner"
android:scaleType="fitXY"
android:src="@drawable/banner3"
android:layout_width="match_parent"
android:layout_height="200dp" />
<com.hankkin.gradationscroll.NoScrollListview
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</com.hankkin.gradationscroll.NoScrollListview>
</LinearLayout>
</com.hankkin.gradationscroll.GradationScrollView>
<TextView
android:paddingBottom="10dp"
android:id="@+id/textview"
android:layout_width="match_parent"
android:layout_height="55dp"
android:gravity="center|bottom"
android:text=" "
android:textSize="18sp"
android:textColor="@color/transparent"
android:background="#00000000" />
</RelativeLayout>
public class GradationScrollView extends ScrollView {
public interface ScrollViewListener {
void onScrollChanged(GradationScrollView scrollView, int x, int y,
int oldx, int oldy);
}
private ScrollViewListener scrollViewListener = null;
public GradationScrollView(Context context) {
super(context);
}
public GradationScrollView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
}
public GradationScrollView(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);
}
}
}
/**
* ，
*/
private void initListeners() {
ViewTreeObserver vto = ivBanner.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
textView.getViewTreeObserver().removeGlobalOnLayoutListener(
this);
height = ivBanner.getHeight();
scrollView.setScrollViewListener(QQSpeakActivity.this);
}
});
}
/**
*
* @param scrollView
* @param x
* @param y
* @param oldx
* @param oldy
*/
@Override
public void onScrollChanged(GradationScrollView scrollView, int x, int y,
int oldx, int oldy) {
// TODO Auto-generated method stub
if (y <= 0) { //
textView.setBackgroundColor(Color.argb((int) 0, 144,151,166));
} else if (y > 0 && y <= height) { // banner ，
float scale = (float) y / height;
float alpha = (255 * scale);
textView.setTextColor(Color.argb((int) alpha, 255,255,255));
textView.setBackgroundColor(Color.argb((int) alpha, 144,151,166));
} else { // banner
textView.setBackgroundColor(Color.argb((int) 255, 144,151,166));
}
}