1.介绍

看下效果图，gif录的有些卡顿，在真机上运行效果很好。

2.实现

很有意思的一个效果，原理其实很简单，就是通过监听ScrollView在Y轴的滑动距离，然后在代码中动态设置头像的位置和大小。

public class MainActivity extends AppCompatActivity {private CircleImageView ivPortrait;private ObservableScrollView scrollView;private ViewGroup.MarginLayoutParams marginLayoutParams;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initView();}private void initView() {ivPortrait = (CircleImageView) findViewById(R.id.iv_portrait);scrollView = (ObservableScrollView) findViewById(R.id.scrollView);marginLayoutParams = new ViewGroup.MarginLayoutParams(ivPortrait.getLayoutParams());scrollView.setScrollViewListener(new ObservableScrollView.ScrollViewListener() {@Overridepublic void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy) {// 设置头像距离顶部的距离int top = dp2px(70) - y;if (top < dp2px(10)) {// 固定在标题栏marginLayoutParams.setMargins(dp2px(20), dp2px(10), 0, 0);} else {// 向上移动marginLayoutParams.setMargins(dp2px(20), dp2px(70) - y, 0, 0);}// 根据向上滑动的距离设置头像的大小FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(marginLayoutParams);// 头像最大为45dp，最小为30dpint height = dp2px(45) - y < dp2px(30) ? dp2px(30) : dp2px(45) - y;layoutParams.height = height;layoutParams.width = height;ivPortrait.setLayoutParams(layoutParams);}});}private int dp2px(float dp) {return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,getResources().getDisplayMetrics());}
}

布局文件

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#FFF"><LinearLayout
        android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><RelativeLayout
            android:layout_width="match_parent"android:layout_height="50dp"android:background="#F2F4F7">...</RelativeLayout><com.yl.jdfinanceindex.ObservableScrollView
            android:id="@+id/scrollView"android:layout_width="match_parent"android:layout_height="match_parent"android:overScrollMode="never"android:scrollbars="none"><LinearLayout
                android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><RelativeLayout
                    android:layout_width="match_parent"android:layout_height="80dp"android:background="#F2F4F7">...</RelativeLayout><View
                    android:layout_width="match_parent"android:layout_height="1000dp" /></LinearLayout></com.yl.jdfinanceindex.ObservableScrollView></LinearLayout><com.yl.jdfinanceindex.CircleImageView
        android:id="@+id/iv_portrait"android:layout_width="45dp"android:layout_height="45dp"android:layout_marginLeft="20dp"android:layout_marginTop="70dp"android:src="@mipmap/ic_portrait" /></FrameLayout>

原生的ScrollView是不支持滑动监听的，需要自定义一个ObservableScrollView。

public class ObservableScrollView extends ScrollView {private ScrollViewListener scrollViewListener;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;}@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);}}public interface ScrollViewListener {void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);}
}

3.写在最后

欢迎同学们吐槽评论，如果你觉得本篇博客对你有用，那么就留个言或者顶一下吧(＾－＾)

完整的Demo下载