仿QQ空间头部可拉伸控件 --ZoomHeardListView

2017-07-28

效果图

原本自己也有实现过这个效果，但是写的非常复杂，今天无意看到QQ群里的公开课，写的很简洁，极有功底，特作此记录

public class ZoomHeardListView  extends ListView{

    private int mImageViewHeight;
    private ImageView mImageView;
    public ZoomHeardListView(Context context) {
        this(context,null);
    }

    public ZoomHeardListView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public ZoomHeardListView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //默认高度
        mImageViewHeight = context.getResources().getDimensionPixelSize(R.dimen.size_default_height);
    }

    //设置图片
    public void setImageView(ImageView imageView){
        mImageView = imageView;
    }

    /**
     * deltaY - 往下拉过度距离
     * deltaY + 往上拉过度距离
     * 3.0之后，所有滑动控件都有此监听方法，监听是否拉到头或着尾。
     通过设置centerCrop
     通过Imageview+scaleType="centerCrop"
     */
    @Override
    protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
        mImageView.getLayoutParams().height=mImageView.getHeight()-deltaY;
        mImageView.requestLayout();
        return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, maxOverScrollY, isTouchEvent);
    }


    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        ViewGroup header= (ViewGroup) mImageView.getParent();
        int deltaY = header.getTop();
        if(mImageView.getHeight()>mImageViewHeight){
            mImageView.getLayoutParams().height=mImageView.getHeight()+deltaY;
            //由于滑出去了一截，所以要让header父容器重新摆放
            header.layout(header.getLeft(),0,header.getRight(),header.getHeight());
            mImageView.requestLayout();
        }
        super.onScrollChanged(l, t, oldl, oldt);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if(ev.getAction()==MotionEvent.ACTION_UP){
            ResetAnimation resetAnimation=new ResetAnimation();
            resetAnimation.setDuration(700);
            mImageView.startAnimation(resetAnimation);
        }

        return super.onTouchEvent(ev);
    }

    public class ResetAnimation extends Animation {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
//            interpolatedTime 0.0-1.0 执行的百分比
            mImageView.getLayoutParams().height= (int) (mImageView.getHeight()-((mImageView.getHeight()-mImageViewHeight)*interpolatedTime));
            mImageView.requestLayout();
            super.applyTransformation(interpolatedTime, t);
        }
    }
}

Activity中

@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list);
        qqScrollview = (ZoomHeardListView) findViewById(R.id.lsitview);
        qqScrollview.setAdapter(new ArrayAdapter<String>(this,R.layout.list_itme,new String[]{"哈哈哈 ","小磊子","Android","iOS","教程"}));
        View inflate = LayoutInflater.from(this).inflate(R.layout.heardview, null);
        ImageView heardView= (ImageView) inflate.findViewById(R.id.herdimage);
        qqScrollview.addHeaderView(inflate);
        qqScrollview.setImageView(heardView);
    }