自定义View笔记

1.带删除按钮的ListView

public class MyListView extends ListView implements OnGestureListener, View.OnTouchListener {

    private final GestureDetector gestureDetector;
    private boolean isDeleteButtonShow;
    private OnDeleteListener mListener;
    private ViewGroup itemLayout;
    private View deleteButton;
    private int seletedItem;

    public MyListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        //创建GestureDetector对象，处理手势
        gestureDetector = new GestureDetector(context, this);
        setOnTouchListener(this);
    }

    interface OnDeleteListener {
        void onDelete(int position);
    }

    public void setOnDeleteListener(OnDeleteListener listener) {
        mListener = listener;
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (isDeleteButtonShow) {
            itemLayout.removeView(deleteButton);
            deleteButton = null;
            isDeleteButtonShow = false;
            return false;
        }
        //将触摸事件交给手势处理器处理
            return gestureDetector.onTouchEvent(event);
    }

    @Override
    public boolean onDown(MotionEvent e) {
        if(!isDeleteButtonShow){
            //根据触摸点的坐标计算出当前点击的是ListView条目的位置
            seletedItem = pointToPosition((int)e.getX(),(int)e.getY());
        }
        return false;
    }

    @Override
    public void onShowPress(MotionEvent e) {

    }

    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        return false;
    }

    @Override
    public void onLongPress(MotionEvent e) {

    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        if (!isDeleteButtonShow && Math.abs(velocityX) > Math.abs(velocityY)) {
            deleteButton = LayoutInflater.from(getContext()).inflate(R.layout.delete_button, null);
            deleteButton.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    itemLayout.removeView(deleteButton);
                    deleteButton = null;
                    isDeleteButtonShow = false;
                    mListener.onDelete(seletedItem);
                }
            });
            //获得当前可见位置的View
            itemLayout = (ViewGroup) getChildAt(seletedItem - getFirstVisiblePosition());
            //动态添加到相对布局中，这里不能用getParams来获取布局参数，因为布局文件中Button是最顶层节点
            RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams
                    (RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
            params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
            params.addRule(RelativeLayout.CENTER_VERTICAL);
            itemLayout.addView(deleteButton,params);
            isDeleteButtonShow = true;
        }
        return false;
    }
}