AlertDialog.Builder builder = new AlertDialog.Builder(this);

        AlertDialog dialog = builder.create();

        int screenWidth_px = PX_DP_utils.getScreenWidth_PX(this);

        int screenHeight_px = PX_DP_utils.getScreenheight_PX(this);

        dialog.show();

//需要设置属性,否则dialog的大小不起作用!必须先show再set属性

        WindowManager.LayoutParams params = dialog.getWindow().getAttributes();

        params.width = (int) (screenWidth_px * 0.7 + 0.5f);

        params.height = (int) (0.6 * screenHeight_px + 0.5f);
//设置位置的属性

 Window dialogWindow = dialog.getWindow();
        WindowManager.LayoutParams lp = dialogWindow.getAttributes();
        dialogWindow.setGravity(Gravity.LEFT | Gravity.TOP);

        /*
         * lp.x与lp.y表示相对于原始位置的偏移.
         * 当参数值包含Gravity.LEFT时,对话框出现在左边,所以lp.x就表示相对左边的偏移,负值忽略.
         * 当参数值包含Gravity.RIGHT时,对话框出现在右边,所以lp.x就表示相对右边的偏移,负值忽略.
         * 当参数值包含Gravity.TOP时,对话框出现在上边,所以lp.y就表示相对上边的偏移,负值忽略.
         * 当参数值包含Gravity.BOTTOM时,对话框出现在下边,所以lp.y就表示相对下边的偏移,负值忽略.
         * 当参数值包含Gravity.CENTER_HORIZONTAL时
         * ,对话框水平居中,所以lp.x就表示在水平居中的位置移动lp.x像素,正值向右移动,负值向左移动.
         * 当参数值包含Gravity.CENTER_VERTICAL时
         * ,对话框垂直居中,所以lp.y就表示在垂直居中的位置移动lp.y像素,正值向右移动,负值向左移动.
         * gravity的默认值为Gravity.CENTER,即Gravity.CENTER_HORIZONTAL |
         * Gravity.CENTER_VERTICAL.
         * 
         * 本来setGravity的参数值为Gravity.LEFT | Gravity.TOP时对话框应出现在程序的左上角,但在
         * 我手机上测试时发现距左边与上边都有一小段距离,而且垂直坐标把程序标题栏也计算在内了,
         * Gravity.LEFT, Gravity.TOP, Gravity.BOTTOM与Gravity.RIGHT都是如此,据边界有一小段距离
         */
        lp.x = 100; // 新位置X坐标
        lp.y = 100; // 新位置Y坐标
        lp.width = 300; // 宽度
        lp.height = 300; // 高度
        lp.alpha = 0.7f; // 透明度

        // 当Window的Attributes改变时系统会调用此函数,可以直接调用以应用上面对窗口参数的更改,也可以用setAttributes
        // dialog.onWindowAttributesChanged(lp);
        dialogWindow.setAttributes(lp);
Window dialogWindow = dialog.getWindow();dialogWindow.getDecorView().setPadding(0, 0, 0, 0);//去除边框

        // 必须使用这个方法,不能使用dialog.setView()的方法

        dialog.getWindow().setContentView(R.layout.dialog_picpick_three);

        //设置dialog的背景颜色为透明色,就可以显示圆角了!!

        dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));

        dialog.getWindow().setAttributes(params);

//------------------------------------EditText相关代码,能够获取到焦点,能够直接弹出软键盘.

//解决dilaog中EditText无法弹出输入的问题
        dialog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM);

        //弹出对话框后直接弹出键盘
        et_newReason.setFocusableInTouchMode(true);
        et_newReason.requestFocus();
        CmzBossApplication.handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                InputMethodManager inputManager =(InputMethodManager) et_newReason.getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
                inputManager.showSoftInput(et_newReason, 0);
            }
        }, 100);
//---------------------------解决RecycleView下的matchparent不好用的问题

class MyRVAdapter extends RecyclerView.Adapter<MyRVAdapter.VH> {
    @Override
    public VH onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.exchangeveg_reason_item, parent, false);//必须用这种方式来填充View

        return new VH(view);
    }

    @Override
    public void onBindViewHolder(VH holder, final int position) {
        holder.tv_reason.setText(exchange_veg_reasons.get(position).reason);
        holder.iv_reason_reduce.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //删除本行的ITEM
                String reason_id = exchange_veg_reasons.get(position).id;
                HttpCashManger.getInstance().postExchangeReduceReason(reason_id, new HttpCallback() {
                    @Override
                    public void onSuccess(String result) {
                        System.out.println("删除备注信息成功:" + result);
                        exchange_veg_reasons.remove(exchange_veg_reasons.get(position));
                        myRVAdapter.notifyDataSetChanged();
                    }

                    @Override
                    public void onFail(Exception e) {

                    }
                });
            }
        });

    }

    @Override
    public int getItemCount() {
        return exchange_veg_reasons.size();
    }

    class VH extends RecyclerView.ViewHolder {
        public TextView tv_reason;
        public ImageView iv_reason_reduce;

        public VH(View itemView) {
            super(itemView);
            tv_reason = (TextView) itemView.findViewById(R.id.ecr_tuicai_tv_item_reason);
            iv_reason_reduce = (ImageView) itemView.findViewById(R.id.ecr_tuicai_iv_item_reaosn_reduce);
        }
    }

}