为什么需要检查converview == null？

Question

好，所以我在使用listview适配器时遇到了问题。当我向下或向上滚动时，它的位置错误，因此在我的视图上生成了错误的信息。 然后我在getView方法中更改了

View v = convertView;
if (v == null) {
    LayoutInflater vi;
    vi = LayoutInflater.from(mContext);
    v = vi.inflate(resourceLayout, null);
}

到

LayoutInflater vi;
vi = LayoutInflater.from(mContext);
View v = vi.inflate(resourceLayout, null);

它解决了问题。但是我不知道为什么。我的猜测是它正在创建新视图而不是回收它们。如果是这样，会消耗大量内存并降低性能吗？

编辑： 有人告诉我最好发布我的getView方法，所以它是这样的：

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    LayoutInflater vi;
    vi = LayoutInflater.from(mContext);
    View v = vi.inflate(resourceLayout, null);

    MessageInChat message = getItem(position);
    if (message.uri == null) {
        if (message.location == null) {
            RoundedImageView imageView = v.findViewById(R.id.image_in_chat);
            imageView.setVisibility(View.GONE);
            TextView textView = v.findViewById(R.id.message_template_text);
            LinearLayout container = v.findViewById(R.id.message_container);
            container.setVisibility(View.VISIBLE);
            LinearLayout linearLayout = v.findViewById(R.id.linear_message_container);
            textView.setText(message.text);
            if (message.author) {
                textView.setTextColor(mContext.getResources().getColor(R.color.white));
                linearLayout.setGravity(Gravity.END);
                container.setBackground(mContext.getResources().getDrawable(R.drawable.self_message_background));
            } else {
                textView.setTextColor(mContext.getResources().getColor(R.color.textColor));
                linearLayout.setGravity(Gravity.START);
                container.setBackground(mContext.getResources().getDrawable(R.drawable.other_message_background));
            }
        } else {
            RoundedImageView imageView = v.findViewById(R.id.image_in_chat);
            imageView.setVisibility(View.GONE);
            final TextView textView = v.findViewById(R.id.message_template_text);
            LinearLayout container = v.findViewById(R.id.message_container);
            container.setVisibility(View.VISIBLE);
            LinearLayout linearLayout = v.findViewById(R.id.linear_message_container);
            textView.setText(message.location);
            textView.setPaintFlags(textView.getPaintFlags() | Paint.UNDERLINE_TEXT_FLAG);

            if (message.author) {
                textView.setTextColor(mContext.getResources().getColor(R.color.white));
                linearLayout.setGravity(Gravity.END);
                container.setBackground(mContext.getResources().getDrawable(R.drawable.self_message_background));
            } else {
                textView.setTextColor(mContext.getResources().getColor(R.color.textColor));
                linearLayout.setGravity(Gravity.START);
                container.setBackground(mContext.getResources().getDrawable(R.drawable.other_message_background));
            }
            final String location = message.location;
            textView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(mContext, ViewLocationActivity.class);
                    intent.putExtra("URL", location);
                    mContext.startActivity(intent);
                }
            });
        }
    } else {
        ImageView imageView = v.findViewById(R.id.image_in_chat);
        imageView.setVisibility(View.VISIBLE);
        LinearLayout container = v.findViewById(R.id.message_container);
        container.setVisibility(View.GONE);
        LinearLayout linearLayout = v.findViewById(R.id.linear_message_container);
        if (message.author) {
            linearLayout.setGravity(Gravity.END);
        } else {
            linearLayout.setGravity(Gravity.START);
        }
        String uri = message.uri;
        try {
            int width = message.width;
            int height = message.height;
            int layoutWidth = imageView.getLayoutParams().width;
            int resultHeight = layoutWidth * height / width;
            imageView.getLayoutParams().height = resultHeight;
            Glide.with(mContext).load(Uri.parse(uri)).into(imageView);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    return v;
}

它用于基本的聊天屏幕，其中包含三种类型的消息：普通文本，图像和Google地图链接