listview - 带有 2 行布局的 ListView 的 AsyncTask

Question

我有一个包含 2 种不同行类型的列表视图（就像在这个问题中一样）。它工作正常，但滚动时非常滞后。所以我读到解决这个问题的方法是使用 AsyncTask。当使用两种不同的行类型时，我该如何实现？

我尝试使用两个不同的 AsyncTasks（膨胀 doInBackground 中的行），但我得到了各种各样的错误：

在 getView() 中：

if (convertView == null) {

            switch (type) {
            case TYPE_DAY:

                new ForecastDayTask(position, forecastHolder, convertView,
                        forecastHolder, mInflater, forecastdata).execute();

                break;
            case TYPE_DATA:
                new ForecastTask(position, forecastHolder, convertView,
                        forecastHolder, mInflater, forecastdata).execute();
                break;
            }

我也尝试过使用相同的 AsyncTask 类并传递相同的数据和 TYPE_DAY/TYPE_DATA 但这非常复杂，我得到了 NullPointerExceptions。

有任何想法吗？提前致谢！

score 0 · Accepted Answer

我这样解决了：

我扩展了一个 BaseAdapter，其中包含所有可能的 ListItems 的列表。
getView 使用 ViewHolderPattern 来回收视图
View 的宽度取决于 HolderItem 。在需要的时间（它是一个水平列表，显示不同持续时间的广播）
GetView 启动一个 AsyncTask，它需要两个 Holder，ViewHolder 和 DataHolder
需要 AsyncTask 来启动 onPostExecute 一个执行 GUIStuff、DrawRunnable 的线程
在 DrawRunnable 中，我决定如何为背景着色，以及应该根据广播的持续时间向用户呈现什么

我喜欢根据类型启动两个不同任务的方式。在我的情况下，这将是不同的持续时间类型。所以我应该在 onPostExecute 创建 DrawBroadcastRunnable 时决定哪个 DrawXTypeRunnable 应该开始。我用 if(XTYPE) 标记了代码中的位置

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

    ViewBroadcastItemHolder viewItemHolder;
    if (convertView == null) {
        convertView = (RelativeLayout) layoutInflater.inflate(layoutId,
                parent, false);
        viewItemHolder = new ViewBroadcastItemHolder();
        viewItemHolder.logo = (ImageView) convertView
                .findViewById(R.id.broadcast_guide_image);
        viewItemHolder.time = (TextView) convertView
                .findViewById(R.id.broadcast_guide_time);
        viewItemHolder.title = (TextView) convertView
                .findViewById(R.id.broadcast_guide_title);
        viewItemHolder.divider = convertView
                .findViewById(R.id.broadcast_guide_divider);
        viewItemHolder.layout = (LinearLayout) convertView
                .findViewById(R.id.broadcast_guide_item_linear_layout);
        convertView.setTag(viewItemHolder);
    } else {
        viewItemHolder = (ViewBroadcastItemHolder) convertView.getTag();
        convertView.setVisibility(View.GONE);
    }
    BroadcastHolder broadcastItem = getItem(position);
    viewItemHolder.layout.getLayoutParams().width = broadcastItem.width;

    BroadcastHolderAsyncArgument holder = new BroadcastHolderAsyncArgument(
            convertView, viewItemHolder, broadcastItem, position);

    holder.bcViewHolder.logo
            .setImageBitmap(controller.getLogoPlaceholder());
    BroadcastHolderAsyncArgument[] argument = { holder };
    new AsyncTask<BroadcastHolderAsyncArgument, Void, BroadcastHolderAsyncArgument>() {

        @Override
        protected BroadcastHolderAsyncArgument doInBackground(
                BroadcastHolderAsyncArgument... bcHolderArg) {
            return bcHolderArg[0];
        }

        @Override
        protected void onPostExecute(
                BroadcastHolderAsyncArgument bcHolderArg) {
  // Where to put in the decision which Strategy has to get done
  //if(XTYPE){ new DrawBroadcast30ViewRunnable(..).run()}
        //else if(YTYPE){new DrawBroadcast200ViewRunnable(..).run()}
        //else if(ZTYPE){new DrawBroadcast10ViewRunnable(..).run()}
        //else{new DrawBroadcast5ViewRunnable(..).run()}

            new DrawBroadcastViewRunnable(bcHolderArg, position).run();
        }
    }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, argument);

    return convertView;
}

public class DrawBroadcastViewRunnable implements Runnable {

    private BroadcastHolderAsyncArgument bcAsyncArgumentHolder;
    private int position;

    public DrawBroadcastViewRunnable(
            BroadcastHolderAsyncArgument bcHolderArgument, int position) {
        super();
        this.bcAsyncArgumentHolder = bcHolderArgument;
        this.position = position;
    }

    public void run() {

        if (bcAsyncArgumentHolder.position == position) {

            // Set Background Color of CatchUp, Live and Upcomming
            if (Helper.isLiveBroadcast(
                    bcAsyncArgumentHolder.bcItemHolder.start,
                    bcAsyncArgumentHolder.bcItemHolder.stop)) {
                bcAsyncArgumentHolder.bcViewHolder.isCatchup = false;
                bcAsyncArgumentHolder.convertView
                        .setBackgroundColor(context.getResources()
                                .getColor(R.color.guide_live_broadcast));
            } else if (bcAsyncArgumentHolder.bcViewHolder.isCatchup = Helper
                    .isCatchupBroadcast(
                            bcAsyncArgumentHolder.bcItemHolder.start,
                            bcAsyncArgumentHolder.bcItemHolder.stop)) {
                bcAsyncArgumentHolder.convertView
                        .setBackgroundColor(context.getResources()
                                .getColor(R.color.guide_replay_broadcast));
            } else {
                // Upcoming Broadcast
                bcAsyncArgumentHolder.convertView
                        .setBackgroundColor(context.getResources()
                                .getColor(R.color.guide_upcoming_broadcast));
                bcAsyncArgumentHolder.bcViewHolder.isCatchup = false;
            }

            // very large layout, more than 30min
            if (bcAsyncArgumentHolder.bcItemHolder.width >= 20 * controller
                    .getPixelPerMinute()) {
                bcAsyncArgumentHolder.bcViewHolder.logo
                        .setVisibility(View.VISIBLE);
                ImageLoader.getInstance().displayImage(
                        bcAsyncArgumentHolder.bcItemHolder.imageUrl,
                        bcAsyncArgumentHolder.bcViewHolder.logo);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.time
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setText(bcAsyncArgumentHolder.bcItemHolder.title);
                bcAsyncArgumentHolder.bcViewHolder.time.setText(Helper
                        .formatBroadcastTime(
                                bcAsyncArgumentHolder.bcItemHolder.start,
                                bcAsyncArgumentHolder.bcItemHolder.stop));
            }
            // medium layout, between 20 to 15min
            if (bcAsyncArgumentHolder.bcItemHolder.width < 20 * controller
                    .getPixelPerMinute()
                    && bcAsyncArgumentHolder.bcItemHolder.width > 15 * controller
                            .getPixelPerMinute()) {
                ImageLoader.getInstance().displayImage(
                        bcAsyncArgumentHolder.bcItemHolder.imageUrl,
                        bcAsyncArgumentHolder.bcViewHolder.logo);
                bcAsyncArgumentHolder.bcViewHolder.logo
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.time
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setText(bcAsyncArgumentHolder.bcItemHolder.title);
                bcAsyncArgumentHolder.bcViewHolder.time.setText(Helper
                        .formatBroadcastTime(
                                bcAsyncArgumentHolder.bcItemHolder.start,
                                bcAsyncArgumentHolder.bcItemHolder.stop));
            }

            // medium layout, between 15 to 5min
            if (bcAsyncArgumentHolder.bcItemHolder.width <= 15 * controller
                    .getPixelPerMinute()
                    && bcAsyncArgumentHolder.bcItemHolder.width > 5 * controller
                            .getPixelPerMinute()) {
                bcAsyncArgumentHolder.bcViewHolder.logo
                        .setVisibility(View.GONE);
                bcAsyncArgumentHolder.bcViewHolder.time
                        .setVisibility(View.GONE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setVisibility(View.VISIBLE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setText(bcAsyncArgumentHolder.bcItemHolder.title);
            }

            // smal layout, to 5min
            if (bcAsyncArgumentHolder.bcItemHolder.width <= 5 * controller
                    .getPixelPerMinute()) {
                bcAsyncArgumentHolder.bcViewHolder.logo
                        .setVisibility(View.GONE);
                bcAsyncArgumentHolder.bcViewHolder.time
                        .setVisibility(View.GONE);
                bcAsyncArgumentHolder.bcViewHolder.title
                        .setVisibility(View.GONE);
            }

            if (bcAsyncArgumentHolder.bcItemHolder.dummy) {
                bcAsyncArgumentHolder.bcViewHolder.divider
                        .setVisibility(View.GONE);
            } else {
                bcAsyncArgumentHolder.bcViewHolder.divider
                        .setVisibility(View.VISIBLE);
            }

            if (!bcAsyncArgumentHolder.bcItemHolder.id.equalsIgnoreCase("")) {
                bcAsyncArgumentHolder.bcViewHolder.broadcastId = Long
                        .parseLong(bcAsyncArgumentHolder.bcItemHolder.id);
            }
            bcAsyncArgumentHolder.convertView.setVisibility(View.VISIBLE);
        }
    }

那么你是如何解决你的问题的呢？我的解决方案有问题，viewRecycling 导致视图混淆，导致渲染 5 分钟布局而不是 40 分钟布局，因为如果我快速滚动会有一些并发性。我知道为什么会这样，但我不知道如何解决它，但是:-D

listview - 带有 2 行布局的 ListView 的 AsyncTask

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