如何在ListView项更新进度 [英] How to update progressbar in a ListView item

问题描述

我有一个的ListView 连接到 ArrayAdapter 。当用户点击下载按钮在的ListView项目下载开始使用下载管理器。

I have a ListView attached to an ArrayAdapter. When the user clicks a download button for an item in the ListView a download starts using the DownloadManager.

我想要做的是跟踪一个进度条（放置在项目布局）下载进度。如何才能实现这一目标？

What I want to do is to track the download progress with a progress bar (placed in the item layout). How can this be achieved?

的方式袖珍演员确实是exacly我后：

The way Pocket Cast does it is exacly what I'm after:

注：我知道如何与下载管理器，它的进度栏是棘手的即时更新工作的

Note: I know how to work with the DownloadManager, it's the instant update of the progress bar that is tricky.

推荐答案

这是这样，我终于解开了它（多次迭代和不同的实现之后）。这是一个有点棘手，但基本上你需要三样东西：

This is the way I finally solved it (after many iterations and different implementations). It's a bit tricky but basically you need three things:

1. 在它收集的元数据的AsyncTask的
2. 在一个滚动监听器，它告诉我们，当用户停止滚动/扔
3. 在一个聪明的算法，认为需要更新，并要求适配器仅更新任何可见行的特定行

这是我设计并实现它的方式：

This is the way I designed and implemented it:

我更详细地写了一篇关于在这里和请参阅<一href="https://github.com/slidese/SGU/blob/3be1888115ba56b4a015b127b249c35af5dc11d0/src/se/slide/sgu/ContentFragment.java">github code 的完整imlementation。

I wrote in more detail about it here, and please see the github code for the complete imlementation.

    private class UpdaterAsyncTask extends AsyncTask<Void, Void, Void> {

    boolean isRunning = true;

    public void stop() {
        isRunning = false;
    }

    @Override
    protected Void doInBackground(Void... params) {

        while (isRunning) {

            // Gather data about your adapter objects
            // If an object has changed, mark it as dirty                

            publishProgress();

            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Void... params) {
        super.onProgressUpdate();

        // Update only when we're not scrolling, and only for visible views
        if (mScrollState == OnScrollListener.SCROLL_STATE_IDLE) {
            int start = mListview.getFirstVisiblePosition();
            for(int i = start, j = mListview.getLastVisiblePosition(); i<=j; i++) {
                View view = mListview.getChildAt(i-start);
                if (((Content)mListview.getItemAtPosition(i)).dirty) {
                    mListview.getAdapter().getView(i, view, mListview); // Tell the adapter to update this view
                }

            }
        }

      }
    }

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