android - 如何将异步任务应用到这里

Question

经过几个小时的尝试，我仍然无法弄清楚如何将 asynctask 合并到下面的代码中。

我试过线程，但也没有用。我只想在后台运行扫描并显示进度条。

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}

private void populateView() {

    List<PackageInfo> adPackages = getAdPackages();
    PackageManager pm = getPackageManager();

    List<Map<String, String>> data = new ArrayList<Map<String, String>>(adPackages.size());
    for(PackageInfo pkg : adPackages) {
        Map<String, String> attrs = new HashMap<String, String>();
        attrs.put("App Name", pm.getApplicationLabel(pkg.applicationInfo).toString());
        attrs.put("Package Name", pkg.packageName);
        data.add(attrs);
    }

    String[] from = new String[] {
        "App Name",
        "Package Name"
    };
    int[] to = new int[] {
        android.R.id.text1,
        android.R.id.text2
    };
    SimpleAdapter adapter = new SimpleAdapter(
            this, data, android.R.layout.two_line_list_item, from, to);

    setListAdapter(adapter);
    mPackages = adPackages;
}

.

private List<PackageInfo> getAdPackages() {
    Set<PackageInfo> adPackages = new HashSet<PackageInfo>();

//[...]
    List<ApplicationInfo> appInfos = pm.getInstalledApplications(0);

    for(ApplicationInfo appInfo : appInfos) {

        try {

            //[Heavy Stuff]

    return new ArrayList<PackageInfo>(adPackages);

   }
}

Answer 1

是的，这是可以做到的。

您必须将您的getPackages 逻辑移动到AsyncTask 的doInBackground。当你想更新进度条时，你必须从 doInBackground 调用 publishProgress。

一旦 doInBackground 完成，就会调用 onPostExecute。将适配器和适配器本身的所有数据逻辑放在其中。也在函数中设置适配器。

以下是您可以引用的一些引用文档:

Async Task Worker Threads

这是一些示例:

 private class GetPackageTask extends AsyncTask<Void, Integer, List<PackageInfo>> {
 protected List<PackageInfo> doInBackground(URL... urls) {

     // Put your code of getPackages in here

     // You can call publish like it is done below
     //for (int i = 0; i < count; i++) {
     //    totalSize += Downloader.downloadFile(urls[i]);
     //    publishProgress((int) ((i / (float) count) * 100));
     //}

     // adPackages is what you returning from your getPackages function
     return adPackages;
 }

 protected void onProgressUpdate(Integer... progress) {
     setProgressPercent(progress[0]);
 }

 protected void onPostExecute(List<PackageInfo> result) {
     // Here you will have all the setAdapter related code
 }
}

onCreate 将包含

新的 DownloadFilesTask().execute();