加載ListView期間的進度欄

Question

因此，我想在填充ListView時顯示旋轉的加載指示器。 我已經成功實現了進度條，但是由於某種原因，它在顯示所有列表之前就消失了。 我想要的是在清單的TOTAL加載時間內出現的進度欄。 基本上，看起來，每個清單一次顯示一次，而不是一次全部顯示。 我正在做的是1.創建一個新的自定義適配器類2.使用此適配器類在AsyncTask中填充ListView 3.將ListView設置為此適配器

這可以正常工作，進度條僅在顯示所有列表之前消失。 有人有什么想法嗎？

活動課：

public class MainActivity extends ActionBarActivity {

ArrayList<Location> arrayOfLocations;
LocationAdapter adapter;
// public static Bitmap bitmap;
Button refresh;
ProgressBar progress;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    progress=(ProgressBar)findViewById(R.id.progressbar_loading);
    // Construct the data source
    arrayOfLocations = new ArrayList<Location>();

    // Create the adapter to convert the array to views
    adapter = new LocationAdapter(this, arrayOfLocations);

    FillLocations myFill = new FillLocations();
    myFill.execute();



    refresh = (Button) findViewById(R.id.refresh);
    refresh.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            finish();
            startActivity(getIntent());
        }
    });

}


private class FillLocations extends AsyncTask<Integer, Void, String> {
    String msg = "Done";

    protected void onPreExecute() {
        progress.setVisibility(View.VISIBLE);
    }

    // Decode image in background.
    @Override
    protected String doInBackground(Integer... params) {

        String result = "";
        InputStream isr = null;
        try {
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://afs.spotcontent.com/"); // YOUR
                                                                                // PHP
                                                                                // SCRIPT
                                                                                // ADDRESS
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            isr = entity.getContent();
            // resultView.setText("connected");
        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }
        // convert response to string
        try {
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(isr, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            isr.close();

            result = sb.toString();
        } catch (Exception e) {
            Log.e("log_tag", "Error  converting result " + e.toString());
        }

        // parse json data
        try {
            JSONArray jArray = new JSONArray(result);

            for (int i = 0; i < jArray.length(); i++) {
                final JSONObject json = jArray.getJSONObject(i);

                try {

                    BitmapWorkerTask myTask = new BitmapWorkerTask(
                            json.getInt("ID"), json);
                    myTask.execute();

                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }

        } catch (Exception e) {
            // TODO: handle exception
            Log.e("log_tag", "Error Parsing Data " + e.toString());
        }
        return msg;

    }

    protected void onPostExecute(String msg) {
        // Attach the adapter to a ListView
        ListView listView = (ListView) findViewById(R.id.listView1);

        // View header = (View) getLayoutInflater().inflate(
        // R.layout.listview_header, null);
        // listView.addHeaderView(header);

        listView.setAdapter(adapter);
        progress.setVisibility(View.GONE);

    }
}
}

適配器類：

public class LocationAdapter extends ArrayAdapter<Location> {
public LocationAdapter(Context context, ArrayList<Location> locations) {
   super(context, R.layout.item_location, locations);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
   // Get the data item for this position
   Location location = getItem(position);    
   // Check if an existing view is being reused, otherwise inflate the view
   if (convertView == null) {
      convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_location, parent, false);
   }

   // Lookup view for data population
   TextView tvName = (TextView) convertView.findViewById(R.id.tvName);
   TextView tvDetails = (TextView) convertView.findViewById(R.id.tvDetails);
   TextView tvDistance = (TextView) convertView.findViewById(R.id.tvDistance);
   TextView tvHours = (TextView) convertView.findViewById(R.id.tvHours);
   ImageView ivIcon = (ImageView) convertView.findViewById(R.id.imgIcon);

   // Populate the data into the template view using the data object
   tvName.setText(location.name);
   tvDetails.setText(location.details);
   tvDistance.setText(location.distance);
   tvHours.setText(location.hours);
   ivIcon.setImageBitmap(location.icon);
   // Return the completed view to render on screen
   return convertView;
}
}

Answer 1

該行為的原因是您正在啟動多個線程。

FillLocations preExecute --> SHOW ProgressBar
BitmapWorkerTask_1 --> new thread
BitmapWorkerTask_2 --> new thread
...
BitmapWorkerTask_N --> new thread

FillLocations postExecute --> HIDE ProgressBar
BitmapWorkerTask_K --> continue execution
BitmapWorkerTask_K+1 --> continue execution

等等

如果要在列表全部加載之前顯示該列表，只需使BitmapWorker的處理同步即可。 如果您仍然想立即顯示列表，但要保持微調框直到全部完成，則在活動中保留一個計數器，並通過設置器在BitmapWorker的postExecute中增加它，並在它的postExecute中減少它。 一旦計數器達到0，請刪除隱藏progressBar。

活動中：

private int asynchCounter = 0;
private void updateCounter(int delta){
    asynchCounter+=delta;
    if(asynchCounter<=0){
        progress.setVisibility(View.GONE);
    }else{
        progress.setVisibility(View.VISIBLE);
    }
}

而不是使用BitmapWorkerTask

class CountedBitmapWorkerTask extends BitmapWorkerTask {
protected void onPreExecute() {
    super.onPreExecute();
    updateCounter(1);
}
protected void onPostExecute(String msg) {
        super.onPostExecute();
        updateCounter(-1);

    }
}

Answer 2

我遇到了這個確切的問題，要解決它，我必須編寫AsyncTask完整的偵聽器。 它向UI線程發送一條通知，該通知已加載數據並且它必須更改某些內容，在這種情況下，請隱藏ProgressBar 。

這是外觀的基本示例。 將其復制到項目后，我不確定這是否對您有用，但是您需要完整的偵聽器，因此在研究了這種情況之后，您應該能夠找到解決方案。

AsyncTaskCompleteListener.java-偵聽器接口。

public interface AsyncTaskCompleteListener {
       public void onTaskComplete();
}

LoadDataTask.java

class LoadDataTask extends AsyncTask<Object, Object, Object> { 
    /* Your object types according to your task. */

    private AsyncTaskCompleteListener callback; // Callback field

    public LoadDataTask(AsyncTaskCompleteListener cb){
        this.callback = cb; 
    }

    @Override
        protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Object doInBackground(String... urls) {
        /* Your task here */
        return result;
    }

    @Override
    protected void onPostExecute(Object o) {
           callback.onTaskComplete(); // Set the Callback
    }
}

MainActivity.java

   public class MainActivity implements AsyncTaskCompleteListener{
       /* ...Other methods and fields... */


       /* onTaskComplete method which fires after your data is loaded. */
       @Override
       public void onTaskComplete(){
           // Hide ProgressBar
       }
   }

Answer 3

自我插件： https : //github.com/horvste/EasyWebPageDownloadForAndroid

這將使線程與實現分離，並解決您的問題。 除了已經為您實現之外，這與Tony建議的非常相似。

Github自述文件：

非常適合連接REST API，HTML解析和許多其他用途。 使用這個庫很容易：

1. 創建一個實現OnProgressUpdate的類

公共類SampleClass實現OnProgressUpdate {

    @Override
    public void onUpdate(Integer percentProgress) {

    }

    @Override
    public void onUpdateFailure() {

    }

    @Override
    public void onSuccess(StringBuilder result) {

    }

    @Override
    public void onFailure() {

    }
}

實例化DownloadWebPage對象

DownloadWebPage webPage = new DownloadWebPage(new SampleClass(), myUrl);

從DownloadWebPage調用.downloadHtml（）

webPage.downloadHtml();

另外，如果asynchtask正確更新，並且項目數量很大，請看這里： 列出listview在android中占用太多時間和內存

另一個選擇是僅列出一定數量的項目，然后使用下一頁按鈕或手勢來處理ListView加載太慢。