Question

我从Firebase数据库加载ListView，我希望在加载ListView时，它会显示进度条。

我已经阅读了一些指南，但我尝试了一些事情，但它对我没用。

这是我的代码：

public class Event_List_Activity extends Activity {
private static final String FIREBASE_URL="https://****.firebaseio.com/";
private Firebase firebaseRef;
final ProgressBar pb=(ProgressBar)findViewById(R.id.progressBar);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.content_event__list_);
    Firebase.setAndroidContext(this);
    firebaseRef = new Firebase(FIREBASE_URL);

    //populateEventList();
    new MyTask().execute();

    final ListView listView = (ListView)findViewById(R.id.listView1);

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            openEventInfo(parent,view,position,id);

    }
    });

}



class MyTask extends AsyncTask<String,Integer,String>
{

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

@Override
protected String doInBackground(String...strings)
{
    populateEventList();
    return null;
}

@Override
protected void onProgressUpdate(Integer...values)
{
    super.onProgressUpdate(values);
    pb.setProgress(values[0]);

}

@Override
protected void onPostExecute(String s)
{
    super.onPostExecute(s);
}
}





private void populateEventList()
{
    firebaseRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {


            ArrayList<String> subTitles = new ArrayList<String>();
            ArrayList<EventClass> eventList = new ArrayList<EventClass>();
            ArrayList<String> titles = new ArrayList<String>();
            for (DataSnapshot user : snapshot.child("users").getChildren()) {

                String event_title = user.child("event/event_title").getValue().toString();

                String event_date = user.child("event/event_date").getValue().toString();
                subTitles.add(event_date);
                String event_content = user.child("event/event_content").getValue().toString();
                String age_limit = user.child("event/age_limit").getValue().toString();
                String event_hour = user.child("event/event_hour").getValue().toString();
                String location_left = user.child("location_left").getValue().toString();
                String location_right = user.child("location_right").getValue().toString();

                EventClass oneEvent = new EventClass(event_title, event_date, event_content, age_limit, event_hour, location_left, location_right);
                eventList.add(oneEvent);

            }


            for (EventClass event : eventList) {
                titles.add(event.getEvent_title());
            }
            ArrayAdapter adapter = new ArrayAdapter(Event_List_Activity.this, android.R.layout.simple_list_item_1, titles) {

                @Override
                public View getView(int position, View convertView,
                                    ViewGroup parent) {
                    View view = super.getView(position, convertView, parent);

                    TextView textView = (TextView) view.findViewById(android.R.id.text1);
                    textView.setTextColor(Color.WHITE);

                    return view;
                }
            };
            ListView listView = (ListView) findViewById(R.id.listView1);

            listView.setAdapter(adapter);


        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {
            String message = "Error";
            Toast.makeText(Event_List_Activity.this, message, Toast.LENGTH_SHORT).show();
        }
    });

}

private void openEventInfo(AdapterView<?> parent, View view, int position, long id)
{
    final String selectedTitle = parent.getItemAtPosition(position).toString();
    firebaseRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot user : dataSnapshot.child("users").getChildren()) {
                String event_title = user.child("event/event_title").getValue().toString();
                if (selectedTitle.equals(event_title)) {

                    String event_date = user.child("event/event_date").getValue().toString();
                    String event_content = user.child("event/event_content").getValue().toString();
                    String age_limit = user.child("event/age_limit").getValue().toString();
                    String event_hour = user.child("event/event_hour").getValue().toString();
                    String location_left = user.child("location_left").getValue().toString();
                    String location_right = user.child("location_right").getValue().toString();
                    final SharedPreferences sp = getSharedPreferences("key", 0);
                    final SharedPreferences.Editor sedt = sp.edit();

                    sedt.putString("event_title", event_title);
                    sedt.putString("event_date", event_date);
                    sedt.putString("event_content", event_content);
                    sedt.putString("age_limit", age_limit);
                    sedt.putString("event_hour", event_hour);
                    sedt.putString("location_left", location_left);
                    sedt.putString("location_right", location_right);

                    sedt.commit();

                }

            }
            Intent intent = new Intent(Event_List_Activity.this, EventInfo.class);
            startActivity(intent);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {
            Toast.makeText(Event_List_Activity.this, "Error", Toast.LENGTH_LONG).show();
        }
    });

}




}

阅读评论后，这是我在MyTask()方法中所做的更改：

class MyTask extends AsyncTask<String,Integer,String>
{

@Override
protected void onPreExecute()
{
    super.onPreExecute();
    listView.setVisibility(View.INVISIBLE);
    pb.setVisibility(View.VISIBLE);
}

@Override
protected String doInBackground(String...strings)
{
    populateEventList();
    return null;
}

@Override
protected void onProgressUpdate(Integer...values)
{
    super.onProgressUpdate(values);
    pb.setProgress(values[0]);
    pb.setMax(values[1]);


}

@Override
protected void onPostExecute(String s)
{
    super.onPostExecute(s);
    pb.setVisibility(View.GONE);
    listView.setVisibility(View.VISIBLE);
}
}

Answer 1

好FireBase为每项任务提供完整的解决方案。以下是我们在下载或上传内容时如何显示进度的方法。如this blog所述，我们可以使用FireBase API的内置方法。

首先，请删除所有AsyncTask代码，以便下载并显示进度。 FireBase已经在其他线程上工作，因此不需要AsyncTask。所以你做了类似的事情

StorageReference storageRef = FirebaseStorage.getInstance().reference().child("folderName/file.jpg");
Uri file = Uri.fromFile(new File("path/to/images/file.jpg"));
UploadTask uploadTask = storageRef.putFile(file);
uploadTask.addOnProgressListener(new OnProgressListener() {
@Override
public void onProgress(UploadTask.TaskSnapshot snapshot) {
    System.out.println(snapshot.getBytesTransferred().toString());
}
});

让我知道它是否对你有帮助。

Answer 2

您必须在某处publishProgress手动拨打doInBackground AsyncTask publishProgress

编辑：

让我更具体一点...... 如果您只想在加载数据时显示进度条，则可以执行类似的操作。

在onPreExecute中，您可以隐藏listView并将visibility的{{1}}设置为progressBar。

然后在VIEW.VISIBLE每次收到新数据集时，您可以使用当前接收数据数和最大数量来调用doInBackground。

然后在publishProgress(current, max)中，您按照onProgressUpdate(Integer... values)和实际值pb.setMax(values[1])设置新的最大值。

加载每个数据集后，pb.setProgress(values[0])将被调用，您将onPostExecute()的可见性更改回progressBar，并将VIEW.GONE的可见性设置回{{ 1}}。

如何在加载ListView时显示进度条？

2 个答案: