How to show ProgressBar and make it progress?(Xama

问题:

I call a web service which gets 4 files, and while these files are loading I want to show progress to the user (circular or horizontal it doesn't matter). I've followed the examples on internet but nothing appears on screen.

MobileSellReference.Service1 service = new MobileSellReference.Service1();
service.Url = settings.Synchronization.Msellurl;
ProgressBar progressBar = FindViewById<ProgressBar>(Resource.Id.progressBar);
progressBar.Max = 100;
progressBar.Progress = 0;
byte[][] basedataResult = service.ToPPC(basedataZipName, objectId);
progressBar.IncrementProgressBy(25);
byte[][] dutybasedataResult = service.ToPPC(dutybasedataZipName, objectId);
progressBar.IncrementProgressBy(25);
byte[][] tranbasedataResult = service.ToPPC(tranbasedataZipName, objectId);
progressBar.IncrementProgressBy(25);
byte[][] vendbasedataResult = service.ToPPC(vendbasedataZipName, objectId);
progressBar.IncrementProgressBy(25);

I've found a lot of examples using external progressbar libraries but they all want to change the theme of the Activity. Instead I want some simple ProgressBar built into Xamarin.Android. For example when the first file is downloaded I want 1/4 of the circle to be filled, when 2 files are downloaded 1/2 of the circle to be filled et cetera. Similarly for a horizontal ProgressBar.

回答1:

Use AsyncTask

.axml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/tv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="0" />
    <ProgressBar
        android:id="@+id/pb"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleHorizontal" />
</LinearLayout>

MainActivity:

public class MainActivity : Activity
{
    ProgressBar pb;
    TextView tv;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);
        pb = FindViewById<ProgressBar>(Resource.Id.pb);
        tv = FindViewById<TextView>(Resource.Id.tv);
        UpdatePB uptask = new UpdatePB(this,pb,tv);
        uptask.Execute(100);
    }

   public class UpdatePB : AsyncTask<int, int, string>
    {
        Activity mcontext;
        ProgressBar mpb;
        TextView mtv;
        public UpdatePB(Activity context,ProgressBar pb,TextView tv) {
            this.mcontext = context;
            this.mpb = pb;
            this.mtv = tv;
        }
        protected override string RunInBackground(params int[] @params)
        {
            // TODO Auto-generated method stub
            for (int i = 1; i <= 4; i++)
            {
                try
                {
                    Thread.Sleep(3000);
                }
                catch (InterruptedException e)
                {
                    // TODO Auto-generated catch block
                    Android.Util.Log.Error("lv",e.Message);
                }
                mpb.IncrementProgressBy(25);
                PublishProgress(i * 25);

            }
            return "finish";
        }

        protected override void OnProgressUpdate(params int[] values)
        {
            mtv.Text = String.ValueOf(values[0]);
            Android.Util.Log.Error("lv==", values[0] + "");
        }
        protected override void OnPostExecute(string result)
        {
            mcontext.Title = result;
        }


    }
}

回答2:

This might be a helpful link:

https://developer.android.com/reference/android/widget/ProgressBar.html

Code:

 <ProgressBar
  android:id="@+id/determinateBar"
  style="@android:style/Widget.ProgressBar.Horizontal"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:progress="25"/>

... and then you just change the progress; 25, 50, 75, 100?

回答3:

After running into the same problem, I found another solution that got it working. I was reluctant to define a new class (like AsyncTask) to fix this, so looked into async await and threading. I found that after defining an Android.Widget.ProgressBar in an .axml layout file like so:

<ProgressBar
    android:id="@+id/progressBar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:progress="0"
    style="?android:attr/progressBarStyleHorizontal" />

I could get it to update if I put the updating tasks in a System.Threading.Tasks.Task.Run and passing in an action that does the updates with RunOnUiThread call like:

btnDoStuff.Click += (sender, e) =>
{
    Task.Run(() =>
    {
        RunOnUiThread(() => 
        {
            progressBar.Max = 100;
            progressBar.Progress = 0;
            progressBar.Visibility = ViewStates.Visible;
        });

        DoSomeWork1(arguments);
        RunOnUiThread(() => progressBar.Progress += 25);

        DoSomeWork2(arguments);
        RunOnUiThread(() => progressBar.Progress += 25);

        DoSomeWork3(arguments);
        RunOnUiThread(() => progressBar.Progress += 25);

        DoSomeWork4(arguments);
        RunOnUiThread(() => progressBar.Progress += 25);
    });
}

But even then I've had some inconsistent behavior - there may be an element of timing to it as well...