[Tut] Updating UI from a Thread

[qlimax]

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Using xml Syntax Highlighting

1. <?xml version="1.0" encoding="utf-8"?>
2.  
3. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
4.  
5.    android:orientation="vertical"
6.  
7.    android:layout_width="fill_parent"
8.  
9.    android:layout_height="fill_parent"
10.  
11.    >
12.  
13. <TextView  
14.  
15.    android:layout_width="fill_parent"
16.  
17.    android:layout_height="wrap_content"
18.  
19.    android:text="press start to begin"
20.  
21.    android:id="@+id/loadingTv"
22.  
23.    android:inputType="textMultiLine"
24.  
25.    />
26.  
27.  
28.  
29. <Button
30.  
31. android:text="start"
32.  
33. android:id="@+id/startButton"
34.  
35. android:layout_width="wrap_content"
36.  
37. android:layout_height="wrap_content">
38.  
39. </Button>
40.  
41. </LinearLayout>

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Using java Syntax Highlighting

1.  
2. package ch.egsolutions.updatingui;
3.  
4.  
5.  
6. import java.util.Random;
7.  
8.  
9.  
10. import android.app.Activity;
11.  
12. import android.os.AsyncTask;
13.  
14. import android.os.Bundle;
15.  
16. import android.view.View;
17.  
18. import android.view.View.OnClickListener;
19.  
20. import android.widget.Button;
21.  
22. import android.widget.TextView;
23.  
24.  
25.  
26. public class Demo extends Activity {
27.  
28.  
29.  
30.         TextView loadingTv;
31.  
32.  
33.  
34.         @Override
35.  
36.         public void onCreate(Bundle savedInstanceState) {
37.  
38.                 super.onCreate(savedInstanceState);
39.  
40.                 setContentView(R.layout.main);
41.  
42.  
43.  
44.                 loadingTv = (TextView) findViewById(R.id.loadingTv);
45.  
46.                 Button start = (Button) findViewById(R.id.startButton);
47.  
48.  
49.  
50.                 start.setOnClickListener(new OnClickListener() {
51.  
52.  
53.  
54.                         @Override
55.  
56.                         public void onClick(View arg0) {
57.  
58.                                 LoadingStuffTask task = new LoadingStuffTask();
59.  
60.                                 task.execute("Process started!");
61.  
62.                                 // the string will be passed to the doInBackground
63.  
64.                                 // if necessary call task.getStatus() to know the current task
65.  
66.                                 // status
67.  
68.  
69.  
70.                         }
71.  
72.                 });
73.  
74.  
75.  
76.         }
77.  
78.  
79.  
80.         private class LoadingStuffTask extends AsyncTask<String, String, String> {
81.  
82.                 // String,String,String are relatively the
83.  
84.                 // doInBackground params Type
85.  
86.                 // onProgressUpdate params Type
87.  
88.                 // onPostExecure params Type
89.  
90.                 //-- of course you can specify any type you need...
91.  
92.  
93.  
94.                 @Override
95.  
96.                 protected String doInBackground(String... params) {
97.  
98.                         publishProgress("\n" + params[0]);
99.  
100.                         // string passed to the onProgressUpdate
101.  
102.  
103.  
104.                         Random rand = new Random();
105.  
106.  
107.  
108.                         publishProgress("Loading module 1 ...");
109.  
110.  
111.  
112.                         while (rand.nextInt(1000000) != 2) {
113.  
114.                         }
115.  
116.                         // simulating
117.  
118.                         // extreme
119.  
120.                         // calculations
121.  
122.                         publishProgress("Loading module 2 ...");
123.  
124.                         while (rand.nextInt(1000000) != 1) {
125.  
126.                         }
127.  
128.  
129.  
130.                         return "Finish !";
131.  
132.                         // string passed to the onPostExecute
133.  
134.                 }
135.  
136.  
137.  
138.                 @Override
139.  
140.                 protected void onProgressUpdate(String... values) {
141.  
142.                         loadingTv.append(values[0] + "\n");
143.  
144.                 }
145.  
146.  
147.  
148.                 @Override
149.  
150.                 protected void onPostExecute(String result) {
151.  
152.                         loadingTv.append(result + "\n");
153.  
154.                 }
155.  
156.  
157.  
158.         }
159.  
160.  
161.  
162. }
163.  
164. //there is another override you can do: onPreExecute.
165.  
166. //It will run on the UI thread, and lets you do some ui tweaks (if needed) before
167.  
168. //the doInBackground is called
169.  
170.  

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btw,
to update the ui using the classic java threading method, use handlers
look here: http://developer.android.com/guide/appe ... #threading

bye

[nobb]

Thanks for your tutorial. That's exactly what I was trying to do.

Btw – Is there a reason why the TextView is final but the Button isn't?

[pskink]

hi everyone.
First of all, although this is the advanced tutorial section, I post here because the beginner tutorial section seem to be a mix of question/answare/tutorial/off-topic, pretty much a mess.

two remarks:

1) why you use custom Thread instead of using AsyncTask? using the latter you avoid creating Handlers/Messages and so on

2) don't create Messages directly, use Message.obtain() instead, also when sending empty Messages you can use Handler.sendEmptyMessage[Delayed]() methods

[erwan]

Cannot find the tut, but it is just what I've been looking for. so ... where is the tut?

[qlimax]

Cannot find the tut, but it is just what I've been looking for. so ... where is the tut?

I've updated the post.