Develop Reference

setVisibility not working even in uiThread

I want to toggle visibility of some elements. I have read some Q/A that the main problem was doing this in main thread but I am running the code in runOnUiThread but not works yet:
TextView progress;
TextView registrationFailed;
Button tryAgainRegistration;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.registration);
sp = this.getSharedPreferences("settings", this.MODE_PRIVATE);
progress = (TextView) findViewById(R.id.progress);
registrationFailed = (TextView) findViewById(R.id.registrationFailed);
tryAgainRegistration=(Button) findViewById(R.id.tryAgainRegistration);
Setstat(0); // For test
}
public void Setstat(final Integer a){
runOnUiThread(new Runnable() {
#Override
public void run() {
Log.e("progress",a.toString()); // It shows 0 and 1 correctly
if (a == 1) {
progress.setVisibility(View.VISIBLE);
registrationFailed.setVisibility(View.GONE);
tryAgainRegistration.setVisibility(View.GONE);
} else {
progress.setVisibility(View.GONE);
registrationFailed.setVisibility(View.VISIBLE);
tryAgainRegistration.setVisibility(View.VISIBLE);
}
}
});
}
for more details this is the UI xml:
<TextView
android:id="#+id/progress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal|center_vertical"
android:text="Registeration in progress"
android:visibility="visible" />
<TextView
android:id="#+id/registrationFailed"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal|center_vertical"
android:text="Registeration in progress"
android:visibility="gone" />
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="Try again"
android:id="#+id/tryAgainRegistration"
android:visibility="gone"
/>

Try running this in on create.
Just to see if it is because of the threads or not:
findViewById(R.id.yourView).setVisibility(View.GONE);
The runOnUiThread method needs a reference to the activity.
Otherwise it doesn't know which one the UI thread is.
You might get a warning about memory leaks. If you are worried about that, google for WeakReference.
((Activity)context).runOnUiThread(new Runnable() {

My specific problem was that I had created the XML view using constrainLayout but modified it manually without removing original settings of constrainLayout. So I guess the layout was not well recognized by system Ui.
In fact I made a mistake by manually renaming android.support.constraint.ConstraintLayout to LinearLayout as the root element.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context=".Registration"
tools:showIn="#layout/activity_registration">

Get Search results from Google in android app

In my android application I want to get search query from user, and search google with that query, get search results and populate a list with the search results. Custom Search API limits to 100 free searches per day. So is there any alternative for searching?

This is something which you can use.
http://google.com/complete/search?output=toolbar&q=query
It returns an XML file. Parse that xml to get the results.
But google may change the format of the query in future. Thats the only concern here. Otherwise it works great.
For future reference, note the following queries for other useful websites. Some return in JSON and others in XML formats.
http://suggestqueries.google.com/complete/search?hl=en&ds=yt&client=youtube&hjson=t&cp=1&q=query&alt=json
http://search.yahooapis.com/WebSearchService/V1/relatedSuggestion?appid=YahooDemo&query=query
http://en.wikipedia.org/w/api.php?action=opensearch&search=query&limit=10&namespace=0&format=json
http://anywhere.ebay.com/services/suggest/?q=query&s=0
http://completion.amazon.com/search/complete?method=completion&q=query&search-alias=aps&mkt=1
http://api.bing.net/osjson.aspx?Query=query&Market=en-us

You can try using this code
MainActivity.java
private EditText editTextInput;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_g__search);
editTextInput = (EditText) findViewById(R.id.editTextInput);
}
public void onSearchClick(View v)
{
try {
Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
String term = editTextInput.getText().toString();
intent.putExtra(SearchManager.SUGGEST_URI_PATH_QUERY, term);
startActivity(intent);
} catch (Exception e) {
// TODO: handle exception
}
}
Activity_layout.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<EditText
android:id="#+id/editTextInput"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10" >
<requestFocus />
</EditText>
<Button
android:id="#+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#+id/editTextInput"
android:layout_below="#+id/editTextInput"
android:layout_marginRight="43dp"
android:layout_marginTop="60dp"
android:onClick="onSearchClick"
android:text="CLICK" />
Also add permission for internet

Android SetText Null pointer Exception

I've just begin Android development and I'm sure you can help with this (I'm sorry about my bad English)
I have a main activity, and at a certain moment i want to call another activity, in wich a want to change a textview with some message. At this moment I get a Null pointer Exception if I dont put
setContentView(R.layout.register);
But when I put that line, I see for a milisecond correctly the Register activiy with my new text "Android2" and then jump again to a register activity with no text. I mean I draw it twice.
I hope I have explained enough.
The question is Where do I have to put setcontentview and with what layaout.
Thank you very much, Daniel
I show you some code:
My main activity has this method:
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
if (requestCode == REQUEST_CODE && resultCode == RESULT_OK)
{
Intent i = new Intent(this, register.class);
startActivity(i);
setContentView(R.layout.register);
TextView text = (TextView) findViewById(R.id.texto);
try {
text.setText("Android2");
}catch(Exception e) {
Log.i("Log", e.getMessage()+"Error!"); // LogCat message
}
}
//super.onActivityResult(requestCode, resultCode, data);
}
My second activity class called register:
public class register extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.register);
}
}
The register Interface is register.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/about_content"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="#string/register" />
<TextView
android:id="#+id/texto"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="#+id/continue_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="#string/save" />
<Button
android:id="#+id/new_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="#string/repeat" />
</LinearLayout>
</LinearLayout>

What you basically do is the following:
you prepare an intent to start another activity
you start the activity you prepared the intent for
you set the current activity's content to R.layout.register
you get the textView (on the current activity)
you set the text of the textView to Android2
And, at this moment the new activity appears on the screen. Please note that your code is not correct, since you manipulate UI elements in the current activity and you expect changes on the newly started activity.
Move this code
TextView text = (TextView) findViewById(R.id.texto);
try {
text.setText("Android2");
}catch(Exception e) {
Log.i("Log", e.getMessage()+"Error!"); // LogCat message
}
to the register activity's onCreate() method.
BTW, usually, when you create a class, it's name should begin with a capital letter according to the standards.

You have two different activities. One of them is using the register.xml view, and the second one is trying to access the register view. The view only exists in your "register" activity. The other activity seems to have no view? That's probably why you're getting NULL.
You should merge those two classes together, since it looks like you're trying to access texto from the same view.
So, to summarise, findViewById should be called from within the activity that calls setContentView.

Remove this line and it should work
startActivity(i);
Not sure why you are calling that as an external activity.
Otherwise move below code to your register class
setContentView(R.layout.register);
TextView text = (TextView) findViewById(R.id.texto);
try {
text.setText("Android2");
}catch(Exception e) {
Log.i("Log", e.getMessage()+"Error!"); // LogCat message
}
}

Coupling Android layout to its logic outside of the owner Activity

I'm facing some complexities when developing a medium-complex Android application. I'm searching for information about the possibility of using code-behind-like techniques for easier maintanability of Android software.
Currently (please highlight anything wrong), I have found that in order to make a multi-step wizard with extra dialogs (eg. dialogs that are not part of the main sequence) I need to code a single XML layout file with a single ViewFlipper containing each subview as child node. Today I discovered how to navigate across views more than forward/backward (viewFlipper.setDisplayedChild(i)), giving access to extra views.
Now all the Java code is contained within the main Activity class, which is beginning to look bad. As an experienced .NET developer I have learned how to use custom controls to wrap both layout and business logic inside modules.
I know that in Android I can define a view programmatically as an independent class and add it to the main layout programmatically, however I want to know if it's possible in Android to define a layout by XML (for easier WYSIWYG creation/editing) and define all the code within a dedicated class, with initialization logic, button callbacks, async tasks, etc.
I'm not sure if it's feasible or there is a good compromise that can be achieved.
I have read this question without clearing my doubts.
Thank you.
Code examples:
An extract of the layout file (I expect 4 wizard steps, a help view and an EULA view)
<?xml version="1.0" encoding="utf-8"?>
<ViewFlipper xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/view_phone"
style="#android:style/Theme.Light.NoTitleBar"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<!-- First screen/welcome -->
<LinearLayout
android:id="#+id/view_phone_screen1"
style="#android:style/Theme.Light.NoTitleBar"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="100" >
<TextView
android:id="#+id/view_phone_screen1_lblChooseProvider"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"
android:text="#string/view_phone_lblChooseProvider_1ststep"
android:textAppearance="?android:attr/textAppearanceLarge" />
<ImageButton
android:id="#+id/view_phone_btnFrecciarossa"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:clickable="true"
android:contentDescription="#string/provider_FRECCIAROSSA"
android:gravity="center_vertical|clip_vertical"
android:padding="10dp"
android:src="#drawable/logo_frecciarossa"
android:tag="#+id/provider_FRECCIAROSSA" />
<ImageButton
android:id="#+id/view_phone_btnItalo"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:clickable="true"
android:contentDescription="#string/provider_ITALO"
android:gravity="center_vertical|clip_vertical"
android:padding="10dp"
android:src="#drawable/logo_italo"
android:tag="#+id/provider_ITALO" />
</LinearLayout>
<!-- Second screen - will need to do some asynchronous task -->
<RelativeLayout
android:id="#+id/view_phone_screen2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="#+id/view_phone_screen2_lblConnectingToWifi"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"
android:text="#string/view_phone_lblConnectToWifi_2ndstep"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="#+id/view_phone_step2_lblConnectedToWifi"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/imageView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="58dp"
android:text="#string/view_phone_step2_connectingToWifi"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="#+id/view_phone_step2_lblPhoneNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/editText1"
android:layout_below="#+id/view_phone_step2_lblConnectedToWifi"
android:layout_marginTop="51dp"
android:text="#string/view_phone_step2_msgInputPhoneNumber"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="#+id/view_phone_step2_lblUnableDetectPhoneNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:text="#string/view_phone_step2_msgUnableDetectPhoneNumber"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<Button
android:id="#+id/view_phone_screen2_backward"
style="#style/buttonBackward" />
<Button
android:id="#+id/view_phone_screen2_forward"
style="#style/buttonForward_disabled"
android:enabled="false" />
<EditText
android:id="#+id/view_phone_step2_txtPhoneNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignRight="#+id/view_phone_step2_lblPhoneNumber"
android:layout_below="#+id/view_phone_step2_lblPhoneNumber"
android:inputType="phone"
android:singleLine="true" >
<requestFocus />
</EditText>
</RelativeLayout>
</ViewFlipper>
Code example from Activity (expect to implement ALL the logic of 4+2 step wizard)
public class MyActivity extends Activity {
/** Called when the activity is first created. */
private final static String LOG_TAG = "LOG_TAG";
private int stepNumber;
#Override
public void onCreate(Bundle savedInstanceState) {
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
super.onCreate(savedInstanceState);
this.stepNumber=1;
setContentView(R.layout.view_phone);
//This class wraps the click for the two buttons
ProviderSelectionListener providerSelectionListener = new ProviderSelectionListener(this);
this.findViewById(R.id.view_phone_btnFrecciarossa).setOnClickListener(providerSelectionListener);
this.findViewById(R.id.view_phone_btnItalo).setOnClickListener(providerSelectionListener);
}
#Override
protected void onPause() {
super.onPause();
try {
if (MyApplication.getPlatformManager() != null)
MyApplication.getPlatformManager().onApplicationPause();
} catch (MyCustomException e) {
// WTF (Worse Than Failure!)
Log.e(LOG_TAG, super.getString(R.string.zf_error_unknown_error_pauseactivity), e);
e.printStackTrace();
}
}
#Override
protected void onResume() {
super.onResume();
try {
if (MyApplication.getPlatformManager() != null)
MyApplication.getPlatformManager().onApplicationResume();
} catch (MyCustomException e) {
// WTF (Worse Than Failure!)
Log.e(LOG_TAG, super.getString(R.string.zf_error_unknown_error_pauseactivity), e);
e.printStackTrace();
}
}
/*
* SLIDE INIZIO
*/
protected void slideNext() {
ViewFlipper vf = (ViewFlipper) findViewById(R.id.view_phone);
vf.setOutAnimation(getApplicationContext(), R.anim.slide_out_left);
vf.setInAnimation(getApplicationContext(), R.anim.slide_in_right);
vf.showNext();
}
protected void slidePrevious() {
ViewFlipper vf = (ViewFlipper) findViewById(R.id.view_phone);
vf.setOutAnimation(getApplicationContext(), R.anim.slide_out_right);
vf.setInAnimation(getApplicationContext(), R.anim.slide_in_left);
vf.showPrevious();
}
/*
* SLIDE FINE
*/
/*
* STEP 1 INIZIO
*/
public void completeStep1(ISmsWifiProvider provider) {
if (provider == null) {
Log.e(LOG_TAG, "Provider nullo");
return;
}
MyApplication.setAuthenticationProvider(provider);
slideNext();
initializeStep2();
}
public void returnToStep1() {
MyApplication.setAuthenticationProvider(null);
slidePrevious();
}
/*
* STEP 1 FINE
*/
/*
* STEP 2 INIZIO
*/
private void initializeStep2() {
// Event handler
Button backButton = (Button) findViewById(R.id.view_phone_screen2_backward), fwButton = (Button) findViewById(R.id.view_phone_screen2_forward);
fwButton.setEnabled(false);
backButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
returnToStep1();
}
});
}
/*
* STEP 2 FINE
*/
#Override
public void onBackPressed() {
// This will be called either automatically for you on 2.0
// or later, or by the code above on earlier versions of the
// platform.
return;
}
}

I want to know if it's possible in Android to define a layout by XML (for easier WYSIWYG creation/editing) and define all the code within a dedicated class, with initialization logic, button callbacks, async tasks, etc.
Yes. It is one of the techniques for creating a custom View. For example, I have a custom ColorMixer widget in this project, which can be used directly in an activity, or in a dialog, or in a custom preference.
I agree with your tactical decision to implement a wizard via a ViewFlipper -- see this answer to another StackOverflow question for "Murphy's Theory of the Activity".
I suspect that the right answer, longer term, is for somebody (who might be me) to come up with a Fragment-based wizard pattern, as that gives you the decoupling you desire.

Android Null Button

What might be the reasons why the button is NULL?
Button press;
//...
press = (Button) findViewById (R.id.enter);
if (press != null)
press.setOnClickListener(this);
I checked the manifest, the xml file, the code... I don't have any duplicate of R.id.enter, still the button is NULL... It all happened after I introduced a new Activity...
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
press = (Button) findViewById (R.id.enter);
if (press != null)
press.setOnClickListener(this);
}
the XML here (main.xml):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#drawable/gift2"
>
<Button
android:id="#+id/enter"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="415dp"
android:background="#drawable/pattern"
android:layout_gravity="center_horizontal"
android:text="Open your box now!"
android:textSize="20sp"
/>
</LinearLayout>

One possibility is that the auto-generated R.java file has somehow got out of sync or has invalid values in it.
In this case, R.id.enter may no longer be valid and as a result findViewById(R.id.enter) can no longer find a valid object to return.
If using Eclipse, try using "Project -> Clean..." - this will delete all auto-generated files and re-create them.