The setText() method returns null in my application why?
public class GetValue extends Activity {
char letter = 'g';
int ascii = letter;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView textView = (TextView)findViewById(R.id.txt_1);
textView.setText(ascii);
}
}
It doesn't matter what text i put in, it crashes anyway. Why does setText() keep returning null?
Thank you, in advance
Solution: My error was in the xml file. I wrote:
android:text="#+id/txt_1"
When it should say:
android:id="#+id/txt_1"
Thanks a lot for all the answers and comments!
You tried to pass an integer as parameter to setText, which assumes it is a resource ID. To display computed text, pass it as a string: textView.setText("g");
Edited: Check your XML file, I have test with something very basic and it works
<?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">
<TextView
android:id="#+id/txt_1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="myTextView"/>
</LinearLayout>
Maybe try to clean your project (Project->Clean in Eclipse), I recently have some trouble with R generation on the last ADT version.
Try this:
textView.setText(Integer.toString(ascii));
Also make sure that your layout xml has TextView txt_1
I've tried :
Integer.toString(char) and String.valueOf(char)
both didnt work.
The only solution is :
txt.setText(""+char);
This is not very efficient from optimization point of view but it does the trick :)
Related
I'm completely new to Android programming, so I'm not really sure what I should be searching for. I have a LinearLayout element on one of my activities.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:id="#+id/comment_area"
android:orientation="vertical"/>
I have a JSON array of comments (userName, commentText, commentDate) that I want to add into this LinearLayout though a loop. I created a comment_view.xml layout and created a CommentWidget class extending LinearLayout. Frankly I have no idea if this is the correct approach, and I don't think it is because I can't get the comments to load in.
My class is
public class CommentWidget extends LinearLayout {
private String text;
public void setText(String text) {
this.text = text;
}
public CommentWidget(Context context){
super(context);
}
public CommentWidget(Context context,AttributeSet attrs){
super(context,attrs);
}
#Override
protected void onFinishInflate(){
super.onFinishInflate();
TextView textView=(TextView) findViewById(R.id.comment_text);
textView.setText(text);
}
}
My widget layout is
<?xml version="1.0" encoding="utf-8"?>
<com.myproject.CommentWidget xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/comment_text"/>
</com.myproject.CommentWidget>
Inside my loop on the activity I was calling:
CommentWidget w = new CommentWidget(this);
w.setText(comment.getText());
mtxtArea.addView(w);
But nothing shows up. Can someone point me in the right direction? I'm correctly receiving the JSON into an array already.
Update: Answer
Windsurfer's answer below set me on the right track to use a ListView for what I am trying to accomplish. Using his links and some searching I found out that extending the ArrayAdapter is the most appropriate for JSON type data. I ended up following the tutorial at the following link
https://devtut.wordpress.com/2011/06/09/custom-arrayadapter-for-a-listview-android/
You can very well extend the LinearLayout to do this, but Android already has a couple of widgets designed for this. I believe you're looking for a ListView to display an array of data. Rather than creating a new widget, take a look at how a ListView works. A ListView uses an adapter to bind data to it. You will still have to design the layout for a single comment item, but a lot of the heavy lifting is done by the ListView and it's adapter.
Here are some links to get you started:
http://developer.android.com/guide/topics/ui/layout/listview.html
http://www.vogella.com/tutorials/AndroidListView/article.html
Take a look at this link by Romain Guy who introduces ListViews too.
I'm new to Android programming, and I'm trying to make a simple button which displays a toast notification when clicked.
I tried to initialize a button called "button" in my MainActivity like so:
public class MainActivity extends Activity implements View.OnClickListener {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button =(Button)findViewById(R.id.button1);
button.setOnClickListener(this);
}
public void onClick(View v){
Toast toast = Toast.makeText(this, "Click Me", Toast.LENGTH_LONG);
toast.show();
}
}
Also, here is activity_main.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">
<Button
android:id="#+id/button1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/button1">
</Button>
</RelativeLayout>
UPDATE: findViewById now works fine after importing android.R. However, this created a new error when I call setContentView(R.layout.activity_main);
Okay a bit of background here. strings.xml is for defining pieces of text. For instance the text that might go on a button (but this does not define the button itself).
The button is going to have to be defined in a layout file in the res/layout/ directory. Yours is likely called activity_main.xml.
You'll need to create a button element in this file and assign the id to something descriptive. This kind of id is what findViewById is going to search on.
An example:
<Button
android:id="#+id/thebuttonsid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="96dp"
android:text="#string/button1" />
You can get a handle to this button like so:
Button button = (Button)findViewById(R.id.thebuttonsid);
Notice how I set the text to #string/button1? This is what the strings.xml file is for. However the layout files in the layout directory are where you define controls like buttons.
The button's ID name is same to the button's text name. You'd better change any one to other name.It must be work.
I would clean the project and build again. Or reimport the project. Eclipse is ... just hard to use. Try to use Android Studio.
When there is some "mismatch" with resources cleaning a project is a good advice. IN the past it was even more so.
Next what I would check if your resources compile as such. You might have an error somewhere in your resources, therefore the R does net get compiled and any reference to R.id.* is not valid.
If I get the error "android.content.res.Resources$NotFoundException: Resource ID #0x7f050007 type #0x12 is not valid" can I find some what this resource is if I know its ID?
ListView list = (ListView)findViewById(R.id.messages_list_view);
list.setAdapter(new ArrayAdapter<String>(context,
R.layout.messages_list, headers));
messages_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="#+id/messages_list_layout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<ListView android:id="#+id/messages_list_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
I Got this error when using ListView in a Fragment.
Resolved by moving the setAdapter lines to the onViewCreated function of the Fragment. (makes sense that before the view is created the ListView is invalid).
so you get :
public void onViewCreated(View view,Bundle savedInstanceState){
ListView list = (ListView) getView().findViewById(R.id.thelist);
list.setAdapter(mAdapter);
}
For those whom other mentioned solutions don't work.
I did this silly mistake:-
setContentView(R.id.something);
Instead of
setContentView(R.layout.something);
Corrected that, and error was gone :D
You can either use the search function in eclipse, search for "0x7f050007" or go to projectfolder/gen/path/R.java that contains your resources.
You'll find something like this:
public static final int lineItem=0x7f07001c;
Then search for(in this example) lineItem with Eclipses search function. It'll take you to your resource in code.
Check your imports (at the top of your class-file). Maybe you imported
android.R
(which provides access to the platform-resources) instead of
{your_package_name}.R
(you can also leave it blank).
I have the following code:
public class Level extends Activity{
public static String TAG="Level";
Level_Score_bar score_bar;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.level_layout);
score_bar=(Level_Score_bar) findViewById(R.id.Score_Bar);
Log.d(TAG,"score_bar="+score_bar);
}
}
The XML code looks like this (R.layout.level_layout) (Non-important stuff removed)
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="fill_parent" android:layout_width="fill_parent" android:orientation="vertical">
<pearsonartphoto.AJEG.Level_Score_bar android:id="#+id/Score_Bar" android:layout_height="wrap_content" android:layout_width="fill_parent">
</pearsonartphoto.AJEG.Level_Score_bar>
</LinearLayout>
The log statement reads "score_bar=null".As you can see, there is a resource named R.id.Score_Bar. Am I missing something? I need to use the function for some other stuff. Thanks!
There are a number of things that can cause this. The most common being that for one reason or another R.id was not generated correctly. Usually doing a simple 'clean' will fix this. If that doesn't work another thing to check would be the constructor for the custom view. You can find this and other suggestions from this question.
I am starting out on Android and trying to make a custom ListView layout. I've followed some guides and have made the following code:
public class CheckInList extends ListActivity {
...
#Override
public void onCreate(Bundle savedInstanceState) {
...
mAdapter = new ArrayAdapter<String>(this, R.layout.checkinlist_item, R.id.checkinlist_item_text, mNames);
setListAdapter(mAdapter);
...
}
}
This is the code for checkinlist_item.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#drawable/checkinlist_item_bg">
<TextView android:id="#+id/checkinlist_item_text"
style="#style/RegisterText" />
</RelativeView>
If I use android.R.layout.simple_list_item_1 instead of my above template then everything is fine and my ListView works, however whenever I use the above code my activity crashes. I am running things on Android 1.5.
Any ideas why things are crashing?
Could it be because RelativeView does not exist?
I might suggest adding the attributes android:layout_width="fill_parent" and android:layout_height="fill_parent" or set them to whatever you want, but those are required. And yes, use RelativeLayout as Matthew said, since RelativeView doesn't exist.
at first sight there is no width/height values for your textView ?