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Android: java.lang.ClassCastException [duplicate]

I am getting an error when trying to set my view to display the ListView for the file I want to display(text file). I am pretty sure it has something to do with the XML. I just want to display the information from this.file = fileop.ReadFileAsList("Installed_packages.txt");. My code:
public class Main extends Activity {
private TextView tv;
private FileOperations fileop;
private String[] file;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.fileop = new FileOperations();
this.file = fileop.ReadFileAsList("Installed_packages.txt");
setContentView(R.layout.main);
tv = (TextView) findViewById(R.id.TextView01);
ListView lv = new ListView(this);
lv.setTextFilterEnabled(true);
lv.setAdapter(new ArrayAdapter<String>(this, R.layout.list_item, this.file));
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// When clicked, show a toast with the TextView text
Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_SHORT).show();
}
});
setContentView(lv);
}
}
list_item.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"
android:padding="10dp"
android:textSize="16sp"
android:textColor="#000">
</LinearLayout>
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:weightSum="1">
<ScrollView
android:id="#+id/SCROLLER_ID"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fillViewport="true">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="5sp"
android:id="#+id/TextView01"
android:text="#string/hello"/>
</ScrollView>
</LinearLayout>

The ArrayAdapter requires the resource ID to be a TextView XML exception means you don't supply what the ArrayAdapter expects. When you use this constructor:
new ArrayAdapter<String>(this, R.layout.a_layout_file, this.file)
R.Layout.a_layout_file must be the id of a xml layout file containing only a TextView(the TextView can't be wrapped by another layout, like a LinearLayout, RelativeLayout etc!), something like this:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
// other attributes of the TextView
/>
If you want your list row layout to be something a little different then a simple TextView widget use this constructor:
new ArrayAdapter<String>(this, R.layout.a_layout_file,
R.id.the_id_of_a_textview_from_the_layout, this.file)
where you supply the id of a layout that can contain various views, but also must contain a TextView with and id(the third parameter) that you pass to your ArrayAdapter so it can know where to put the Strings in the row layout.

Soution is here
listitem.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/textview"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</TextView>
</LinearLayout>
Java code :
String[] countryArray = {"India", "Pakistan", "USA", "UK"};
ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.listitem,R.id.textview, countryArray);
ListView listView = (ListView) findViewById(R.id.listview);
listView.setAdapter(adapter);

If you are getting that message when you are extending an ArrayAdapter, you are getting that error because you have not provided the correct resource id to display the item. Call the super class in the constructor and pass in the resource id of the TextView:
//Pass in the resource id: R.id.text_view
SpinnerAdapter spinnerAddToListAdapter = new SpinnerAdapter(MyActivity.this,
R.id.text_view,
new ArrayList<>());
Adapter:
public class SpinnerAdapter extends ArrayAdapter<MyEntity> {
private Context context;
private List<MyEntity> values;
public SpinnerAdapter(Context context, int textViewResourceId,
List<MyEntity> values) {
//Pass in the resource id: R.id.text_view
super(context, textViewResourceId, values);
this.context = context;
this.values = values;
}

The problem is in the line:
lv.setAdapter(new ArrayAdapter<String>(this, R.layout.list_item, this.file));
Because when i change it to:
lv.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, this.file));
It works!

Android - Display Query's Result in an Activity

I have the result of a sql query expressed in this way :
//The column attributes of a result table
ArrayList<String> columns_attributes;
// This contains the data of every row of the result
ArrayList<ArrayList<String>> rows_data;
How can i dinamically display it on an activity ? Thanks

MainActivity
public class MainActivity extends AppCompatActivity {
List<String> list = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
list.add("Android");
list.add("iPhone");
list.add("Windows");
list.add("Blackberry");
list.add("Mac");
list.add("Laptop");
list.add("LCD");
list.add("Dell");
ArrayAdapter adapter = new ArrayAdapter<String>(MainActivity.this, R.layout.list_view_item, list);
ListView listView = (ListView) findViewById(R.id.mobile_list);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, "Clicked: " + list.get(position), Toast.LENGTH_SHORT).show();
}
});
listView.setAdapter(adapter);
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
tools:context="com.vzw.www.listviewalert.MainActivity">
<ListView
android:id="#+id/mobile_list"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</RelativeLayout>
list_view_item.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/label"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="10dip"
android:textSize="16dip"
android:textStyle="bold" >
</TextView>

You can iterate over these list with simple for loops like this:
// for columns
for (String colAttr : columns_attributes) {
// do something with the string value
}
// for rows
for (List<String> row : rows_data) {
for (String rowAttr : row) {
// do something with the string value
}
}

To display a dynamic amount of data, a ListView is recommended to do the job. If you just want to display those strings, you can use a ListActivity and assign a ArrayAdapter to that ListView with the setListAdapter() method.
You may want to check this tutorial to get this done.
http://androidexample.com/Create_Listview_With_ListActivity_-_Android_Example/index.php?view=article_discription&aid=66

Unfortunately, Listview has stopped working (android error)

I'm experiencing the problem "Unfortunately, your listview has stopped working" when i was using the android emulator to run my codes.
Please take a look at my codes thanks!
For activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<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"
android:orientation="vertical"
tools:context="com.example.it3783.listview.MainActivity">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Choose a location..."/>
<ListView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:drawSelectorOnTop="false"
android:id="#+id/spLocations"></ListView>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#+id/superHerosTV"
/>
</LinearLayout>
For MainActivity.java:
public class MainActivity extends AppCompatActivity {
ArrayAdapter<CharSequence>adapter;
TextView tvSelection;
ListView lvLocation;
String []strArray;
String []superHeros = {"1. Batman\n 2. SpiderMan", "1. Peter Pan\n2. Superman",
"1. IronMan\n2. Peter Pan", "1. SnowWhite \n2. Gingerbreadman"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter = new ArrayAdapter<CharSequence>(this, android.R.layout.simple_list_item_1, strArray);
tvSelection = (TextView) findViewById(R.id.superHerosTV);
lvLocation = (ListView) findViewById(R.id.spLocations);
Resources myRes = this.getResources();
strArray = myRes.getStringArray(R.array.locationArea);
lvLocation.setAdapter(adapter);
lvLocation.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String text = strArray[position];
tvSelection.setText(text);
}
});
adapter = ArrayAdapter.createFromResource(this, R.array.locationArea, android.R.layout.simple_list_item_1);
}
}
For strings.xml:
<resources>
<string name="app_name">ListView</string>
<string-array name="locationArea">
<item>North</item>
<item>South</item>
<item>East</item>
<item>West</item>
</string-array>
</resources>

adapter = new ArrayAdapter<CharSequence>(this,android.R.layout.simple_list_item_1, strArray);
This line in your onCreate methods takes the strArray, which is not initialized so its value is null.
Now when you set the adapter with null data to the listview, it crashes.

Displaying ListView on Android

How do I create a working ListView in Android?
I am not looking for you to just fix my code, but am looking for a simple working example of a ListView in Android so I can understand the process of creating one and working with it. But I have included my code so you can see where I am coming from and what I have been trying.
I have done the following and had no success:
--
Made a xml layout with only a TextView item in it:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/dir_text_view"
/>
Created the following class as per the instructions at the following tutorial:
http://www.vogella.com/tutorials/AndroidListView/article.html
public class DataTempleArrayAdapter extends ArrayAdapter<String> {
HashMap<String, Integer> mIdMap = new HashMap<String, Integer>();
public DataTempleArrayAdapter(Context context, int textViewResourceId,
List<String> objects) {
super(context, textViewResourceId, objects);
for (int i = 0; i < objects.size(); ++i) {
mIdMap.put(objects.get(i), i);
}
}
#Override
public long getItemId(int position) {
String item = getItem(position);
return mIdMap.get(item);
}
#Override
public boolean hasStableIds() {
return true;
}
}
And in the main activity I have a snippet of code where I attempt to add a list of strings to the ArrayList associated with the DataTempleArrayAdapter here:
int i;
for (i=0;i<dirContents.length;i++) {
dirList.add(dirContents[i]);
//Toast.makeText(this, dirList.get(i), Toast.LENGTH_SHORT).show();
}
adapter.notifyDataSetChanged();
dirList is successfully populated, while the adapter doesn't update the ListView at all.
--
Before you ask for it, here I am including the rest of the relevant code:
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="org.hacktivity.datatemple.MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="text"
android:hint="#string/directory"
android:ems="10"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:id="#+id/dirEditText" />
<Button
android:text="→"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:id="#+id/dirButton"
android:onClick="populateDirList" />
</LinearLayout>
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:id="#+id/dirListView" />
</LinearLayout>
</RelativeLayout>
And alas the MainActivity class:
public class MainActivity extends AppCompatActivity {
ListView dirListView;
EditText et;
DataTempleArrayAdapter adapter;
ArrayList<String> dirList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dirListView = (ListView) findViewById(R.id.dirListView);
et = (EditText) findViewById(R.id.dirEditText);
dirList = new ArrayList<String>();
dirListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(getApplicationContext(),
"Click ListItem Number " + position, Toast.LENGTH_LONG)
.show();
populateDirList(view);
}
});
ArrayList<String> dirList = new ArrayList<String>();
adapter = new DataTempleArrayAdapter(this,
R.id.dir_text_view, dirList);
dirListView.setAdapter(adapter);
}
public void populateDirList (View view) {
File f;
// NO INPUT.
if (et.getText().toString().equals("")) {
Toast.makeText(this, "empty string", Toast.LENGTH_SHORT).show();
return;
}
f = new File(et.getText().toString());
if (f == null) { return; }
String dirContents[] = f.list();
if (dirContents == null) { return; }
dirList = new ArrayList<String>(Arrays.asList(f.list()));
adapter.clear();
int i;
for (i=0;i<dirContents.length;i++) {
dirList.add(dirContents[i]);
//Toast.makeText(this, dirList.get(i), Toast.LENGTH_SHORT).show();
}
adapter.notifyDataSetChanged();
}
}

One of the best resources for understanding ListView is indeed the
one you mentioned from Vogella
Another cool resource to understand how the the
notifyDataSetChanged() method works in ListView this post from StackOverflow
For a short, simple explanation of how to use CustomLayouts in
ListView (without the ViewHolder pattern) check another of the best
references available: Mkyong
Discussing the benefits of the ViewHolder pattern in ListView:
check this StackOverflow post
Concise example and explanation of the ViewHolder pattern in
ListView: check this example from JavaCodeGeeks
And to fix your code I think the answer given before is only part of the problem:
You must indeed comment the line
//ArrayList<String> dirList = new ArrayList<String>();
because, like #F43nd1r mentioned this would also be a different instance of a list passed into the adapter
but there is more, when you do this:
dirList = new ArrayList<String>(Arrays.asList(f.list()));
you are instantiating a new, different, list, the old reference held by the adapter will NOT be changed... it will still hold the OLD object list
you should perhaps substitute it for something like:
dirList.clear();
dirList.addAll(Arrays.asList(f.list()));
Hope this helps!

Excerpt from your code:
#Override
protected void onCreate(Bundle savedInstanceState) {
//...
dirList = new ArrayList<String>();
//...
ArrayList<String> dirList = new ArrayList<String>();
adapter = new DataTempleArrayAdapter(this,
R.id.dir_text_view, dirList);
//...
}
I bet you already see what the problem is, but in case you don't: You have a field and a local variable with the same name. You pass the local variable to the adapter. It is only naturally that the adapter does not react to changes on the field, as it has no knowledge of its existence.

I think what you have done wrong is to supply a UI Component to the Array Adapter with:
adapter = new DataTempleArrayAdapter(this, R.id.dir_text_view, dirList);
The second item should not be an ID, but a layout file. Android have already implemented a List item layout with a textview that you can use: android.R.layout.simple_list_item_1.
so replace your row with
adapter = new DataTempleArrayAdapter(this, android.R.layout.simple_list_item_1, dirList);
and you are one step closer.
(This way you don't need your "xml layout with only a TextView item in it")

ListView won't populate (from file)

I am trying to populate a ListView from a .txt file but somehow fail to it.
The file read and is added to the ArrayList properly. I have tried the ArrayAdapter to the ArrayList and set it as the Adapter of the ListView under OnCreate() and call notifyDataSetChanged() after the list is updated.
I'm fairly new to java, I'm more used to (and prefer) C#
Here's parts of my code:
public class MainActivity extends ActionBarActivity{
ArrayAdapter<String> arrayAdapter = null;
ArrayList<String> arrayList = null;
ListView listView = null;
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
listView = (ListView) findViewById(R.id.lv_Run);
arrayList = new ArrayList<String>();
arrayList.clear();
arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);
listView.setAdapter(arrayAdapter);
}
//<...>
if (file.isFile() && file.getName().endsWith(".txt")){
Button btn = new Button(ll1.getContext());
btn.setText(file.getName().replace(".txt", ""));
btn.setTag(file.getName().replace(".txt", ""));
btn.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
String btnString = v.getTag().toString();
UpdateList(btnString);
}
});
btn.setLayoutParams(new TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT, TableLayout.LayoutParams.WRAP_CONTENT));
ll1.addView(btn);
}
//<...>
public void UpdateList(String btnString){
try{
File file = new File(runs.getAbsolutePath()+ File.separator + btnString + ".txt");
arrayList = getFileContent(file.getAbsolutePath());
arrayAdapter.notifyDataSetChanged();
catch (IOException e){
e.printStackTrace();
}
}
//<...>
public static ArrayList<String> getFileContent(String fileName) throws IOException{
ArrayList<String> result = new ArrayList<>();
File aFile = new File(fileName);
BufferedReader reader;
String aLine;
if (!aFile.isFile()){
return result;
}
try{
reader = new BufferedReader(new FileReader(aFile));
}
catch (FileNotFoundException e1){
e1.printStackTrace();
return result;
}
while ((aLine = reader.readLine()) != null){
result.add(aLine + "\n");
}
reader.close();
return result;
}
//<...>
<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="match_parent"
tools:context=".MainActivity"
android:background="#ff000000"
android:baselineAligned="false"
android:id="#+id/pan_MasterPan">
<LinearLayout android:orientation="vertical"
android:layout_weight="2.5"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:id="#+id/pan_Left">
<LinearLayout android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="top"
android:layout_weight="8"
android:id="#+id/pan_SelRun">
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/select_run"
android:id="#+id/btn_LoadRun"
android:clickable="true"
android:onClick="runSelectClick"/>
</LinearLayout>
<LinearLayout android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="bottom"
android:layout_weight="1"
android:focusableInTouchMode="false"
android:id="#+id/pan_RunPOI">
<ListView
android:id="#+id/lv_Run"
android:layout_width="match_parent"
android:layout_height="0dp"
android:visibility="visible"
android:layout_weight="1"
android:dividerHeight="1dp"
android:drawSelectorOnTop="true"
android:clickable="true"
android:choiceMode="singleChoice"
android:divider="#android:color/black"/>
</LinearLayout>
</LinearLayout>
<LinearLayout android:orientation="vertical"
android:layout_weight="1"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:background="#ff1A1A1A"
android:id="#+id/pan_Right">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/ForDebug"
android:text="#string/debugbtnstrg"
android:clickable="true"
android:onClick="ForDebug_OnClick"
android:longClickable="false"
android:textStyle="italic"/>
</LinearLayout>
</LinearLayout>
Two days I try this and that without any difference between every try...
Thanks a lot for you time, it's really appreciated.
---- Edit ----
Updated Code: (sorry to show only parts, this is part of a massive and messy code...)
public void UpdateList(String btnString){
try{
File file = new File(runs.getAbsolutePath()+ File.separator + btnString + ".txt");
arrayList = getFileContent(file.getAbsolutePath());
Toast.makeText(getApplicationContext(), "aL_Size: " + arrayList.size(), Toast.LENGTH_LONG).show();
//return 5
arrayAdapter.addAll(arrayList);
Toast.makeText(getApplicationContext(), "aA_Count: " + arrayAdapter.getCount(), Toast.LENGTH_LONG).show();
//return 5
arrayAdapter.notifyDataSetChanged();
catch (IOException e){
e.printStackTrace();
}
}
---- Edit 2 ----
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
listView = (ListView) findViewById(R.id.lv_Run);
arrayList = new ArrayList<String>();
arrayList.clear();
arrayList.add("TEST1");
arrayList.add("TEST2");
arrayList.add("TEST3");
arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);
listView.setAdapter(arrayAdapter);
}

Call ArrayAdapter.addAll method for adding new items in current adapter of ListView before calling notifyDataSetChanged :
arrayList = getFileContent(file.getAbsolutePath());
arrayAdapter.addAll(arrayList);
arrayAdapter.notifyDataSetChanged();