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();
}
}
