#arrayadapter

original source : https://youtu.be/I5ztEeRHFMc

original source : https://www.caveofprogramming.com/guest-posts/simple-listview-using-arrayadapter.html

Simple listView using ArrayAdapter

GridView layout is used to display data in two dimensional grid. It is a subclass of AdapterView. You can bind data from an external source to the GridView only by using an Adapter. Adapter acts as a bridge between the UI components and data source. It simply retrieves and fills the data to the UI components like gridview, listview or spinner.

Attributes:

1) numColumns: defines the number of columns to be displayed in a grid. You can assign a value "auto_fit" which displays as many columns as possible to fill the available space.

2) columnWidth:  It specifies the fixed width for each column.

3) gravity: It specifies the gravity/ alignment within each cell.

4) stretchMode: You can specify certain values for this attribute as shown below

none: stretching is disabled

spacingWidth: The spacing between each column is stretched.

columnWidth: Each column is stretched equally.

spacingWidthUniform: The spacing between each column is uniformly stretched.

5) padding: It adds space between content and border i.e. padding top, bottom, right and left.

6) margin: It adds space between border and its parent layout. Like padding, adds space on top, bottom, left and right.

7) horizontalSpacing: It adds space between cells in each row or say spacing between each column (horizontally). This could be in px, dp, sp, in or mm.

8) verticalSpacing: It adds space between cells in each column or say spacing between each row (vertically). This could be in px, dp, sp, in or mm.

9) scrollbars: It defines which scrollbar should be displayed on scrolling or not. i.e. horizontal or vertical or none.

10) background: It sets a drawable background or specific background color for the view.

 You can get or set the values of each attribute at runtime. Some of the get and set methods have been defined as follows:

 Get  Methods

public  int getNumColumns()

public  int getColumnWidth()

public  int getGravity()

public  int getHorizontalSapcing()

public  int getVerticalSpacing()

public  int getStretchMode()

public  ListAdapter getAdapter()

Set  Methods

public  void setNumColumns(int numColumns)

public  void setColumnWidth(int columnWidth)

public  int getGravity(int Gravity)

public  int getHorizontalSapcing(int horizontalSpacing)

public  int getVerticalSpacing(int verticalSpacing)

public  int getStretchMode(int stretchMode)

public  ListAdapter getAdapter(ListAdapter adapter)

 To load String array using ArrayAdapter:

· ArrayAdapter fits in between an ArrayList (data source) and the GridView (visual representation) and configures two aspects: (i) Which array to use as the data source for the grid; (ii) How to convert any given item in the array into a corresponding View object.

·ArrayAdapter arr = new ArrayAdapter(Context c, int Resource, String[] objects);

where,

Context  defines the activity instance.

Resource  defines the XML layout to be used.

objects  defines the array of data.

 Example:

gridview_layout.xml

<?xml version="1.0" encoding="utf-8"?> <GridView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:id="@+id/lGridSimple"    android:numColumns="auto_fit"    android:columnWidth="100dp"    android:gravity="center"    android:stretchMode="columnWidth"> </GridView>

Gridview_code.java

public class GridView_code extends Activity {

   GridView grid_alpha;    static final String[] numbers = new String[]{            "A", "B", "C", "D","E",            "F", "G", "H", "I", "J", "K",            "L","M","N","O", "P",            "Q", "R", "S", "T", "U",            "V", "W", "X", "Y", "Z"    };      @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.gridview_layout);        grid_alpha = (GridView) findViewById(R.id.lGridSimple);        ArrayAdapter<String> adapter = new ArrayAdapter<String> (this,   android .R.layout.simple_list_item_1, numbers);        grid_alpha.setAdapter(adapter);

    grid_alpha.setOnItemClickListener(new AdapterView.OnItemClickListener () {     @Override

   public void onItemClick(AdapterView<?> parent, View view, int position, long id) {    Toast.makeText(getApplicationContext(),"You have pressed " + ((TextView) view).getText(), Toast.LENGTH_SHORT).show();      }   }); } }

 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    package="com.example.admin.androidstuff" >    <application        android:allowBackup="true"        android:label="@string/app_name"

AndroidのListViewでは独自のAdapterを作ってListViewにセットすることができます。 今回、独自のAdapterを作ってその中からあるアイコンをタップした時に別画面へ遷移させる方法がわからなかったので調べてみました。

(more…)

This is kind of an old post actually, but I finally got around to finishing it today.

I've spent a good amount of time looking over how to do ListViews recently, and the associated ArrayAdapter that goes with. 

Turns out there are 2 real ways to get the nice scrolly list in you app. The first is to use the ListActivity, which actually has the ListView built in to the activity, so long as you create a layout with a ListView element with id of "@id/android:list". The second way is to add the ListView using findViewById, and setting the appropriate parameters for it. 

Either way about it, in order for the list to be any sort of useful, we must give it an adapter, typically an ArrayAdapter, although there are quite a few other kinds, all with a list of items that make up your list. The adapter is responsible for creating the row view at each position. This is why I used the constructor signature ArrayAdapter(Context context, int resourceId, List<T> objects), with the resourceId being the layout id of the individual rows in the list. This is also used later on in the adapter's getView(int position, View convertView, ViewGroup parent) function (actually does not have very good documentation), which actually does the inflating of the individual row item views of the list. This function can actually be kind of tricky, tricky enough that Google actually dedicated an entire session to it at Google I/O 2010, which I attended as well. The gist of it really comes down to the fact that the convertView parameter can be re-used, so your code should only inflate new item views in cases where there is no view to re-use. 

As a result, I figure most code that does this will look something like this:

https://gist.github.com/593218

From this point on, you are now free to populate the view variable with your information. 

If your layout is relative, make sure you pass in parent to the inflater, as your layout may require the parent in order to be laid out correctly.

Now that the adapter is set to generate the correct view, we need to attach data to it. This is typically done by associating an ArrayList of row objects with the adapter, which will then sort out the rest. All you have to do is add items to the ArrayList associated with the adapter, and tell it that the data has changed, using the ArrayAdapter.notifyDataSetChanged() function. Now the only thing left to do is associate the ArrayAdapter with the ListView, which is a simple call to ListView.setAdapter(Adapter). For ListActivity, use ListActivity.setListAdapter(Adapter) instead. 

Lastly, I want to point out that I personally don't like ListActivity much, since the full range of ListView functionality isn't exposed through it. There's nothing stopping you from finding the ListView by using the getListView() function and manually operating on it, which completely defeats the point of using ListActivity anyway. 

The built in ArrayAdapter assumes that you have a list of objects where obj.toString() is to populate each row of a ListView.

Well what happens when your object contains multiple fields that you want to populate various views within your ListView.

You then need to subclass that built-in ArrayAdapter - this link covers the details