Practice
In this
article I will show you how to work with files on the sd-card (saving and
loading). And as we expand the possible actions with our list by using the main
and context menu. The result of the program you can see in the screenshots,
below.
1. Save /
Load the list
To access
the SD-card uses the class Environment. This class provides access to
environment variables. We use the method getExternalStorageDirectory().GetAbsolutePath()
to get the path to the SD-card device.
In class
Utils add line:
// Directory on the SD-card where stores the list public static File cacheDir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/customlistview");
To save and
load list, use the following idea: save the object (ArrayList) wholly in the
binary. For correct operation the previous article, we have added an interface
Serializable for the class ToDoItem.
/**
* Save the list on the SD-card
*/
private synchronized void saveList() {
try {
File infoFile = new File(Utils.cacheDir, "cache");
infoFile.createNewFile();
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(infoFile));
out.writeObject(list);
out.close();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Load a list of SD-Card
*/
@SuppressWarnings("unchecked")
public boolean loadList() {
try {
Utils.cacheDir.mkdir();
File infoFile = new File(Utils.cacheDir, "cache");
infoFile.createNewFile();
ObjectInputStream in = new ObjectInputStream(new FileInputStream(infoFile));
list = (List<ToDoItem>) in.readObject();
in.close();
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
Make
changes to the existing algorithms:
In the
method onCreate() instead initList() will use loadList().
It is also
necessary to add saving a list on change status for element. This happens in
Handler.
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what)
{
...
case MSG_CHANGE_ITEM: // Do / not do case
ToDoItem item = list.get(msg.arg1);
item.setCheck(!item.isCheck());
Utils.sorting(list, 0);
saveList();
adapter.notifyDataSetChanged();
setCountPurchaseProduct();
break;
}
}
};
2. Development of the main menu
The main menu appears in the application when
you press the menu button on the device.
With our main menu application can perform the
following functions:
- Add an element;
- Remove all the elements;
- To mark all the elements;
- Remove marks from all the elements.
First, add all the string resources in the file
strings.xml.
<string name="menu_item_add">Add</string>
<string name="menu_item_remove">Remove</string>
<string name="menu_item_rename">Rename</string>
<string name="menu_item_remove_all">Remove all</string>
<string name="menu_item_check_all">Check all</string>
<string name="menu_item_uncheck_all">Remove all checks</string>
<string name="btn_yes">Yes</string>
<string name="btn_no">No</string>
<string name="msg_empty">The name can not be
empty</string>
Now,
designed layout for the menu. Need to create a directory menu in res folder. There
create a file menu.xml
Source code
(menu.xml):
<menu xmlns:android="http://schemas.android.com/apk/res/android"
>
<item
android:id="@+id/menu_item_add"
android:title="@string/menu_item_add"/>
<item
android:id="@+id/menu_item_remove_all"
android:title="@string/menu_item_remove_all"/>
<item
android:id="@+id/menu_item_check_all"
android:title="@string/menu_item_check_all"/>
<item
android:id="@+id/menu_item_uncheck_all"
android:title="@string/menu_item_uncheck_all"/>
</menu>
Now it is necessary to develop
methods that will be executed when selecting menu items.
- Add Item (showAddToDoItemDialog)
This method will create a dialog box
with an input field name. After you click "Yes" to the list to add a
new element.
/**
* Open dialog box to add an item
*/
private void showAddToDoItemDialog()
{
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle(getString(R.string.menu_item_add));
final Context context = this;
final EditText input = new EditText(this);
builder.setView(input);
builder.setPositiveButton(getString(R.string.btn_yes), new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int whichButton) {
String value = input.getText().toString();
if (value.equals(""))
Toast.makeText(context, getString(R.string.msg_empty), Toast.LENGTH_SHORT).show();
else
{
list.add(new ToDoItem(value, getIndexFromList() + 1));
Utils.sorting(list, 0);
saveList();
getHandler().sendEmptyMessage(MainActivity.MSG_UPDATE_ADAPTER);
}
}
});
builder.setNegativeButton(getString(R.string.btn_no), new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
return;
}
});
AlertDialog alert = builder.create();
alert.show();
}
- Remove all the elements (removeAll)
This method will be fully clear the
list.
/**
* Removing all items from the list
*/
private void removeAll() {
list.clear();
saveList();
getHandler().sendEmptyMessage(MainActivity.MSG_UPDATE_ADAPTER);
}
- Checking / unchecking all items (setCheckAll)
This method, depending on the
parameter sets / clears selection of each item in the list.
/**
* Do / not do all cases
*/
private void setCheckAll(boolean check)
{
Iterator<ToDoItem> it = list.iterator();
while (it.hasNext())
{
ToDoItem item = it.next();
item.setCheck(check);
}
Utils.sorting(list, 0);
saveList();
getHandler().sendEmptyMessage(MainActivity.MSG_UPDATE_ADAPTER);
}
- Get the last index in the list (getIndexFromList)
This method returns the last index
of in the list.
/**
* Get the last index in the list
*/
private int getIndexFromList()
{
int index = 0;
Iterator<ToDoItem> it = list.iterator();
while (it.hasNext())
{
ToDoItem item = it.next();
if (item.getIndex() > index)
index = item.getIndex();
}
return index;
}
Now add the
menu in Activity.
/**
* Creating the main menu
*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu, menu);
return true;
}
/**
* Processing clicking on an item of the main menu
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (id)
{
case R.id.menu_item_add: // Adding an item
showAddToDoItemDialog();
return true;
case R.id.menu_item_remove_all: // Removing all items
removeAll();
return true;
case R.id.menu_item_check_all: // Do all cases
setCheckAll(true);
return true;
case R.id.menu_item_uncheck_all: // Redo list to its original state
setCheckAll(false);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
3.
Development of the context menu
The context
menu for the ListView appears when you long press on an item. Registered by the
method registerForContextMenu(). The context menu of our application will be
able to perform the following functions:
- Delete the item;
- Rename the item.
First
developed a method for the context menu.
- Delete selected item (removeItem)
Removes the
specified item from the list. After removal of the list is re-indexed.
/**
* Removing all items from the list
*/
private void removeItem(int index) {
list.remove(index);
reindexList();
saveList();
getHandler().sendEmptyMessage(MainActivity.MSG_UPDATE_ADAPTER);
}
- Rename the selected item (showRenameDialog)
/**
* Open a dialog box to rename an item
*/
private void showRenameDialog(final int index)
{
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle(getString(R.string.menu_item_rename));
final Context context = this;
final EditText input = new EditText(this);
input.setText(list.get(index).getName());
builder.setView(input);
builder.setPositiveButton(getString(R.string.btn_yes), new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int whichButton) {
String value = input.getText().toString();
if (value.equals(""))
Toast.makeText(context, getString(R.string.msg_empty), Toast.LENGTH_SHORT).show();
else
{
list.get(index).setName(value);
saveList();
getHandler().sendEmptyMessage(MainActivity.MSG_UPDATE_ADAPTER);
}
}
});
builder.setNegativeButton(getString(R.string.btn_no), new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
return;
}
});
AlertDialog alert = builder.create();
alert.show();
}
- Reindexing list (reindexList)
This method
orders index in the list after removing an element.
/**
* Reallocate indexes for items in the list
*/
private void reindexList()
{
int index = 1;
Utils.sorting(list, 1);
Iterator<ToDoItem> it = list.iterator();
while (it.hasNext())
{
ToDoItem item = it.next();
item.setIndex(index);
index++;
}
Utils.sorting(list, 0);
}
Now let's
add a context menu in Activity.
Register
the menu to ListView in method onCreate():
registerForContextMenu(listview); // Register the context menu for ListView
Add methods
in Activity:
/**
* Creating context menu for ListView
*/
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
int index = ((AdapterView.AdapterContextMenuInfo)menuInfo).position;
if (index == list.size() + 1 || index == 0)
return;
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(0, MSG_REMOVE_ITEM, Menu.NONE, R.string.menu_item_remove);
menu.add(0, MSG_RENAME_ITEM, Menu.NONE, R.string.menu_item_rename);
}
/**
* Processing clicking on an item context menu
*/
@Override
public boolean onContextItemSelected(MenuItem item) {
super.onContextItemSelected(item);
AdapterView.AdapterContextMenuInfo menuInfo = (AdapterView.AdapterContextMenuInfo)item.getMenuInfo();
int index = menuInfo.position - 1;
switch (item.getItemId())
{
case MSG_REMOVE_ITEM: // Remove an item
removeItem(index);
return true;
case MSG_RENAME_ITEM: // Rename an item
showRenameDialog(index);
return true;
}
return false;
}
No comments:
Post a Comment