Loader Example in Android

package com.example.loaders;
 
import android.annotation.SuppressLint;
import android.app.ListActivity;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Intent;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
 
@SuppressLint("NewApi")
public class MainActivity extends ListActivity implements
        LoaderManager.LoaderCallbacks<Cursor> {
    private static final int ACTIVITY_CREATE = 0;
    private static final int ACTIVITY_EDIT = 1;
    private static final int DELETE_ID = Menu.FIRST + 1;
    private SimpleCursorAdapter adapter;
 
        @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.todo_list);
        this.getListView().setDividerHeight(2);
        fillData();
        registerForContextMenu(getListView());
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.insert:
            createTodo();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
 
    @Override
    public boolean onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case DELETE_ID:
            AdapterContextMenuInfo info = (AdapterContextMenuInfo) item
                    .getMenuInfo();
            Uri uri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/"
                    + info.id);
            getContentResolver().delete(uri, null, null);
            fillData();
            return true;
        }
        return super.onContextItemSelected(item);
    }
 
    private void createTodo() {
        Intent i = new Intent(this, TodoDetailActivity.class);
        startActivity(i);
    }
 
    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Intent i = new Intent(this, TodoDetailActivity.class);
        Uri todoUri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);
 
        startActivity(i);
    }
 
    private void fillData() {
        String[] from = new String[] { TodoTable.COLUMN_SUMMARY };
        int[] to = new int[] { R.id.label };
 
        getLoaderManager().initLoader(0, null, this);
        adapter = new SimpleCursorAdapter(this, R.layout.todo_row, null, from,
                to, 0);
 
        setListAdapter(adapter);
    }
 
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
            ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        menu.add(0, DELETE_ID, 0, R.string.menu_delete);
    }
 
    // Creates a new loader after the initLoader () call
    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        String[] projection = { TodoTable.COLUMN_ID, TodoTable.COLUMN_SUMMARY };
        CursorLoader cursorLoader = new CursorLoader(this,
                MyTodoContentProvider.CONTENT_URI, projection, null, null, null);
        return cursorLoader;
    }
 
    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        adapter.swapCursor(data);
    }
 
    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        // data is not available anymore, delete reference
        adapter.swapCursor(null);
    }
 
}

package com.example.loaders;
 
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
 
public class TodoDetailActivity extends Activity {
    private Spinner mCategory;
    private EditText mTitleText;
    private EditText mBodyText;
 
    private Uri todoUri;
 
    @Override
    protected void onCreate(Bundle bundle) {
        super.onCreate(bundle);
        setContentView(R.layout.todo_edit);
 
        mCategory = (Spinner) findViewById(R.id.category);
        mTitleText = (EditText) findViewById(R.id.todo_edit_summary);
        mBodyText = (EditText) findViewById(R.id.todo_edit_description);
        Button confirmButton = (Button) findViewById(R.id.todo_edit_button);
 
        Bundle extras = getIntent().getExtras();
 
        // Check from the saved Instance
        todoUri = (bundle == null) ? null : (Uri) bundle
                .getParcelable(MyTodoContentProvider.CONTENT_ITEM_TYPE);
 
        // Or passed from the other activity
        if (extras != null) {
            todoUri = extras
                    .getParcelable(MyTodoContentProvider.CONTENT_ITEM_TYPE);
 
            fillData(todoUri);
        }
 
        confirmButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                if (TextUtils.isEmpty(mTitleText.getText().toString())) {
                    makeToast();
                } else {
                    setResult(RESULT_OK);
                    finish();
                }
            }
 
        });
    }
 
    private void fillData(Uri uri) {
        String[] projection = { TodoTable.COLUMN_SUMMARY,
                TodoTable.COLUMN_DESCRIPTION, TodoTable.COLUMN_CATEGORY };
        Cursor cursor = getContentResolver().query(uri, projection, null, null,
                null);
        if (cursor != null) {
            cursor.moveToFirst();
            String category = cursor.getString(cursor
                    .getColumnIndexOrThrow(TodoTable.COLUMN_CATEGORY));
 
            for (int i = 0; i < mCategory.getCount(); i++) {
 
                String s = (String) mCategory.getItemAtPosition(i);
                if (s.equalsIgnoreCase(category)) {
                    mCategory.setSelection(i);
                }
            }
 
            mTitleText.setText(cursor.getString(cursor
                    .getColumnIndexOrThrow(TodoTable.COLUMN_SUMMARY)));
            mBodyText.setText(cursor.getString(cursor
                    .getColumnIndexOrThrow(TodoTable.COLUMN_DESCRIPTION)));
 
            // Always close the cursor
            cursor.close();
        }
    }
 
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        saveState();
        outState.putParcelable(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);
    }
 
    @Override
    protected void onPause() {
        super.onPause();
        saveState();
    }
 
    private void saveState() {
        String category = (String) mCategory.getSelectedItem();
        String summary = mTitleText.getText().toString();
        String description = mBodyText.getText().toString();
 
 
        if (description.length() == 0 && summary.length() == 0) {
            return;
        }
 
        ContentValues values = new ContentValues();
        values.put(TodoTable.COLUMN_CATEGORY, category);
        values.put(TodoTable.COLUMN_SUMMARY, summary);
        values.put(TodoTable.COLUMN_DESCRIPTION, description);
 
        if (todoUri == null) {
            // New todo
            todoUri = getContentResolver().insert(
                    MyTodoContentProvider.CONTENT_URI, values);
        } else {
            // Update todo
            getContentResolver().update(todoUri, values, null, null);
        }
    }
 
    private void makeToast() {
        Toast.makeText(TodoDetailActivity.this, "Please maintain a summary",
                Toast.LENGTH_LONG).show();
    }
}

package com.example.loaders;
 
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
 
public class TodoTable {
 
    // Database table
    public static final String TABLE_TODO = "todo";
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_CATEGORY = "category";
    public static final String COLUMN_SUMMARY = "summary";
    public static final String COLUMN_DESCRIPTION = "description";
 
    // Database creation SQL statement
    private static final String DATABASE_CREATE = "create table " + TABLE_TODO
            + "(" + COLUMN_ID + " integer primary key autoincrement, "
            + COLUMN_CATEGORY + " text not null, " + COLUMN_SUMMARY
            + " text not null," + COLUMN_DESCRIPTION + " text not null" + ");";
 
    public static void onCreate(SQLiteDatabase database) {
        database.execSQL(DATABASE_CREATE);
    }
 
    public static void onUpgrade(SQLiteDatabase database, int oldVersion,
            int newVersion) {
        Log.w(TodoTable.class.getName(), "Upgrading database from version "
                + oldVersion + " to " + newVersion
                + ", which will destroy all old data");
        database.execSQL("DROP TABLE IF EXISTS " + TABLE_TODO);
        onCreate(database);
    }
}