如何创建新活动，我可以选择从数据库添加新项目？

Question

I have created database following this tutorial, and I have created one button in main activity which will take users to another activity where they would add some new items. But I don't know how would I do this with ArrayList because I want to add new items in ListView . I want something like this to have in my application. Any help would be appricieated.

Here's the code of DataBase :

    public class DatabaseHandler extends SQLiteOpenHelper {

    // All Static variables
    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "itemManager";

    // Contacts table name
    private static final String TABLE_ITEMS = "items";

    // Contacts Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_TITLE = "title";
    private static final String KEY_PRICE = "price";

    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_ITEMS_TABLE = "CREATE TABLE " + TABLE_ITEMS + "("
                + KEY_ID + " INTEGER PRIMARY KEY," + KEY_TITLE + " TEXT,"
                + KEY_PRICE + " TEXT" + ")";
        db.execSQL(CREATE_ITEMS_TABLE);
    }

    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_ITEMS);

        // Create tables again
        onCreate(db);
    }
    /**
     * All CRUD(Create, Read, Update, Delete) Operations
     */

    // Adding new item
    void addItem(Item item) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_TITLE, item.getTitle()); // Title Name
        values.put(KEY_PRICE, item.getPrice()); // Price

        // Inserting Row
        db.insert(TABLE_ITEMS, null, values);
        db.close(); // Closing database connection
    }

    // Getting item
    Item getItem(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_ITEMS, new String[] { KEY_ID,
                KEY_TITLE, KEY_PRICE }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Item item = new Item(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2));
        // return item
        return item;
    }

    // Getting All Items
    public List<Item> getAllItems() {
        List<Item> itemsList = new ArrayList<Item>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_ITEMS;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Item item = new Item();
                item.setID(Integer.parseInt(cursor.getString(0)));
                item.setTitle(cursor.getString(1));
                item.setPrice(cursor.getString(2));
                // Adding contact to list
                itemsList.add(item);
            } while (cursor.moveToNext());
        }

        // return items list
        return itemsList;
    }

    // Updating single item
    public int updateItem(Item item) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_TITLE, item.getTitle());
        values.put(KEY_PRICE, item.getPrice());

        // updating row
        return db.update(TABLE_ITEMS, values, KEY_ID + " = ?",
                new String[] { String.valueOf(item.getID()) });
    }

    // Deleting single item
    public void deleteItem(Item item) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_ITEMS, KEY_ID + " = ?",
                new String[] { String.valueOf(item.getID()) });
        db.close();
    }

    // Getting items Count
    public int getItemsCount() {
        String countQuery = "SELECT  * FROM " + TABLE_ITEMS;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();

        // return count
        return cursor.getCount();
    }

}    

and here is the code of MainActivity:

    public class MainActivity extends BaseActivity {

    Button addItem;
    private Toolbar toolbar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FrameLayout frameLayout = (FrameLayout)findViewById(R.id.frame_container);

         // inflate the custom activity layout
        LayoutInflater layoutInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View activityView = layoutInflater.inflate(R.layout.activity_main, null,false);

        frameLayout.addView(activityView);

        // Setting toolbar
        toolbar = (Toolbar) findViewById(R.id.app_bar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

        DatabaseHandler db = new DatabaseHandler(this);

        addItem = (Button) findViewById(R.id.button1);
        addItem.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, AddActivity.class);
                startActivity(intent);

            }
        });
    }
}

Here's my Main Activity layout:

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mainContent"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <include
        android:id="@+id/app_bar"
        layout="@layout/app_bar" />

    <Button
        android:id="@+id/button1"
        style="@style/MyCustomButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:text="@string/button" />

    <ListView
        android:id="@+id/list"
        android:layout_margin="5dp"
        android:layout_below="@+id/relativeLayout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/button1"
        android:layout_centerHorizontal="true"
        android:divider="@color/list_divider_row"
        android:dividerHeight="10.0sp"
        android:listSelector="@drawable/list_row_selector" >
    </ListView>

    <RelativeLayout
        android:id="@+id/relativeLayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/listView1"
        android:layout_alignRight="@+id/listView1"
        android:layout_below="@+id/app_bar"
        android:padding="10dp" >

        <TextView
            android:id="@+id/item_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="4dp"
            android:text="Items"
            android:textColor="#474747"
            android:textSize="16sp" />

        <TextView
            android:id="@+id/item_count"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="4dp"
            android:layout_toRightOf="@+id/item_text"
            android:text="(2)"
            android:textColor="#474747"
            android:textSize="14sp" />

        <TextView
            android:id="@+id/total_amount"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            android:text="Rs. 5700"
            android:textColor="#000000"
            android:textSize="20dp" />

    </RelativeLayout>

</RelativeLayout>

Answer 1

In a nutshell, you need to pass the "result" of adding an item back to the main activity. Then, if there was an item added, you should call your adapter to update the adapter data.

 // Your previous code       
addItem = (Button) findViewById(R.id.button1);
        addItem.setOnClickListener(new View.OnClickListener() {

            @Override 
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, AddActivity.class);
                startActivityForResult(intent, ADD_ITEM_REQ_CODE);

            } 
        }); 

// Then handle the result
public void onActivityResult(int reqCode, int resultCode, Intent data){
  if (reqCode == ADD_ITEM_REQ_CODE && resultCode == RESULT_OK){
    // get your ListView adapter and update data
    mListAdapter.notifyDataSetChanged();
  }
}

Your second activity, the one that adds an item should call setResult(RESULT_OK) when the item was added successfully and setResult(RESULT_CANCELLED) otherwise.

There some other things with your code, for instance, where do you populate your ListView? Normally, you would get the instance though a findViewById and set an adapter to that ListView, with the corresponding data.

Honestly, I think you should have a look to the tutorials again, specially these: http://developer.android.com/training/basics/intents/result.html http://developer.android.com/guide/topics/ui/layout/listview.html