我在this教程之后创建了数据库，并且我在主要活动中创建了一个按钮，该按钮将用户带到另一个活动，在那里他们将添加一些新项目。但我不知道如何使用ArrayList执行此操作，因为我想在ListView中添加新项目。我希望在我的应用程序中有this之类的东西。任何帮助都会被贬低。
以下是DataBase的代码：
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();
}
}
，这是MainActivity的代码：
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);
}
});
}
}
这是我的主要活动布局：
<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>
答案 0 :(得分：0)
简而言之，您需要传递将项目添加回主要活动的“结果”。然后，如果添加了项目，则应调用适配器以更新适配器数据。
// 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();
}
}
您的第二项活动，即添加项目的活动，应在成功添加项目时调用setResult(RESULT_OK)，否则调用setResult(RESULT_CANCELLED)。
您的代码还有其他一些内容，例如，您在哪里填充ListView？通常，您可以通过findViewById获取实例，并使用相应的数据为该ListView设置适配器。
老实说，我认为你应该再看看这些教程，特别是这些： http://developer.android.com/training/basics/intents/result.html http://developer.android.com/guide/topics/ui/layout/listview.html