1
嘿，我只是希望有人能夠揭示這個代碼是如何工作的，更具體地說是simpleCursorAdapter。完整的程序是一個應用程序，它是一個待辦事項列表，它是一個非常簡單的教程，用戶可以使用遊標和加載器輸入數據或「筆記」並保存到sqlite數據庫。尋求一些洞察力，瞭解simpleCursorAdapter是如何工作的
所以我的問題是，有一個具體的方法，我很難掌握它是如何工作的，因此我無法操縱數據的顯示方式。我認爲問題在於我不明白適配器如何採用與顯示內容不同的佈局，並將其全部顯示在列表視圖中。
private void fillData() {
// Fields from the database (projection)
// Must include the _id column for the adapter to work
String[] from = new String[] { TodoTable.COLUMN_SUMMARY };
// Fields on the UI to which we map
int[] to = new int[] { R.id.label }; //I don't quite understand but I know it's just a value for the adapter
getLoaderManager().initLoader(0, null, this);
adapter = new SimpleCursorAdapter(this, R.layout.todo_row, null, from,
to, 0); /*This line specifically I don't understand how it is working.
R.layout.todo_row is a near blank xml, used when there are no "todos"
with no listviews. R.layout.todo_list has the listview's but when
assigned in the adapter it doesn't work.
setListAdapter(adapter);
}
總的來說，我試圖讓3個列表並排讀取數據庫中的數據，只是玩弄。如果有人能幫助我，那將非常感激，謝謝。
R.layout.todo_row
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<ImageView
android:id="@+id/icon"
android:layout_width="30dp"
android:layout_height="24dp"
android:layout_marginLeft="4dp"
android:layout_marginRight="8dp"
android:layout_marginTop="8dp"
android:src="@drawable/reminder" >
</ImageView>
<TextView
android:id="@+id/label"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="6dp"
android:lines="1"
android:text="@+id/TextView01"
android:textSize="24dp"
>
</TextView>
</LinearLayout>
和R.layout.todo_list
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@android:id/list"
android:layout_width="110dp"
android:layout_height="200dp" >
</ListView>
<ListView
android:id="@+id/listMiddle"
android:layout_width="110dp"
android:layout_height="200dp"
android:layout_toRightOf="@android:id/list" >
</ListView>
<ListView
android:id="@+id/listRight"
android:layout_width="110dp"
android:layout_height="200dp"
android:layout_toRightOf="@id/listMiddle" >
</ListView>
<TextView
android:id="@android:id/empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/no_todos" />
</RelativeLayout>
全班低於
package de.vogella.android.todos;
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;
import de.vogella.android.todos.contentprovider.MyTodoContentProvider;
import de.vogella.android.todos.database.TodoTable;
/*
* TodosOverviewActivity displays the existing todo items
* in a list
*
* You can create new ones via the ActionBar entry "Insert"
* You can delete existing ones via a long press on the item
*/
public class TodosOverviewActivity 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 Cursor cursor;
private SimpleCursorAdapter adapter;
private SimpleCursorAdapter middleAdapter;
private SimpleCursorAdapter rightAdapter;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.todo_list);
this.getListView().setDividerHeight(2);
fillData();
registerForContextMenu(getListView());
}
// Create the menu based on the XML defintion
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.listmenu, menu);
return true;
}
// Reaction to the menu selection
@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);
}
// Opens the second activity if an entry is clicked
@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() {
// Fields from the database (projection)
// Must include the _id column for the adapter to work
String[] from = new String[] { TodoTable.COLUMN_SUMMARY };
String[] middleId = new String[] { TodoTable.COLUMN_ID };
// Fields on the UI to which we map
int[] to = new int[] { R.id.label };
int[] two = new int[] { R.id.label };
getLoaderManager().initLoader(0, null, this);
adapter = new SimpleCursorAdapter(this, R.layout.todo_row, null, from,
to, 0);
middleAdapter = new SimpleCursorAdapter(this, R.layout.todo_row, null, middleId,
two, 0);
setListAdapter(adapter);
// setListAdapter(middleAdapter);
}
@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);
}
}
什麼是「near blank xml」？ – 2013-02-28 01:44:14