我正在嘗試學習Android開發。作爲一個學習項目,我正在創建一個「待辦事宜」應用程序。無法用sqlite數據庫中的數據填充列表視圖
我試圖來用我的表中的數據列表,這是我到目前爲止有:
ListCursorAdapter.java
package com.ryansmurphy.listado;
import android.content.Context;
import android.database.Cursor;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
/**
* Created by ryanmurphy on 24/02/15.
*/
public class ListCursorAdapter extends CursorAdapter {
public ListCursorAdapter(Context context, Cursor cursor) {
super(context, cursor, 0);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
return LayoutInflater.from(context).inflate(R.layout.item_todo, parent, false);
}
public void bindView(View view, Context context, Cursor cursor) {
// Find fields to populate in inflated template
TextView todo = (TextView) view.findViewById(R.id.todoText);
// Extract properties from cursor
String todoTextDB = cursor.getString(cursor.getColumnIndexOrThrow("todo"));
// Populate fields with extracted properties
todo.setText(todoTextDB);
}
}
我收到兩條錯誤的位置:
- 對
extends cursor
。我收到錯誤Cannot resolve symbol
。 - 對
super(context, cursor, 0);
。我收到錯誤Object() in Object cannot be applied to
。
DatabaseHelper.java
package com.ryansmurphy.listado;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* Created by ryanmurphy on 23/02/15.
*/
public class DatabaseHelper extends SQLiteOpenHelper {
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "listado";
// Table Name
private static final String TABLE_TODO = "todos";
// Column names
private static final String KEY_ID = "id";
private static final String KEY_TODO = "todo";
private static final String KEY_STATUS = "status";
private static final String KEY_CREATED_AT = "created_at";
// Table Create Statements
// Todo table create statement
private static final String CREATE_TABLE_TODO = "CREATE TABLE "
+ TABLE_TODO + "(" + KEY_ID + " INTEGER PRIMARY KEY," + KEY_TODO
+ " TEXT," + KEY_STATUS + " INTEGER," + KEY_CREATED_AT
+ " DATETIME" + ")";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// creating required table
db.execSQL(CREATE_TABLE_TODO);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// on upgrade drop older tables
db.execSQL("DROP TABLE IF EXISTS " + TABLE_TODO);
// create new tables
onCreate(db);
}
public void addRecord()
{
SQLiteDatabase database = getWritableDatabase();
ContentValues values = new ContentValues();
values.put("todo", "todo example");
values.put("status", "not completed");
database.insert("todos", null, values);
database.close();
}
public Cursor getAll()
{
SQLiteDatabase database = getReadableDatabase();
Cursor cursor = database.rawQuery("select * from todos",null);
return cursor;
}
}
現在我的列表視圖各行的xml: list_item.xml
<?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="match_parent">
<TextView
android:id="@+id/todoText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="24dp"
android:padding="6dp" />
</LinearLayout>
ActivityMain.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<TextView android:text="To Do List" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/title" />
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/listview"
android:layout_below="@id/title"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="42dp" />
</RelativeLayout>
MainActivity.Java
package com.ryansmurphy.listado;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView lvItems = (ListView) findViewById(R.id.listview);
// Setup cursor adapter using cursor from last step
DatabaseHelper db = new DatabaseHelper();
Cursor allRows = db.getAll();
ListCursorAdapter todoAdapter = new ListCursorAdapter(this, allRows);
//Attach cursor adapter to the ListView
lvItems.setAdapter(todoAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
if(id == R.id.addItem)
{
addItem();
}
return super.onOptionsItemSelected(item);
}
public void addItem()
{
Intent addItemIntent= new Intent(MainActivity.this, AddItem.class);
startActivity(addItemIntent);
}
}
我正在這裏有兩個誤區:
- 在
DatabaseHelper db = new DatabaseHelper();
。我收到錯誤DatabaseHelper(Context) in DatabaseHelper cannot be applied
。 - 對
lvItems.setAdapter(todoAdapter);
。我收到錯誤setAdapter(android.widget.ListAdapter) in ListView cannot be applied
。
上面我已經從google搜索和試圖嘗試。我從來沒有真正知道我從一開始就一直在做什麼,但我慢慢地選擇了這一點,並且想知道如果你們在得到這些之後能夠幫助我。謝謝
對於這行'DatabaseHelper db = new DatabaseHelper();'''MainActivity'',你應該傳遞'Context'對象。 'ActionBarActivity'是'Context'的一個子類,所以你可以將'this'作爲'Context'傳遞。 – 2015-02-24 16:13:17