【发布时间】：2021-09-28 03:18:47
【问题描述】：
我正在尝试为我的应用程序实现数据库。这是我第一次这样做。 我有一个带有列表视图的布局，我使用 SimpleCoursorAdapter 将数据从数据库传输到我的 ListView。该应用程序没有显示任何内容。 ListView 是空的，我不知道为什么。
这是我的 TopLevelActivity
public class TopLevelActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_top_level);
AdapterView.OnItemClickListener itemClickListener =
new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> listView,
View v,
int position,
long id) {
if(position == 0){
Intent intent = new Intent(TopLevelActivity.this, DrinkCategoryActivity.class);
startActivity(intent);
}
if(position == 1){
Intent intent = new Intent(TopLevelActivity.this, SnacksCategoryActivity.class);
startActivity(intent);
}
}
};
ListView listView = (ListView) findViewById(R.id.list_options);
listView.setOnItemClickListener(itemClickListener);
}
}
来自TopLevelActivity的xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".TopLevelActivity">
<ImageView
android:layout_width="200dp"
android:layout_height="100dp"
android:src="@drawable/starbuzz_logo"
android:contentDescription="@string/starbuzz_logo"/>
<ListView
android:id="@+id/list_options"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="@array/options"/>
</LinearLayout>
我认为这里的 DrinkCategoryActivity 有些错误
public class DrinkCategoryActivity extends Activity {
private SQLiteDatabase db;
private Cursor cursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_drink_category);
ListView listDrinks = (ListView) findViewById(R.id.list_drinks);
SQLiteOpenHelper coffeinaDatabaseHelper = new CoffeinaDatabaseHelper(this);
try {
db = coffeinaDatabaseHelper.getReadableDatabase();
cursor = db.query("DRINK",
new String[]{"_id", "NAME"},
null, null, null, null, null);
SimpleCursorAdapter listAdapter = new SimpleCursorAdapter
(this,
android.R.layout.simple_list_item_1,
cursor,
new String[]{"NAME"},
new int[]{android.R.id.text1},0
);
listDrinks.setAdapter(listAdapter);
} catch (SQLiteException e) {
Toast toast = Toast.makeText(this, "Baza danych jest niedostepna",
Toast.LENGTH_SHORT);
toast.show();
}
AdapterView.OnItemClickListener itemClickListener =
new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> listDrinks,
View itemView,
int position,
long id) {
Intent intent = new Intent(DrinkCategoryActivity.this,
DrinkActivity.class);
intent.putExtra(DrinkActivity.EXTRA_DRINKID, (int) id);
startActivity(intent);
}
};
listDrinks.setOnItemClickListener(itemClickListener);
}
public void onDestroy() {
super.onDestroy();
cursor.close();
db.close();
}
}
来自 DrinkCategoryActivity 的xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:orientation="vertical"
android:layout_height="match_parent"
tools:context=".DrinkCategoryActivity">
<ListView
android:id="@+id/list_drinks"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
饮酒活动
public class DrinkActivity extends AppCompatActivity {
public static final String EXTRA_DRINKID = "drinkId";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_drink);
int drinkId = (Integer)getIntent().getExtras().get(EXTRA_DRINKID);
SQLiteOpenHelper starbuzzDatabaseHelper = new CoffeinaDatabaseHelper(this);
try{
SQLiteDatabase db = starbuzzDatabaseHelper.getReadableDatabase();
Cursor cursor = db.query("DRINK",
new String[]{"NAME", "DESCRIPTION", "IMAGE_RESORUCE_ID"},
"_id = ?",
new String[]{Integer.toString(drinkId)},
null, null, null);
if(cursor.moveToFirst()){
String nameText = cursor.getString(0);
String descriptionText = cursor.getString(1);
int photoId = cursor.getInt(2);
TextView name = (TextView)findViewById(R.id.name);
name.setText(nameText);
TextView description = (TextView)findViewById(R.id.description);
description.setText(descriptionText);
ImageView photo = (ImageView)findViewById(R.id.latte);
photo.setImageResource(photoId);
photo.setContentDescription(nameText);
}
cursor.close();
db.close();
}catch (SQLiteException e){
Toast toast = Toast.makeText(this, "Bada danych jest niedostepna",
Toast.LENGTH_SHORT);
toast.show();
}
}
}
来自 DrinkActivity 的xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".DrinkActivity">
<ImageView
android:id="@+id/latte"
android:layout_width="190dp"
android:layout_height="190dp"/>
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView
android:id="@+id/description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
我的 DataBaseHelper 和这里也可能有些错误。 复杂器没有显示任何错误。
package com.hfad.coffeina;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class CoffeinaDatabaseHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "coffeina";
private static final int DB_VERSION = 2;
CoffeinaDatabaseHelper(Context context){
super(context, DB_NAME, null, DB_VERSION);
}
public void onCreate(SQLiteDatabase db){
updateMyDatabase(db, 0, DB_VERSION);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
updateMyDatabase(db, oldVersion, newVersion);
}
private static void insertDrink(SQLiteDatabase db, String name, String description,
int resourceId){
ContentValues drinkValues = new ContentValues();
drinkValues.put("NAME", name);
drinkValues.put("DESCRIPTION", description);
drinkValues.put("IMAGE_RESOURCE_ID", resourceId);
db.insert("DRINK", null, drinkValues);
}
private void updateMyDatabase(SQLiteDatabase db, int oldVersion, int newVersion){
if(oldVersion < 1){
db.execSQL("CREATE TABLE DRINK (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
+"NAME TEXT, "
+"DESCRIPTON TEXT , "
+"IMAGE_RESOURCE_ID INTEGER);");
insertDrink(db, "Latte", "Czarne espresso z gorącym mlekiem i mleczną pianką.",
R.drawable.latte);
insertDrink(db, "Cappucciono", "Czarne espresso z dużą ilościa spienionego mleka",
R.drawable.cappuccino);
insertDrink(db, "Espresso", "Czarna kawa ze świeżo mielonych ziaren najwyższej jakości.",
R.drawable.filter);
}
if(oldVersion < 2){
db.execSQL("ALTER TABLE DRINK ADD COLUMN FAVORITE NUMERIC;");
}
}
}
来自模拟器enter image description here的打印屏幕
【问题讨论】：
标签： java android database sqlite listview