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對於我的軟件工程類，我們必須將SQLite數據庫合併到我們的應用程序項目中。通過活動傳遞對象（Android）
對於我們的應用程序，這個數據庫類必須可以從多個活動訪問。我已經把數據庫定義爲單，然後調用
DBInterface database = Database.getInstance(this)
設置一個變量來引用數據庫，以訪問每個必要的類它的方法和它的作品。但是，我們應該在代碼中使用依賴注入，我的教授特意告訴我們，應該可以從我們的數據庫類切換到我們在前一次迭代中使用的存根數據庫，只需更改一行代碼即可。
顯然，這意味着要改變以上
DBInterface database = StubDB.getInstance(this)
但是在做這個我還是不得不在每一個使用數據庫的方法活動的這種變化。
所以我的問題是這樣的：有沒有辦法在我們的init活動中初始化我的數據庫，然後在沒有上面的賦值代碼的情況下傳遞對每個必要活動的引用？
相關代碼
辛格爾頓數據庫類
public class RecipeDatabase extends Activity implements DBInterface {
private dbHelper Helper;
private static RecipeDatabase sInstance;
private static Context sContext;
public static synchronized RecipeDatabase getInstance(Context context){
if(sInstance == null){
sInstance = new RecipeDatabase(context.getApplicationContext());
}
return sInstance;
}
private RecipeDatabase(Context context){
Helper = new dbHelper(context);
sContext = context;
}
@Override
public void addRecipe(Recipe recipe)
{
String ingredients = recipe.ingredientString();
String directions = recipe.directionString();
SQLiteDatabase db = Helper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(Recipe.KEY_rID, recipe.getrID());
values.put(Recipe.KEY_mealtype, recipe.getMealType());
values.put(Recipe.KEY_mainingredient, recipe.getMainIngredient());
values.put(Recipe.KEY_description, recipe.getDescription());
values.put(Recipe.KEY_ingredients, ingredients);
values.put(Recipe.KEY_directions, directions);
values.put(Recipe.KEY_notes, recipe.getNotes());
values.put(Recipe.KEY_rating, recipe.getRating());
values.put(Recipe.KEY_cooktime, recipe.getCooktime());
db.insert(Recipe.TABLE, null, values);
db.close();
}
@Override
public void editRecipe(Recipe recipe)
{
SQLiteDatabase db = Helper.getWritableDatabase();
ContentValues values = new ContentValues();
String ingredients = recipe.ingredientString();
String directions = recipe.directionString();
values.put(Recipe.KEY_rID, recipe.getrID());
values.put(Recipe.KEY_mealtype, recipe.getMealType());
values.put(Recipe.KEY_mainingredient, recipe.getMainIngredient());
values.put(Recipe.KEY_description, recipe.getDescription());
values.put(Recipe.KEY_ingredients, ingredients);
values.put(Recipe.KEY_directions, directions);
values.put(Recipe.KEY_notes, recipe.getNotes());
values.put(Recipe.KEY_rating, recipe.getRating());
values.put(Recipe.KEY_cooktime, recipe.getCooktime());
db.update(Recipe.TABLE, values, Recipe.KEY_rID + " = ?", new String[]{String.valueOf(recipe.getrID())});
db.close();
}
@Override
public void deleteRecipe(Recipe recipe)
{
SQLiteDatabase db = Helper.getWritableDatabase();
db.delete(Recipe.TABLE, Recipe.KEY_rID + " = ", new String[]{String.valueOf(recipe.getrID())});
db.close();
}
public ArrayList<Recipe> getList()
{
ArrayList<Recipe> result = new ArrayList<>();
SQLiteDatabase db = Helper.getReadableDatabase();
String selectQuery = "SELECT " + Recipe.KEY_rID + ", " +
Recipe.KEY_name + ", " +
Recipe.KEY_mealtype + ", " +
Recipe.KEY_mainingredient + ", " +
Recipe.KEY_description + ", " +
Recipe.KEY_ingredients + ", " +
Recipe.KEY_directions + ", " +
Recipe.KEY_notes + ", " +
Recipe.KEY_rating + ", " +
Recipe.KEY_cooktime + " FROM " + Recipe.TABLE;
Cursor cursor = db.rawQuery(selectQuery, null);
if(cursor.moveToFirst()) {
do {
ArrayList<String> ingredients = new ArrayList<>(); // Temp Storage
ArrayList<String> directions = new ArrayList<>(); // Temp Storage
String tempIngredient = cursor.getString(cursor.getColumnIndex(Recipe.KEY_ingredients));
String[] temp = tempIngredient.split("- "); //Split up ingredients to individual strings
for(int x=0; x < temp.length; x++) {
ingredients.add(temp[x]);
}
String tempDirection = cursor.getString(cursor.getColumnIndex(Recipe.KEY_ingredients));
temp = tempDirection.split("- ");//split up directions into individual strings
for(int x=0; x < temp.length; x++) {
directions.add(temp[x]);
}
//Get Values for Recipe Object
int rID = cursor.getInt(cursor.getColumnIndex(Recipe.KEY_rID));
String name = cursor.getString(cursor.getColumnIndex(Recipe.KEY_name));
String mealType = cursor.getString(cursor.getColumnIndex(Recipe.KEY_mealtype));
String mainIngredient = cursor.getString(cursor.getColumnIndex(Recipe.KEY_mainingredient));
int rating = cursor.getInt(cursor.getColumnIndex(Recipe.KEY_rating));
String description = cursor.getString(cursor.getColumnIndex(Recipe.KEY_description));
int cooktime = cursor.getInt(cursor.getColumnIndex(Recipe.KEY_cooktime));
String notes = cursor.getString(cursor.getColumnIndex(Recipe.KEY_notes));
//Create new Recipe from Row
Recipe tempRecipe = new Recipe(rID, name, description, mealType, mainIngredient,
rating, cooktime, notes, ingredients, directions);
//Add the recipe to the ArrayList
result.add(tempRecipe);
}while (cursor.moveToNext());
}
//Return the populated ArrayList for use
return result;
}
}
初始化類
public class init extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_init);
//The code to change to switch from stub to database
DBInterface repository = RecipeDatabase.getInstance(this);
//DBInterface repository = new StubDB(this);
ArrayList<Recipe> recipes = repository.getList();
ArrayList<String> recipeDisplay = new ArrayList<>();
for(int i=0; i<recipes.size(); i++) {
recipeDisplay.add(recipes.get(i).getName());
}
ArrayAdapter<String> myArrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, recipeDisplay);
ListView lv = this.getListView();
lv.setAdapter(myArrayAdapter);
}
@Override
protected void onListItemClick(ListView l, View v, int pos, long id){
super.onListItemClick(l, v, pos, id);
Intent myIntent = new Intent(this, Details.class);
myIntent.putExtra("recipePosition", pos);
startActivity(myIntent);
}
public void shoppingListButton(View view){
startActivity(new Intent(this, ShoppingList.class));
}
public void addRecipeButton(View view){
Intent myIntent = new Intent(this, Edit.class);
myIntent.putExtra("editType", 1); // 1 corresponds to add recipe
startActivity(myIntent);
}
}
一個需要的DB方法活動課
public class Details extends ListActivity {
int recipePosition = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
//want to avoid this call
DBInterface repository = RecipeDatabase.getInstance(this);
recipePosition = getIntent().getIntExtra("recipePosition", 0);
Recipe clickedRecipe = repository.getList().get(recipePosition);
ArrayList<String> recipeDetails = new ArrayList<>();
recipeDetails.add(clickedRecipe.getName());
recipeDetails.add(clickedRecipe.getDescription());
recipeDetails.add("Ingredients:");
for(int i=0; i<clickedRecipe.getIngredients().size(); i++){
recipeDetails.add(clickedRecipe.getIngredients().get(i));
}
recipeDetails.add("Instructions:");
for(int i=0; i<clickedRecipe.getDirections().size(); i++){
recipeDetails.add(clickedRecipe.getDirections().get(i));
}
ArrayAdapter<String> myArrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, recipeDetails);
ListView lv = this.getListView();
lv.setAdapter(myArrayAdapter);
}
public void editButton(View view){
Intent myIntent = new Intent(this, Edit.class);
myIntent.putExtra("recipePosition", recipePosition);
myIntent.putExtra("editType", 2); // 2 corresponds to modify recipe
startActivity(myIntent);
}
}
數據庫助手類
public class dbHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "ROSE.db";
public dbHelper(Context context){
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db){
//Creates the Recipe Table which stores recipes
String CREATE_TABLE_RECIPES = "CREATE TABLE " + Recipe.TABLE +
"(" + Recipe.KEY_rID + " INTEGER PRIMARY KEY, " +
Recipe.KEY_name + " TEXT, " +
Recipe.KEY_mealtype + " TEXT, " +
Recipe.KEY_mainingredient + " TEXT, " +
Recipe.KEY_description + " TEXT, " +
Recipe.KEY_ingredients + " TEXT, " +
Recipe.KEY_directions + " TEXT, " +
Recipe.KEY_notes + " TEXT, " +
Recipe.KEY_rating + " INTEGER, " +
Recipe.KEY_cooktime + " INTEGER)";
db.execSQL(CREATE_TABLE_RECIPES);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
db.execSQL("DROP TABLE IF EXISTS recipes");
onCreate(db);
}
}
在Android中搜索應用程序類的使用 –