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通過AsyncTask從SQLite數據庫中檢索數據並顯示它

2016-09-21 60 views
0

所以我有這個程序在過去的幾周裏一直在使用SQLite數據庫來存儲由通過AsyncTask運行並存儲的用戶添加的食譜。食譜可以添加和刪除，但現在我必須使用AsyncTask來顯示在某些類別中輸入的食譜。例如，如果用戶添加「麪包」食譜，則在用戶點擊「麪包」按鈕時在主屏幕上顯示食譜。以下是我迄今爲止：通過AsyncTask從SQLite數據庫中檢索數據並顯示它

MyDBHandler.java：

package com.example.healthylife; 

import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.content.Context; 
import android.content.ContentValues; 
import android.database.Cursor; 


public class MyDBHandler extends SQLiteOpenHelper { 

private static final int DATABASE_VERSION = 1; 
private static final String DATABASE_NAME = "recipeDB.db"; 
private static final String TABLE_RECIPE = "recipe"; 

private static final String COLUMN_ID = "_id"; 
private static final String COLUMN_RECIPENAME = "_recipename"; 
private static final String COLUMN_CATEGORY = "_category"; 
private static final String COLUMN_INGREDIENTS = "_ingredients"; 
private static final String COLUMN_INSTRUCTIONS = "_instructions"; 

public MyDBHandler(Context context, String name, 
        SQLiteDatabase.CursorFactory factory, int version){ 
    super(context, DATABASE_NAME, factory, DATABASE_VERSION); 
} 

@Override 
public void onCreate(SQLiteDatabase db){ 
    String CREATE_RECIPE_TABLE = "CREATE TABLE " + TABLE_RECIPE + "(" + 
      COLUMN_ID + " INTEGER PRIMARY KEY," + COLUMN_RECIPENAME + " TEXT," + 
      COLUMN_CATEGORY + " TEXT," + COLUMN_INGREDIENTS + " TEXT," + 
      COLUMN_INSTRUCTIONS + " TEXT" + ")"; 
    db.execSQL(CREATE_RECIPE_TABLE); 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){ 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_RECIPE); 
    onCreate(db); 
} 

public void addRecipe(Recipe recipe){ 
    ContentValues values = new ContentValues(); 
    values.put(COLUMN_RECIPENAME, recipe.getRecipeName()); 
    values.put(COLUMN_CATEGORY, recipe.getCategory()); 
    values.put(COLUMN_INGREDIENTS, recipe.getIngredients()); 
    values.put(COLUMN_INSTRUCTIONS, recipe.getInstructions()); 

    SQLiteDatabase db = this.getWritableDatabase(); 
    db.insert(TABLE_RECIPE, null, values); 
    db.close(); 
} 

public Recipe findRecipe(String recipename){ 
    String query = "Select * FROM " + TABLE_RECIPE + "WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 

    SQLiteDatabase db = this.getWritableDatabase(); 

    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 

    if (cursor.moveToFirst()){ 
     cursor.moveToFirst(); 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     recipe.setRecipeName(cursor.getString(1)); 
     recipe.setCategory(cursor.getString(2)); 
     recipe.setIngredients(cursor.getString(3)); 
     recipe.setInstructions(cursor.getString(4)); 
     cursor.close(); 
    }else{ 
     recipe = null; 
    } 
    db.close(); 
    return recipe; 
} 

public boolean deleteRecipe(String recipename) { 
    boolean result = false; 

    String query = "Select * FROM " + TABLE_RECIPE + " WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 

    SQLiteDatabase db = this.getWritableDatabase(); 

    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 

    if (cursor.moveToFirst()) { 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     db.delete(TABLE_RECIPE, COLUMN_ID + " = ?", 
       new String[] { String.valueOf(recipe.getID()) }); 
     cursor.close(); 
     result = true; 
    } 
    db.close(); 
    return result; 
} 

public Recipe getBread(String recipename) { 
    SQLiteDatabase db = this.getWritableDatabase(); 

    String query = "Select * FROM " + TABLE_RECIPE + "WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 
    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 
    if (cursor != null) { 
     cursor.moveToFirst(); 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     recipe.setRecipeName(cursor.getString(1)); 
     recipe.setCategory(cursor.getString(2)); 
     recipe.setIngredients(cursor.getString(3)); 
     recipe.setInstructions(cursor.getString(4)); 
     cursor.close(); 
    }else{ 
     recipe = null; 
    } 
    db.close(); 
    return recipe; 
} 

public Recipe getFruit(String recipename) { 
    SQLiteDatabase db = this.getReadableDatabase(); 

    String query = "Select * FROM " + TABLE_RECIPE + "WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 
    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 
    if (cursor != null) { 
     cursor.moveToFirst(); 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     recipe.setRecipeName(cursor.getString(1)); 
     recipe.setCategory(cursor.getString(2)); 
     recipe.setIngredients(cursor.getString(3)); 
     recipe.setInstructions(cursor.getString(4)); 
     cursor.close(); 
    }else{ 
     recipe = null; 
    } 
    db.close(); 
    return recipe; 
} 

public Recipe getVeg(String recipename) { 
    SQLiteDatabase db = this.getReadableDatabase(); 

    String query = "Select * FROM " + TABLE_RECIPE + "WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 
    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 
    if (cursor != null) { 
     cursor.moveToFirst(); 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     recipe.setRecipeName(cursor.getString(1)); 
     recipe.setCategory(cursor.getString(2)); 
     recipe.setIngredients(cursor.getString(3)); 
     recipe.setInstructions(cursor.getString(4)); 
     cursor.close(); 
    }else{ 
     recipe = null; 
    } 
    db.close(); 
    return recipe; 
} 

public Recipe getSoup(String recipename) { 
    SQLiteDatabase db = this.getReadableDatabase(); 

    String query = "Select * FROM " + TABLE_RECIPE + "WHERE " + COLUMN_RECIPENAME + " = \"" + 
      recipename + "\""; 
    Cursor cursor = db.rawQuery(query, null); 

    Recipe recipe = new Recipe(); 
    if (cursor != null) { 
     cursor.moveToFirst(); 
     recipe.setID(Integer.parseInt(cursor.getString(0))); 
     recipe.setRecipeName(cursor.getString(1)); 
     recipe.setCategory(cursor.getString(2)); 
     recipe.setIngredients(cursor.getString(3)); 
     recipe.setInstructions(cursor.getString(4)); 
     cursor.close(); 
    }else{ 
     recipe = null; 
    } 
    db.close(); 
    return recipe; 
}

[Recipe.java有getter/setter方法]

的DatabaseActivity類使用添加和刪除的AsyncTask功能：

package com.example.healthylife; 



import android.os.AsyncTask; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.TextView; 


public class DatabaseActivity extends AppCompatActivity { 


TextView idView; 
EditText RecipeBox; 
EditText CategoryBox; 
EditText IngredientsBox; 
EditText InstructionsBox; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_database); 

    idView = (TextView) findViewById(R.id.Recipe_ID); 
    RecipeBox = (EditText) findViewById(R.id.edit_RecipeName); 
    CategoryBox = (EditText) findViewById(R.id.input_category); 
    IngredientsBox = (EditText) findViewById(R.id.edit_Ingredients); 
    InstructionsBox = (EditText) findViewById(R.id.edit_Instructions); 
} 

public void newRecipe (View view){ 

    AsyncTaskSave op = new AsyncTaskSave(); 
    op.execute(); 

} 

public void lookupRecipe (View view){ 
    MyDBHandler dbHandler = new MyDBHandler(this, null, null, 1); 

    Recipe recipe = dbHandler.findRecipe(RecipeBox.getText().toString()); 

    if (recipe != null){ 
     idView.setText(String.valueOf(recipe.getID())); 

     CategoryBox.setText(String.valueOf(recipe.getCategory())); 
     IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
     InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 
    }else { 
     idView.setText("No Match Found"); 
    } 
} 

public void removeRecipe (View view){ 

    AsyncTaskDelete task = new AsyncTaskDelete(); 
    task.execute(); 
} 

private class AsyncTaskSave extends AsyncTask <Object, Object, String> { 

    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (DatabaseActivity.this, null, null, 1); 
     Recipe recipe = new Recipe(); 
     dbHandler.addRecipe(recipe); 

     return null; 
    } 
    @Override 
    protected void onPostExecute(String result) { 
     Recipe recipe = new Recipe(); 
     RecipeBox.setText(String.valueOf(recipe.getRecipeName())); 
     CategoryBox.setText(String.valueOf(recipe.getCategory())); 
     IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
     InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 

     result = "Added Successfully"; 
     idView.setText(result); 
    } 
} 

private class AsyncTaskDelete extends AsyncTask<Object, String, String>{ 
    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (DatabaseActivity.this, null, null, 1); 
     dbHandler.deleteRecipe(null); 

     return null; 
    } 

    @Override 
    protected void onPostExecute(String result){ 

     if (result == null){ 
      idView.setText("Record Deleted"); 
      RecipeBox.setText(""); 
      CategoryBox.setText(""); 
      IngredientsBox.setText(""); 
      InstructionsBox.setText(""); 
     }else 
      idView.setText("No Match Found"); 
    } 
} 

}

的SyncActivity.java類應該顯示由DatabaseActivity類中添加的食譜，並呼籲他們在屏幕上時，我的主屏幕按鈕預ssed：

package com.example.healthylife; 

import android.os.AsyncTask; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.TextView; 

public class SyncActivity extends AppCompatActivity{ 

TextView idView; 
TextView RecipeBox; 
TextView CategoryBox; 
TextView IngredientsBox; 
TextView InstructionsBox; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_sync); 

    idView = (TextView) findViewById(R.id.Recipe_ID); 
    RecipeBox = (TextView) findViewById(R.id.edit_RecipeName); 
    CategoryBox = (TextView) findViewById(R.id.input_category); 
    IngredientsBox = (TextView) findViewById(R.id.edit_Ingredients); 
    InstructionsBox = (TextView) findViewById(R.id.edit_Instructions); 
} 

public void getBread (View view) { 

    AsyncTaskBread os = new AsyncTaskBread(); 
    os.execute(); 
} 

public void getFruit (View view){ 
    AsyncTaskFruit ob = new AsyncTaskFruit(); 
    ob.execute(); 
} 

public void getVeg (View view){ 
    AsyncTaskVeg ow = new AsyncTaskVeg(); 
    ow.execute(); 
} 

public void getSoup (View view){ 
    AsyncTaskSoup ox = new AsyncTaskSoup(); 
    ox.execute(); 
} 

private class AsyncTaskBread extends AsyncTask <Object, Object, String>{ 

    MyDBHandler dbHandler; 

    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1); 
     dbHandler.getBread("Bread"); 
     return "Bread"; 
    } 

    @Override 
    protected void onPostExecute(String result){ 
     Recipe recipe = dbHandler.getBread(CategoryBox.getText().toString()); 

     if(recipe != null){ 
      idView.setText(String.valueOf(recipe.getID())); 
      RecipeBox.setText(String.valueOf(recipe.getRecipeName())); 
      IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
      InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 
     }else { 
      result = "No Match Found"; 
      idView.setText(result); 
     } 
    } 
} 

private class AsyncTaskFruit extends AsyncTask <Object, Object, String>{ 

    MyDBHandler dbHandler; 

    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1); 
     dbHandler.getFruit("Fruit"); 
     return "Fruit"; 

    } 

    @Override 
    protected void onPostExecute(String result){ 
     Recipe recipe = dbHandler.getFruit(CategoryBox.getText().toString()); 

     if(recipe != null){ 
      idView.setText(String.valueOf(recipe.getID())); 
      RecipeBox.setText(String.valueOf(recipe.getRecipeName())); 
      IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
      InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 
     }else { 
      result = "No Match Found"; 
      idView.setText(result); 
     } 
    } 
} 

private class AsyncTaskVeg extends AsyncTask <Object, Object, String>{ 

    MyDBHandler dbHandler; 

    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1); 
     dbHandler.getVeg("Vegetables"); 
     return "Vegetables"; 

    } 

    @Override 
    protected void onPostExecute(String result){ 
     Recipe recipe = dbHandler.getVeg(CategoryBox.getText().toString()); 

     if(recipe != null){ 
      idView.setText(String.valueOf(recipe.getID())); 
      RecipeBox.setText(String.valueOf(recipe.getRecipeName())); 
      IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
      InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 
     }else { 
      result = "No Match Found"; 
      idView.setText(result); 
     } 
    } 
} 

private class AsyncTaskSoup extends AsyncTask <Object, Object, String>{ 

    MyDBHandler dbHandler; 

    @Override 
    protected String doInBackground(Object...objects){ 
     MyDBHandler dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1); 
     dbHandler.getSoup("Soup"); 
     return "Soup"; 

    } 

    @Override 
    protected void onPostExecute(String result){ 
     Recipe recipe = dbHandler.getSoup(CategoryBox.getText().toString()); 

     if(recipe != null){ 
      idView.setText(String.valueOf(recipe.getID())); 
      RecipeBox.setText(String.valueOf(recipe.getRecipeName())); 
      IngredientsBox.setText(String.valueOf(recipe.getIngredients())); 
      InstructionsBox.setText(String.valueOf(recipe.getInstructions())); 
     }else { 
      result = "No Match Found"; 
      idView.setText(result); 
     } 
    } 
} 
}

現在，這裏是主屏幕：

Home Screen in app

當食譜在食譜中添加後，點擊每個按鈕時，應顯示在某些領域，而是細節我字段爲空：

Recipe call when buttons are clicked

現在SyncActivity類應檢索在v數據庫中的數據庫已通過DatabaseActivity類輸入，但事實並非如此。在myDBHandler的代碼中是否需要更改某些內容？或者它在SyncActivity中？

來源

2016-09-21 Mateo

回答

0

問題是，例如類AsyncTaskBread中的私人對象dbHandler永遠不會被初始化。您在doInBackground中初始化dbHandler，但該對象只存在於該函數中。嘗試更改行MyDBHandler dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1);到dbHandler = new MyDBHandler (SyncActivity.this, null, null, 1);我還建議您將sql查詢從onPostExecute移動到doInBackground，因爲onPostExecute在UI（主）線程上運行。

來源

2016-09-21 23:30:01

+0

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