如何在我的数据库操作代码中实现ASyncTask

Question

我有一个Android Studio程序（使用Java），该程序可以从用户那里收集数据，然后允许他们a）按下“添加”按钮将该数据输入到表中，或者b）从表中删除该信息（如果按“删除”按钮。这并不令人惊奇，但是它是实践并且有效。问题是我要使这些操作在后台线程而不是UI线程中进行。

我似乎无法弄清楚该怎么做。我发现的所有建议解决方案要么都不适合我的情况，要么我尝试实现它们并失败了（或者它们没有用；我无法说出我当前的技能水平与众不同）。帮助将不胜感激。相关文件如下。 （请注意，我从此处的代码中删除了程序包名称，因为它们中包含我的真实姓名，但它们在实际文件中）。

DataEntryForm.java（这是我的“添加”和“删除”按钮及其onClick方法的位置）

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class DataEntryForm extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_data_entry_form);
    final Spinner spinner = findViewById(R.id.categorySelect);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, 
R.array.categories_Array, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);
    final DBAdapter db = new DBAdapter(this);
    db.open();
    final EditText recipeNameInput = findViewById(R.id.recipeNameInput);
    final Spinner categorySelect = findViewById(R.id.categorySelect);
    final EditText ingredientsInput = findViewById(R.id.ingredientsInput);
    final EditText instructionsInput = findViewById(R.id.instructionsInput);
    Button addBtn = findViewById(R.id.addBtn);
    Button deleteBtn = findViewById(R.id.deleteBtn);
    addBtn.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v) {
            new BackgroundThread().execute();
            String editRecipeName = recipeNameInput.getText().toString();
            String chooseCategory = categorySelect.getSelectedItem().toString();
            String editIngredients = ingredientsInput.getText().toString();
            String editInstructions = instructionsInput.getText().toString();
            db.insertRecipeChoice(editRecipeName, chooseCategory, editIngredients, editInstructions);
            Toast.makeText(DataEntryForm.this, "Recipe added!", Toast.LENGTH_LONG).show();

        }
    });

    deleteBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            new BackgroundThread().execute();
            if (db.deleteChoice(1))
                Toast.makeText(DataEntryForm.this, "Recipe deleted!", Toast.LENGTH_LONG).show();
            else
                Toast.makeText(DataEntryForm.this, "Recipe deletion failed!", 
               Toast.LENGTH_LONG).show();
        }
                                 }
    );


  }

}

请注意，我之前尝试进行此操作的其中之一是其中存在“ new BackgroundThread.execute（）”行。我暂时保留了它，以防万一这是正确的想法。我不希望它滑走。

DBAdapter.java

    import android.content.ContentValues;
    import android.content.Context;
    import android.database.SQLException;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.util.Log;
    import android.os.Bundle;
    import androidx.appcompat.app.AppCompatActivity;

   public class DBAdapter extends AppCompatActivity{
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.adapter_db);
}
static final String KEY_ROWID = "_id";
static final String KEY_RECIPENAME = "RecipeName";
static final String KEY_CATEGORY = "Category";
static final String KEY_INGREDIENTS = "Ingredients";
static final String KEY_INSTRUCTIONS = "Instructions";
static final String TAG = "DBAdapter";
static final String DATABASE_NAME = "MyDB";
static final String DATABASE_TABLE = "MyChoices";
static final int DATABASE_VERSION = 1;
static final String DATABASE_CREATE = "create table MyChoices (_id integer primary key autoincrement, " + "RecipeName text not null, category text not null, ingredients text not null, instructions text not null);";
final Context context;
DatabaseHelper DBHelper;
SQLiteDatabase db;
public DBAdapter(Context ctx) {
    this.context = ctx;
    DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper {
    DatabaseHelper(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        try {
            db.execSQL(DATABASE_CREATE);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data");
        db.execSQL("DROP TABLE IF EXISTS MyChoices");
        onCreate(db);
    }
}
//---opens the database----
public DBAdapter open() throws SQLException {
    db = DBHelper.getWritableDatabase();
    return this;
}
//---closes the database----
public void close() {
    DBHelper.close();
}
//---insert a recipe choice into the database---
public long insertRecipeChoice(String recipeName, String category, String ingredients, String instructions) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_RECIPENAME, recipeName);
    initialValues.put(KEY_CATEGORY, category);
    initialValues.put(KEY_INGREDIENTS, ingredients);
    initialValues.put(KEY_INSTRUCTIONS, instructions);
    return db.insert(DATABASE_TABLE, null, initialValues);
}
//---deletes a particular recipe choice---
public boolean deleteChoice(long rowId) {
    return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
}

BackgroundThread.java这基本上是空的，因为我迷路了，想弄清楚是否需要这个单独的类，如果需要，我应该在这里放什么。

 import android.content.Context;
 import android.os.AsyncTask;

 public class BackgroundThread extends AsyncTask<Void, Void, Void> {

@Override
protected Void doInBackground(Void... voids) {
    return null;
}

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);
 }

}

[请让我知道是否需要其他任何内容来获得此问题的答案，但我认为这些是相关的文件。其他所有内容都不会影响或影响表或数据。

Answer 1

所以这就是异步任务的工作方式