Question

我想在点击按钮时在SQLite数据库中添加一些数据值在下面给出的代码中，我无法在单击侦听器的Button上访问构造函数（DatabaseHandler db = new DatabaseHandler（this）;）。如何通过单击Button？

将变量str1和str2的值输入数据库

package com.androidhive.androidsqlite;

import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;


public class AndroidSQLiteTutorialActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  final EditText editText = (EditText)findViewById(R.id.editText3); 
   final EditText editText2 = (EditText)findViewById(R.id.editText4); 
   Button button = (Button)findViewById(R.id.button1);
   button.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        String str1 = editText.getText().toString();
        String str2 = editText2.getText().toString();   


    }

 });

    DatabaseHandler db = new DatabaseHandler(this);


    /**
     * CRUD Operations
     * */
    // Inserting Contacts
    Log.d("Insert: ", "Inserting ..");
    db.addContact(new Contact(str1, str2));
    //db.addContact(new Contact(str2, "9199999999"));
    //db.addContact(new Contact("Tommy", "9522222222"));
    //db.addContact(new Contact("Karthik", "9533333333"));

    // Reading all contacts
    Log.d("Reading: ", "Reading all contacts..");
    List<Contact> contacts = db.getAllContacts();       

    for (Contact cn : contacts) {
        String log = "Id: "+cn.getID()+" ,Name: " + cn.getName() + " ,Phone: " + cn.getPhoneNumber();
            // Writing Contacts to log
    Log.d("Name: ", log);

    }



   }
}

在此类构造函数中定义

package com.androidhive.androidsqlite;

import java.util.ArrayList;
import java.util.List;

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

public class DatabaseHandler extends SQLiteOpenHelper {

// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "contactsManager";

// Contacts table name
private static final String TABLE_CONTACTS = "contacts";

// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PH_NO = "phone_number";

public DatabaseHandler(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
    String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
            + KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"
            + KEY_PH_NO + " TEXT" + ")";
    db.execSQL(CREATE_CONTACTS_TABLE);
}

// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);

    // Create tables again
    onCreate(db);
}

/**
 * All CRUD(Create, Read, Update, Delete) Operations
 */

// Adding new contact
void addContact(Contact contact) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_NAME, contact.getName()); // Contact Name
    values.put(KEY_PH_NO, contact.getPhoneNumber()); // Contact Phone

    // Inserting Row
    db.insert(TABLE_CONTACTS, null, values);
    db.close(); // Closing database connection
}

// Getting single contact
Contact getContact(int id) {
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
            KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null, null);
    if (cursor != null)
        cursor.moveToFirst();

    Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
            cursor.getString(1), cursor.getString(2));
    // return contact
    return contact;
}

// Getting All Contacts
public List<Contact> getAllContacts() {
    List<Contact> contactList = new ArrayList<Contact>();
    // Select All Query
    String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS;

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            Contact contact = new Contact();
            contact.setID(Integer.parseInt(cursor.getString(0)));
            contact.setName(cursor.getString(1));
            contact.setPhoneNumber(cursor.getString(2));
            // Adding contact to list
            contactList.add(contact);
        } while (cursor.moveToNext());
    }

    // return contact list
    return contactList;
}

// Updating single contact
public int updateContact(Contact contact) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_NAME, contact.getName());
    values.put(KEY_PH_NO, contact.getPhoneNumber());

    // updating row
    return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
            new String[] { String.valueOf(contact.getID()) });
}

// Deleting single contact
public void deleteContact(Contact contact) {
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(TABLE_CONTACTS, KEY_ID + " = ?",
            new String[] { String.valueOf(contact.getID()) });
    db.close();
}


// Getting contacts Count
public int getContactsCount() {
    String countQuery = "SELECT  * FROM " + TABLE_CONTACTS;
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(countQuery, null);
    cursor.close();

    // return count
    return cursor.getCount();
}

}

Answer 1

如果要在DatabaseHandler db的onClick方法中初始化OnClickListener实例，请使用DatabaseHandler而不是引用的AndroidSQLiteTutorialActivity.this将活动上下文传递给this类构造函数到onClick方法上下文。这样做：

   button.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
          // your code here..
       db = new DatabaseHandler(AndroidSQLiteTutorialActivity.this);
       // Insert str1 and str2 in db here
          Log.d("Insert: ", "Inserting ..");
       db.addContact(new Contact(str1, str2));
       //...your code here
    }
 });

建议而不是使用内联代码创建一个方法，将str1和str2作为参数，然后在单独的方法中执行所有插入相关的代码

如何在onClickListener下编码构造函数

1 个答案: