Android開發之Sqlite的使用

時間 2019-11-29

原文原文鏈接

在Android中存儲數據能夠用文件、數據庫、網絡，其中文件和數據庫是最經常使用的，數據庫咱們經常使用的就是Sqlite，它是一種經量級的、嵌入式的關係型數據庫；在android中當須要操做SQLite數據庫的時候須要獲得一個SQLiteOpenHelper對象，而SQLiteOpenHelper是一個抽象類，用戶須要繼承這個類html

package com.example.sqlite.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * DatabaseHelper做爲一個訪問SQLite的助手類，提供兩個方面的功能，
 * 第一，getReadableDatabase(),getWritableDatabase()能夠得到SQLiteDatabse對象，經過該對象能夠對數據庫進行操做
 * 第二，提供了onCreate()和onUpgrade()兩個回調函數，容許咱們在建立和升級數據庫時，進行本身的操做
 * @author Administrator
 *
 */
public class DatabaseHelper extends SQLiteOpenHelper{

	public static final int VERSION = 1;
	public DatabaseHelper(Context context, String name, CursorFactory factory,
			int version) {
		super(context, name, factory, version);
		// TODO Auto-generated constructor stub
	}
	public DatabaseHelper(Context context, String name){
		this(context, name, VERSION);
		Log.i("debug", "DatabaseHelper");
	}
	public DatabaseHelper(Context context, String name, int version){
		this(context, name, null, version);
	}
	
	
	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		Log.i("debug", "create a database");
		//執行SQL語句
		db.execSQL("create table user (id int, name varchar(20))");
	}
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		Log.i("debug", "Upgrade a database");
	}
}

下面是對數據庫的進行增、刪、改、查操做java

佈局文件android

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/create_db"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/create_db"/> 
    <Button
        android:id="@+id/update_db"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/update_db"/> 
    <Button
        android:id="@+id/insert"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/insert"/> 
    <Button 
        android:id="@+id/update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/update"/>
    <Button 
        android:id="@+id/query"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/query"/>
    <Button 
        android:id="@+id/delete"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/delete"/>

</LinearLayout>

在Activity處理代碼sql

package com.example.sqlite;

import com.example.sqlite.db.DatabaseHelper;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

/**
 * SQLite的建立、更新、修改、插入、查詢、刪除操做
 * @author Administrator
 *
 */
public class SqliteActivity extends Activity {

	private Button create_db;
	private Button update_db;   //更新數據庫的版本號
	private Button insert;
	private Button update;
	private Button query;
	private Button delete;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_sqlite);
		create_db = (Button)findViewById(R.id.create_db);
		update_db = (Button)findViewById(R.id.update_db);
		insert = (Button)findViewById(R.id.insert);
		update = (Button)findViewById(R.id.update);
		query = (Button)findViewById(R.id.query);
		delete = (Button)findViewById(R.id.delete);
		create_db.setOnClickListener(new CreateListener());
		update_db.setOnClickListener(new UpdateDBListener());
		insert.setOnClickListener(new InsertListener());
		update.setOnClickListener(new UpdateListener());
		query.setOnClickListener(new QueryListener());
		delete.setOnClickListener(new Deletelistener());
	}

	class CreateListener implements OnClickListener{

		@Override
		public void onClick(View arg0) {
			// TODO Auto-generated method stub
			Log.i("debug", "on create db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			//只有調用了DatabaseHelper的getReadableDatabase()或getWritableDatabase()纔會建立數據庫
			SQLiteDatabase db = dbHelper.getWritableDatabase();
		}
		
	}
	/**
	 * 更新數據庫的版本號
	 * @author Administrator
	 *
	 */
	class UpdateDBListener implements OnClickListener{

		@Override
		public void onClick(View arg0) {
			// TODO Auto-generated method stub
			Log.i("debug", "on update db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db", 2);
			SQLiteDatabase db = dbHelper.getReadableDatabase();
		}
		
	}
	
	class InsertListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "insert db");
			ContentValues values = new ContentValues();
			//向該對象插入鍵值對，其中鍵是列名，值是但願插入這一列的值，值的數據類型必須一致
			values.put("id", 1);
			values.put("name", "zhang");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			//調用insert方法插入數據
			db.insert("user", null, values);
		}
		
	}
	class UpdateListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "update db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			ContentValues values = new ContentValues();
			values.put("name", "zhangsanfeng");
			//第一個參數是要更新的表名
			//第二個參數是一個ContentValeus對象
			//第三個參數是where子句
			db.update("user", values, "id=?", new String[]{"1"});	
		}
		
	}
	class QueryListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "query db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getReadableDatabase();
			Cursor cursor = db.query("user", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);
			int count = cursor.getCount();
			System.out.println("query---count = >" + count);
			while(cursor.moveToNext()){
				String name = cursor.getString(cursor.getColumnIndex("name"));
				System.out.println("query--->" + name);
			}
		}
		
	}
	class Deletelistener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "delete db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			db.delete("user", "id=?", new String[]{"1"});
		}
		
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_sqlite, menu);
		return true;
	}

}

運行效果數據庫