ANDROID_MARS学习笔记_S01原始版_009_SQLite

Posted 2020-06-13

一、代码
1.xml
(1)activity_main.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:orientation="vertical"
 4     android:layout_width="fill_parent"
 5     android:layout_height="fill_parent"
 6     >
 7 <Button
 8     android:id="@+id/createDatabase"
 9     android:layout_width="fill_parent" 
10     android:layout_height="wrap_content" 
11     android:text="createDatabase"
12     />
13     
14 <Button
15     android:id="@+id/updateDatabase"
16     android:layout_width="fill_parent" 
17     android:layout_height="wrap_content" 
18     android:text="updateDatabase"
19     />
20 
21 <Button
22     android:id="@+id/insert"
23     android:layout_width="fill_parent" 
24     android:layout_height="wrap_content" 
25     android:text="insert"/>
26 <Button
27     android:id="@+id/update"
28     android:layout_width="fill_parent" 
29     android:layout_height="wrap_content" 
30     android:text="update"/>
31 <Button
32     android:id="@+id/query"
33     android:layout_width="fill_parent" 
34     android:layout_height="wrap_content" 
35     android:text="query"/>
36     
37 </LinearLayout>

 

2.java
(1)MainActivity.java

  1 package com.example.s01_original_e16_sqlite;
  2 
  3 import android.app.Activity;
  4 import android.content.ContentValues;
  5 import android.database.Cursor;
  6 import android.database.sqlite.SQLiteDatabase;
  7 import android.database.sqlite.SQLiteOpenHelper;
  8 import android.os.Bundle;
  9 import android.util.Log;
 10 import android.view.View;
 11 import android.view.View.OnClickListener;
 12 import android.widget.Button;
 13 
 14 public class MainActivity extends Activity {
 15 
 16     /** Called when the activity is first created. */
 17     private Button createButton;
 18     private Button insertButton;
 19     private Button updateButton;
 20     private Button updateRecordButton;
 21     private Button queryButton;
 22     @Override
 23     public void onCreate(Bundle savedInstanceState) {
 24         super.onCreate(savedInstanceState);
 25         setContentView(R.layout.activity_main);
 26         createButton = (Button)findViewById(R.id.createDatabase);
 27         updateButton = (Button)findViewById(R.id.updateDatabase);
 28         insertButton = (Button)findViewById(R.id.insert);
 29         updateRecordButton = (Button)findViewById(R.id.update);
 30         queryButton = (Button)findViewById(R.id.query);
 31         createButton.setOnClickListener(new CreateListener());
 32         updateButton.setOnClickListener(new UpdateListener());
 33         insertButton.setOnClickListener(new InsertListener());
 34         updateRecordButton.setOnClickListener(new UpdateRecordListener());
 35         queryButton.setOnClickListener(new QueryListener());
 36     }
 37     class CreateListener implements OnClickListener{
 38         @Override
 39         public void onClick(View v) {
 40             //创建一个DatabaseHelper对象
 41             DBHelper dbHelper = new DBHelper(MainActivity.this, "my_sqlite_db");
 42             //只有调用了DatabaseHelper对象的getReadableDatabase()方法，或者是getWritableDatabase()方法之后，才会创建，或打开一个数据库
 43             SQLiteDatabase db = dbHelper.getReadableDatabase();
 44         }
 45     }
 46     class UpdateListener implements OnClickListener{
 47 
 48         @Override
 49         public void onClick(View v) {
 50             DBHelper dbHelper = new DBHelper(MainActivity.this,"my_sqlite_db",2);
 51             SQLiteDatabase db = dbHelper.getReadableDatabase();
 52         }
 53         
 54     }
 55     class InsertListener implements OnClickListener{
 56 
 57         @Override
 58         public void onClick(View v) {
 59             //生成ContentValues对象
 60             ContentValues values = new ContentValues();
 61             //想该对象当中插入键值对，其中键是列名，值是希望插入到这一列的值，值必须和数据库当中的数据类型一致
 62             values.put("id", 1);
 63             values.put("name","zhangsan");
 64             DBHelper dbHelper = new DBHelper(MainActivity.this,"my_sqlite_db",2);
 65             SQLiteDatabase db = dbHelper.getWritableDatabase();
 66             //调用insert方法，就可以将数据插入到数据库当中
 67             db.insert("user", null, values);
 68         }
 69     }
 70     //更新操作就相当于执行SQL语句当中的update语句
 71     //UPDATE table_name SET XXCOL=XXX WHERE XXCOL=XX...
 72     class UpdateRecordListener implements OnClickListener{
 73 
 74         @Override
 75         public void onClick(View arg0) {
 76             // TODO Auto-generated method stub
 77             //得到一个可写的SQLiteDatabase对象
 78             DBHelper dbHelper = new DBHelper(MainActivity.this,"my_sqlite_db",2);
 79             SQLiteDatabase db = dbHelper.getWritableDatabase();
 80             ContentValues values = new ContentValues();
 81             values.put("name", "zhangsanfeng");
 82             //第一个参数是要更新的表名
 83             //第二个参数是一个ContentValeus对象
 84             //第三个参数是where子句
 85             db.update("user", values, "id=?", new String[]{"1"});
 86         }
 87     }
 88     class QueryListener implements OnClickListener{
 89 
 90         @Override
 91         public void onClick(View v) {
 92             System.out.println("aaa------------------");
 93             Log.d("myDebug", "myFirstDebugMsg");
 94             
 95             DBHelper dbHelper = new DBHelper(MainActivity.this,"my_sqlite_db",2);
 96             SQLiteDatabase db = dbHelper.getReadableDatabase();
 97             Cursor cursor = db.query("user", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);
 98             while(cursor.moveToNext()){
 99                 String name = cursor.getString(cursor.getColumnIndex("name"));
100                 System.out.println("query--->" + name);
101             }
102         }
103     }
104 
105 }

 

(2)DBHelper.java

 

 1 package com.example.s01_original_e16_sqlite;
 2 
 3 import android.content.Context;
 4 import android.database.sqlite.SQLiteDatabase;
 5 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 6 import android.database.sqlite.SQLiteOpenHelper;
 7 
 8 public class DBHelper extends SQLiteOpenHelper {
 9 
10     private static final int VERSION = 1;
11     //在SQLiteOepnHelper的子类当中，必须有该构造函数
12     public DBHelper(Context context, String name, CursorFactory factory,
13             int version) {
14         //必须通过super调用父类当中的构造函数
15         super(context, name, factory, version);
16         // TODO Auto-generated constructor stub
17     }
18     public DBHelper(Context context,String name){
19         this(context,name,VERSION);
20     }
21     public DBHelper(Context context,String name,int version){
22         this(context, name,null,version);
23     }
24 
25     //该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候，才会调用这个方法
26     @Override
27     public void onCreate(SQLiteDatabase db) {
28         // TODO Auto-generated method stub
29         System.out.println("create a Database");
30         //execSQL函数用于执行SQL语句
31         db.execSQL("create table user(id int,name varchar(20))");
32     }
33 
34     @Override
35     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
36         // TODO Auto-generated method stub
37         System.out.println("update a Database");
38     }
39 
40 }