SQLite数据库增删改查

例如：

SQLiteDatabase dbWrite = db.getWritableDatabase();

SQLiteDatabase详细的介绍可参照谷歌方法API： http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html

三：案例展示：

创建一个DB 类，继承 SQLiteOpenHelper，factory制定为空，版本指定为1,代码如下：

（注意：SQLite数据库需要为表创建一个主键，且规定主键的形式为“_id”命名）

 1 package activity.cyq.sqlitelearn;  2   3 import android.content.Context;  4 import android.database.sqlite.SQLiteDatabase;  5 import android.database.sqlite.SQLiteOpenHelper;  6   7   8 public class DB extends SQLiteOpenHelper {  9     public DB(Context context) { 10         super(context, "db", null, 1); 11         /*db:数据库名称  null:操作数据库工厂  1:数据库版本号*/ 12     } 13  14     @Override 15     public void onCreate(SQLiteDatabase db) { 16         db.execSQL("Create Table user( _id INTEGER PRIMARY KEY AUTOINCREMENT, username TEXT DEFAULT NONE , password TEXT DEFAULT NONE) "); 17     } 18  19     @Override 20     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 21  22     } 23 }

案例页面布局如下，通过添加数据按钮实现将用户名和密码添加如数据库中。

布局XML文件如下 ：activity_main.xml   itemview.xml

activity_main.xml如下：

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  2     xmlns:tools="http://schemas.android.com/tools"  3     android:layout_width="match_parent"  4     android:layout_height="match_parent"  5     android:orientation="vertical"  6     android:paddingBottom="@dimen/activity_vertical_margin"  7     android:paddingLeft="@dimen/activity_horizontal_margin"  8     android:paddingRight="@dimen/activity_horizontal_margin"  9     android:paddingTop="@dimen/activity_vertical_margin" 10     tools:context=".MainActivity"> 11  12     <LinearLayout 13         android:layout_width="match_parent" 14         android:layout_height="wrap_content" 15         android:orientation="horizontal"> 16  17         <TextView 18             android:layout_width="wrap_content" 19             android:layout_height="wrap_content" 20             android:layout_weight="1" 21             android:text="用户名：" /> 22  23         <EditText 24             android:id="@+id/usernameEdit" 25             android:layout_width="wrap_content" 26             android:layout_height="wrap_content" 27             android:layout_weight="6" /> 28  29         <TextView 30             android:layout_width="wrap_content" 31             android:layout_height="wrap_content" 32             android:layout_weight="1" 33             android:text="密码：" /> 34  35         <EditText 36             android:id="@+id/passwordEdit" 37             android:layout_width="wrap_content" 38             android:layout_height="wrap_content" 39             android:layout_weight="6" /> 40  41         <Button 42             android:id="@+id/addDataBtn" 43             android:layout_width="wrap_content" 44             android:layout_height="wrap_content" 45             android:layout_weight="1" 46             android:text="添加数据" /> 47  48     </LinearLayout> 49  50     <RelativeLayout 51         android:layout_width="match_parent" 52         android:layout_height="wrap_content"> 53  54         <LinearLayout 55             android:layout_width="match_parent" 56             android:layout_height="wrap_content" 57             android:layout_centerInParent="true"> 58  59             <TextView 60                 android:layout_width="match_parent" 61                 android:layout_height="wrap_content" 62                 android:layout_centerInParent="true" 63                 android:text="数据展示" 64                 android:textSize="20dp" /> 65         </LinearLayout> 66     </RelativeLayout> 67  68     <LinearLayout 69         android:layout_width="match_parent" 70         android:layout_height="wrap_content"> 71  72         <TextView 73             android:layout_width="wrap_content" 74             android:layout_height="wrap_content" 75             android:layout_weight="1" 76             android:text="用户名" 77             android:textSize="20dp" /> 78  79         <TextView 80             android:layout_width="wrap_content" 81             android:layout_height="wrap_content" 82             android:layout_weight="1" 83             android:text="密    码" 84             android:textSize="20dp" /> 85     </LinearLayout> 86  87     <ListView 88         android:id="@android:id/list" 89         android:layout_width="match_parent" 90         android:layout_height="wrap_content" 91         android:layout_weight="10" 92         android:background="@color/material_blue_grey_800"></ListView> 93  94  95 </LinearLayout>

itemview.xml：如下：

 1 <?xml version="1.0" encoding="utf-8"?>  2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  3     android:layout_width="match_parent"  4     android:layout_height="match_parent"  5     android:orientation="horizontal">  6   7     <TextView  8         android:id="@+id/usernameItem"  9         android:layout_width="wrap_content" 10         android:layout_height="wrap_content" 11         android:layout_weight="1" 12         android:text="username" 13         android:textSize="20dp" /> 14  15     <TextView 16         android:id="@+id/passwordItem" 17         android:layout_width="wrap_content" 18         android:layout_height="wrap_content" 19         android:layout_weight="1" 20         android:text="password" 21         android:textSize="20dp" /> 22  23  24 </LinearLayout>

MainActivity中代码如下：

 1 package activity.cyq.sqlitelearn;  2   3   4 import android.app.AlertDialog;  5 import android.app.ListActivity;  6 import android.content.ContentValues;  7 import android.content.DialogInterface;  8 import android.database.Cursor;  9 import android.database.sqlite.SQLiteDatabase; 10 import android.os.Bundle; 11 import android.view.View; 12 import android.widget.AdapterView; 13 import android.widget.Button; 14 import android.widget.EditText; 15 import android.widget.SimpleCursorAdapter; 16  17 public class MainActivity extends ListActivity implements View.OnClickListener, AdapterView.OnItemLongClickListener { 18  19     private EditText username; 20     private EditText password; 21     private Button addData; 22     private SQLiteDatabase dbWrite, dbRead; 23     private SimpleCursorAdapter adapter; 24     private DB db; 25  26  27     @Override 28     protected void onCreate(Bundle savedInstanceState) { 29         super.onCreate(savedInstanceState); 30         setContentView(R.layout.activity_main); 31  32         username = (EditText) findViewById(R.id.usernameEdit); 33         password = (EditText) findViewById(R.id.passwordEdit); 34         addData = (Button) findViewById(R.id.addDataBtn); 35         addData.setOnClickListener(this); 36         /*创建数据库*/ 37         db = new DB(MainActivity.this); 38         dbWrite = db.getWritableDatabase(); 39         dbRead = db.getReadableDatabase(); 40  41         adapter = new SimpleCursorAdapter(MainActivity.this, R.layout.itemview, null, new String[]{"username", "password"}, 42                 new int[]{R.id.usernameItem, R.id.passwordItem}); 43         setListAdapter(adapter); 44         refresh(); 45  46         getListView().setOnItemLongClickListener(this); 47  48     } 49  50     /*刷新ListView数据*/ 51     public void refresh() { 52         Cursor cursor = dbRead.query("user", null, null, null, null, null, null, null); 53         adapter.changeCursor(cursor); 54     } 55  56     /*添加数据点击事件*/ 57     @Override 58     public void onClick(View v) { 59         String usernameData = username.getText().toString(); 60         String passwordData = password.getText().toString(); 61         ContentValues values = new ContentValues(); 62         values.put("username", usernameData); 63         values.put("password", passwordData); 64         dbWrite.insert("user", null, values); 65         values.clear(); 66  67         refresh(); 68     } 69  70     /*编辑item按钮的点击事件*/ 71  72  73     /*ListViewItem的长按事件处理*/ 74     @Override 75     public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) { 76  77         new AlertDialog.Builder(MainActivity.this).setTitle("警告").setMessage("是否删除该数据").setIcon(R.drawable.delete) 78                 .setPositiveButton("是", new DialogInterface.OnClickListener() { 79                     @Override 80                     public void onClick(DialogInterface dialog, int which) { 81                         Cursor c = adapter.getCursor(); 82                         //  c.moveToPosition(position);/*????*/ 83                         int item_id = c.getInt(c.getColumnIndex("_id")); 84                         dbWrite.delete("user", "_id=?", new String[]{item_id + ""}); 85                         refresh(); 86                     } 87                 }).setNegativeButton("否", null) 88                 .show(); 89  90  91         return true; 92     } 93 }