Android 第三章 SQLite 資料庫
阿新 • • 發佈：2018-12-11
1，使用execSQL API 操作資料庫。 步驟1，建立Class MyOpenHelper實現介面SQLiteOpenHelper，複寫建構函式、onCreate、onUpgrade方法； 步驟2，在建立MyOpenHelper物件myOpenHelper後，使用 myOpenHelper 相關API進行操作資料庫。
package com.xiaohui.createdb; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class MyOpenHelper extends SQLiteOpenHelper { public MyOpenHelper(Context context) { super(context,"xiaohui2.db", null, 1); } /** * 當第一次建立庫的時候執行 * Called when the database is created for the first time */ @Override public void onCreate(SQLiteDatabase db) { String sql = "create table user(_id integer primary key autoincrement,name varchar(20),phone varchar(12))"; db.execSQL(sql); } /** * 當資料庫版本升級的時候呼叫 */ @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub // System.out.println("onUpgrade。。。"); // String sql = "alter table user add phone varchar(20)"; // db.execSQL(sql ); } }
package com.xiaohui.createdb; import android.app.Activity; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.View; import android.widget.EditText; import android.widget.TextView; public class MainActivity extends Activity { private MyOpenHelper myOpenHelper; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); myOpenHelper = new MyOpenHelper(getApplicationContext()); } public void insert(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); EditText etPhone = (EditText)findViewById(R.id.et_phone); wdb.execSQL("insert into user(name,phone) values(?,?)", new Object[]{etName.getText().toString(),etPhone.getText().toString()}); wdb.close(); } public void delete(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); wdb.execSQL("delete from user where name=?", new Object[]{etName.getText().toString()}); wdb.close(); } public void update(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); EditText etPhone = (EditText)findViewById(R.id.et_phone); wdb.execSQL("update user set phone=? where name=?", new Object[]{etPhone.getText().toString(),etName.getText().toString()}); wdb.close(); } public void select(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); Cursor cursor = wdb.rawQuery("select * from user", null); String list = ""; if(cursor != null && cursor.getCount() > 0){ while (cursor.moveToNext()) { String id = cursor.getString(cursor.getColumnIndex("_id")); int i = cursor.getColumnIndex("name"); String name = cursor.getString(i); String phone = cursor.getString(cursor.getColumnIndex("phone")); list += "{id="+id+",name="+name+",phone="+phone+"},"; } } TextView tVlist = (TextView)findViewById(R.id.tv_list); tVlist.setText(list); } }
2，使用AndroidAPI操作資料庫。 步驟同上面，所使用Android自帶相關API
package com.xiaohui.createdb; import com.xiaohui.createdb4API.R; import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.View; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity { private MyOpenHelper myOpenHelper; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); myOpenHelper = new MyOpenHelper(getApplicationContext()); } public void insert(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); EditText etPhone = (EditText)findViewById(R.id.et_phone); // wdb.execSQL("insert into user(name,phone) values(?,?)", new Object[]{etName.getText().toString(),etPhone.getText().toString()}); ContentValues values = new ContentValues(); values.put("name", etName.getText().toString()); values.put("phone", etPhone.getText().toString()); long insert = wdb.insert("user", null, values ); wdb.close(); if(insert>0){ Toast.makeText(getApplicationContext(), "新增成功", 1).show(); }else{ Toast.makeText(getApplicationContext(), "新增失敗", 1).show(); } } public void delete(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); // wdb.execSQL("delete from user where name=?", new Object[]{etName.getText().toString()}); int delete = wdb.delete("user", "name=?", new String[]{etName.getText().toString()}); wdb.close(); Toast.makeText(getApplicationContext(), "刪除了"+delete+"條", 1).show(); } public void update(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); EditText etName = (EditText)findViewById(R.id.et_name); EditText etPhone = (EditText)findViewById(R.id.et_phone); // wdb.execSQL("update user set phone=? where name=?", new Object[]{etPhone.getText().toString(),etName.getText().toString()}); ContentValues values = new ContentValues(); values.put("phone", etPhone.getText().toString()); int update = wdb.update("user", values , "name=?", new String[]{etName.getText().toString()}); wdb.close(); Toast.makeText(getApplicationContext(), "修改了"+update+"條", 1).show(); } public void select(View v){ SQLiteDatabase wdb = myOpenHelper.getWritableDatabase(); // Cursor cursor = wdb.rawQuery("select * from user", null); EditText etName = (EditText)findViewById(R.id.et_name); Cursor cursor = wdb.query("user", null,"name != ?", new String[]{etName.getText().toString()}, null, null, null); String list = ""; if(cursor != null && cursor.getCount() > 0){ while (cursor.moveToNext()) { String id = cursor.getString(cursor.getColumnIndex("_id")); int i = cursor.getColumnIndex("name"); String name = cursor.getString(i); String phone = cursor.getString(cursor.getColumnIndex("phone")); list += "{id="+id+",name="+name+",phone="+phone+"},"; } } TextView tVlist = (TextView)findViewById(R.id.tv_list); tVlist.setText(list); } }
3，SQLite資料庫事務控制 文件中標準的格式描述如下
Here is the standard idiom for transactions:
db.beginTransaction();
try {
...
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}
package com.xiaohui.transation;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class MyDBHelper extends SQLiteOpenHelper {
public MyDBHelper(Context context) {
super(context, "Account.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table account(idCard carchar(20),name varchar(20),money varchar(15))");
db.execSQL("insert into account(idCard,name,money) values(?,?,?)",new String[]{"111","張三","2000"});
db.execSQL("insert into account(idCard,name,money) values(?,?,?)",new String[]{"222","李四","3000"});
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
package com.xiaohui.transation;
import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends Activity {
SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MyDBHelper dbHelper = new MyDBHelper(getApplicationContext());
db = dbHelper.getReadableDatabase();
}
public void trans(View v) {
db.beginTransaction();
try {
db.execSQL("update account set money=money-100 where idCard=?",new String[]{"1111"});
if(Math.random()*10 > 5){
throw new Exception();
}
db.execSQL("update account set money=money+100 where idCard=?",new String[]{"2222"});
db.setTransactionSuccessful();
Toast.makeText(getApplicationContext(), "轉賬成功", 1).show();
}catch(Exception e){
Toast.makeText(getApplicationContext(), "轉賬失敗", 1).show();
} finally {
db.endTransaction();
}
}
}
4，使用命令列檢視資料
在class配置了Android的SDK環境後使用相關命令：adb shell;sqlite3;以及標準SQL進行資料庫操作。
