Android中SQLlite数据库的增删改查

public class MyHelper extends SQLiteOpenHelper {
    public MyHelper(Context context) {
        super(context, "itcast.db", null, 1);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
    //创建数据库
        db.execSQL("CREATE TABLE information(_id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR(20),  phone VARCHAR(20))");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

                SQLiteDatabase db;
                ContentValues values;
                //获取数据
                name=et_name.getText().toString().trim();
                phone=et_phone.getText().toString().trim();
                //添加数据对象
                values=new ContentValues();
                values.put("name",name);
                values.put("phone",phone);
                db=myHelper.getWritableDatabase();
                db.insert("information",null,values);//插入数据
                Toast.makeText(this,"添加成功",Toast.LENGTH_SHORT).show();//吐司
                db.close();

              SQLiteDatabase db;
             ContentValues values;
             db=myHelper.getReadableDatabase();
             Cursor cursor= db.query("information",null,null,null,null,null,null);//查询内容放入cuisor
             //输出数据
             //判断是否为空
             if (cursor.getColumnCount()==0){
                 Toast.makeText(this,"没有数据",Toast.LENGTH_SHORT).show();
             }else {
                 cursor.moveToFirst();//将指针移动到第一条数据
              tv_show.setText("name:"+cursor.getString(1)+"   tel:"+cursor.getString(cursor.getColumnIndex("phone")));
             }
             while (cursor.moveToNext()){
             //append为追加输出
                 tv_show.append("name:"+cursor.getString(1)+"   tel:"+cursor.getString(cursor.getColumnIndex("phone")));
             }

                SQLiteDatabase db;
                ContentValues values;
                db=myHelper.getWritableDatabase();
                values=new ContentValues();
                values.put("phone",et_phone.getText().toString().trim());
                db.update("information",values,"name=?",new String[]{et_name.getText().toString().trim()});
                Toast.makeText(this,"数据更新成功",Toast.LENGTH_SHORT).show();
                db.close();

                SQLiteDatabase db;
                ContentValues values;
                db=myHelper.getWritableDatabase();
                 db.delete("information","name=?",new String[]{et_name.getText().toString().trim()});
                Toast.makeText(this,"删除成功",Toast.LENGTH_SHORT).show();
                 db.close();