SQLite数据库
这次的作业是完成以下任务：
1）将学生信息存入数据库；
2）显示所有学生信息列表；
3）删除数据库表中第一条信息。
布局代码xml如下：
<EditText
android:id="@+id/edit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/add"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="增加新纪录"
android:textSize="18dp"/>
<Button
android:id="@+id/delete"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2"
android:text="删除第一条记录"
android:textSize="18dp"/>
</LinearLayout>
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:choiceMode="singleChoice"
android:listSelector="#ffaa00"
android:layout_weight="1"
android:layout_height="0dp" />
</LinearLayout>
获取数据，封装相关信息：
public class Student implements Serializable {
private int _id;
private String name;
public Student(){
}
public Student(String name){
this.name=name;
}
public int get_id() {
return _id;
}
public void set_id(int _id) {
this._id = _id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
打开或创建数据库：
studentdao
public class StudentDAO {
private Context context;
private MyDBHelper helper;
private SQLiteDatabase db;
public StudentDAO(Context context) {
helper = new MyDBHelper(context);
}
public void insert(Student student){
db = helper.getWritableDatabase();
// 第一种方法
// 2. 生成数据集合
ContentValues values = new ContentValues();
values.put("name", student.getName());
// 3. 执行语句
db.insert("student", null, values);
}
public Cursor selectAll() {
db = helper.getReadableDatabase();
Cursor cursor = db.query("student",null,null,null,null,null,null);
return cursor;
}
public void delete(int id){
db = helper.getWritableDatabase();
//根据数据的id号来删除数据
db.delete("student","_id=?",new String[]{String.valueOf(id)});
}
}
mydhbhelper
public class MyDBHelper extends SQLiteOpenHelper {
//student表创建语句，字段包括：关键字id，姓名name，班级classmte，年龄age
private String sql="create table student(_id integer primary key autoincrement,"
+"name text not null ,classmate text not null,age integer)";
public MyDBHelper(Context context) {
super(context,"studentInfo",null,1);
}
//当app中没有数据库或数据库的版本为1的时候会被调用，且调用一次
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(sql);
}
//升级数据库表，当newVersion>oldVersion，会被调用
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists stdent");
onCreate(db);
}
}
MyCursorAdapter
public class MyCursorAdapter extends CursorAdapter {
psuper(context, cursor,0);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup viewGroup) {
return LayoutInflater.from(context).inflate(R.layout.activity_main,viewGroup,false);
}
//给item的每个主键赋值
@Override
public void bindView(View view, Context context, Cursor cursor) {
TextView name=(TextView)view.findViewById(R.id.et_name);
name.setText(cursor.getString(cursor.getColumnIndex("name")));
}
}
MainActivity中实现数据库表中第一条信息的删除：
MainActivity
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private ListView studentList;
private Button btnzj;
private Button btnsc;
private EditText etname;
private MyCursorAdapter adapter;
private StudentDAO studentDao;
private Student student;
private Cursor cursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
studentList = (ListView) findViewById(R.id.list_view);
etname=(EditText)findViewById(R.id.et_name);
btnzj = (Button) findViewById(R.id.btn_zj);
btnzj.setOnClickListener(this);
btnsc = (Button) findViewById(R.id.btn_sc);
btnsc.setOnClickListener(this);
// 创建Adapter:CursorAdpater
studentDao = new StudentDAO(this);
if(cursor != null) {
adapter = new MyCursorAdapter(this, cursor);
studentList.setAdapter(adapter);
}
// ListView的item点击事件
studentList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
Cursor cursor = (Cursor) adapterView.getItemAtPosition(i);
if(cursor != null) {
cursor.moveToPosition(i);
student = new Student();
student.setName(cursor.getString(cursor.getColumnIndex("name")));
}
}
});
}
public void onClick(View view) {
switch (view.getId()) {
case R.id.btn_zj:
String name = etname.getText().toString();
//对必填项做非空判断
if (TextUtils.isEmpty(name)) {
Toast.makeText(MainActivity.this, "姓名不能为空", Toast.LENGTH_SHORT).show();
return;
}
//将这些数据存储到数据库
//组装name对象
Student student = new Student(name);
//调用nameDAO的insert()方法插入数据库
StudentDAO studentDAO = new StudentDAO(this);
studentDAO.insert(student);
Cursor cursor = studentDao.selectAll();
adapter.changeCursor(cursor);
Toast.makeText(this, "添加成功", Toast.LENGTH_SHORT).show();
break;
case R.id.btn_sc:
if (student!= null) {
cursor.moveToFirst();
student = new Student();
student.set_id(cursor.getInt(cursor.getColumnIndex("_id")));
studentDao.delete(student.get_id());
studentDao = new StudentDAO(this);
cursor = studentDao.selectAll();
adapter = new MyCursorAdapter(this, cursor);
studentList.setAdapter(adapter);
Toast.makeText(MainActivity.this, "删除成功", Toast.LENGTH_SHORT).show();
}
Toast.makeText(MainActivity.this, "记录为空", Toast.LENGTH_SHORT).show();
break;
}
}
}
