5.16 SQL
作业内容：实现数据加入数据库，显示加入的内容，删除第一条信息
一，界面布局
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.example.administrator.sql_liuhao.MainActivity">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="onClick"
android:id="@+id/ed_"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/bu_zeng"
android:text="增加一条新纪录"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
<Button
android:id="@+id/bu_shan"
android:text="删除第一条记录"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
</LinearLayout>
<ListView
android:id="@+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</ListView>
</LinearLayout>
ListView还需要一个xml来显示文本，只需要写一个TextView即可id为name
二，新建CursorAdapter.java
public class CursorAdapter extends CursorAdapter {
public CursorAdapter(Context context, Cursor cursor) {
super(context, cursor, 0);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup viewGroup) {
return LayoutInflater.from(context).inflate(R.layout.activity_main, viewGroup, false);
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
TextView name = (TextView) view.findViewById(R.id.ed_);
name.setText(cursor.getString(cursor.getColumnIndex("name")));
}
}
三，新建Student.java
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;
}
}
四，新建DBHelper.java
public class DBHelper extends SQLiteOpenHelper {
private String sql="create table student(_id integer primary key autoincrement,"
+"name text not null ,classmate text not null,age integer)";
public DBHelper(Context context) {
super(context,"studentInfo",null,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(sql);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists stdent");
onCreate(db);
}
}
五，新建StudentDAO.java
public class StudentDAO {
private Context context;
private DBHelper helper;
private SQLiteDatabase db;
public StudentDAO(Context context) {
helper = new DBHelper(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);
}
ublic 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)});
}
}
六，MainActivity.java住代码
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private EditText ed_;
private Button bu_zengj;
private Button bu_shan;
private ListView list;
private Student student;
private CursorAdapter adapter;
private StudentDAO studentDao;
private Cursor cursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
studentList = (ListView) findViewById(R.id.list);
ed_=(EditText)findViewById(R.id.ed_);
bu_zeng = (Button) findViewById(R.id.bu_zeng);
bu_zeng.setOnClickListener(this);
bu_shan = (Button) findViewById(R.id.bu_shan);
bu_shan.setOnClickListener(this);
studentDao = new StudentDAO(this);
if(cursor != null) {
adapter = new CursorAdapter(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.bu_zeng:
String name = ed_.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);
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.bu_shan:
if (studentList!= 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;
}
}
}
