SQLite

结合本任务所学内容，完成以下任务，界面如图所示

a)将学生信息存入数据库

b)显示所有学生信息列表

c)删除数据库表中第一条信息

主界面代码：

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context="cn.edu.niit.sqlite1.MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/et_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:ems="20" />

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">

<Button
    android:id="@+id/btn_add"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:onClick="onClick"
    android:text="增加记录"/>

<Button
    android:id="@+id/btn_delete"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:onClick="onClick"
    android:text="删除第一条记录" />

</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>

新建一个xml布局，代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/tv_name"
        android:textSize="20sp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>
效果图如下所示;

java部分代码

MainActivity.java:

package cn.edu.niit.sqlite1;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.database.Cursor;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {
    private EditText et_input;
    private ListView lv_data;
    private MyCursorAdapter myCursorAdapter;
    private PersonerDAO personerDAO;
    private Cursor cursor;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        et_input = (EditText)findViewById(R.id.et_name);

        lv_data = (ListView)findViewById(R.id.list_view);
       
        personerDAO = new PersonerDAO(this);
        cursor = personerDAO.selectAll();
        if(cursor!=null){
            myCursorAdapter = new MyCursorAdapter(MainActivity.this,cursor);
            lv_data.setAdapter(myCursorAdapter);
        }


    }

    public void onClick(View view) {
        switch(view.getId()){
            case R.id.btn_add:
                String name = et_input.getText().toString();
                personerDAO.insert(name);
                cursor = personerDAO.selectAll();
                if(cursor!=null){
                    myCursorAdapter = new MyCursorAdapter(this,cursor);
                    lv_data.setAdapter(myCursorAdapter);
                }
                break;
            case R.id.btn_delete:
                if(cursor!=null){
                    if(cursor.moveToFirst()){
                        personerDAO.delete(cursor.getString(cursor.getColumnIndex("_id")));
                        cursor = personerDAO.selectAll();
                    }
                }
                myCursorAdapter = new MyCursorAdapter(this,cursor);
                lv_data.setAdapter(myCursorAdapter);
                break;
        }

    }
}
MyDBHelper.java：

package cn.edu.niit.sqlite1;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by Lenovo on 2017/5/16.
 */

public class MyDBHelper extends SQLiteOpenHelper {
    private String sql = "create table person(id integer primary key autoincrement,name txt)";
    public MyDBHelper(Context context) {
        super(context,"personInfo",null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("drop table if exists person");
        onCreate(sqLiteDatabase);
    }
}
PersonerDAO.java:

package cn.edu.niit.sqlite1;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
/**
 * Created by Lenovo on 2017/5/16.
 */

public class PersonerDAO {

    private MyDBHelper dbHelper;
    private SQLiteDatabase sqLiteDatabase;

    public PersonerDAO(Context context){
        dbHelper = new MyDBHelper(context);
    }

    public void insert(String name){
        sqLiteDatabase = dbHelper.getWritableDatabase();
        String sql = "insert into person(name) values('"+name+"')";
        sqLiteDatabase.execSQL(sql);
    }

    public Cursor selectAll() {
        sqLiteDatabase = dbHelper.getReadableDatabase();
        Cursor cursor = sqLiteDatabase.query("person", null, null, null, null, null, null);
        return cursor;
    }

    public void delete(String id){
        sqLiteDatabase = dbHelper.getWritableDatabase();
        String sql = "delete from person where _id="+String.valueOf(id);//"delete from student where _id="+id
        sqLiteDatabase.execSQL(sql);
    }
}

MyCursorAdapter.java:

package cn.edu.niit.sqlite1;
import android.content.Context;
import android.database.Cursor;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CursorAdapter;
import android.widget.TextView;

/**
 * Created by Lenovo on 2017/5/16.
 */

public class MyCursorAdapter extends CursorAdapter {
    public MyCursorAdapter(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.listview,viewGroup,false);
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        TextView name = (TextView) view.findViewById(R.id.tv_name);
        name.setText(cursor.getString(cursor.getColumnIndex("name")));
    }
}