将数据库数据添加到listview上

package com.example.sqlclass;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private MyDataBase dbHelper;
    private EditText etname;
    private EditText etage;
    private EditText etgrade;
    private ListView list_view;
    private ArrayList
 
   studentlist;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHelper = new MyDataBase(this);
        list_view= (ListView) findViewById(R.id.list_view);
        Button show = (Button) findViewById(R.id.show);
        Button add = (Button) findViewById(R.id.add);
        etname = (EditText) findViewById(R.id.et_name);
        etage = (EditText) findViewById(R.id.et_age);
        etgrade = (EditText) findViewById(R.id.et_grade);
        dbHelper.getWritableDatabase();
        show.setOnClickListener(this);
        add.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.show:
                querystudent();
                break;
            case R.id.add:
                add();
            default:
                break;
        }
    }

    private void querystudent() {
        studentlist = new ArrayList<>();
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Cursor cur = db.query("info", null, null, null, null, null, null);
        if (cur != null && cur.getCount() > 0){
            while (cur.moveToNext()) {
                String name = cur.getString(cur.getColumnIndex("name"));
                String age = cur.getString(cur.getColumnIndex("age"));
                String grade = cur.getString(cur.getColumnIndex("grade"));
                student_info st = new student_info(name, age, grade);
                st.setName(name);
                st.setAge(age);
                st.setGrade(grade);
                studentlist.add(st);
            }
            list_view.setAdapter(new BaseAdapter() {
                @Override
                public int getCount() {
                    return studentlist.size();
                }

                @Override
                public Object getItem(int position) {
                    return null;
                }

                @Override
                public long getItemId(int position) {
                    return 0;
                }

                @Override
                public View getView(int position, View convertView, ViewGroup parent) {
                  View view;
                  if (convertView==null){
                      view=View.inflate(MainActivity.this,R.layout.student_item,null);
                  }
                  else {
                      view=convertView;
                  }
                    student_info st = studentlist.get(position);
                    TextView tvname = (TextView) view.findViewById(R.id.tvname);
                    TextView tvage = (TextView) view.findViewById(R.id.tvage);
                    TextView tvgrade = (TextView) view.findViewById(R.id.tvgrade);
                    tvname.setText(st.getName());
                    tvage.setText(st.getAge());
                    tvgrade.setText(st.getGrade());
                    return view;
                }
            });
        }
    }

    private void add() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        String stuname = etname.getText().toString().trim();
        String stuage = etage.getText().toString().trim();
        String stugrade = etgrade.getText().toString().trim();
        values.put("name", stuname);
        values.put("age", stuage);
        values.put("grade", stugrade);

        db.insert("info",null,values);
        db.close();
        Toast.makeText(MainActivity.this, "success", Toast.LENGTH_SHORT).show();
    }
}
 

package com.example.sqlclass;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;


public class MyDataBase extends SQLiteOpenHelper {


    public MyDataBase(Context context) {
        super(context, "student.db", null, 1);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),age varchar(20),grade varchar(20))");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

package com.example.sqlclass;

/**
 * Created by Lancer on 2017/11/22.
 */

public class student_info {

    private String name;
    private String age;
    private String grade;



    public void setName(String name) {
        this.name = name;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public student_info( String name, String age, String grade) {

        this.name = name;
        this.age = age;
        this.grade = grade;
    }



    public void setGrade(String grade) {
        this.grade = grade;
    }



    public String getName() {
        return name;
    }

    public String getAge() {
        return age;
    }

    public String getGrade() {
        return grade;
    }
}