5.16 作业

此次作业有点复杂，涉及到多方面知识的运用。首先还是老套路，设计好界面的布局，
再是通过Java使代码得以运行，使输进去的数值能够输出。下面请看第一段界面布局代码，代码如下：

android:id="@+id/w"

android:id="@+id/a"

android:id="@+id/t"

布局效果如图：

再写一个Listview界面，代码如下：

android:id="@+id/n"

其次是Java代码部分：

package com.example.mpyypm.qwer;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {
private EditText w;
private ListView t;
private MyCursorAdapter myCursorAdapter;
private PersonDAO personDAO;
private Cursor cursor;

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

w = (EditText)findViewById(R.id.w);

t = (ListView)findViewById(R.id.t);

personDAO = new PersonDAO(this);
cursor = personDAO.selectAll();
if(cursor!=null){
myCursorAdapter = new MyCursorAdapter(MainActivity.this,cursor);
t.setAdapter(myCursorAdapter);
}

}

public void onClick(View view) {
switch(view.getId()){
case R.id.a:

String name = w.getText().toString();
personDAO.insert(name);
cursor = personDAO.selectAll();
if(cursor!=null){
myCursorAdapter = new MyCursorAdapter(this,cursor);
t.setAdapter(myCursorAdapter);
}
break;
case R.id.d:

if(cursor!=null){
if(cursor.moveToFirst()){
personDAO.d(cursor.getString(cursor.getColumnIndex("_id")));
cursor = personDAO.selectAll();
}
}
myCursorAdapter = new MyCursorAdapter(this,cursor);
t.setAdapter(myCursorAdapter);
break;
}

}
}

第二部分Java代码personDAO:

package com.example.mpyypm.qwer;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class PersonDAO {

private MyDBHelper dbHelper;
private SQLiteDatabase sqLiteDatabase;

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

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

第三部分Java代码：

package com.example.mpyypm.qwer;

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;

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.item,viewGroup,false);
}

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