package com.example.asus.gary_0400;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.ArrayAdapter;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Spinner;

import android.widget.TextView;

import java.util.ArrayList;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final String[] countriesStr = {"周一","周二","周三","周四","周五"};

    private TextView myTextView;

    private EditText myEditText;

    private Button myButton_add;

    private Button myButton_remove;

    private Spinner mySpinner;

    private ArrayAdapter<String>adapter;

    private List<String> allCountries;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        allCountries = new ArrayList<String>();

        for(int i=0;i<countriesStr.length;i++)

        {

            allCountries.add(countriesStr[i]);

        }

        //新建ArrayAdapter对象并将allCountries传入

        adapter = new ArrayAdapter<String>(this,

                android.R.layout.simple_spinner_dropdown_item,allCountries);

        adapter.setDropDownViewResource(

                android.R.layout.simple_spinner_dropdown_item);

        //以findViewById()取的对象

        myTextView = (TextView)findViewById(R.id.myTextView);

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

        myButton_add=(Button)findViewById(R.id.myButton_add);

        myButton_remove = (Button)findViewById(R.id.myButton_remove);

        mySpinner = (Spinner)findViewById(R.id.myspinner);

        //将ArrayAdapter添加到Spinner对象中

        mySpinner.setAdapter(adapter);

        myButton_add.setOnClickListener(new Button.OnClickListener() {

            @Override

            public void onClick(View v) {

                String newCountry = myEditText.getText().toString();

                //先比较添加的值是否存在，不存在才可以添加

                for(int i=0;i<adapter.getCount();i++)

                {

                    if(newCountry.equals(adapter.getItem(i))){

                        return;

                    }

                }

                if(!newCountry.equals(""))

                {

                    //将值添加至adapter

                    adapter.add(newCountry);

                    //取得添加的值的位置

                    int position = adapter.getPosition(newCountry);

                    //将Spinner选择在添加的值的位置

                    mySpinner.setSelection(position);

                    //将myEditText清空

                    myEditText.setText("");

                }

            }

        });

        //为myButton_remove添加OnclickListener

        myButton_remove.setOnClickListener(new Button.OnClickListener() {

            @Override

            public void onClick(View v) {

                if(mySpinner.getSelectedItem()!=null)

                {

                    //删除mySpinner的值

                    adapter.remove(mySpinner.getSelectedItem().toString());

                    //将myEditText清空

                    myEditText.setText("");

                    if(adapter.getCount()==0)

                    {

                        //将myTextView清空

                        myTextView.setText("");

                    }

                }

            }

        });

        //为mySpinner添加OnItemSelextedListener

        mySpinner.setOnItemSelectedListener(new Spinner.OnItemSelectedListener() {

            @Override

            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

                //将所选mySpinner的值带入myTextView中

                myTextView.setText(parent.getSelectedItem().toString());

            }

            @Override

            public void onNothingSelected(AdapterView<?> parent) {

            }

        });

    }

}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    tools:context="com.example.asus.gary_0400.MainActivity"

    android:weightSum="1">

    <TextView

        android:id="@+id/myTextView"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="Gary_动态添加或删除菜单"

        android:textSize="40px" />

    <EditText

        android:id="@+id/myEditText"

        android:layout_width="match_parent"

        android:layout_height="50dp"

        android:ems="10"

        android:hint="填写添加项"

        android:inputType="textPersonName" />

    <Button

        android:id="@+id/myButton_add"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="添加" />

    <Button

        android:id="@+id/myButton_remove"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="删除" />

    <Spinner

        android:id="@+id/myspinner"

        android:layout_width="match_parent"

        android:layout_height="50px"

        android:layout_weight="0.13" />

</LinearLayout>