使用ArrayList动态数组的依赖性实现动态增减Spinner下拉菜单选项功能。
设置一个EditText输入框，当用户输入了文字并单击【添加】按钮的同时，就会将输入的值添加Spinner至下拉菜单的最后一项，接着Spinner会停留在刚刚添加的选项上，单击【删除】按钮则会删除选择的Spinner选项。
运行截图：
程序结构
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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>
一、界面布局
一个TextView显示框用来显示添加所选项的字符串， EditText作为输入框，两个Button按钮作为”添加“和“删除”对Spinner菜单进行操作
二、实现程序功能
1、创建ArrayAdapter对象并将当前Spinner菜单中数据个数多少的值传入
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item,allCountries); adapter.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item);
2、将ArrayAdapter添加到Spinner对象中
// mySpinner = (Spinner)findViewById(R.id.myspinner); //mySpinner取得Spinner控件对象 mySpinner.setAdapter(adapter);
3、实现"添加"按钮功能
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(""); } } });
4、实现"删除"按钮功能
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(""); } } } });
5、实现TextView控件功能(显示添加进入Spinner中的字符串)
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) { } });