Go语言视频零基础入门到精通

彩虹糖梦

动态添加╱删除的 Spinner 菜单
ArrayList 与 Widget 的依赖性


①创建新工程
②修改 mian.xml 布局，添加 UI 元素
<?xml version="1.0" encoding="utf-8"?>

<LinearLayout

android:id="@+id/widget92"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

androidrientation="vertical"

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

>

<TextView

android:id="@+id/TextView_Show_yourChoice"

android:layout_width="190px"

android:layout_height="wrap_content"

android:text="TextView"

android:textSize="25sp"

android:layout_gravity="center_horizontal"

>

</TextView>

<EditText

android:id="@+id/EditView_Input"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:textSize="18sp"

>

</EditText>

<Button

android:id="@+id/Button_ADD"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="添加"

>

</Button>

<Button

android:id="@+id/Button_DEL"

android:layout_width="fill_parent"

android:layout_height="wrap_content



android:text="删除"

>

</Button>

<Spinner

android:id="@+id/Spinner_Slecte"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

>

</Spinner>

</LinearLayout>
复制代码
③定义创建一个 List<T>
/*定义*/

private String[] cities;

private List<String> cityList;





/*初始化字符串数组*/

cities = new String[] { "Android", "BlackBerry", "J2ME", "Symbian",

"Broncho", "LinuxMobile", &quotalm", "WindwosMobile" };

/*初始化List实例 ArrayList的对象*/

cityList = new ArrayList<String>();

/*遍历，把字符串数组添加到ArrayList中*/

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

cityList.add(cities);

}
复制代码④定义创建一个ArrayAdapter<String> /*定义*/

private ArrayAdapter<String> arrayAdapter;

/* 这里应该使用List<> ,如果使用String[]则会出错 */

/*初始化下拉菜单的内容适配器*/

arrayAdapter = new ArrayAdapter<String>(this,

android.R.layout.simple_spinner_item, cityList);
复制代码⑤设置ArrayAdapter<String>在下拉菜单中的显示布局
/*设置下拉菜单显示内容的风格*/

arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_

item);
复制代码⑥给下拉菜单添加内容 Adapter 适配器
/*给下拉菜单对象添加内容适配器*/

city_Spinner.setAdapter(arrayAdapter);
复制代码
⑦修改该mainActivity.java，实现动态添加和删除
package zyf.Ex_Ctrl_9ME;

/*使用的包导入*/

import java.util.ArrayList;

import java.util.List;

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

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 android.widget.Toast;





public class Ex_Ctrl_9ME extends Activity implements Button.OnClickListener,

Spinner.OnItemSelectedListener {

/** Called when the activity is first created. */

/*声明程序使用的对象*/

private TextView show_yourChoice_TextView;

private EditText input_City_EditText;

private Button Add_Button, Del_Button;

private Spinner city_Spinner;

private ArrayAdapter<String> arrayAdapter;

private String[] cities;

private String addString;

private List<String> cityList;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

/*设置主屏显示布局为main.xml*/

setContentView(R.layout.main);

/*findViewByID()获取XML中的UI元素*/

show_yourChoice_TextView =

(TextView) findViewById(R.id.TextView_Show_yourChoice);

input_City_EditText = (EditText) findViewById(R.id.EditView_Input);

Add_Button = (Button) findViewById(R.id.Button_ADD);

Del_Button = (Button) findViewById(R.id.Button_DEL);

city_Spinner = (Spinner) findViewById(R.id.Spinner_Slecte);

/*初始化字符串数组*/

cities = new String[] { "Android", "BlackBerry", "J2ME",



"Symbian","Broncho", "LinuxMobile",

"Palm", "WindwosMobile" };

/*初始化List实例 ArrayList的对象*/

cityList = new ArrayList<String>();

/*遍历，把字符串数组添加到ArrayList中*/

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

cityList.add(cities);

}

/* 这里应该使用List<> ,如果使用String[]则会出错 */

/*初始化下拉菜单的内容适配器*/

arrayAdapter = new ArrayAdapter<String>(this,

android.R.layout.simple_spinner_item, cityList);

/*设置下拉菜单显示内容的风格*/

arrayAdapter





.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

/*给下拉菜单对象添加内容适配器*/

city_Spinner.setAdapter(arrayAdapter);

/*默认启动时 文本标题显示*/

show_yourChoice_TextView.setText(arrayAdapter.getItem(0));

/*默认启动时 下拉菜单第一项被选中*/

city_Spinner.setSelection(0);

/*为按钮添加点击事件监听器*/

Add_Button.setOnClickListener(this);

Del_Button.setOnClickListener(this);

/*为下拉菜单添加选项选中事件监听器*/

city_Spinner.setOnItemSelectedListener(this);

}

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

switch (v.getId()) {

/*区别按钮来进行不同动作*/

case R.id.Button_ADD:

/*显示Toast提示*/

Toast.makeText(this, "添加", Toast.LENGTH_SHORT).show();

/*获得输入框中的将要添加的字符串*/

addString = input_City_EditText.getText().toString();

/*遍历，比较是否和下拉菜单中内容重复*/

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

if (addString.equals(arrayAdapter.getItemId(i))) {

return;

/*重复了，则跳出*/

}



}

/*如果添加字符串不为""*/

if (!addString.equals("")) {

/*添加进适配器中*/

arrayAdapter.add(addString);

/*获取刚刚添加进的字符串位置*/

int post = arrayAdapter.getPosition(addString);

/*设置刚刚添加进的下拉菜单内容被选中*/

city_Spinner.setSelection(post);

/*清空输入框*/

input_City_EditText.setText("");

}

break;

case R.id.Button_DEL:





if (city_Spinner.getSelectedItem() != null) {





/* 删除mySpinner 的值 */

arrayAdapter.remove(city_Spinner.getSelectedItem().toString());





/* 将myEditText 清空 */

input_City_EditText.setText("");

if (arrayAdapter.getCount() == 0) {

/* 将myTextView 清空 */

Toast.makeText(this, "删完了", Toast.LENGTH_SHORT).show();

show_yourChoice_TextView.setText("");

}

}

break;

default:

break;

}

}

/*下拉菜单选项被选中事件处理*/

@Override

public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,

long arg3) {

// TODO Auto-generated method stub

show_yourChoice_TextView.setText(arrayAdapter.getItem(arg2));

}

/*未被选中 事件处理*/

@Override

public void onNothingSelected(AdapterView<?> arg0) {

// TODO Auto-generated method stub



}



/*添加Menu菜单



进行退出操作*/



@Override

public boolean onCreateOptionsMenu(Menu menu) {

// TODO Auto-generated method stub

menu.add("Exit");

return super.onCreateOptionsMenu(menu);

}

/*Menu菜单 退出*/

@Override

public boolean onOptionsItemSelected(MenuItem item) {

// TODO Auto-generated method stub

finish();

return super.onOptionsItemSelected(item);

}

}
复制代码结果：