Android：有关==下拉菜单导航==的学习

因为先前的学习都没想着记录自己的学习历程，所以该博客才那么迟才开始写。

内容： ==下拉菜单导航==

学习网站：android Spinner控件详解

Spinner提供了从一个数据集合中快速选择一项值的办法。默认情况下Spinner显示的是当前选择的值，点击Spinner会弹出一个包含所有可选值的==dropdown菜单==，从该菜单中可以为Spinner选择一个新值。

阶段一：最简单的Spinner

1、在布局文件中添加Spinner控件

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"tools:context="com.example.dropdownlayout.MainActivity">//AppBarLayout和Toolbar是对布局页面顶部的条进行操作<android.support.design.widget.AppBarLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:theme="@style/AppTheme.AppBarOverlay"><android.support.v7.widget.Toolbarandroid:id="@+id/toolbar"android:layout_width="match_parent"android:layout_height="?attr/actionBarSize"android:background="?attr/colorPrimary"app:popupTheme="@style/AppTheme.PopupOverlay" />//该部分才是下拉菜单的本体<Spinnerandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/spinner"android:entries="@array/places"></Spinner>//从这行可以看到资源都是从@array来的，因此需要一个这样的存放资源的xml文件</android.support.design.widget.AppBarLayout><include layout="@layout/content_main" /></android.support.design.widget.CoordinatorLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources><string-array name="places"><item>Beijing</item><item>Guangzhou</item><item>Shanghai</item></string-array>
</resources>

效果：

但是这个终究只是效果，若要对选择进行回应就需要更加复杂的步骤来完善。一般情况下我们是需要响应Spinner选择事件的,可以通过==OnItemSelectedListener==的回调方法实现

MainActivity:

package com.example.dropdownlayout;import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
import android.widget.Toast;public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener{private Spinner spinner ;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);initUI();}private void initUI(){spinner = (Spinner)findViewById(R.id.spinner);spinner.setOnItemSelectedListener(this);}@Overridepublic void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {String[] places = getResources().getStringArray(R.array.places);Toast.makeText(MainActivity.this,"你点击的是:"+places[i],Toast.LENGTH_SHORT).show();}@Overridepublic void onNothingSelected(AdapterView<?> adapterView) {}
}

效果：

阶段二：学会设置Spinner的BaseAdapter

通过BaseAdapter可以自定义自己的菜单形式，但菜单的形式需要自己来设计

spinnerview:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="horizontal" android:layout_width="match_parent"android:layout_height="match_parent"><TextViewandroid:id="@+id/personName"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="personName  "android:textSize="20dp"android:textColor="@color/colorAccent"/><TextViewandroid:id="@+id/personAddress"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="personAddress"android:textSize="20dp"android:textColor="@color/colorAccent"/></LinearLayout>

main.xml中的spinner要把enteries这一项去掉。

Person.java

package com.example.dropdownlayout;/*** Created by Funny_One on 2017/8/18.*/public class Person {public String personName,personAddress;public Person(String personName,String personAddress){this.personAddress = personAddress;this.personName = personName;}public String getPersonAddress() {return personAddress;}public String getPersonName() {return personName;}
}

Myadapter.java

package com.example.dropdownlayout;import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;import java.util.List;/*** Created by Funny_One on 2017/8/18.*/public class Myadapter extends BaseAdapter {public List<Person> mList;public Context context;public View mView;public Myadapter(Context context,List<Person> mList){this.mList = mList;this.context = context;}@Overridepublic int getCount() {return mList.size();}@Overridepublic Object getItem(int i) {return mList.get(i);}@Overridepublic long getItemId(int i) {return i;}@Overridepublic View getView(int i, View view, ViewGroup viewGroup) {LayoutInflater layoutInflater = LayoutInflater.from(context);mView = layoutInflater.inflate(R.layout.spinnerview,null);TextView personName = (TextView)mView.findViewById(R.id.personName);TextView personAddress=(TextView)mView.findViewById(R.id.personAddress);personAddress.setText(mList.get(i).getPersonAddress());personName.setText(mList.get(i).getPersonName());return mView;}
}

MainActivity:

    package com.example.dropdownlayout;import android.app.Activity;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
import android.widget.Toast;import java.util.ArrayList;
import java.util.List;public class MainActivity extends Activity {private Spinner spinner ;private List<Person> persons;private Myadapter myadapter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);spinner = (Spinner)findViewById(R.id.spinner);persons = new ArrayList<Person>();persons.add(new Person(" 袁逸灏 "," 广东 "));persons.add(new Person(" 春旺 "," 云南 "));persons.add(new Person(" 刘先润 "," 重庆 "));persons.add(new Person(" 刘诚昊 "," 湖南 "));myadapter = new Myadapter(this,persons);spinner.setAdapter(myadapter);}}

效果：