Android：有关下拉菜单导航的学习（供自己参考）

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.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android: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
        <Spinner
            android: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 ;

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

    private void initUI(){
        spinner = (Spinner)findViewById(R.id.spinner);
        spinner.setOnItemSelectedListener(this);
    }

    @Override
    public 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();
    }

    @Override
    public 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">

    <TextView
        android:id="@+id/personName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="personName  "
        android:textSize="20dp"
        android:textColor="@color/colorAccent"/>

    <TextView
        android: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;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int i) {
        return mList.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public 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;

    @Override
    protected 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：