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：

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

    
    
         //AppBarLayout和Toolbar是对布局页面顶部的条进行操作    
             
                      //该部分才是下拉菜单的本体        
      //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    
         
     
    

    
        
             
      
       Beijing
              
      
       Guangzhou
              
      
       Shanghai
          
     
    

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:

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
    
      mList;    public Context context;    public View mView;    public Myadapter(Context context,List
     
       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
    
      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
     
      ();        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：