Android Spinner和GridView组件的使用示例
一. 概述：
spinner是我们所熟悉的下拉框列表。与listview类似，我们必须为spinner对象指定一个adapter。我们从spinner的简单用法开始讲述。
二. 实现
mainactivity.java
package com.example.demo03_29;
import androidx.appcompat.app.appcompatactivity;
import android.os.bundle;
import android.view.view;
import android.widget.adapter;
import android.widget.adapterview;
import android.widget.arrayadapter;
import android.widget.spinner;
import android.widget.textview;
public class mainactivity extends appcompatactivity implements adapterview.onitemselectedlistener {
textview choice;
arrayadapter<charsequence> adapter;
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
choice=(textview) this.findviewbyid(r.id.choice);
spinner spinner=(spinner)this.findviewbyid(r.id.sp1);
adapter=arrayadapter.createfromresource(this, r.array.habit,
android.r.layout.simple_spinner_item);
adapter.setdropdownviewresource(android.r.layout.simple_spinner_dropdown_item);
spinner.setadapter(adapter);
spinner.setonitemselectedlistener(this);
}
@override
public void onitemselected(adapterview<?> adapterview, view view, int i, long l) {
choice.settext(adapter.getitem(i));
}
@override
public void onnothingselected(adapterview<?> adapterview) {
}
}在values包下的 string.xml
<resources>
<string name="app_name">demo03-29</string>
<string-array name="habit">
<item>10公里夜跑</item>
<item>爬山</item>
<item>游泳</item>
<item>吃饭</item>
<item>打代码</item>
</string-array>
</resources>activity_main.xml
<?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=".mainactivity">
<linearlayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<textview
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="你喜欢的运动"/>
<spinner
android:id="@+id/sp1"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</linearlayout>
<view
android:layout_width="match_parent"
android:layout_height="30dp"
android:background="#05adf8"/>
<textview
android:id="@+id/choice"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
/>
</linearlayout>sipnner_down.xml
<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<imageview
android:id="@+id/p01"
android:layout_width="64dp"
android:layout_height="64dp"
/>
<linearlayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<textview
android:id="@+id/t1"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<textview
android:id="@+id/t2"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</linearlayout>
</linearlayout>这个布局比较简单，就是在linearlayout中放置一个linearlayout、一个分隔组件用的view和一个显示所选结果的textview。在其中嵌套的linearlayout中放置一个用于提示用的textview和下拉框spinner。
三. 美化
myadapter.java
package com.example.demo03_29;
import android.content.context;
import android.view.layoutinflater;
import android.view.view;
import android.view.viewgroup;
import android.widget.arrayadapter;
import android.widget.imageview;
import android.widget.textview;
import androidx.annotation.nonnull;
public class myarrayapater extends arrayadapter {
private layoutinflater minflater;
string[] titles;
string[] desc={
"集成工具",
"高速保存，随时存储",
"优质资源，尽在迅雷",
"集成开发工具",
"学习神器"
};
int[] photos={r.drawable.p1,r.drawable.p2,r.drawable.p3,r.drawable.p4,r.drawable.p5};
public myarrayapater(@nonnull context context, int resource, charsequence[] objects) {
super(context, resource, objects);
minflater=(layoutinflater) context.getsystemservice(context.layout_inflater_service);
titles=context.getresources().getstringarray(r.array.habit);
}
@override
public int getcount(){
return titles.length;
}
@override
public view getdropdownview(int position, view convertview, viewgroup parent){
view v;
v=minflater.inflate(r.layout.spinner_down,parent,false);
imageview iv=(imageview)v.findviewbyid(r.id.p01);
iv.setimageresource(photos[position]);
textview tv01=(textview) v.findviewbyid(r.id.t1);
tv01.settext(titles[position]);
textview tv02=(textview) v.findviewbyid(r.id.t2);
tv02.settext(desc[position]);
return v;
}
}修改 mainactivity.java
四. gridview
gridview以二维表格的方式显示数据，若数据比较多，该组件将提供垂直滚动条。我们用一个列子来说明gridview的使用方法。
activity_main.xml
<?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"
tools:context=".mainactivity">
<gridview
android:id="@+id/gr1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:numcolumns="4"
/>
</linearlayout>imgeadapter.java
package com.example.demo0330;
import android.content.context;
import android.view.view;
import android.view.viewgroup;
import android.widget.baseadapter;
import android.widget.gridview;
import android.widget.imageview;
public class imageadapter extends baseadapter {
private int[] images={
r.drawable.p1, r.drawable.p2, r.drawable.p3, r.drawable.p4,
r.drawable.p1, r.drawable.p2, r.drawable.p3, r.drawable.p4,
r.drawable.p1, r.drawable.p2, r.drawable.p3, r.drawable.p4,
r.drawable.p1, r.drawable.p2, r.drawable.p3, r.drawable.p4,
r.drawable.p1, r.drawable.p2, r.drawable.p3, r.drawable.p4,
};
private context context;
public imageadapter(context context){
this.context=context;
}
@override
public int getcount() {
return images.length;
}
@override
public object getitem(int position) {
return images[position];
}
@override
public long getitemid(int position) {
return position;
}
@override
public view getview(int position, view convertview, viewgroup parent) {
imageview imageview;
if (convertview==null){
imageview=new imageview(context);
int width= gridview.layoutparams.match_parent;
int heght= gridview.layoutparams.match_parent;
imageview.setlayoutparams(new viewgroup.layoutparams(width,heght));
imageview.setscaletype(imageview.scaletype.center_inside);
}else{
imageview=(imageview) convertview;
}
imageview.setimageresource(images[position]);
return imageview;
}
}mainactivity.java
package com.example.demo0330;
import androidx.appcompat.app.appcompatactivity;
import android.os.bundle;
import android.view.view;
import android.widget.adapterview;
import android.widget.gridview;
import android.widget.toast;
public class mainactivity extends appcompatactivity {
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
gridview gridview=(gridview) findviewbyid(r.id.gr1);
gridview.setadapter(new imageadapter(this));
gridview.setonitemclicklistener(new adapterview.onitemclicklistener() {
@override
public void onitemclick(adapterview<?> adapterview, view view, int position, long l) {
toast.maketext(mainactivity.this,"现在点击的是位置在"+(position+1)+"张照片",toast.length_long).show();
}
});
}
}效果图:
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