Android 應用開發---ViewPager----1.相關基本知識
ViewPager 詳解(一)---基本入門
效果圖:
實現了三個view間的相互滑動
第一個VIEW向第二個VIEW滑動 第二個VIEW向第三個VIEW滑動
一、新建專案,引入ViewPager控制元件
ViewPager。它是google SDk中自帶的一個附加包的一個類,可以用來實現螢幕間的切換。
1.在主佈局檔案里加入
- <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
- xmlns:tools="http://schemas.android.com/tools"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- tools:context="com.example.testviewpage_1.MainActivity" >
- <android.support.v4.view.ViewPager
- android:id="@+id/viewpager"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="center" />
- </RelativeLayout>
其中 <android.support.v4.view.ViewPager /> 是ViewPager對應的元件,要將其放到想要滑動的位置
2、新建三個layout,用於滑動切換的檢視
從效果圖中也可以看到,我們的三個檢視都非常簡單,裡面沒有任何的控制元件,大家當然可以往裡新增各種控制元件,但這裡是個DEMO,只詳解原理即可,所以我這裡僅僅用背景來區別不用layout佈局。
佈局程式碼分別如下:
layout1.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:background="#ffffff"
- android:orientation="vertical" >
- </LinearLayout>
layout2.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:background="#ffff00"
- android:orientation="vertical" >
- </LinearLayout>
layout3.xml [html] view plain copy
- <?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:background="#ff00ff"
- android:orientation="vertical" >
- </LinearLayout><span style="color:#660000;">
- </span>
二、程式碼實戰
先上整體程式碼,然後逐步講解。 [java] view plain copy
- package com.example.testviewpage_1;
- /**
- * @author harvic
- * @date 2014.8.9
- */
- import java.util.ArrayList;
- import java.util.List;
- import java.util.zip.Inflater;
- import android.app.Activity;
- import android.os.Bundle;
- import android.support.v4.view.PagerAdapter;
- import android.support.v4.view.ViewPager;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.ViewGroup;
- public class MainActivity extends Activity {
- private View view1, view2, view3;
- private ViewPager viewPager; //對應的viewPager
- private List<View> viewList;//view陣列
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- viewPager = (ViewPager) findViewById(R.id.viewpager);
- LayoutInflater inflater=getLayoutInflater();
- view1 = inflater.inflate(R.layout.layout1, null);
- view2 = inflater.inflate(R.layout.layout2,null);
- view3 = inflater.inflate(R.layout.layout3, null);
- viewList = new ArrayList<View>();// 將要分頁顯示的View裝入陣列中
- viewList.add(view1);
- viewList.add(view2);
- viewList.add(view3);
- PagerAdapter pagerAdapter = new PagerAdapter() {
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
- // TODO Auto-generated method stub
- return arg0 == arg1;
- }
- @Override
- public int getCount() {
- // TODO Auto-generated method stub
- return viewList.size();
- }
- @Override
- public void destroyItem(ViewGroup container, int position,
- Object object) {
- // TODO Auto-generated method stub
- container.removeView(viewList.get(position));
- }
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- // TODO Auto-generated method stub
- container.addView(viewList.get(position));
- return viewList.get(position);
- }
- };
- viewPager.setAdapter(pagerAdapter);
- }
- }
程式碼量很小,全部放在了OnCreate()函式中。
1、先看宣告的變數的意義:
- private View view1, view2, view3;
- private List<View> viewList;//view陣列
- private ViewPager viewPager; //對應的viewPager
首先viewPager對應 <android.support.v4.view.ViewPager/>控制元件。
view1,view2 ,view3對應我們的三個layout,即layout1.xml,layout2.xml,layout3.xml
viewList是一個View陣列,盛裝上面的三個VIEW
2、接下來是他們的初始化過程:
- viewPager = (ViewPager) findViewById(R.id.viewpager);
- LayoutInflater inflater=getLayoutInflater();
- view1 = inflater.inflate(R.layout.layout1, null);
- view2 = inflater.inflate(R.layout.layout2,null);
- view3 = inflater.inflate(R.layout.layout3, null);
- viewList = new ArrayList<View>();// 將要分頁顯示的View裝入陣列中
- viewList.add(view1);
- viewList.add(view2);
- viewList.add(view3);
初始化過程難度不大,就是將資源與變數聯絡起來佈局,最後將例項化的view1,view2,view3新增到viewList中
3、PageAdapter——PageView的介面卡
介面卡這個東東想必大家都不莫生,在ListView中也有介面卡,listView通過重寫GetView()函式來獲取當前要載入的Item。而PageAdapter不太相同,畢竟PageAdapter是單個VIew的合集。
PageAdapter 必須重寫的四個函式:
- boolean isViewFromObject(View arg0, Object arg1)
- int getCount()
- void destroyItem(ViewGroup container, int position,Object object)
- Object instantiateItem(ViewGroup container, int position)
先看看各個函式,我們上面都做了什麼吧:
- @Override
- public int getCount() {
- // TODO Auto-generated method stub
- return viewList.size();
- }
getCount():返回要滑動的VIew的個數
- @Override
- public void destroyItem(ViewGroup container, int position,
- Object object) {
- // TODO Auto-generated method stub
- container.removeView(viewList.get(position));
- }
destroyItem():從當前container中刪除指定位置(position)的View; [java] view plain copy
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- // TODO Auto-generated method stub
- container.addView(viewList.get(position));
- return viewList.get(position);
- }
- };
instantiateItem():做了兩件事,第一:將當前檢視新增到container中,第二:返回當前View [java] view plain copy
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
- // TODO Auto-generated method stub
- return arg0 == arg1;
- }
isViewFromObject():對於這個函式就先不做講解,大家目前先知道它要這樣重寫就行了,後面我們會對它進行改寫。