ViewPager 入门一

使用ViewPager能够得到不同view的切换效果

例如以下图，实现了四个view间的相互滑动

一、新建项目，引入ViewPager控件

ViewPager。它是google SDk中自带的一个附加包的一个类，能够用来实现屏幕间的切换。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.skyfin.viewpage.MainActivity" >
	<android.support.v4.view.ViewPager
	    android:id="@+id/pager"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    >
	</android.support.v4.view.ViewPager>
</LinearLayout>

2、新建四个LinearLayout，用于滑动切换的视图

<?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="@color/antiquewhite"
    android:gravity="center"
    android:orientation="vertical" >
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="tab2"
        android:textSize="20dp"
        android:textColor="@color/black"
        />
</LinearLayout>

3加载代码段将视图加载Viewpager中

import android.R.id;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.PagerTabStrip;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;

public class MainActivity extends Activity {

	ViewPager ViewPager = null;
	public String TAG = "tag";
	ArrayList<View> viewContainter = new ArrayList<View>();
    ArrayList<String> titleContainer = new ArrayList<String>();

	@SuppressWarnings("deprecation")
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		ViewPager = (ViewPager)findViewById(R.id.pager);

        View view1 = LayoutInflater.from(this).inflate(R.layout.tab1, null);
        View view2 = LayoutInflater.from(this).inflate(R.layout.tab2, null);
        View view3 = LayoutInflater.from(this).inflate(R.layout.tab3, null);
        View view4 = LayoutInflater.from(this).inflate(R.layout.tab4, null);
        //viewpager開始加入view
        viewContainter.add(view1);
        viewContainter.add(view2);
        viewContainter.add(view3);
        viewContainter.add(view4);

        ViewPager.setAdapter(new PagerAdapter() {

            //viewpager中的组件数量
            @Override
            public int getCount() {
                return viewContainter.size();
            }
          //滑动切换的时候销毁当前的组件
            @Override
            public void destroyItem(ViewGroup container, int position,
                    Object object) {
                ((ViewPager) container).removeView(viewContainter.get(position));
            }
          //每次滑动的时候生成的组件
            @Override
            public Object instantiateItem(ViewGroup container, int position) {
                ((ViewPager) container).addView(viewContainter.get(position));
                return viewContainter.get(position);
            }

            @Override
            public boolean isViewFromObject(View arg0, Object arg1) {
                return arg0 == arg1;
            }

            @Override
            public int getItemPosition(Object object) {
                return super.getItemPosition(object);
            }

        });

        ViewPager.setOnPageChangeListener(new OnPageChangeListener() {
            @Override
            public void onPageScrollStateChanged(int arg0) {
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {

            }

            @Override
            public void onPageSelected(int arg0) {

            }
        });

	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}

代码具体解释

1.定义一个ViewPager的容器

ViewPager ViewPager = null;
ArrayList<View> viewContainter = new ArrayList<View>();

2.初始化换View和ViewPager且加入到View的容器viewContainter中

       View view1 = LayoutInflater.from(this).inflate(R.layout.tab1, null);
        View view2 = LayoutInflater.from(this).inflate(R.layout.tab2, null);
        View view3 = LayoutInflater.from(this).inflate(R.layout.tab3, null);
        View view4 = LayoutInflater.from(this).inflate(R.layout.tab4, null);
        //viewpager開始加入view
        viewContainter.add(view1);
        viewContainter.add(view2);
        viewContainter.add(view3);
        viewContainter.add(view4);

3.加入到PagerAdapter中而且设置监听

ViewPager.setAdapter(new PagerAdapter() {

            //viewpager中的组件数量
            @Override
            public int getCount() {
                return viewContainter.size();
            }
          //滑动切换的时候销毁当前的组件
            @Override
            public void destroyItem(ViewGroup container, int position,
                    Object object) {
                ((ViewPager) container).removeView(viewContainter.get(position));
            }
          //每次滑动的时候生成的组件
            @Override
            public Object instantiateItem(ViewGroup container, int position) {
                ((ViewPager) container).addView(viewContainter.get(position));
                return viewContainter.get(position);
            }

            @Override
            public boolean isViewFromObject(View arg0, Object arg1) {
                return arg0 == arg1;
            }

            @Override
            public int getItemPosition(Object object) {
                return super.getItemPosition(object);
            }

            @Override
            public CharSequence getPageTitle(int position) {
                return titleContainer.get(position);
            }
        });

        ViewPager.setOnPageChangeListener(new OnPageChangeListener() {
            @Override
            public void onPageScrollStateChanged(int arg0) {
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {

            }

            @Override
            public void onPageSelected(int arg0) {

            }
        });

PageAdapter 必须重写的四个函数：

• boolean isViewFromObject(View arg0, Object arg1)
• int getCount()
• void destroyItem(ViewGroup container, int position,Object object)
• Object instantiateItem(ViewGroup container, int position)

先看看各个函数，我们上面都做了什么吧：

[java] view
plaincopy

1. @Override
2. public int getCount() {
3. // TODO Auto-generated method stub
4. return viewList.size();
5. }

getCount():返回要滑动的VIew的个数

[java] view
plaincopy

1. @Override
2. public void destroyItem(ViewGroup container, int position,
3. Object object) {
4. // TODO Auto-generated method stub
5. container.removeView(viewList.get(position));
6. }

destroyItem（）：从当前container中删除指定位置（position）的View;

[java] view
plaincopy

1. @Override
2. public Object instantiateItem(ViewGroup container, int position) {
3. // TODO Auto-generated method stub
4. container.addView(viewList.get(position));
5. return viewList.get(position);
6. }
7. };

instantiateItem()：做了两件事，第一：将当前视图加入到container中，第二：返回当前View

[java] view
plaincopy

1. @Override
2. public boolean isViewFromObject(View arg0, Object arg1) {
3. // TODO Auto-generated method stub
4. return arg0 == arg1;
5. }

isViewFromObject():对于这个函数就先不做解说，大家眼下先知道它要这样重写即可了