ViewPager 详解（一）——基本入门

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

在主布局中放入Viewpager

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:orientation="vertical">

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

新建3个要进行切换的布局：layout1，layout2，layout3

layout1.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:background="#ff0000"
              android:orientation="vertical">


</LinearLayout>

layout2.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:background="#00ff00"
              android:orientation="vertical">


</LinearLayout>

layout3.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:background="#0000ff"
              android:orientation="vertical">


</LinearLayout>

MainActivity.xml

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;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {
    private View view1,view2,view3;
    private ViewPager viewPager;
    private List<View> viewList;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = (ViewPager)findViewById(R.id.viewpager);
        LayoutInflater layoutInflater = getLayoutInflater();
        view1 = layoutInflater.inflate(R.layout.layout1,null);
        view2 = layoutInflater.inflate(R.layout.layout2,null);
        view3 = layoutInflater.inflate(R.layout.layout3,null);

        viewList = new ArrayList<View>();
        viewList.add(view1);
        viewList.add(view2);
        viewList.add(view3);

        PagerAdapter pagerAdapter = new PagerAdapter() {
            @Override
            public int getCount() {
                return viewList.size();
            }

            @Override
            public boolean isViewFromObject(View view, Object object) {
                return view == object;
            }

            @Override
            public void destroyItem(ViewGroup container, int position,
                                    Object object) {
                container.removeView(viewList.get(position));
            }

            @Override
            public Object instantiateItem(ViewGroup container, int position) {
                container.addView(viewList.get(position));
                return viewList.get(position);
            }
        };

        viewPager.setAdapter(pagerAdapter);
    }
}

对其中PageAdapter作说明：

//getCount():返回要滑动的VIew的个数
@Override
            public int getCount() {
                return viewList.size();
            }

//destroyItem（）：从当前container中删除指定位置（position）的View;
@Override
            public void destroyItem(ViewGroup container, int position,
                                    Object object) {
                container.removeView(viewList.get(position));
            }

//instantiateItem()：做了两件事，第一：将当前视图添加到container中，第二：返回当前View
 @Override
            public Object instantiateItem(ViewGroup container, int position) {
                container.addView(viewList.get(position));
                return viewList.get(position);
            }

//下一篇讲
 @Override
            public boolean isViewFromObject(View view, Object object) {
                return view == object;
            }