ViewPager的简单使用

ViewPager用于实现多页面的切换效果，该类继承于ViewGroup，存在于Google的兼容包里：android-support-v4.jar，使用时记得构建路径，ViewPager使用非常简单，下面用一个简单示例来演示：

Activity：

package com.home.activity;

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

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;

import com.home.view.MyView;
import com.home.viewpager.R;

public class ViewPagerTestActivity extends Activity {
	// 声明ViewPager对象
	private ViewPager viewPager;
	// 声明存放在ViewPager里面的View的集合
	private List<View> viewList = new ArrayList<View>();
	// 声明自定义组件
	private MyView myView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		// 实例化自定义组件
		myView = new MyView(this);
		// 得到界面上的ViewPager实例
		viewPager = (ViewPager) findViewById(R.id.main_viewpager);
		// 为viewList集合添加View
		viewList.add(getLayoutInflater().inflate(R.layout.firstview, null));
		viewList.add(getLayoutInflater().inflate(R.layout.secondview, null));
		viewList.add(myView);
		PagerAdapter adapter = new PagerAdapter() {
			// 用来初始化ViewPager中的view组件
			@Override
			public Object instantiateItem(View container, int position) {
				((ViewGroup) container).addView(viewList.get(position));
				return viewList.get(position);
			}

			// 当页面需要销毁时从ViewPager中去掉
			@Override
			public void destroyItem(View container, int position, Object object) {
				((ViewGroup) container).removeView(viewList.get(position));
			}

			// ViewPager中存放的页面个数
			@Override
			public int getCount() {
				return viewList.size();
			}

			// 判断切换的两个界面是否是同一个
			@Override
			public boolean isViewFromObject(View arg0, Object arg1) {
				return arg0 == arg1;
			}
		};
		// 为viewPager设置适配器
		viewPager.setAdapter(adapter);
	}

}

自定义组件类（MyView）：

package com.home.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {

	public MyView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public MyView(Context context) {
		super(context);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		Paint paint = new Paint();
		canvas.drawColor(Color.BLUE);
		paint.setColor(Color.RED);
		canvas.drawCircle(30, 30, 30, paint);
		canvas.drawText("第三个页面", 270, 480, paint);
	}
}

Activity的布局XML：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

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

</RelativeLayout>

firstview.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="#FF00FF"
    android:gravity="center" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="第一个页面" />

</LinearLayout>

secondview.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="#00FF00"
    android:gravity="center" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="第二个页面" />

</LinearLayout>