这是谷歌官方给我们提供的一个兼容低版本安卓设备的软件包,里面包囊了只有在安卓3.0以上可以使用的api。而viewpager就是其中之一利用它,我们可以做很多事情,从最简单的导航,到页面菜单等等。那如何使用它呢,与LisstView类似,我们也需要一个适配器,他就是PagerAdapter。看一下api的图片,
ViewPager的功能就是可以使视图滑动,就像Lanucher左右滑动那样。分三个步骤来使用它:
1.在住布局文件里加入
- <android.support.v4.view.ViewPager 这个组件,注意这个组件是用来显示左右滑动的界面的,如果不加载xml布局文件,他是不会显示内容的。
- android:id="@+id/viewpager"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="center" >
2.加载要显示的页卡,
- LayoutInflater lf = getLayoutInflater().from(this);
- view1 = lf.inflate(R.layout.layout1, null);
- view2 = lf.inflate(R.layout.layout2, null);
- view3 = lf.inflate(R.layout.layout3, null);
-
- viewList = new ArrayList<View>();
- viewList.add(view1);
- viewList.add(view2);
- viewList.add(view3);
3.在Activity里实例化ViewPager组件,并设置它的Adapter(就是PagerAdapter,方法与ListView一样的),在这里一般需要重写PagerAdapter。
- PagerAdapter pagerAdapter = new PagerAdapter() {
-
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
-
- return arg0 == arg1;
- }
-
- @Override
- public int getCount() {
-
- return viewList.size();
- }
-
- @Override
- public void destroyItem(ViewGroup container, int position,
- Object object) {
- container.removeView(viewList.get(position));
-
- }
-
- @Override
- public int getItemPosition(Object object) {
-
- return super.getItemPosition(object);
- }
-
- @Override
- public CharSequence getPageTitle(int position) {
-
- return titleList.get(position);
- }
-
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- container.addView(viewList.get(position));
- weibo_button=(Button) findViewById(R.id.button1);
- weibo_button.setOnClickListener(new OnClickListener() {
-
- public void onClick(View v) {
- intent=new Intent(ViewPagerDemo.this,WeiBoActivity.class);
- startActivity(intent);
- }
- });
- return viewList.get(position);
- }
-
- };
- viewPager.setAdapter(pagerAdapter);
这是重写PagerAdapter的一个方法,我们还可以这样做:
- public class MyViewPagerAdapter extends PagerAdapter{
- private List<View> mListViews;
-
- public MyViewPagerAdapter(List<View> mListViews) {
- this.mListViews = mListViews;
- }
-
- @Override
- public void destroyItem(ViewGroup container, int position, Object object) {
- container.removeView(mListViews.get(position));
- }
-
-
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- container.addView(mListViews.get(position), 0);
- return mListViews.get(position);
- }
-
- @Override
- public int getCount() {
- return mListViews.size();
- }
-
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
- return arg0==arg1;
- }
- }
大同小异,有一定很重要,就是我们需要重写哪些方法。从上面的图片可以看到,ViewPager的适配器是PagerAdapter,它是基类提供适配器来填充页面ViewPager内部,你很可能想要使用一个更具体的实现,如FragmentPagerAdapter或FragmentStatePagerAdapter。在这里需要说明一下,其实ViewPager应该和Fragment一起使用,至少谷歌官方是这么想的,但是在3.0之下,我们没有必要这么做。下面要注意,当你实现一个PagerAdapter,你必须至少覆盖以下方法:
instantiateItem(ViewGroup, int)
destroyItem(ViewGroup, int, Object)
getCount()
isViewFromObject(View, Object)
从上面的例子中可以看到,我们最少也是实现了上面四个方法,当然如果你想让程序更健壮或是功能更全面,你可以重写其他的方法。下面看一下第一个完整的示例代码:
主页面Activity:
- package com.example.viewpagerdemo;
-
- import java.util.ArrayList;
- import java.util.List;
- import android.os.Bundle;
- import android.app.Activity;
- import android.content.Context;
- import android.content.Intent;
- import android.support.v4.view.PagerAdapter;
- import android.support.v4.view.PagerTabStrip;
- import android.support.v4.view.PagerTitleStrip;
- import android.support.v4.view.ViewPager;
- import android.util.AttributeSet;
- import android.view.LayoutInflater;
- import android.view.Menu;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.view.ViewGroup;
- import android.widget.Button;
-
- public class ViewPagerDemo extends Activity {
-
- private View view1, view2, view3;
- private ViewPager viewPager;
- private PagerTitleStrip pagerTitleStrip;
- private PagerTabStrip pagerTabStrip;
- private List<View> viewList;
- private List<String> titleList;
- private Button weibo_button;
- private Intent intent;
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_view_pager_demo);
- initView();
- }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- view1 = findViewById(R.layout.layout1);
- view2 = findViewById(R.layout.layout2);
- view3 = findViewById(R.layout.layout3);
-
- LayoutInflater lf = getLayoutInflater().from(this);
- view1 = lf.inflate(R.layout.layout1, null);
- view2 = lf.inflate(R.layout.layout2, null);
- view3 = lf.inflate(R.layout.layout3, null);
-
- viewList = new ArrayList<View>();
- viewList.add(view1);
- viewList.add(view2);
- viewList.add(view3);
-
- titleList = new ArrayList<String>();
- titleList.add("wp");
- titleList.add("jy");
- titleList.add("jh");
-
- PagerAdapter pagerAdapter = new PagerAdapter() {
-
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
-
- return arg0 == arg1;
- }
-
- @Override
- public int getCount() {
-
- return viewList.size();
- }
-
- @Override
- public void destroyItem(ViewGroup container, int position,
- Object object) {
- container.removeView(viewList.get(position));
-
- }
-
- @Override
- public int getItemPosition(Object object) {
-
- return super.getItemPosition(object);
- }
-
- @Override
- public CharSequence getPageTitle(int position) {
-
- return titleList.get(position);
-
- }
-
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- container.addView(viewList.get(position));
- weibo_button=(Button) findViewById(R.id.button1);
- weibo_button.setOnClickListener(new OnClickListener() {
-
- public void onClick(View v) {
- intent=new Intent(ViewPagerDemo.this,WeiBoActivity.class);
- startActivity(intent);
- }
- });
- return viewList.get(position);
- }
-
- };
- viewPager.setAdapter(pagerAdapter);
- }
-
- @Override
- public boolean onCreateOptionsMenu(Menu menu) {
- getMenuInflater().inflate(R.menu.activity_view_pager_demo, menu);
- return true;
- }
-
- }
它的布局文件:
- <?xml version="1.0" encoding="utf-8"?>
- <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="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="center" >
-
- <android.support.v4.view.PagerTabStrip
- android:id="@+id/pagertab"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="top"/>
-
- </android.support.v4.view.ViewPager>
-
- </LinearLayout>
- <!--注意事项:
- 1.这里ViewPager和 PagerTabStrip都要把包名写全了,不然会ClassNotFount
- 2.API中说:在布局xml把PagerTabStrip当做ViewPager的一个子标签来用,不能拿出来,不然还是会报错
- 3.在PagerTabStrip标签中可以用属性android:layout_gravity=TOP|BOTTOM来指定title的位置
- 4.如果要显示出PagerTabStrip某一页的title,需要在ViewPager的adapter中实现getPageTitle(int)-->
这样就完成了一个简单的ViewPager的使用示例,看一下效果图:
可以左右滑动页卡,但是仔细看一下,标题的效果不好,不能一次显示一个,而且标题还滑动。其实在api里面提供了一个
pagerTabStrip.setTextSpacing()来设置标题的距离,但是我在这里设置了,没有效果不知道为什么,明白的朋友希望能够赐教一下。
所以就有人使用下面这样的方法来仿微博的效果,,
这个标题就固定了,而且可以左右滑动,也有下面的横线,来指示页卡。方法和上面的差不多,区别在于这个横线需要我们自己来做,其实就是一个图片。这个例子是网上的一篇文章,看代码:
主Activity:
- package com.example.viewpagerdemo;
-
- import java.util.ArrayList;
- import java.util.List;
- import android.app.Activity;
- import android.graphics.BitmapFactory;
- import android.graphics.Matrix;
- import android.os.Bundle;
- import android.support.v4.view.PagerAdapter;
- import android.support.v4.view.ViewPager;
- import android.support.v4.view.ViewPager.OnPageChangeListener;
- import android.util.DisplayMetrics;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.view.animation.Animation;
- import android.view.animation.TranslateAnimation;
- import android.view.ViewGroup;
- import android.widget.ImageView;
- import android.widget.TextView;
- import android.widget.Toast;
-
- public class WeiBoActivity extends Activity {
-
- private ViewPager viewPager;
- private ImageView imageView;
- private TextView textView1,textView2,textView3;
- private List<View> views;
- private int offset = 0;
- private int currIndex = 0;
- private int bmpW;
- private View view1,view2,view3;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.weibo);
- InitImageView();
- InitTextView();
- InitViewPager();
- }
-
- private void InitViewPager() {
- viewPager=(ViewPager) findViewById(R.id.vPager);
- views=new ArrayList<View>();
- LayoutInflater inflater=getLayoutInflater();
- view1=inflater.inflate(R.layout.lay1, null);
- view2=inflater.inflate(R.layout.lay2, null);
- view3=inflater.inflate(R.layout.lay3, null);
- views.add(view1);
- views.add(view2);
- views.add(view3);
- viewPager.setAdapter(new MyViewPagerAdapter(views));
- viewPager.setCurrentItem(0);
- viewPager.setOnPageChangeListener(new MyOnPageChangeListener());
- }
-
-
-
-
- private void InitTextView() {
- textView1 = (TextView) findViewById(R.id.text1);
- textView2 = (TextView) findViewById(R.id.text2);
- textView3 = (TextView) findViewById(R.id.text3);
-
- textView1.setOnClickListener(new MyOnClickListener(0));
- textView2.setOnClickListener(new MyOnClickListener(1));
- textView3.setOnClickListener(new MyOnClickListener(2));
- }
-
-
-
-
-
- private void InitImageView() {
- imageView= (ImageView) findViewById(R.id.cursor);
- bmpW = BitmapFactory.decodeResource(getResources(), R.drawable.a).getWidth();
- DisplayMetrics dm = new DisplayMetrics();
- getWindowManager().getDefaultDisplay().getMetrics(dm);
- int screenW = dm.widthPixels;
- offset = (screenW / 3 - bmpW) / 2;
- Matrix matrix = new Matrix();
- matrix.postTranslate(offset, 0);
- imageView.setImageMatrix(matrix);
- }
- <img src="http://img.my.csdn.net/uploads/201211/10/1352554452_1685.jpg" alt="">
-
-
-
- private class MyOnClickListener implements OnClickListener{
- private int index=0;
- public MyOnClickListener(int i){
- index=i;
- }
- public void onClick(View v) {
- viewPager.setCurrentItem(index);
- }
-
- }
-
- public class MyViewPagerAdapter extends PagerAdapter{
- private List<View> mListViews;
-
- public MyViewPagerAdapter(List<View> mListViews) {
- this.mListViews = mListViews;
- }
-
- @Override
- public void destroyItem(ViewGroup container, int position, Object object) {
- container.removeView(mListViews.get(position));
- }
-
-
- @Override
- public Object instantiateItem(ViewGroup container, int position) {
- container.addView(mListViews.get(position), 0);
- return mListViews.get(position);
- }
-
- @Override
- public int getCount() {
- return mListViews.size();
- }
-
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
- return arg0==arg1;
- }
- }
-
- public class MyOnPageChangeListener implements OnPageChangeListener{
-
- int one = offset * 2 + bmpW;
- int two = one * 2;
- public void onPageScrollStateChanged(int arg0) {
-
-
- }
-
- public void onPageScrolled(int arg0, float arg1, int arg2) {
-
-
- }
-
- public void onPageSelected(int arg0) {
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Animation animation = new TranslateAnimation(one*currIndex, one*arg0, 0, 0);
- currIndex = arg0;
- animation.setFillAfter(true);
- animation.setDuration(300);
- imageView.startAnimation(animation);
- Toast.makeText(WeiBoActivity.this, "您选择了"+ viewPager.getCurrentItem()+"页卡", Toast.LENGTH_SHORT).show();
- }
-
- }
- }
它的布局文件:
- <?xml version="1.0" encoding="utf-8"?>
- lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:orientation="vertical" >
-
- <LinearLayout
- android:id="@+id/linearLayout1"
- android:layout_width="fill_parent"
- android:layout_height="40.0dip"
- android:background="#FFFFFF" >
-
- <TextView
- android:id="@+id/text1"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:layout_weight="1.0"
- android:gravity="center"
- android:text=" @我"
- android:textColor="#000000"
- android:textSize="20.0dip" />
-
- <TextView
- android:id="@+id/text2"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:layout_weight="1.0"
- android:gravity="center"
- android:text="评论"
- android:textColor="#000000"
- android:textSize="20.0dip" />
-
- <TextView
- android:id="@+id/text3"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:layout_weight="1.0"
- android:gravity="center"
- android:text="私信"
- android:textColor="#000000"
- android:textSize="20.0dip" />
- </LinearLayout>
-
- <ImageView
- android:id="@+id/cursor"
- android:layout_width="fill_parent"
- android:layout_height="wrap_content"
- android:scaleType="matrix"
- android:src="@drawable/a" />
-
- <android.support.v4.view.ViewPager
- android:id="@+id/vPager"
- android:layout_width="wrap_content"
- android:layout_height="0dp"
- android:layout_gravity="center"
- android:layout_weight="1.0"
- android:background="#000000"
- android:flipInterval="30"
- android:persistentDrawingCache="animation" />
- lt;/LinearLayout>
效果如下:
下面使用ViewPager来实现一个程序引导的demo:
一般来说,引导界面是出现第一次运行时出现的,之后不会再出现。所以需要记录是否是第一次使用程序,办法有很多,最容易想到的就是使用SharedPreferences来保存。步骤如下:
1、程序进入欢迎界面,SplashActivity,在这里读取SharedPreferences里面的变量,先设置为true。进入引导界面,然后设置为false。
2、之后每次进入欢迎界面读取SharedPreferences里面的变量,因为是false,所以不会运行引导界面了。
代码如下:
SplashActivity.java,欢迎界面。
- import android.app.Activity;
- import android.content.Intent;
- import android.content.SharedPreferences;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Message;
-
-
-
-
- public class SplashActivity extends Activity {
- boolean isFirstIn = false;
-
- private static final int GO_HOME = 1000;
- private static final int GO_GUIDE = 1001;
-
- private static final long SPLASH_DELAY_MILLIS = 3000;
-
- private static final String SHAREDPREFERENCES_NAME = "first_pref";
-
-
-
-
- private Handler mHandler = new Handler() {
-
- @Override
- public void handleMessage(Message msg) {
- switch (msg.what) {
- case GO_HOME:
- goHome();
- break;
- case GO_GUIDE:
- goGuide();
- break;
- }
- super.handleMessage(msg);
- }
- };
-
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.splash);
-
- init();
- }
-
- private void init() {
-
-
- SharedPreferences preferences = getSharedPreferences(
- SHAREDPREFERENCES_NAME, MODE_PRIVATE);
-
-
- isFirstIn = preferences.getBoolean("isFirstIn", true);
-
-
- if (!isFirstIn) {
-
- mHandler.sendEmptyMessageDelayed(GO_HOME, SPLASH_DELAY_MILLIS);
- } else {
- mHandler.sendEmptyMessageDelayed(GO_GUIDE, SPLASH_DELAY_MILLIS);
- }
-
- }
-
- private void goHome() {
- Intent intent = new Intent(SplashActivity.this, MainActivity.class);
- SplashActivity.this.startActivity(intent);
- SplashActivity.this.finish();
- }
-
- private void goGuide() {
- Intent intent = new Intent(SplashActivity.this, GuideActivity.class);
- SplashActivity.this.startActivity(intent);
- SplashActivity.this.finish();
- }
- }
GuideActivity.java引导界面:
ViewPagerAdapter.java。ViewPager的适配器:
- import java.util.List;
- import android.app.Activity;
- import android.content.Context;
- import android.content.Intent;
- import android.content.SharedPreferences;
- import android.content.SharedPreferences.Editor;
- import android.os.Parcelable;
- import android.support.v4.view.PagerAdapter;
- import android.support.v4.view.ViewPager;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.widget.ImageView;
- import cn.eoe.leigo.splash.MainActivity;
- import cn.eoe.leigo.splash.R;
-
-
-
- public class ViewPagerAdapter extends PagerAdapter {
-
-
- private List<View> views;
- private Activity activity;
- private static final String SHAREDPREFERENCES_NAME = "first_pref";
- public ViewPagerAdapter(List<View> views, Activity activity) {
- this.views = views;
- this.activity = activity;
- }
-
-
- @Override
- public void destroyItem(View arg0, int arg1, Object arg2) {
- ((ViewPager) arg0).removeView(views.get(arg1));
- }
-
- @Override
- public void finishUpdate(View arg0) {
- }
-
-
- @Override
- public int getCount() {
- if (views != null) {
- return views.size();
- }
- return 0;
- }
-
-
- @Override
- public Object instantiateItem(View arg0, int arg1) {
- ((ViewPager) arg0).addView(views.get(arg1), 0);
- if (arg1 == views.size() - 1) {
- ImageView mStartWeiboImageButton = (ImageView) arg0
- .findViewById(R.id.iv_start_weibo);
- mStartWeiboImageButton.setOnClickListener(new OnClickListener() {
-
- @Override
- public void onClick(View v) {
-
- setGuided();
- goHome();
-
- }
-
- });
- }
- return views.get(arg1);
- }
-
- private void goHome() {
-
- Intent intent = new Intent(activity, MainActivity.class);
- activity.startActivity(intent);
- activity.finish();
- }
-
-
-
-
- private void setGuided() {
- SharedPreferences preferences = activity.getSharedPreferences(
- SHAREDPREFERENCES_NAME, Context.MODE_PRIVATE);
- Editor editor = preferences.edit();
-
- editor.putBoolean("isFirstIn", false);
-
- editor.commit();
- }
-
-
- @Override
- public boolean isViewFromObject(View arg0, Object arg1) {
- return (arg0 == arg1);
- }
-
- @Override
- public void restoreState(Parcelable arg0, ClassLoader arg1) {
- }
-
- @Override
- public Parcelable saveState() {
- return null;
- }
-
- @Override
- public void startUpdate(View arg0) {
- }
-
- }
至于MainActivity随便了。
效果如下:
所以总结一下,我们可以使用ViewPager做什么:
1.程序使用导航,外加底部圆点的效果,这个在微信示例里介绍了
2.页卡滑动,加上菜单的效果,不管是之前的支持手势也支持底部图标点击的微信,还是今天的微博。
代码下载连接