android欢迎界面代码（一）
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。
package com.fang.myviewpager;
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;
// 延迟3秒
private static final long SPLASH_DELAY_MILLIS = 3000;
private static final String SHAREDPREFERENCES_NAME = "first_pref";
/**
* Handler:跳转到不同界面
*/
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() {
// 读取SharedPreferences中需要的数据
// 使用SharedPreferences来记录程序的使用次数
SharedPreferences preferences = getSharedPreferences(
SHAREDPREFERENCES_NAME, MODE_PRIVATE);
// 取得相应的值，如果没有该值，说明还未写入，用true作为默认值
isFirstIn = preferences.getBoolean("isFirstIn", true);
// 判断程序与第几次运行，如果是第一次运行则跳转到引导界面，否则跳转到主界面
if (!isFirstIn) {
// 使用Handler的postDelayed方法，3秒后执行跳转到MainActivity
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, MainActivity.class);
SplashActivity.this.startActivity(intent);
SplashActivity.this.finish();
}
}
GuideActivity.java引导界面：
package com.fang.myviewpager;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
/**
*
*
*/
public class GuideActivity extends Activity implements OnPageChangeListener {
private ViewPager vp;
private ViewPagerAdapter vpAdapter;
private List<View> views;
// 底部小点图片
private ImageView[] dots;
// 记录当前选中位置
private int currentIndex;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 初始化页面
initViews();
// 初始化底部小点
initDots();
}
private void initViews() {
// 加载要显示的页卡
LayoutInflater inflater = LayoutInflater.from(this);
views = new ArrayList<View>(); //将要分页显示的View装入数组中
views.add(inflater.inflate(R.layout.view1, null));
views.add(inflater.inflate(R.layout.view2, null));
views.add(inflater.inflate(R.layout.view3, null));
views.add(inflater.inflate(R.layout.view4, null));
// 初始化Adapter
vpAdapter = new ViewPagerAdapter(views, this);
vp = (ViewPager) findViewById(R.id.viewpager);
/*LayoutInflater的作用类似于 findViewById(),不同点是LayoutInflater是用来找layout文件夹下的xml布局文件，并且实例化！ 而
findViewById()是找具体某一个xml下的具体 widget控件(如:Button,TextView等)。*/
vp.setAdapter(vpAdapter);
// 绑定回调
vp.setOnPageChangeListener(this);
}
private void initDots() {
LinearLayout ll = (LinearLayout) findViewById(R.id.ll);
dots = new ImageView[views.size()];
// 循环取得小点图片
for (int i = 0; i < views.size(); i++) {
dots[i] = (ImageView) ll.getChildAt(i);
dots[i].setEnabled(true);// 都设为灰色
}
currentIndex = 0;
dots[currentIndex].setEnabled(false);// 设置为白色，即选中状态
}
private void setCurrentDot(int position) {
if (position < 0 || position > views.size() - 1
|| currentIndex == position) {
return;
}
dots[position].setEnabled(false);
dots[currentIndex].setEnabled(true);
currentIndex = position;
}
// 当滑动状态改变时调用
@Override
public void onPageScrollStateChanged(int arg0) {
}
// 当当前页面被滑动时调用
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
// 当新的页面被选中时调用
@Override
public void onPageSelected(int arg0) {
// 设置底部小点选中状态
setCurrentDot(arg0);
}
}
ViewPagerAdapter.java。ViewPager的适配器：
package com.fang.myviewpager;
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;
/**
*/
public class ViewPagerAdapter extends PagerAdapter {
// 界面列表
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;
}
// 销毁arg1位置的界面
@Override
public void destroyItem(View arg0, int arg1, Object arg2) {
((ViewPager) arg0).removeView(views.get(arg1));
}
/*public void destroyItem (ViewGroup container, int position, Object object)
Remove a page for the given position. The adapter is responsible for removing the view from its container, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup).
Parameters
| container | The containing View from which the page will be removed. |
|---|---|
| position | The page position to be removed. |
| object | The same object that was returned by instantiateItem(View, int). |
该方法实现的功能是移除一个给定位置的页面。适配器有责任从容器中删除这个视图。这是为了确保在finishUpdate(viewGroup)返回时视图能够被移除。*/
@Override
public void finishUpdate(View arg0) {
}
// 获得当前界面数
@Override
public int getCount() {
if (views != null) {
return views.size();
}
return 0;
}
/*public Object instantiateItem (ViewGroup container, int position)
Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns fromfinishUpdate(ViewGroup).
Parameters
| container | The containing View in which the page will be shown. |
|---|---|
| position | The page position to be instantiated. |
Returns
- Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page.*/
// 初始化arg1位置的界面
@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);
mStartWeiboImageButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// 设置已经引导
setGuided();
goHome();
}
});
}
return views.get(arg1);
}
private void goHome() {
// 跳转
Intent intent = new Intent(activity, MainActivity.class);
activity.startActivity(intent);
activity.finish();
}
/**
*
* method desc：设置已经引导过了，下次启动不用再次引导
*/
private void setGuided() {
SharedPreferences preferences = activity.getSharedPreferences(
SHAREDPREFERENCES_NAME, Context.MODE_PRIVATE);
Editor editor = preferences.edit();
// 存入数据
editor.putBoolean("isFirstIn", false);
// 提交修改
editor.commit();
}
// 判断是否由对象生成界面 isViewFromObject(View arg0,Object arg1)函数的功能：该函数用来判断instantiateItem(ViewGroup, int)函数所返回来的Key与一个页面视图是否是代表的同一个视图(即它俩是否是对应的，对应的表示同一个View)
返回值：如果对应的是同一个View，返回True，否则返回False。
@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。
主布局文件activity_main.xml：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<LinearLayout
android:id="@+id/ll"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="24.0dp"
android:orientation="horizontal" >
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:clickable="true"
android:padding="15.0dip"
android:src="@drawable/dot" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:clickable="true"
android:padding="15.0dip"
android:src="@drawable/dot" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:clickable="true"
android:padding="15.0dip"
android:src="@drawable/dot" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:clickable="true"
android:padding="15.0dip"
android:src="@drawable/dot" />
</LinearLayout>
</RelativeLayout>
splash.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="@drawable/splash"
android:orientation="vertical" >
</LinearLayout>
view1.xml view2.xml view3.xml :
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/guide1" />
</RelativeLayout>
view4.xml :
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerInParent="true"
android:adjustViewBounds="false"
android:background="@drawable/guide4"
android:focusable="true"
android:scaleType="centerCrop" />
<ImageView
android:id="@+id/iv_start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="108dp"
android:background="@drawable/button"
android:focusable="true" />
</RelativeLayout>
drawable文件夹下新建dot.xml：
<?xml version="1.0" encoding="UTF-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/page_indicator_unfocused" android:state_enabled="true"/>
<item android:drawable="@drawable/page_indicator_focused" android:state_enabled="false"/>
</selector>
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。
