1、ViewPager講解
ViewPager不直接處理每一個視圖而是將各個視圖與一個鍵聯繫起來。這個鍵用來跟蹤且唯一代表一個頁面,不僅如此,該鍵還獨立於這個頁面所在adapter的位置。當PagerAdapter將要改變的時候他會調用startUpdate函數,接下來會調用一次或多次的instantiateItem或者destroyItem。最後在更新的後期會調用finishUpdate。當finishUpdate返回時 instantiateItem返回的對象應該添加到父ViewGroup destroyItem返回的對象應該被ViewGroup刪除。methodisViewFromObject(View, Object)代表了當前的頁面是否與給定的鍵相關聯。
2、應用ViewPager實現圖片自動切換
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.wlx.activity.HomeActivity"
tools:ignore="MergeRootFrame"
>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<android.support.v4.view.ViewPager
android:id="@+id/imageViewPager"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="23dp"
android:gravity="center"
android:layout_gravity="bottom"
android:orientation="horizontal"
android:background="#33000000"
>
<View
android:id="@+id/dot_0"
android:layout_width="7dp"
android:layout_height="7dp"
android:layout_marginTop="8dp"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="@drawable/dot_normal"
/>
<View
android:id="@+id/dot_1"
android:layout_width="7dp"
android:layout_height="7dp"
android:layout_marginTop="8dp"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="@drawable/dot_normal"
/>
<View
android:id="@+id/dot_2"
android:layout_width="7dp"
android:layout_height="7dp"
android:layout_marginTop="8dp"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="@drawable/dot_normal"
/>
<View
android:id="@+id/dot_3"
android:layout_width="7dp"
android:layout_height="7dp"
android:layout_marginTop="8dp"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="@drawable/dot_normal"
/>
<View
android:id="@+id/dot_4"
android:layout_width="7dp"
android:layout_height="7dp"
android:layout_marginTop="8dp"
android:layout_marginLeft="3dp"
android:layout_marginRight="5dp"
android:background="@drawable/dot_normal"
/>
</LinearLayout>
</FrameLayout>
</LinearLayout>
package com.wlx.activity;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import com.example.hangzhouapp.R;
import com.example.hangzhouapp.R.id;
import com.example.hangzhouapp.R.layout;
import com.example.hangzhouapp.R.menu;
import android.R.integer;
import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.os.Build;
public class HomeActivity extends Activity {
private List<ImageView> imageViewList;
private List<View> dotList;
private int prePosition;
private int curPosition;
private ViewPager imageViewPager;
private ViewPagerAdapter imageViewPagerAdapter;
private ScheduledExecutorService scheduledExecutorService;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
initView();
imageViewPagerAdapter = new ViewPagerAdapter();
imageViewPager.setAdapter(imageViewPagerAdapter);
imageViewPager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// TODO Auto-generated method stub
dotList.get(prePosition).setBackgroundResource(R.drawable.dot_normal);
dotList.get(position).setBackgroundResource(R.drawable.dot_focused);
prePosition = position;
curPosition = position;
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
// TODO Auto-generated method stub
}
@Override
public void onPageScrollStateChanged(int arg0) {
// TODO Auto-generated method stub
}
});
}
@Override
public void onStart()
{
super.onStart();
//創建大小爲1的固定線程池
scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
//使得ScollImageTask()每隔兩秒執行一次
scheduledExecutorService.scheduleWithFixedDelay(new ScollImageTask(), 2, 2, TimeUnit.SECONDS);
}
Handler hander = new Handler(){
@Override
public void handleMessage(Message msg)
{
imageViewPager.setCurrentItem(curPosition);
}
};
private void initView() {
// TODO Auto-generated method stub
imageViewList = new ArrayList<ImageView>();
imageViewList.add(CreateImageView(R.drawable.a));
imageViewList.add(CreateImageView(R.drawable.b));
imageViewList.add(CreateImageView(R.drawable.c));
imageViewList.add(CreateImageView(R.drawable.d));
imageViewList.add(CreateImageView(R.drawable.e));
dotList = new ArrayList<View>();
dotList.add(findViewById(R.id.dot_0));
dotList.add(findViewById(R.id.dot_1));
dotList.add(findViewById(R.id.dot_2));
dotList.add(findViewById(R.id.dot_3));
dotList.add(findViewById(R.id.dot_4));
dotList.get(0).setBackgroundResource(R.drawable.dot_focused);
imageViewPager = (ViewPager) findViewById(R.id.imageViewPager);
}
private ImageView CreateImageView(int resourceId)
{
ImageView imageView = new ImageView(this);
imageView.setBackgroundResource(resourceId);
return imageView;
}
private class ViewPagerAdapter extends PagerAdapter
{
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
// TODO Auto-generated method stub
container.removeView(imageViewList.get(position));
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
// TODO Auto-generated method stub
container.addView(imageViewList.get(position));
return imageViewList.get(position);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return imageViewList.size();
}
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
// TODO Auto-generated method stub
return arg0 == arg1;
}
}
private class ScollImageTask implements Runnable
{
@Override
public void run() {
// TODO Auto-generated method stub
curPosition = (curPosition + 1) % imageViewList.size();
hander.obtainMessage().sendToTarget();
}
}
}
在圖片的右下角有圓點會跟隨圖片的滑動而改變,這裏定義了兩種圓點的樣式,代碼如下:<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<corners android:radius="7dp"/>
<solid android:color="#55000000"/>
</shape>
dot_focused.xml<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<corners android:radius="7dp"/>
<solid android:color="#aaFFFFFF"/>
</shape>
效果圖如下: