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Android实现自定义轮播图片控件详解

首先上效果图

实现原理

要完成一个轮播图片，首先想到的应该是使用ViewPager来实现。ViewPager已经有了滑动的功能，我们只要让它自己滚动。再加上下方的小圆点就行了。所以我们本次的自定义控件就是由ViewPager和LinearLayout叠加起来组成的。

一、创建一个自定义的ViewPager

先上完整的代码

package com.kcode.autoscrollviewpager.view;

import android.content.Context;
import android.os.Message;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;

import java.util.Timer;
import java.util.TimerTask;

/**
 * Created by caik on 2016/10/10.
 */

public class AutoViewPager extends ViewPager {

 private static final String TAG = "AutoViewPager";

 private int currentItem;

 private Timer mTimer;
 private AutoTask mTask;

 private boolean isFirst = true;

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

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


 public void start(){
  if (mTimer == null) {
   mTimer = new Timer();
  }
  mTimer.schedule(new AutoTask(),3000,3000);

 }

 private Runnable runnable = new Runnable() {
  @Override
  public void run() {
   currentItem = getCurrentItem();
   if(currentItem == getAdapter().getCount() - 1){
    currentItem = 0 ;
   }else {
    currentItem++ ;
   }
   setCurrentItem(currentItem);
  }
 };

 private AutoHandler mHandler = new AutoHandler();

 public void updatePointView(int size) {
  if (getParent() instanceof AutoScrollViewPager){
   AutoScrollViewPager pager = (AutoScrollViewPager) getParent();
   pager.initPointView(size);
  }else {
   Log.e(TAG,"parent view not be AutoScrollViewPager");
  }
 }

 public void onPageSelected(int position) {
  AutoScrollViewPager pager = (AutoScrollViewPager) getParent();
  pager.updatePointView(position);
 }

 private class AutoTask extends TimerTask{

  @Override
  public void run() {
   mHandler.post(runnable);
  }
 }

 private final static class AutoHandler extends android.os.Handler{
  @Override
  public void handleMessage(Message msg) {
   super.handleMessage(msg);

  }
 }

 public void onStop(){
  //先取消定时器
  if (mTimer != null) {
   mTimer.cancel();
   mTimer = null;
  }
 }

 public void onDestroy(){
  onStop();
 }

 public void onResume(){
  start();
 }

 @Override
 public boolean onTouchEvent(MotionEvent ev) {
  switch (ev.getAction()){
   case MotionEvent.ACTION_DOWN:
    Log.i(TAG,"down");
    onStop();
    break;
   case MotionEvent.ACTION_MOVE:
    Log.i(TAG,"move");
    break;
   case MotionEvent.ACTION_UP:
    Log.i(TAG,"up");
    onResume();
    break;
  }
  return super.onTouchEvent(ev);
 }
}

AutoViewPager 继承至ViewPager，我们通过Timer来启动一个定时器。

public void start(){
  if (mTimer == null) {
   mTimer = new Timer();
  }
  mTimer.schedule(new AutoTask(),3000,3000);

 }

 private Runnable runnable = new Runnable() {
  @Override
  public void run() {
   currentItem = getCurrentItem();
   if(currentItem == getAdapter().getCount() - 1){
    currentItem = 0 ;
   }else {
    currentItem++ ;
   }
   setCurrentItem(currentItem);
  }
 };

每隔三秒去更新一下页面。这样就能起到一个自己滚动的效果。

二、设置Adapter

要实现无限循环，只要把Adapter中的getCount()方法返回无限大，直接返回Integer.MAX_VALUE就可以了。

完整的Adapter代码：

package com.kcode.autoscrollviewpager.view;

import android.content.Context;
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 android.widget.ImageView;

import com.kcode.autoscrollviewpager.R;

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

/**
 * Created by caik on 2016/10/11.
 */

public abstract class BaseViewPagerAdapter<T> extends PagerAdapter implements ViewPager.OnPageChangeListener{

 private List<T> data = new ArrayList<>();

 private Context mContext;
 private AutoViewPager mView;

 private OnAutoViewPagerItemClickListener listener;

 public BaseViewPagerAdapter(List<T> t) {
  this.data = t;
 }

 public BaseViewPagerAdapter(Context context, AutoViewPager viewPager) {
  this.mContext = context;
  mView = viewPager;
  mView.setAdapter(this);
  mView.addOnPageChangeListener(this);
  mView.setCurrentItem(0);
 }


 public BaseViewPagerAdapter(Context context, AutoViewPager viewPager,OnAutoViewPagerItemClickListener listener) {
  this.mContext = context;
  mView = viewPager;
  this.listener = listener;
  mView.setAdapter(this);
  mView.addOnPageChangeListener(this);
  mView.setCurrentItem(0);
 }

 public BaseViewPagerAdapter(Context context, List<T> data,AutoViewPager viewPager,OnAutoViewPagerItemClickListener listener) {
  this.mContext = context;
  mView = viewPager;
  this.data = data;
  this.listener = listener;
  mView.setAdapter(this);
  mView.addOnPageChangeListener(this);
  mView.setCurrentItem(0);

  mView.start();
  mView.updatePointView(getRealCount());
 }

 public void add(T t){
  data.add(t);
  notifyDataSetChanged();
  mView.updatePointView(getRealCount());
 }

 @Override
 public int getCount() {
  return data == null ? 0 : Integer.MAX_VALUE;
 }

 public int getRealCount(){
  return data == null ? 0 : data.size();
 }

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

 @Override
 public Object instantiateItem(ViewGroup container, final int position) {
  ImageView view = (ImageView) LayoutInflater.from(mContext)
    .inflate(R.layout.imageview,container,false);
  view.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View view) {
    if (listener != null) {
     listener.onItemClick(position % getRealCount(),data.get(position % getRealCount()));
    }
   }
  });

  loadImage(view,position, data.get(position % getRealCount()));
  container.addView(view);

  return view;
 }

 public abstract void loadImage(ImageView view,int position,T t);

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

 @Override
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

 }

 @Override
 public void onPageSelected(int position) {
  mView.onPageSelected(position % getRealCount());
 }

 @Override
 public void onPageScrollStateChanged(int state) {

 }

 public interface OnAutoViewPagerItemClickListener<T> {
  void onItemClick(int position,T t);
 }
}

这里我们使用了泛型，因为有时候我们可能只传一个url集合进来，也可能是对象集合，方便拓展。加载图片的方法也是一个抽象方法

public abstract void loadImage(ImageView view,int position,T t);

因为每个App使用的图片加载框架都不一样，所以这里的加载就留个App自己实现。使用的时候创建Adapter只要继承这里的BaseViewPagerAdapter，然后重写loadImage(ImageView view,int position,T t)方法，在这里进行图片的加载就行了。

如果你需不要底部的小圆点标示的话，这里就已经完成了。

使用的时候，直接使用

 <com.kcode.autoscrollviewpager.view.AutoViewPager
  android:layout_width="match_parent"
  android:layout_height="200dp">
  
 </com.kcode.autoscrollviewpager.view.AutoViewPager>

代替

 <android.support.v4.view.ViewPager
  android:layout_width="match_parent"
  android:layout_height="match_parent">

 </android.support.v4.view.ViewPager>

就可以了。需要底部的小圆点标示的话，继续往下

三、添加小圆点标示

需要添加小圆点标示的话。其实就是在ViewPager上再加一层。我们新建一个View，继承至RelativeLayout

完整代码如下：

package com.kcode.autoscrollviewpager.view;

import android.content.Context;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

import com.kcode.autoscrollviewpager.R;

import static android.view.Gravity.CENTER;

/**
 * Created by caik on 2016/10/17.
 */

public class AutoScrollViewPager extends RelativeLayout{

 private AutoViewPager mViewPager;

 private Context mContext;

 private LinearLayout layout;

 public AutoScrollViewPager(Context context) {
  super(context);
  init(context);
 }

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

 private void init(Context context){
  mContext = context;
  mViewPager = new AutoViewPager(context);
  layout = new LinearLayout(mContext);
  addView(mViewPager);
 }

 public AutoViewPager getViewPager() {
  return mViewPager;
 }

 public void initPointView(int size){

  layout = new LinearLayout(mContext);
  for (int i = 0; i < size; i++) {
   ImageView imageView = new ImageView(mContext);
   LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(20,20);
   params.leftMargin = 8;
   params.gravity = CENTER;
   imageView.setLayoutParams(params);
   if (i == 0) {
    imageView.setBackgroundResource(R.drawable.point_checked);
   }else {
    imageView.setBackgroundResource(R.drawable.point_normal);
   }

   layout.addView(imageView);
  }

  LayoutParams layoutParams = new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  layoutParams.addRule(ALIGN_PARENT_BOTTOM);
  layoutParams.addRule(ALIGN_PARENT_RIGHT);
  layoutParams.setMargins(12,20,12,20);
  layout.setLayoutParams(layoutParams);
  addView(layout);
 }

 public void updatePointView(int position) {
  int size = layout.getChildCount();
  for (int i = 0; i < size; i++) {
   ImageView imageView = (ImageView) layout.getChildAt(i);
   if (i == position){
    imageView.setBackgroundResource(R.drawable.point_checked);
   }else {
    imageView.setBackgroundResource(R.drawable.point_normal);
   }

  }
 }

}

初始化的时候创建一个ViewPager,一个LinearLayout（用来放小圆点）

 public AutoScrollViewPager(Context context) {
  super(context);
  init(context);
 }

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

 private void init(Context context){
  mContext = context;
  mViewPager = new AutoViewPager(context);
  layout = new LinearLayout(mContext);
  addView(mViewPager);
 }

再通过addView(mViewPager);添加。

需要准备两张图片，这里用Shape进行绘制,Shape的使用可以查看Android Shape使用.

初始化小圆点：

 public void initPointView(int size){

  layout = new LinearLayout(mContext);
  for (int i = 0; i < size; i++) {
   ImageView imageView = new ImageView(mContext);
   LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(20,20);
   params.leftMargin = 8;
   params.gravity = CENTER;
   imageView.setLayoutParams(params);
   if (i == 0) {
    imageView.setBackgroundResource(R.drawable.point_checked);
   }else {
    imageView.setBackgroundResource(R.drawable.point_normal);
   }

   layout.addView(imageView);
  }

  LayoutParams layoutParams = new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  layoutParams.addRule(ALIGN_PARENT_BOTTOM);
  layoutParams.addRule(ALIGN_PARENT_RIGHT);
  layoutParams.setMargins(12,20,12,20);
  layout.setLayoutParams(layoutParams);
  addView(layout);
 }

更新小圆点：

 public void updatePointView(int position) {
  int size = layout.getChildCount();
  for (int i = 0; i < size; i++) {
   ImageView imageView = (ImageView) layout.getChildAt(i);
   if (i == position){
    imageView.setBackgroundResource(R.drawable.point_checked);
   }else {
    imageView.setBackgroundResource(R.drawable.point_normal);
   }

  }
 }

带小圆点的使用以下控件

 <com.kcode.autoscrollviewpager.view.AutoScrollViewPager
  android:id="@+id/viewPager"
  android:layout_width="match_parent"
  android:layout_height="220dp">

 </com.kcode.autoscrollviewpager.view.AutoScrollViewPager>

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流。

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