ViewPager轮播图 Handler方式实现

1.提取的基类BaseActivity

package com.example.viewpager_demo;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;

public abstract class BaseActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(getLayoutResId());
//初始化视图
initView();
//加载数据
initData();
}
protected abstract int getLayoutResId();
//初始化视图
protected abstract void initView();
//加载数据
protected abstract void initData();

}

2.MainActivity主页面

package com.example.viewpager_demo;

import android.annotation.SuppressLint;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.ViewPager;
import android.util.TypedValue;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.example.Ada
4000
per.BunnerAdaper;
import com.example.Bean.BunnerBean;
import com.example.Util.NetUtils;

public class MainActivity extends BaseActivity {
private String imageUrl = "https://api.tianapi.com/wxnew/?key=605fa0a929c8d8b116424df0510c6b2a&num=6&page=1";
private ViewPager viewPager;
private LinearLayout linearLayout;
private TextView textView;
private BunnerAdaper adaper;

@Override
protected int getLayoutResId() {
return R.layout.activity_main;
}

//初始化view
@Override
protected void initView() {
viewPager = findViewById(R.id.v_pager);
linearLayout = findViewById(R.id.L_layout);
textView = findViewById(R.id.text);
//创建适配器
adaper = new BunnerAdaper(this);
//设置给适配器
viewPager.setAdapter(adaper);
//滑动监听
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
//缓存的点
private int index = -1;

@Override
public void onPageScrolled(int i, float v, int i1) {

}

@Override
public void onPageSelected(int i) {
//改变textview
textView.setText(adaper.getItem(i).getTitle());
//改变当前点
linearLayout.getChildAt(i % linearLayout.getChildCount()).setSelected(true);
//还原原来的点
if (index >= 0) {
linearLayout.getChildAt(index % linearLayout.getChildCount()).setSelected(false);
}
index = i;
}

@Override
public void onPageScrollStateChanged(int i) {

}
});
}

//加载数据
@Override
protected void initData() {
NetUtils.getInstance().getRequest(imageUrl, BunnerBean.class, new NetUtils.CallBack<BunnerBean>() {
@Override
public void onSuccess(BunnerBean o) {
if (o == null || !o.isSuccess()) {
Toast.makeText(MainActivity.this, "请求错误", Toast.LENGTH_SHORT).show();
return;
}
adaper.setmList(o.getNewslist());
//初始化小圆点的方法
initDot(o.getNewslist().size());
//切换到中间位置
int center = adaper.getCount() / 2;
center = center - center % o.getNewslist().size();
viewPager.setCurrentItem(center);
//开启轮播
startLooper();
}
});
}

//创建handler
@SuppressLint("HandlerLeak")
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
handler.sendEmptyMessageDelayed(0, 2000);
}
};

//开启轮播
private void startLooper() {
handler.removeCallbacksAndMessages(null);
handler.sendEmptyMessageDelayed(0, 2000);
}

//初始化小圆点
private void initDot(int size) {
linearLayout.removeAllViews();
for (int i = 0; i < size; i++) {
ImageView imageView = new ImageView(this);
imageView.setBackgroundResource(R.drawable.select_dot);
//布局参数 宽高包裹
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT
);
int marage = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 5,
getResources().getDisplayMetrics());
params.leftMargin = marage;
params.rightMargin = marage;
linearLayout.addView(imageView, params);
}
}
}

3.适配器页面

package com.example.Adaper;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.example.Bean.BunnerBean;
import com.nostra13.universalimageloader.core.ImageLoader;

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

public class BunnerAdaper extends PagerAdapter {
private List<BunnerBean.NewslistBean> mList;
private Context mContext;

public BunnerAdaper(Context mContext) {
this.mContext = mContext;
//出始化
mList = new ArrayList<>();
}
public void setmList(List<BunnerBean.NewslistBean> lists){
mList.clear();
if(lists!=null){
mList.addAll(lists);
}
notifyDataSetChanged();
}
@Override
public int getCount() {
return mList.size()>0?5000:0;
}

@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object o) {
return view == o;
}
public BunnerBean.NewslistBean getItem(int position){
return mList.get(position%mList.size());
}
@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position) {
ImageView imageView = new ImageView(mContext);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
container.addView(imageView);
ImageLoader.getInstance().displayImage(getItem(position).getPicUrl(),imageView);
return imageView;
}

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

4.工具类

package com.example.Util;

import android.annotation.SuppressLint;
import android.os.AsyncTask;

import com.google.gson.Gson;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class NetUtils {
private static NetUtils instance;
private Gson gson;
public NetUtils() {
gson = new Gson();
}

public static NetUtils getInstance() {
if(instance == null){
instance = new NetUtils();
}
return instance;
}
//执行一个网络请求返回string
public String getRequest(String urlStr){
String result = "";
try {
//定义url地址
URL url = new URL(urlStr);
//打开连接
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
//设置请求格式
urlConnection.setRequestMethod("GET");
//设置超时
urlConnection.setReadTimeout(5000);
urlConnection.setConnectTimeout(5000);
//获取请求码
int responseCode = urlConnection.getResponseCode();
if(responseCode == 200){
result = stream2String(urlConnection.getInputStream());
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
//将字节流转换为字符流
private String stream2String(InputStream inputStream) throws IOException {
StringBuilder builder = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
for (String tmp = br.readLine();tmp!=null;tmp = br.readLine()){
builder.append(tmp);
}
return builder.toString();
}
//执行一个网络请求返回bean
public <E> E getRequest(String urlStr,Class clazz){
return (E) gson.fromJson(getRequest(urlStr),clazz);
}
//定义接口
public interface CallBack<E>{
void onSuccess(E e);
}
//异步 回调请求
@SuppressLint("StaticFieldLeak")
public void getRequest(String urlStr, final Class clazz, final CallBack callBack){
new AsyncTask<String,Void,Object>(){
@Override
protected Object doInBackground(String... strings) {
return getRequest(strings[0],clazz);
}

@Override
protected void onPostExecute(Object o) {
callBack.onSuccess(o);
}
}.execute(urlStr);
}
}

5.Bean类

package com.example.Bean;

import java.util.List;

public class BunnerBean {

private int code;
private String msg;
private List<NewslistBean> newslist;
private final int SUCCESS_CODE = 200;
public boolean isSuccess(){
return SUCCESS_CODE == code;
}
public int getCode() {
return code;
}

public void setCode(int code) {
this.code = code;
}

public String getMsg() {
return msg;
}

public void setMsg(String msg) {
this.msg = msg;
}

public List<NewslistBean> getNewslist() {
return newslist;
}

public void setNewslist(List<NewslistBean> newslist) {
this.newslist = newslist;
}

public static class NewslistBean {
private String ctime;
private String title;
private String description;
private String picUrl;
private String url;

public String getCtime() {
return ctime;
}

public void setCtime(String ctime) {
this.ctime = ctime;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public String getDescription() {
return description;
}

public void setDescription(String description) {
this.description = description;
}

public String getPicUrl() {
return picUrl;
}

public void setPicUrl(String picUrl) {
this.picUrl = picUrl;
}

public String getUrl() {
return url;
}

public void setUrl(String url) {
this.url = url;
}
}
}

6.Application初始化图片页面

package com.example.Application;

import android.app.Application;
import android.graphics.Bitmap;

import com.example.viewpager_demo.R;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;

public class App extends Application {
@Override
public void onCreate() {

ImageLoader.getInstance().init(new ImageLoaderConfiguration.Builder(this)
.diskCacheSize(50*1024*1024)
.memoryCacheSizePercentage(10)
.defaultDisplayImageOptions(new DisplayImageOptions.Builder()
.cacheInMemory(true)
.cacheOnDisk(true)
.bitmapConfig(Bitmap.Config.RGB_565)
.showImageOnLoading(R.mipmap.ic_launcher)
.showImageForEmptyUri(R.mipmap.ic_launcher)
.showImageOnFail(R.mipmap.ic_launcher)
.build())
.build());
super.onCreate();
}
}

7.布局页面

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.v4.view.ViewPager
android:id="@+id/v_pager"
android:layout_width="0dp"
android:layout_height="200dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
/>
<LinearLayout
android:id="@+id/L_layout"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:orientation="horizontal"
app:layout_constraintRight_toRightOf="@id/v_pager"
app:layout_constraintBottom_toBottomOf="@id/v_pager"
android:padding="8dp"
/>
<TextView
android:id="@+id/text"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:maxLines="1"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toLeftOf="@id/L_layout"
app:layout_constraintBottom_toBottomOf="@id/v_pager"
android:ellipsize="end"
/>
</android.support.constraint.ConstraintLayout>

7.轮播图小圆点

7.1默认圆点颜色
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval"
>
<size
android:width="8dp"
android:height="8dp"
/>
<solid
android:color="#909090"
/>
</shape>

7.2选中圆点颜色
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval"
>
<size
android:width="8dp"
android:height="8dp"
/>
<solid
android:color="#900000"
/>
</shape>

7.3select设置选中
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/shape_sel_dot" android:state_selected="true"></item>
<item android:drawable="@drawable/shape_normal_dot" ></item>
</selector>