android的ViewPager实现加载网络图片并自动轮播

来源：互联网发布：淘宝虚拟试衣编辑：程序博客网时间：2024/05/20 18:16

弄个图好看点。

gif

阅读本文之前，先看下前面打底的两篇文章。

android的ViewPager实现伪循环效果
android的ViewPager实现自动播放

前面已经实现了循环效果和自动播放，现在我们来实现加载网络图片。

使用的是第三方库 facebook的Fresco。

原文

android的ViewPager实现加载网络图片并自动轮播

代码

同以前一样，注意点用注释的形式给出。

这次需要注意下的地方有

build.gradle中加入Fresco
AndroidManifest.xml中加入访问网络的权限
App.java中初始化Fresco

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.qefee.pj.testviewpager">    <!--网络权限-->    <uses-permission android:name="android.permission.INTERNET"/>    <application        android:name=".App"        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <activity android:name=".MainActivity">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>

App.java

package com.qefee.pj.testviewpager;import android.app.Application;import com.facebook.drawee.backends.pipeline.Fresco;public class App extends Application {    @Override    public void onCreate() {        super.onCreate();        Fresco.initialize(this); // 初始化Fresco    }}

MainActivity.java

package com.qefee.pj.testviewpager;import android.net.Uri;import android.os.Bundle;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.View;import android.view.ViewGroup;import com.facebook.drawee.view.SimpleDraweeView;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;public class MainActivity extends AppCompatActivity {    /**     * log tag for MainActivity     */    private static final String TAG = "MainActivity";    ViewPager viewPager;    String[] imageUris = {            "https://pic4.zhimg.com/03b2d57be62b30f158f48f388c8f3f33_b.png",            "https://pic1.zhimg.com/4373a4f045e5e9ae16ebd6a624bf6228_b.png",            "https://pic2.zhimg.com/0364e17a1561f48793993d8bf1cdc785_b.png",            "https://pic2.zhimg.com/55fa74ff3eba164ed1db2037df1a8311_b.png",            "https://pic4.zhimg.com/5dc30569c06e7c6266c9809f6eb80a7b_b.jpg"    };    SimpleDraweeView[] simpleDraweeViews;    int currentItem;    private ScheduledExecutorService executor;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        int size = initSize();        initTextViews(size);        initViewPager();    }    @Override    protected void onResume() {        super.onResume();        startAutoScroll(); // activity激活时候自动播放    }    @Override    protected void onPause() {        super.onPause();        stopAutoScroll(); // activity暂停时候停止自动播放    }    private void startAutoScroll() {        stopAutoScroll();        executor = Executors.newSingleThreadScheduledExecutor();        Runnable command = new Runnable() {            @Override            public void run() {                selectNextItem();            }            private void selectNextItem() {                runOnUiThread(new Runnable() {                    @Override                    public void run() {                        viewPager.setCurrentItem(++currentItem);                    }                });            }        };        int delay = 2;        int period = 2;        TimeUnit timeUnit = TimeUnit.SECONDS;        executor.scheduleAtFixedRate(command, delay, period, timeUnit);    }    private void stopAutoScroll() {        if (executor != null) {            executor.shutdownNow();        }    }    private void initViewPager() {        viewPager = (ViewPager) findViewById(R.id.viewPage);        viewPager.setAdapter(new PagerAdapter() {            @Override            public int getCount() {                return Integer.MAX_VALUE; // 取一个大数字            }            @Override            public boolean isViewFromObject(View view, Object object) {                return view == object;            }            @Override            public Object instantiateItem(ViewGroup container, int position) {                Log.i(TAG, "instantiateItem: instantiateItem + position = " + position);                SimpleDraweeView t = simpleDraweeViews[position % simpleDraweeViews.length];                container.addView(t);                Uri uri = Uri.parse(imageUris[position % simpleDraweeViews.length]);                t.setImageURI(uri);                return t;            }            @Override            public void destroyItem(ViewGroup container, int position, Object object) {                Log.i(TAG, "destroyItem: + position = " + position);                container.removeView((View) object);            }        });        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {            @Override            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {            }            @Override            public void onPageSelected(int position) {                currentItem = position;                startAutoScroll(); // 手动切换完成后恢复自动播放            }            @Override            public void onPageScrollStateChanged(int state) {            }        });        currentItem = imageUris.length * 1000000; // 取一个中间的大数字, 防止接近边界        viewPager.setCurrentItem(currentItem);    }    private void initTextViews(int size) {        SimpleDraweeView[] tvs = new SimpleDraweeView[size];        for (int i = 0; i < tvs.length; i++) {            tvs[i] = new SimpleDraweeView(this);            tvs[i].getHierarchy().setPlaceholderImage(R.mipmap.ic_launcher);            ViewGroup.LayoutParams layoutParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);            tvs[i].setLayoutParams(layoutParams);            simpleDraweeViews = tvs;        }    }    private int initSize() {        int size;        if (imageUris.length > 3) {            size = imageUris.length;        } else {            size = imageUris.length * 2; // 小于3个时候, 需要扩大一倍, 防止出错        }        return size;    }}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.qefee.pj.testviewpager.MainActivity">    <android.support.v4.view.ViewPager        android:id="@+id/viewPage"        android:layout_width="match_parent"        android:layout_height="match_parent"/></RelativeLayout>

build.gradle (app)

apply plugin: 'com.android.application'android {    compileSdkVersion 23    buildToolsVersion "23.0.3"    defaultConfig {        applicationId "com.qefee.pj.testviewpager"        minSdkVersion 15        targetSdkVersion 23        versionCode 1        versionName "1.0"    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'        }    }}dependencies {    compile fileTree(dir: 'libs', include: ['*.jar'])    testCompile 'junit:junit:4.12'    compile 'com.android.support:appcompat-v7:23.4.0'//    加入Fresco    compile 'com.facebook.fresco:fresco:0.10.0'}

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