【第二篇】Volley的使用之加载图片

Volley加载图片有两种方式:
  1,ImageRequest 来对网络图片进行请求,放入请求队列,获取后现在在控件上面。
  2,NetworkImageView 最为自定义控件来自动加载网络图片。

  3,imageloader,对图片大小,质量格式控制来按需加载图片。
下面分别举例子说明使用:

ImageRequest的使用来加载图片:
首先设计界面,是个Gridview来加载图片:
activity_main.xml文章来源地址https://www.yii666.com/article/764394.html

<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=".MainActivity" >
<GridView android:id="@+id/gvImages"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="3"
android:stretchMode="columnWidth"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp">
</GridView>
</RelativeLayout>

GridView的item布局文件如下,上面是图片,下面是文字说明:文章来源地址:https://www.yii666.com/article/764394.html

<?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:id="@+id/ivImage"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:contentDescription="test" />
<TextView
android:id="@+id/tvDesc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/ivImage"
android:layout_centerHorizontal="true" />
</RelativeLayout>

下面是主要的图片加载的逻辑代码,流程如下:

  1,创建请求队列mQueue;
  2,创建ImageRequest 请求,并进行配置,并将请求放入请求队列mqueue中去;
  3,ImageRequest只有一个构造方法:对图片大小和图片格式进行设置;

 /**
* Creates a new image request, decoding to a maximum specified width and
* height. If both width and height are zero, the image will be decoded to
* its natural size. If one of the two is nonzero, that dimension will be
* clamped and the other one will be set to preserve the image's aspect
* ratio. If both width and height are nonzero, the image will be decoded to
* be fit in the rectangle of dimensions width x height while keeping its
* aspect ratio.
*
* @param url URL of the image 网络图片Url
* @param listener Listener to receive the decoded bitmap 接收网络图片的bitmap回调参数
* @param maxWidth Maximum width to decode this bitmap to, or zero for none 宽
* @param maxHeight Maximum height to decode this bitmap to, or zero for 高
* none
* @param decodeConfig Format to decode the bitmap to 编码质量的配置
* @param errorListener Error listener, or null to ignore errors 加载图片失败的回调
*/
public ImageRequest(String url, Response.Listener<Bitmap> listener, int maxWidth, int maxHeight,
Config decodeConfig, Response.ErrorListener errorListener) {
super(Method.GET, url, errorListener);
setRetryPolicy(
new DefaultRetryPolicy(IMAGE_TIMEOUT_MS, IMAGE_MAX_RETRIES, IMAGE_BACKOFF_MULT));
mListener = listener;
mDecodeConfig = decodeConfig;
mMaxWidth = maxWidth;
mMaxHeight = maxHeight;
}
package com.soyoungboy.volleydemo;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.Response.ErrorListener;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.ImageRequest;
import com.android.volley.toolbox.Volley;
/**
* Volley使用demo
*
* @author soyoungboy
*/
public class MainActivity extends Activity {
private static final String[] URLS = {
"http://img.my.csdn.net/uploads/201403/03/1393854094_4652.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_6138.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_1323.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_8439.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854083_6511.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854083_2323.jpg" };
private static final String[] DESCS = { "photo1", "photo2", "photo3",
"photo4", "photo5", "photo6" };
private RequestQueue mQueue;
private GridView gvImages;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gvImages = (GridView) findViewById(R.id.gvImages);
GridAdapter adpater = new GridAdapter();
gvImages.setAdapter(adpater);
mQueue = Volley.newRequestQueue(this);
}
class GridAdapter extends BaseAdapter {
private LayoutInflater layoutInflater;
public GridAdapter() {
layoutInflater = LayoutInflater.from(MainActivity.this);
}
@Override
public int getCount() {
return URLS.length;
}
@Override
public Object getItem(int position) {
return URLS[position];
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
viewHolder = new ViewHolder();
convertView = layoutInflater.inflate(R.layout.grid_item, null);
viewHolder.ivImage = (ImageView) convertView
.findViewById(R.id.ivImage);
viewHolder.tvDesc = (TextView) convertView
.findViewById(R.id.tvDesc);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
loadImgByVolley(URLS[position], viewHolder.ivImage);
viewHolder.tvDesc.setText(DESCS[position]);
return convertView;
}
}
static class ViewHolder {
ImageView ivImage;
TextView tvDesc;
}
public void loadImgByVolley(String imgUrl, final ImageView imageView) {
ImageRequest imgRequest = new ImageRequest(imgUrl,
new Response.Listener<Bitmap>() {
/**
* 加载成功
* @param arg0
*/
@Override
public void onResponse(Bitmap arg0) {
imageView.setImageBitmap(arg0);
}
}, 300, 200, Config.ARGB_8888,
new ErrorListener() {
//加载失败
@Override
public void onErrorResponse(VolleyError arg0) {
imageView.setImageResource(R.drawable.ic_launcher);
}
});
//将图片加载放入请求队列中去
mQueue.add(imgRequest);
}
}

效果:
【第二篇】Volley的使用之加载图片
NetworkImageView加载图片:
首先在布局中使用NetWorkImageView:网址:yii666.com<

<?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" >
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/load_img"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</RelativeLayout>

java代码里面实现:文章地址https://www.yii666.com/article/764394.html

package com.soyoungboy.volleydemo;
import android.app.Activity;
import android.os.Bundle;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.NetworkImageView;
import com.android.volley.toolbox.Volley;
public class NetworkImageViewActivity extends Activity {
private NetworkImageView load_img;
private ImageLoader imageLoader;
private RequestQueue requestQueue;
private LruImageCache lruImageCache;
private static final String IMGURL = "http://imgsrc.baidu.com/forum/w%3D580/sign=f96acdfc08f79052ef1f47363cf1d738/cb2fc65c10385343223c39ce9213b07ecb808870.jpg";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_networkimageview);
load_img = (NetworkImageView) findViewById(R.id.load_img);
lruImageCache = LruImageCache.getInstance();
requestQueue = Volley.newRequestQueue(this);
imageLoader = new ImageLoader(requestQueue, lruImageCache);
load_img.setImageUrl(IMGURL, imageLoader);
}
}

LruImageCache.java缓存类:

package com.soyoungboy.volleydemo;

import android.graphics.Bitmap;
import android.support.v4.util.LruCache; import com.android.volley.toolbox.ImageLoader.ImageCache; public class LruImageCache implements ImageCache{ private static LruCache<String, Bitmap> mMemoryCache; private static LruImageCache lruImageCache; private LruImageCache(){
// Get the Max available memory
int maxMemory = (int) Runtime.getRuntime().maxMemory();
int cacheSize = maxMemory / 8;
mMemoryCache = new LruCache<String, Bitmap>(cacheSize){
@Override
protected int sizeOf(String key, Bitmap bitmap){
return bitmap.getRowBytes() * bitmap.getHeight();
}
};
} public static LruImageCache getInstance(){
if(lruImageCache == null){
lruImageCache = new LruImageCache();
}
return lruImageCache;
} @Override
public Bitmap getBitmap(String arg0) {
return mMemoryCache.get(arg0);
} @Override
public void putBitmap(String arg0, Bitmap arg1) {
if(getBitmap(arg0) == null){
mMemoryCache.put(arg0, arg1);
}
} }

其中LruImageCache是个Lru算法类,主要用于处理缓存的大小问题,可以避免加载图片的时候oom的问题,ImaageLoader是volley提供的另外一种加载图片的方式。最后通过setImageUrl(String url, ImageLoader imageLoader)来进行加载。
NetworkImageView的优势在于他能够根据组件的大小自动进行图片的大小缩放处理。后面文章会在源码分析中进行讲解。
效果:
【第二篇】Volley的使用之加载图片
ImageLoader加载图片:
帮我们对图片进行缓存,还可以过滤掉重复的链接,避免重复发送请求。
  1,创建请求队列;
  2,创建imageloader对象,其中imageloader的构造方法第二个参数为imageCache的实现类,实现图片缓存的算法类。
  3,创建imagelistener对象,主要设置图片加载失败和加载过程中的图片设置。
界面如上面第一个的界面activity_main.xml;
这里主要看下逻辑:

package com.soyoungboy.volleydemo.activity;
import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.ImageLoader.ImageListener;
import com.android.volley.toolbox.Volley;
import com.soyoungboy.volleydemo.LruImageCache;
import com.soyoungboy.volleydemo.R;
public class ImageLoaderActivity extends Activity {
private GridView gvImages;
private static final String[] URLS = {
"http://img.my.csdn.net/uploads/201403/03/1393854094_4652.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_6138.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_1323.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854084_8439.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854083_6511.jpg",
"http://img.my.csdn.net/uploads/201403/03/1393854083_2323.jpg" };
private static final String[] DESCS = { "photo1", "photo2", "photo3",
"photo4", "photo5", "photo6" };
private RequestQueue mQueue;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gvImages = (GridView) findViewById(R.id.gvImages);
mQueue = Volley.newRequestQueue(this);
GridAdapter adpater = new GridAdapter();
gvImages.setAdapter(adpater);
}
class GridAdapter extends BaseAdapter {
private LayoutInflater layoutInflater;
private ImageLoader imageLoader;
public GridAdapter() {
layoutInflater = LayoutInflater.from(ImageLoaderActivity.this);
imageLoader = new ImageLoader(mQueue, LruImageCache.getInstance());
}
@Override
public int getCount() {
return URLS.length;
}
@Override
public Object getItem(int position) {
return URLS[position];
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
viewHolder = new ViewHolder();
convertView = layoutInflater.inflate(R.layout.grid_item, null);
viewHolder.ivImage = (ImageView) convertView
.findViewById(R.id.ivImage);
viewHolder.tvDesc = (TextView) convertView
.findViewById(R.id.tvDesc);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
loadImgByVolley(URLS[position], viewHolder.ivImage);
viewHolder.tvDesc.setText(DESCS[position]);
return convertView;
}
private void loadImgByVolley(String string, ImageView ivImage) {
ImageListener listener = ImageLoader.getImageListener(ivImage,
R.drawable.ic_launcher, R.drawable.ic_launcher);
imageLoader.get(string, listener);
}
}
static class ViewHolder {
ImageView ivImage;
TextView tvDesc;
}
}

界面效果:
【第二篇】Volley的使用之加载图片网址:yii666.com

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