网络图片获取原理

来源：互联网发布：网络问政是什么意思编辑：程序博客网时间：2024/05/22 02:27

现在的手机以离不开网络了，而且网络速度也越来越快，所以网络HTTP协议请求是必不可少的，现在我们简单讲解一下网路图片的获取，这里只是讲解一下获取原理，并不是造轮子给大家用，最后会推荐几个轮子给大家用。

逻辑：

首先需要一个图片地址的URL
然后需要通过HTTP网络请求协议在线获取图片
再将图片转换成一个 Bitmap（这里用Bitmap）
在将图片展示到控件上

Activity代码：

package com.example.administrator.foundationdemo.http;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Handler;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.ImageView;import android.widget.Toast;import com.example.administrator.foundationdemo.R;import com.example.administrator.foundationdemo.http.service.ImageService;import java.io.IOException;public class HttpImageActivity extends AppCompatActivity {    private EditText http_image_edittext;    private Button http_image_button;    private ImageView http_image_imageview;    private String urlString = "http://upload-images.jianshu.io/upload_images/4047773-f6c7549ab7c95bd2?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_http_image);        init();    }    private void init(){        http_image_edittext = (EditText) findViewById(R.id.http_image_edittext);        http_image_imageview = (ImageView) findViewById(R.id.http_image_imageview);        http_image_button = (Button) findViewById(R.id.http_image_button);        http_image_edittext.setText(urlString);        http_image_button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                setImage();            }        });    }    //开启子线程，进行耗时操作    private void setImage(){        Log.d("FLY","请求失败1");        new Thread(new Runnable() {            @Override            public void run() {                String path = http_image_edittext.getText().toString();                byte[] date = new byte[0];                try {                    date = ImageService.getImage(urlString);                } catch (IOException e) {                    e.printStackTrace();                    Log.d("FLY", "获取图片异常\n" + e.toString());                    Toast.makeText(HttpImageActivity.this,"获取图片失败",Toast.LENGTH_SHORT).show();                }                Log.d("FLY","请求失败1");                Bitmap bitmap = BitmapFactory.decodeByteArray(date,0,date.length);                Message msg = new Message();                msg.obj = bitmap;                hadler.sendMessage(msg);            }        }).start();    }    Handler hadler = new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            Log.d("FLY", "请求失败2");            Bitmap bitmap = (Bitmap) msg.obj;            http_image_imageview.setImageBitmap(bitmap);        }    };}

ImageService代码：

package com.example.administrator.foundationdemo.http.service;import android.util.Log;import android.widget.Toast;import com.example.administrator.foundationdemo.http.tool.StreamTool;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;/** * Created by Administrator on 2016/12/29. */public class ImageService {    public static byte[] getImage(String path) throws IOException {        URL url = new URL(path);        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();//得到基于HTTP协议的链接对象        httpURLConnection.setConnectTimeout(5000);//请求超时时间        httpURLConnection.setRequestMethod("GET");//请求方式        if (httpURLConnection.getResponseCode() == 200){            InputStream inputStream = httpURLConnection.getInputStream();            return StreamTool.readInputStream(inputStream);        }else {            Log.d("FLY","请求失败"+httpURLConnection.getResponseCode());        }        return null;    }}

StreamTool 代码：

package com.example.administrator.foundationdemo.http.tool;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;/** * Created by Administrator on 2017/1/3. */public class StreamTool {    public static byte[] readInputStream(InputStream inputStream) throws IOException {        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();        byte[] bytes = new byte[1024];        int bytrsLen = 0;        while((bytrsLen =inputStream.read(bytes)) != -1){            outputStream.write(bytes,0,bytrsLen);        }        inputStream.close();        return outputStream.toByteArray();    }}

XML代码：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    style="@style/MatchMatch"    android:orientation="vertical"    tools:context="com.example.administrator.foundationdemo.http.HttpImageActivity">    <TextView        style="@style/WrapWrap"        android:text="网络图片地址"/>    <EditText        android:id="@+id/http_image_edittext"        style="@style/MatchWrap"/>    <Button        android:id="@+id/http_image_button"        style="@style/WrapWrap"        android:text="获取" />    <ImageView        android:id="@+id/http_image_imageview"        android:layout_width="100dp"        android:layout_height="100dp" /></LinearLayout>

说好的向大家推荐几个很好用的轮子：

Picasso
Fresco

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