请求网络下载图片2(读取是否存在缓存图片)

来源：互联网发布：能至网络瘫痪的攻击编辑：程序博客网时间：2024/05/23 02:29

权限 <uses-permission android:name="android.permission.INTERNET" />

package com.example.net;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.ImageView;import android.widget.Toast;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;public class MainActivity2 extends Activity {    Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what){                case 1:                    ImageView iv = (ImageView) findViewById(R.id.iv);                    iv.setImageBitmap((Bitmap) msg.obj);                    break;                case 2:                    //toast也需要在主线程中更新                    Toast.makeText(MainActivity2.this,"网络出错",Toast.LENGTH_LONG).show();                    break;            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    public void click(View v) {        new Thread() {            @Override            public void run() {                Bitmap bm = null;                //图片的地址                String path = "http://192.168.0.101/news/images/image1.jpg";                //获取缓存文件(getCahcheDir()获取在data/data/包名/cache下的文件)                File file = new File(getCacheDir(), getFileName(path));                Message msg = handler.obtainMessage();                if (file.exists()) {                    System.out.println("读取缓存..");                    //file.getAbsolutePath()获取文件的绝对路径                    bm = BitmapFactory.decodeFile(file.getAbsolutePath());                    msg.obj = bm;                    msg.what=1;                } else {                    try {                        System.out.println("网络下载的..");                        URL url = new URL(path);                        HttpURLConnection conn = (HttpURLConnection) url.openConnection();                        conn.setRequestMethod("GET");                        conn.setReadTimeout(5000);                        conn.setConnectTimeout(5000);                        conn.connect();                        if (conn.getResponseCode() == 200) {                            FileOutputStream fos = new FileOutputStream(file);                            InputStream is = conn.getInputStream();                            int len = 0;                            byte[] b = new byte[1024];                            //将获取的图片写入缓存文件夹中                            while ((len = is.read(b)) != -1) {                                fos.write(b, 0, len);                            }                            //读取从缓存文件夹下的文件                            bm = BitmapFactory.decodeFile(file.getAbsolutePath());                            msg.obj = bm;                            msg.what=1;                        }else{                            //网络读取出错                            msg.what=2;                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }                handler.sendMessage(msg);            }        }.start();    }    /**     * 截取文件名     * @param path     * @return     */    public String getFileName(String path) {        int index = path.lastIndexOf("/");        return path.substring(index, path.length());    }}

布局

<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">    <Button        android:onClick="click"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="下载图片" />    <ImageView        android:id="@+id/iv"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_centerInParent="true"/></RelativeLayout>

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