网上下载图片并保存到手机里面

MainActivity

里面用的是异步任务下载的图片

package com.jj.rikao_15;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private ImageView iv;
    //地址
    private String path="http://ent.k618.cn/ylzx/201607/W020160718836443319007.jpeg";
    private Context context;
    private Bitmap bitmap=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        iv=(ImageView)findViewById(R.id.iv);
        context=this;
        getDate();
    }
    //异步下载
    private void getDate() {
        new AsyncTask(){

            @Override
            protected Bitmap doInBackground(String... strings) {
                
                byte[] bytes=HttpUtils.getDateFrom(path);
                 //保存图片到手机里面
                Bitmap bitmap= BitmapFactory.decodeByteArray(bytes,0,bytes.length);
                File file=new File(context.getExternalCacheDir(),"9007.jpg");
                try {
                    FileOutputStream fos=new FileOutputStream(file);
                    fos.write(bytes);
                    fos.flush();
                    fos.close();
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return bitmap;
            }

            @Override
            protected void onPostExecute(Bitmap bitmap) {
                super.onPostExecute(bitmap);
                if (bitmap!=null){
                    iv.setImageBitmap(bitmap);
                }
            }

        }.execute();
    }

}

  HttpUtils--网上下载

package com.jj.rikao_15;

import android.graphics.Bitmap;
import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Created by jj on 2018/1/12.
 */

public class HttpUtils {
    public static byte[] getDateFrom(String path){
        try {

            URL url=new URL(path);
            HttpURLConnection conn=(HttpURLConnection) url.openConnection();
            //GET下载
            conn.setRequestMethod("GET");
            //提交
            conn.connect();
            //判断是否请求成功
            if (conn.getResponseCode()==200){
                Bitmap bitmap=null;
                InputStream is=conn.getInputStream();
                ByteArrayOutputStream os=new ByteArrayOutputStream();
                int len=0;
                byte[] b=new byte[1024];
                while ((len=is.read(b))!=-1){
                    os.write(b,0,len);
                }
                return os.toByteArray();
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

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