Android中从网上下载一张图片显示进度并显示下载好的图片

前几天在网上看到个网上面试的题，需要完成一段代码，从网络（用底层URlConnection）上下载一个图片并显示进度。

然后总结了一下一个简单的小Demo，跳转即可运行的哦,亲测有效，供大家参考：

1.主界面：

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.widget.ImageView;import android.widget.SeekBar;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.InputStream;import java.net.URL;import java.net.URLConnection;public class DownLoadActivity extends AppCompatActivity {    private SeekBar mSeekBar;    private  final String urlString = "http://f.hiphotos.baidu.com/image/pic/item/b7fd5266d016092446517fdadd0735fae7cd34ff.jpg";    private ImageView mIV;    private int fileLength;    private Bitmap mBitmap;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_down_load);        mSeekBar = (SeekBar)findViewById(R.id.seekbar);        mIV = (ImageView)findViewById(R.id.image);        new Thread(downloadRunn).start();    }    private Runnable downloadRunn = new  Runnable(){        @Override        public void run() {            try {                URL url = new URL(urlString);                URLConnection connection = url.openConnection();                connection.connect();                fileLength = connection.getContentLength();                InputStream in = new BufferedInputStream(connection.getInputStream());                byte[] arr = readStream(in);                mBitmap = BitmapFactory.decodeByteArray(arr,0,arr.length);                connectHanlder.sendEmptyMessage(0);            } catch (Exception e) {                e.printStackTrace();            }        }    };    public  byte[] readStream(InputStream in) throws Exception{        ByteArrayOutputStream bos = new ByteArrayOutputStream();        byte data[] = new byte[1024];        long total = 0;        int count;        while((count = in.read(data))!=-1){            total+=count;            mSeekBar.setProgress((int)(total*100)/fileLength);            bos.write(data,0,count);        }        bos.close();        in.close();        return bos.toByteArray();    }    private Handler connectHanlder = new Handler() {        @Override        public void handleMessage(Message msg) {            // 更新UI，显示图片            if (mBitmap != null) {                mIV.setImageBitmap(mBitmap);// display image            }        }    };}

2.布局文件中：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:padding="10dp"    tools:context="com.othershe.test.DownLoadActivity">    <SeekBar        android:id="@+id/seekbar"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:progress="50"/>    <ImageView        android:id="@+id/image"        android:layout_width="match_parent"        android:layout_height="150dp"        android:scaleType="center"/></LinearLayout>

3.清单文件不要忘记添加权限哦;

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

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