前幾天在網上看到個網上面試的題，需要完成一段程式碼，從網路（用底層URlConnection）上下載一個圖片並顯示進度。

然後總結了一下一個簡單的小Demo，跳轉即可執行的哦,親測有效，供大家參考：

1.主介面：

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，顯示圖片
if (mBitmap != null) {
                mIV.setImageBitmap(mBitmap);// display image
}
        }
    };
}

2.佈局檔案中：

<?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>

<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" />

如有問題，請在下方評論欄留言，或者新增QQ:1119348287(微信同步)。