Android编程实现下载图片及在手机中展示的方法

2019-12-12 03:39:17

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本文实例讲述了Android编程实现下载图片及在手机中展示的方法。分享给大家供大家参考，具体如下：

在项目开发中从互联网上下载图片是经常用到的功能，再次总结一下

1.普通的下载方式

布局文件：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:src="@drawable/icon"   android:layout_width="wrap_content"   android:id="@+id/imgPic"   android:layout_gravity="center|center_vertical"   android:layout_height="fill_parent"> </ImageView></LinearLayout>

java文件

public class DownloadImage extends Activity {  private ImageView imgPic;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.download_image);    imgPic = (ImageView) findViewById(R.id.imgPic);    String url = "http://ww1.sinaimg.cn/bmiddle/6834c769jw1djjf4p3p9rj.jpg";    loadRmoteImage(url);  }  /**   * @param imgUrl   *   远程图片文件的URL   *   *   下载远程图片   */  private void loadRmoteImage(String imgUrl) {    URL fileURL = null;    Bitmap bitmap = null;    try {      fileURL = new URL(imgUrl);    } catch (MalformedURLException err) {      err.printStackTrace();    }    try {      HttpURLConnection conn = (HttpURLConnection) fileURL          .openConnection();      conn.setDoInput(true);      conn.connect();      InputStream is = conn.getInputStream();      int length = (int) conn.getContentLength();      if (length != -1) {        byte[] imgData = new byte[length];        byte[] buffer = new byte[512];        int readLen = 0;        int destPos = 0;        while ((readLen = is.read(buffer)) > 0) {          System.arraycopy(buffer, 0, imgData, destPos, readLen);          destPos += readLen;        }        bitmap = BitmapFactory.decodeByteArray(imgData, 0,            imgData.length);      }    } catch (IOException e) {      e.printStackTrace();    }    imgPic.setImageBitmap(bitmap);  }

2.带进度条的下载

有时候网络差，或者是图片太大，会出现黑屏的情况，用户体验比较差，那么增加一个进度条是提高用户体验的好方法

/** * @author xushilin xsl xushilin@kingtoneinfo.com * @version： 创建时间：2011-7-27 下午02:55:56 * 说 明: android中下载图片 * 修改历史： */public class DownloadImage extends Activity {  private ImageView imgPic;  private ProgressBar progressBar;  private int totalSize=0;  private int size=0;  private Handler mHandler;  String url = "http://ww1.sinaimg.cn/bmiddle/6834c769jw1djjf4p3p9rj.jpg";  private Bitmap bitmap=null;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.download_image);    imgPic = (ImageView) findViewById(R.id.imgPic);    progressBar = (ProgressBar) findViewById(R.id.progressBar);    progressBar.setProgress(getProgressInt(progressBar.getMax()));    mHandler = new Handler() {      public void handleMessage(Message msg) {        progressBar.setProgress(getProgressInt(progressBar.getMax()));        if(bitmap!=null){          imgPic.setImageBitmap(bitmap);        }      }    };    new Thread(){      public void run(){        loadRmoteImage(url);      }    }.start();  }  /**   * @param imgUrl   *   远程图片文件的URL   *   *   下载远程图片   */  private void loadRmoteImage(String imgUrl) {    URL fileURL = null;    try {      fileURL = new URL(imgUrl);    } catch (MalformedURLException err) {      err.printStackTrace();    }    try {      HttpURLConnection conn = (HttpURLConnection) fileURL          .openConnection();      conn.setDoInput(true);      conn.connect();      InputStream is = conn.getInputStream();      int length = (int) conn.getContentLength();      totalSize=length;      if (length != -1) {        byte[] imgData = new byte[length];        byte[] buffer = new byte[512];        int readLen = 0;        int destPos = 0;        while ((readLen = is.read(buffer)) > 0) {          System.arraycopy(buffer, 0, imgData, destPos, readLen);          destPos += readLen;          size=destPos;          mHandler.sendEmptyMessage(1);          Thread.sleep(100);        }        bitmap = BitmapFactory.decodeByteArray(imgData, 0,            imgData.length);        mHandler.sendEmptyMessage(1);      }    } catch (IOException e) {      e.printStackTrace();    } catch (InterruptedException e) {      e.printStackTrace();    }  }  private int getProgressInt(int max) {    int result = (totalSize > 0) ? (int) (size * max * 1.0 / totalSize) : 0;    return result;  }}

效果如下：

下载过程：