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1）從指定的URL獲取對(duì)應(yīng)的流

既然要獲取網(wǎng)絡(luò)資源，那么首先得有個(gè)URL，那么這里我首先封裝一個(gè)打開(kāi)URL連接獲取到的InputStream 流，這樣一來(lái)無(wú)論是圖片資源還是文本文件資源都可以使用該接口方法來(lái)獲取流。

該功能主要應(yīng)用URLConnection和HttpURLConnection來(lái)實(shí)現(xiàn)，具體實(shí)現(xiàn)方案如下：

代碼如下:

private InputStream openHttpConnection(String urlString) throws IOException{

InputStream in = null;

int response = -1;

URL url = new URL(urlString);

URLConnection conn = url.openConnection();

if(!(conn instanceof HttpURLConnection)){

throw new IOException("It is not an HTTP connection");

}

try {

HttpURLConnection httpConn = (HttpURLConnection) conn;

httpConn.setAllowUserInteraction(false);

httpConn.setInstanceFollowRedirects(true);

httpConn.setRequestMethod("GET");

httpConn.connect();

response = httpConn.getResponseCode();

if (response == HttpURLConnection.HTTP_OK) {

in = httpConn.getInputStream();

}

} catch (Exception ex) {

Log.v("Networking",ex.getLocalizedMessage());

throw new IOException("Error connecting");

}

return in;

}

代碼如下:

（2）封裝了上面的獲取流方法接口后，我們就可以利用上面封裝的方法來(lái)獲取并下載相應(yīng)圖片和文本文件內(nèi)容了

獲取并下載圖片資源方法：

代碼如下:

private Bitmap downloadImage(String url){

Bitmap bitmap = null;

InputStream in = null;

try {

in = openHttpConnection(url);

bitmap = BitmapFactory.decodeStream(in);

in.close();

} catch (IOException e) {

// TODO Auto-generated catch block

Log.v("NetworkingActivity", e.getLocalizedMessage());

}

return bitmap;

}

代碼如下:

獲取并下載文本內(nèi)容方法：

代碼如下:

private String downloadText(String url){

int BUFFER_SIZE = 2000;

InputStream is = null;

try {

is = openHttpConnection(url);

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

return "";

}

InputStreamReader isr = new InputStreamReader(is);

int charRead;

String str="";

char[] inputBuffer = new char[BUFFER_SIZE];

try {

while((charRead=isr.read(inputBuffer))>0){

String readString = String.copyValueOf(inputBuffer, 0, charRead);

str += readString;

inputBuffer = new char[BUFFER_SIZE];

}

is.close();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

return "";

}

return str;

}

代碼如下:

（3）在獲取下載圖片資源和文本內(nèi)容資源方法都完成后，現(xiàn)在就可以開(kāi)始下載任務(wù)了，為了防止等待效應(yīng)，一般采用異步任務(wù)來(lái)下載網(wǎng)絡(luò)資源。

對(duì)對(duì)應(yīng)的下載資源任務(wù)封裝各自的異步下載任務(wù)即可。下面就是實(shí)現(xiàn)異步下載任務(wù)的方案：

異步下載圖片任務(wù)：

代碼如下:

private class DownloadImageTask extends AsyncTask<String, Bitmap, Long>{

long imagesCount = 0;

ProgressBar progressBar;

public DownloadImageTask(ProgressBar pBar){

this.progressBar = pBar;

}

@Override

protected Long doInBackground(String... urls) {

// TODO Auto-generated method stub

for(int i = 0; i < urls.length;i++){

Bitmap imageDownloaded = downloadImage(urls[i]);

if(imageDownloaded!=null){

imagesCount ++;

publishProgress(imageDownloaded);

try {

Thread.sleep(300);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

return imagesCount;

}

//display the image downloaded

@Override

protected void onProgressUpdate(Bitmap... bitmaps) {

// TODO Auto-generated method stub

ivImg.setImageBitmap(bitmaps[0]);

progressBar.setProgress((int) imagesCount*10);

}

//when all the images have been downloaded

@Override

protected void onPostExecute(Long imageDownloaded) {

// TODO Auto-generated method stub

String str = "下載完成！一共下載了"+imagesCount +"張圖片";

Toast.makeText(getBaseContext(), str, Toast.LENGTH_SHORT).show();

}

}

代碼如下:

異步下載文本文件內(nèi)容任務(wù)：

代碼如下:

private class DownloadTextTask extends AsyncTask<String, Void, String>{

@Override

protected void onPostExecute(String result) {

// TODO Auto-generated method stub

Toast.makeText(getBaseContext(), result, Toast.LENGTH_LONG).show();

}

@Override

protected String doInBackground(String... urls) {

// TODO Auto-generated method stub

return downloadText(urls[0]);

}

}

代碼如下:

這樣一來(lái)，異步下載網(wǎng)絡(luò)資源就完成了。

下面為了讀者方便測(cè)試，下面提供本文實(shí)例代碼中的相關(guān)網(wǎng)絡(luò)資源URL，以方便大家自己測(cè)試使用。其余非核心代碼就不在貼出來(lái)，望讀者見(jiàn)諒。

代碼如下:

//圖片下載URLs

private String[] mUrl =

{

"

"

"

"

"

"

"

"

"

"

"

"

"

"

};

String strUrl = "

//異步下載文本文件內(nèi)容任務(wù)

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