Question

web做一个下载功能 求代码

Answer 1

WebView控制调用相应的WEB页面进行展示。当碰到页面有下载链接的时候，点击上去是一点反应都没有的。原来是因为WebView默认没有开启文件下载的功能，如果要实现文件下载的功能，需要设置WebView的DownloadListener，通过实现自己的DownloadListener来实现文件的下载。具体操作如下：

1、设置WebView的DownloadListener：
webView.setDownloadListener(new MyWebViewDownLoadListener());

2、实现MyWebViewDownLoadListener这个类，具体可以如下这样：

Java代码
private class MyWebViewDownLoadListener implements DownloadListener{

@Override
public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,
long contentLength) {
Log.i("tag", "url="+url);
Log.i("tag", "userAgent="+userAgent);
Log.i("tag", "contentDisposition="+contentDisposition);
Log.i("tag", "mimetype="+mimetype);
Log.i("tag", "contentLength="+contentLength);
Uri uri = Uri.parse(url);
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
}
[java] view plain copy
private class MyWebViewDownLoadListener implements DownloadListener{

@Override
public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,
long contentLength) {
Log.i("tag", "url="+url);
Log.i("tag", "userAgent="+userAgent);
Log.i("tag", "contentDisposition="+contentDisposition);
Log.i("tag", "mimetype="+mimetype);
Log.i("tag", "contentLength="+contentLength);
Uri uri = Uri.parse(url);
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
}

这只是调用系统中已经内置的浏览器进行下载，还没有WebView本身进行的文件下载，不过，这也基本上满足我们的应用场景了。

我在项目中的运用
项目要求这样：
1，需要使用WebView加载一个网页；
2，网页中有文件下载的链接，点击后需要下载文件到SDcard；
3，然后自动打开文件；
下面是具体解决办法
第一步，对WebView进行一系列设置。

Java代码
WebView webview=(WebView)layout.findViewById(R.id.webview);
webview.getSettings().setJavaScriptEnabled(true);
webview.setWebChromeClient(new MyWebChromeClient());
webview.requestFocus();
// webview.loadUrl("file:///android_asset/risktest.html");
webview.loadUrl(jcrs_sub.get(position).addr);
// 设置web视图客户端
webview.setWebViewClient(new MyWebViewClient());
webview.setDownloadListener(new MyWebViewDownLoadListener());

//内部类
public class MyWebViewClient extends WebViewClient {
// 如果页面中链接，如果希望点击链接继续在当前browser中响应，
// 而不是新开Android的系统browser中响应该链接，必须覆盖 webview的WebViewClient对象。
public boolean shouldOverviewUrlLoading(WebView view, String url) {
L.i("shouldOverviewUrlLoading");
view.loadUrl(url);
return true;
}

public void onPageStarted(WebView view, String url, Bitmap favicon) {
L.i("onPageStarted");
showProgress();
}

public void onPageFinished(WebView view, String url) {
L.i("onPageFinished");
closeProgress();
}

public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
L.i("onReceivedError");
closeProgress();
}
}

// 如果不做任何处理，浏览网页，点击系统“Back”键，整个Browser会调用finish()而结束自身，
// 如果希望浏览的网 页回退而不是推出浏览器，需要在当前Activity中处理并消费掉该Back事件。
public boolean onKeyDown(int keyCode, KeyEvent event) {
// if((keyCode==KeyEvent.KEYCODE_BACK)&&webview.canGoBack()){
// webview.goBack();
// return true;
// }
return false;
}
[java] view plain copy
WebView webview=(WebView)layout.findViewById(R.id.webview);
webview.getSettings().setJavaScriptEnabled(true);
webview.setWebChromeClient(new MyWebChromeClient());
webview.requestFocus();
// webview.loadUrl("file:///android_asset/risktest.html");
webview.loadUrl(jcrs_sub.get(position).addr);
// 设置web视图客户端
webview.setWebViewClient(new MyWebViewClient());
webview.setDownloadListener(new MyWebViewDownLoadListener());

//内部类
public class MyWebViewClient extends WebViewClient {
// 如果页面中链接，如果希望点击链接继续在当前browser中响应，
// 而不是新开Android的系统browser中响应该链接，必须覆盖 webview的WebViewClient对象。
public boolean shouldOverviewUrlLoading(WebView view, String url) {
L.i("shouldOverviewUrlLoading");
view.loadUrl(url);
return true;
}

public void onPageStarted(WebView view, String url, Bitmap favicon) {
L.i("onPageStarted");
showProgress();
}

public void onPageFinished(WebView view, String url) {
L.i("onPageFinished");
closeProgress();
}

public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
L.i("onReceivedError");
closeProgress();
}
}

// 如果不做任何处理，浏览网页，点击系统“Back”键，整个Browser会调用finish()而结束自身，
// 如果希望浏览的网 页回退而不是推出浏览器，需要在当前Activity中处理并消费掉该Back事件。
public boolean onKeyDown(int keyCode, KeyEvent event) {
// if((keyCode==KeyEvent.KEYCODE_BACK)&&webview.canGoBack()){
// webview.goBack();
// return true;
// }
return false;
}

第二步，起线程开始下载文件。

Java代码
//内部类
private class MyWebViewDownLoadListener implements DownloadListener {

@Override
public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,
long contentLength) {
if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
Toast t=Toast.makeText(mContext, "需要SD卡。", Toast.LENGTH_LONG);
t.setGravity(Gravity.CENTER, 0, 0);
t.show();
return;
}
DownloaderTask task=new DownloaderTask();
task.execute(url);
}

}
//内部类
private class DownloaderTask extends AsyncTask<String, Void, String> {

public DownloaderTask() {
}

@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
String url=params[0];
// Log.i("tag", "url="+url);
String fileName=url.substring(url.lastIndexOf("/")+1);
fileName=URLDecoder.decode(fileName);
Log.i("tag", "fileName="+fileName);

File directory=Environment.getExternalStorageDirectory();
File file=new File(directory,fileName);
if(file.exists()){
Log.i("tag", "The file has already exists.");
return fileName;
}
try {
HttpClient client = new DefaultHttpClient();
// client.getParams().setIntParameter("http.socket.timeout",3000);//设置超时
HttpGet get = new HttpGet(url);
HttpResponse response = client.execute(get);
if(HttpStatus.SC_OK==response.getStatusLine().getStatusCode()){
HttpEntity entity = response.getEntity();
InputStream input = entity.getContent();

writeToSDCard(fileName,input);

input.close();
// entity.consumeContent();
return fileName;
}else{
return null;
}
} catch (Exception e) {
e.printStackTrace();
return null;
}
}

@Override
protected void onCancelled() {
// TODO Auto-generated method stub
super.onCancelled();
}

@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
closeProgressDialog();
if(result==null){
Toast t=Toast.makeText(mContext, "连接错误！请稍后再试！", Toast.LENGTH_LONG);
t.setGravity(Gravity.CENTER, 0, 0);
t.show();
return;
}

Toast t=Toast.makeText(mContext, "已保存到SD卡。", Toast.LENGTH_LONG);
t.setGravity(Gravity.CENTER, 0, 0);
t.show();
File directory=Environment.getExternalStorageDirectory();
File file=new File(directory,result);
Log.i("tag", "Path="+file.getAbsolutePath());

Intent intent = getFileIntent(file);

startActivity(intent);

}

@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
showProgressDialog();
}

@Override
protected void onProgressUpdate(Void... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
}

}