WebView中实现文件下载功能

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);

}

}

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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;

}

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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);

}

}

[java] view plain copy

//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);

}

}

第三步，实现一些工具方法。

Java代码







private ProgressDialog mDialog;

private void showProgressDialog(){

if(mDialog==null){

mDialog = new ProgressDialog(mContext);

mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);//设置风格为圆形进度条

mDialog.setMessage("正在加载 ，请等待...");

mDialog.setIndeterminate(false);//设置进度条是否为不明确

mDialog.setCancelable(true);//设置进度条是否可以按退回键取消

mDialog.setCanceledOnTouchOutside(false);

mDialog.setOnDismissListener(new OnDismissListener() {

@Override

public void onDismiss(DialogInterface dialog) {

// TODO Auto-generated method stub

mDialog=null;

}

});

mDialog.show();

}

}

private void closeProgressDialog(){

if(mDialog!=null){

mDialog.dismiss();

mDialog=null;

}

}

public Intent getFileIntent(File file){

// Uri uri = Uri.parse("http://m.ql18.com.cn/hpf10/1.pdf");

Uri uri = Uri.fromFile(file);

String type = getMIMEType(file);

Log.i("tag", "type="+type);

Intent intent = new Intent("android.intent.action.VIEW");

intent.addCategory("android.intent.category.DEFAULT");

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

intent.setDataAndType(uri, type);

return intent;

}

public void writeToSDCard(String fileName,InputStream input){

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){

File directory=Environment.getExternalStorageDirectory();

File file=new File(directory,fileName);

// if(file.exists()){

// Log.i("tag", "The file has already exists.");

// return;

// }

try {

FileOutputStream fos = new FileOutputStream(file);

byte[] b = new byte[2048];

int j = 0;

while ((j = input.read(b)) != -1) {

fos.write(b, 0, j);

}

fos.flush();

fos.close();

} catch (FileNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}else{

Log.i("tag", "NO SDCard.");

}

}

private String getMIMEType(File f){

String type="";

String fName=f.getName();

/* 取得扩展名 */

String end=fName.substring(fName.lastIndexOf(".")+1,fName.length()).toLowerCase();

/* 依扩展名的类型决定MimeType */

if(end.equals("pdf")){

type = "application/pdf";//

}

else if(end.equals("m4a")||end.equals("mp3")||end.equals("mid")||

end.equals("xmf")||end.equals("ogg")||end.equals("wav")){

type = "audio/*";

}

else if(end.equals("3gp")||end.equals("mp4")){

type = "video/*";

}

else if(end.equals("jpg")||end.equals("gif")||end.equals("png")||

end.equals("jpeg")||end.equals("bmp")){

type = "image/*";

}

else if(end.equals("apk")){

/* android.permission.INSTALL_PACKAGES */

type = "application/vnd.android.package-archive";

}

// else if(end.equals("pptx")||end.equals("ppt")){

// type = "application/vnd.ms-powerpoint";

// }else if(end.equals("docx")||end.equals("doc")){

// type = "application/vnd.ms-word";

// }else if(end.equals("xlsx")||end.equals("xls")){

// type = "application/vnd.ms-excel";

// }

else{

// /*如果无法直接打开，就跳出软件列表给用户选择 */

type="*/*";

}

return type;

}