当我尝试从网络视图下载图片时 下载开始但图片未保存在图库中。“我不知道在哪里” 当我删除下载管理器的缓存时，它消失了代码的问题是什么？
package com.example.misrcomp.myapplication;
import android.Manifest;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.DownloadManager;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.os.Handler;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.webkit.DownloadListener;
import android.webkit.URLUtil;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private static int SPLASH_TIME_OUT = 10;
public android.widget.ProgressBar ProgressBar;
@Override
public void onCreateContextMenu(ContextMenu contextMenu,View view,ContextMenu.ContextMenuInfo contextMenuInfo){
super.onCreateContextMenu(contextMenu, view, contextMenuInfo);
final WebView.HitTestResult webViewHitTestResult = mWebView.getHitTestResult();
if (webViewHitTestResult.getType() == WebView.HitTestResult.IMAGE_TYPE ||
webViewHitTestResult.getType() == WebView.HitTestResult.SRC_IMAGE_ANCHOR_TYPE) {
contextMenu.setHeaderTitle("Download Image From Below");
contextMenu.add(0, 1, 0, "Save - Download Image")
.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem menuItem) {
String DownloadImageURL = webViewHitTestResult.getExtra();
if(URLUtil.isValidUrl(DownloadImageURL)){
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(DownloadImageURL));
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
downloadManager.enqueue(request);
Toast.makeText(MainActivity.this,"Image Downloaded Successfully.",Toast.LENGTH_LONG).show();
}
else {
Toast.makeText(MainActivity.this,"Sorry.. Something Went Wrong.",Toast.LENGTH_LONG).show();
}
return false;
}
});
}
}
private Context mContext;
private Activity mActivity;
private LinearLayout mRootLayout;
private WebView mWebView;
private static final int MY_PERMISSION_REQUEST_CODE = 123;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this,"By:Hisham Raafat",Toast.LENGTH_SHORT).show();
}
},SPLASH_TIME_OUT);
ProgressBar = (ProgressBar) findViewById(R.id.prg);
// Get the application context
mContext = getApplicationContext();
mActivity = MainActivity.this;
// Get the widget reference from xml layout
mRootLayout = findViewById(R.id.root_layout);
mWebView = findViewById(R.id.web_view);
// Check permission for write external storage
checkPermission();
// The target url to surf using web view
String url = "http://nekashatspacetoon.yoo7.com/h29-h";
registerForContextMenu(mWebView);
// Load the url in web view
mWebView.loadUrl(url);
mWebView.setWebViewClient(new WebViewClient()
{
@Override
public void onPageStarted(WebView view,String url,Bitmap favicon) {
ProgressBar.setVisibility(View.VISIBLE);
}
@Override
public void onPageFinished(WebView view,String url) {
ProgressBar.setVisibility(view.GONE);
setTitle(view.getTitle());
}
}
);
// Enable java script on web view
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.setDownloadListener(new DownloadListener() {
@Override
public void onDownloadStart(String url, String userAgent, String contentDescription,
String mimetype, long contentLength) {
/*
DownloadManager.Request
This class contains all the information necessary to request a new download.
The URI is the only required parameter. Note that the default download
destination is a shared volume where the system might delete your file
if it needs to reclaim space for system use. If this is a problem,
use a location on external storage (see setDestinationUri(Uri).
*/
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
/*
void allowScanningByMediaScanner ()
If the file to be downloaded is to be scanned by MediaScanner, this method
should be called before enqueue(Request) is called.
*/
request.allowScanningByMediaScanner();
/*
DownloadManager.Request setNotificationVisibility (int visibility)
Control whether a system notification is posted by the download manager
while this download is running or when it is completed. If enabled, the
download manager posts notifications about downloads through the system
NotificationManager. By default, a notification is shown only
when the download is in progress.
It can take the following values: VISIBILITY_HIDDEN, VISIBILITY_VISIBLE,
VISIBILITY_VISIBLE_NOTIFY_COMPLETED.
If set to VISIBILITY_HIDDEN, this requires the permission
android.permission.DOWNLOAD_WITHOUT_NOTIFICATION.
Parameters
visibility int : the visibility setting value
Returns
DownloadManager.Request this object
*/
request.setNotificationVisibility(
DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
/*
DownloadManager
The download manager is a system service that handles long-running HTTP
downloads. Clients may request that a URI be downloaded to a particular
destination file. The download manager will conduct the download in the
background, taking care of HTTP interactions and retrying downloads
after failures or across connectivity changes and system reboots.
*/
/*
String guessFileName (String url, String contentDisposition, String mimeType)
Guesses canonical filename that a download would have, using the URL
and contentDisposition. File extension, if not defined,
is added based on the mimetype
Parameters
url String : Url to the content
contentDisposition String : Content-Disposition HTTP header or null
mimeType String : Mime-type of the content or null
Returns
String : suggested filename
*/
String fileName = URLUtil.guessFileName(url,contentDescription,mimetype);
/*
DownloadManager.Request setDestinationInExternalPublicDir
(String dirType, String subPath)
Set the local destination for the downloaded file to a path within
the public external storage directory (as returned by
getExternalStoragePublicDirectory(String)).
The downloaded file is not scanned by MediaScanner. But it can be made
scannable by calling allowScanningByMediaScanner().
Parameters
dirType String : the directory type to pass to
getExternalStoragePublicDirectory(String)
subPath String : the path within the external directory, including
the destination filename
Returns
DownloadManager.Request this object
Throws
IllegalStateException : If the external storage directory cannot be
found or created.
*/
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,fileName);
DownloadManager dManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
/*
long enqueue (DownloadManager.Request request)
Enqueue a new download. The download will start automatically once the
download manager is ready to execute it and connectivity is available.
Parameters
request DownloadManager.Request : the parameters specifying this download
Returns
long : an ID for the download, unique across the system. This ID is used
to make future calls related to this download.
*/
dManager.enqueue(request);
}
});
}
protected void checkPermission(){
if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.M){
if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED){
if(shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)){
// show an alert dialog
AlertDialog.Builder builder = new AlertDialog.Builder(mActivity);
builder.setMessage("Write external storage permission is required.");
builder.setTitle("Please grant permission");
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
ActivityCompat.requestPermissions(
mActivity,
new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
MY_PERMISSION_REQUEST_CODE
);
}
});
builder.setNeutralButton("Cancel",null);
AlertDialog dialog = builder.create();
dialog.show();
}else {
// Request permission
ActivityCompat.requestPermissions(
mActivity,
new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
MY_PERMISSION_REQUEST_CODE
);
}
}else {
// Permission already granted
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults){
switch(requestCode){
case MY_PERMISSION_REQUEST_CODE:{
if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
// Permission granted
}else {
// Permission denied
}
}
}
}
@Override
public void onBackPressed() {
if (mWebView.canGoBack()) {
mWebView.goBack();
} else {
super.onBackPressed();
}
}
}
答案 0 :(得分：1)
只需在onMenuItemClick下的String DownloadImageURL中输入此内容：
mWebView.setDownloadListener(new DownloadListener() {
@Override
public void onDownloadStart(String url, String userAgent, String contentDescription,
String mimetype, long contentLength) {
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(DownloadImageURL));
request.setNotificationVisibility(
DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,fileName);
DownloadManager dManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
dManager.enqueue(request);
}
});
}