android - 长按从 WebView 保存图像

Question

需要帮助

我正在尝试通过长按照片从 webview 下载图片，
当我用 toast 消息测试长按 Action 时，它起作用了

但它没有下载。

 private View.OnLongClickListener listener=new View.OnLongClickListener() {
        @Override
        public boolean onLongClick(View v) {
            mWebView.setDownloadListener(new DownloadListener() {

                @TargetApi(Build.VERSION_CODES.HONEYCOMB)
                public void onDownloadStart(String url, String userAgent,
                                            String contentDisposition, String mimetype,
                                            long contentLength) {
                    DownloadManager.Request request = new DownloadManager.Request(
                            Uri.parse(url));

                    request.allowScanningByMediaScanner();
                    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED); //Notify client once download is completed!
                    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "Name of your downloadble file goes here, example: Keerthi");
                    DownloadManager dm = (DownloadManager) getActivity().getSystemService(Context.DOWNLOAD_SERVICE);
                    dm.enqueue(request);
                    Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT); //This is important!
                    intent.addCategory(Intent.CATEGORY_OPENABLE); //CATEGORY.OPENABLE
                    intent.setType("*/*");//any application,any extension
                    Toast.makeText(getContext(), "Downloading File", //To notify the Client that the file is being downloaded
                            Toast.LENGTH_LONG).show();

                }
            });
            return true;
        }
    };

Answer 1

Alexander 和 Aashish 的回答都很出色。
但是，这是来自 tutorial I recently found 的完整 Activity 。 .它将所有内容置于清晰的上下文中。

package com.android_examples.saveimagefromwebview_android_examplescom;
import android.app.DownloadManager;
import android.net.Uri;
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.URLUtil;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    WebView webView;
    String HTTP_URL = "https://www.google.com" ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        webView = (WebView)findViewById(R.id.WebView1);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebViewClient(new WebViewClient());

        //Register the WebView to be able to take display a menu...
        //You'll need this menu to choose an action on long press
        registerForContextMenu(webView);
        webView.loadUrl(HTTP_URL);
    }

    @Override
    public void onCreateContextMenu(ContextMenu contextMenu, View view, 
            ContextMenu.ContextMenuInfo contextMenuInfo){
        super.onCreateContextMenu(contextMenu, view, contextMenuInfo);

        final WebView.HitTestResult webViewHitTestResult = webView.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;
                        }
                    });
        }
    }
}