eleventigers · September 9, 2015 07:30 · Sep 9, 2015 · Sep 20, 2014
diff --git a/DemoDocumentProvider → DemoDocumentProvider.java b/DemoDocumentProvider → DemoDocumentProvider.java
diff --git a/DemoDocumentProvider b/DemoDocumentProvider
@@ -0,0 +1,230 @@
+/***
+  Copyright (c) 2014 CommonsWare, LLC
+  Licensed under the Apache License, Version 2.0 (the "License"); you may not
+  use this file except in compliance with the License. You may obtain a copy
+  of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless required
+  by applicable law or agreed to in writing, software distributed under the
+  License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
+  OF ANY KIND, either express or implied. See the License for the specific
+  language governing permissions and limitations under the License.
+
+  From _The Busy Coder's Guide to Android Development_
+    http://commonsware.com/Android
+ */
+
+package com.commonsware.android.documents.provider;
+
+import android.content.res.AssetManager;
+import android.database.Cursor;
+import android.database.MatrixCursor;
+import android.net.Uri;
+import android.os.CancellationSignal;
+import android.os.ParcelFileDescriptor;
+import android.provider.DocumentsContract.Document;
+import android.provider.DocumentsContract.Root;
+import android.provider.DocumentsProvider;
+import android.util.Log;
+import android.webkit.MimeTypeMap;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+
+public class DemoDocumentProvider extends DocumentsProvider {
+    private static final String[] SUPPORTED_ROOT_PROJECTION=new String[] {
+            Root.COLUMN_ROOT_ID, Root.COLUMN_FLAGS, Root.COLUMN_TITLE,
+            Root.COLUMN_DOCUMENT_ID, Root.COLUMN_ICON };
+    private static final String[] SUPPORTED_DOCUMENT_PROJECTION=
+            new String[] { Document.COLUMN_DOCUMENT_ID,
+                    Document.COLUMN_MIME_TYPE, Document.COLUMN_DISPLAY_NAME,
+                    Document.COLUMN_FLAGS};
+    private static final String ROOT_ID="thisIsMyRoot";
+    private static final String ROOT_DOCUMENT_ID="thisCannotBeEmpty";
+    private AssetManager assets;
+
+    @Override
+    public boolean onCreate() {
+        assets=getContext().getAssets();
+
+        return(true);
+    }
+
+    @Override
+    public Cursor queryRoots(String[] projection)
+            throws FileNotFoundException {
+        String[] netProjection=
+                netProjection(projection, SUPPORTED_ROOT_PROJECTION);
+        MatrixCursor result=new MatrixCursor(netProjection);
+        MatrixCursor.RowBuilder row=result.newRow();
+
+        row.add(Root.COLUMN_ROOT_ID, ROOT_ID);
+        row.add(Root.COLUMN_ICON, R.drawable.ic_launcher);
+        row.add(Root.COLUMN_FLAGS, Root.FLAG_LOCAL_ONLY);
+        row.add(Root.COLUMN_TITLE, getContext().getString(R.string.root));
+        row.add(Root.COLUMN_DOCUMENT_ID, ROOT_DOCUMENT_ID);
+
+        return(result);
+    }
+
+    @Override
+    public Cursor queryChildDocuments(String parentDocumentId,
+                                      String[] projection,
+                                      String sortOrder)
+            throws FileNotFoundException {
+        String[] netProjection=
+                netProjection(projection, SUPPORTED_DOCUMENT_PROJECTION);
+        MatrixCursor result=new MatrixCursor(netProjection);
+
+        parentDocumentId=fixUpDocumentId(parentDocumentId);
+
+        try {
+            String[] children=assets.list(parentDocumentId);
+
+            for (String child : children) {
+                // Fix 1 : If it is root, then assetPath will be just <filename>. I
+                // If it is not root, then assetPath will be <dir>/<filename>. Use file separator between components.
+                addDocumentRow(result, child, parentDocumentId == "" ? child : parentDocumentId + File.separator + child);
+            }
+        }
+        catch (IOException e) {
+            Log.e(getClass().getSimpleName(), "Exception reading asset dir", e);
+        }
+
+        return(result);
+    }
+
+    @Override
+    public Cursor queryDocument(String documentId, String[] projection)
+            throws FileNotFoundException {
+        String[] netProjection=
+                netProjection(projection, SUPPORTED_DOCUMENT_PROJECTION);
+        MatrixCursor result=new MatrixCursor(netProjection);
+
+        // Fix 2: Should not be fixed. The documentId should never be null. 
+        // Or else you will get the exception : unsupported uri exception. Fix up should be done only when communicating with asset manager.
+        //documentId=fixUpDocumentId(documentId);
+
+        try {
+            addDocumentRow(result, Uri.parse(documentId).getLastPathSegment(),
+                    documentId);
+        }
+        catch (IOException e) {
+            Log.e(getClass().getSimpleName(), "Exception reading asset dir", e);
+        }
+
+        return(result);
+    }
+
+    @Override
+    public ParcelFileDescriptor openDocument(String documentId,
+                                             String mode,
+                                             CancellationSignal signal)
+            throws FileNotFoundException {
+        ParcelFileDescriptor[] pipe=null;
+
+        try {
+            pipe=ParcelFileDescriptor.createPipe();
+            AssetManager assets=getContext().getResources().getAssets();
+
+            new TransferThread(assets.open(documentId),
+                    new ParcelFileDescriptor.AutoCloseOutputStream(pipe[1])).start();
+        }
+        catch (IOException e) {
+            Log.e(getClass().getSimpleName(), "Exception opening pipe", e);
+            throw new FileNotFoundException("Could not open pipe for: "
+                    + documentId);
+        }
+
+        return(pipe[0]);
+    }
+
+    private void addDocumentRow(MatrixCursor result, String child,
+                                String assetPath) throws IOException {
+        MatrixCursor.RowBuilder row=result.newRow();
+
+        row.add(Document.COLUMN_DOCUMENT_ID, assetPath);
+
+        if (isDirectory(assetPath)) {
+            row.add(Document.COLUMN_MIME_TYPE, Document.MIME_TYPE_DIR);
+        }
+        else {
+            row.add(Document.COLUMN_MIME_TYPE,
+                    MimeTypeMap.getFileExtensionFromUrl(assetPath));
+            row.add(Document.COLUMN_SIZE, lastModified(assetPath));
+        }
+
+        row.add(Document.COLUMN_DISPLAY_NAME, child);
+        row.add(Document.COLUMN_FLAGS, 0);
+    }
+
+    private boolean isDirectory(String assetPath) throws IOException {
+        // Fix 3 : Call fixUpDocumentId. In case of root, the call should be assets.list("").
+        assetPath = fixUpDocumentId(assetPath);
+
+        // Fix 4 : Empty directories are not included in apk. Non empty directory will have atleast 1 file.
+        return(assets.list(assetPath).length>=1);
+    }
+
+    private long lastModified(String assetPath) throws IOException {
+        return(assets.openFd(assetPath).getLength());
+    }
+
+    private String fixUpDocumentId(String documentId) {
+        if (ROOT_DOCUMENT_ID.equals(documentId)) {
+            return("");
+        }
+
+        return(documentId);
+    }
+
+    private static String[] netProjection(String[] requested, String[] supported) {
+        if (requested==null) {
+            return(supported);
+        }
+
+        ArrayList<String> result=new ArrayList<String>();
+
+        for (String request : requested) {
+            for (String support : supported) {
+                if (request.equals(support)) {
+                    result.add(request);
+                    break;
+                }
+            }
+        }
+
+        return(result.toArray(new String[0]));
+    }
+
+    static class TransferThread extends Thread {
+        InputStream in;
+        OutputStream out;
+
+        TransferThread(InputStream in, OutputStream out) {
+            this.in=in;
+            this.out=out;
+        }
+
+        @Override
+        public void run() {
+            byte[] buf=new byte[1024];
+            int len;
+
+            try {
+                while ((len=in.read(buf)) >= 0) {
+                    out.write(buf, 0, len);
+                }
+
+                in.close();
+                out.flush();
+                out.close();
+            }
+            catch (IOException e) {
+                Log.e(getClass().getSimpleName(),
+                        "Exception transferring file", e);
+            }
+        }
+    }
+}
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