DocumentsProvider：什么是内容：//com.android.documentsui.recents/state为什么它不喜欢我？

我正在尝试将DocumentsProvider实现为我的书的演示.虽然提供程序显示在消费者示例应用程序中,但只要我在Storage Access Framework的UI中单击它,我就会得到以下堆栈跟踪：

09-15 18:40:46.290    1765-1829/com.android.documentsui E/AndroidRuntime﹕ FATAL EXCEPTION: ProviderExecutor: com.commonsware.android.documents.provider
    Process: com.android.documentsui,PID: 1765
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:300)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
            at java.util.concurrent.FutureTask.run(FutureTask.java:242)
            at com.android.documentsui.ProviderExecutor.run(ProviderExecutor.java:107)
     Caused by: java.lang.UnsupportedOperationException: Unsupported Uri content://com.android.documentsui.recents/state/com.commonsware.android.documents.provider/thisIsMyRoot/
            at com.android.documentsui.RecentsProvider.query(RecentsProvider.java:192)
            at android.content.ContentProvider.query(ContentProvider.java:857)
            at android.content.ContentProvider$Transport.query(ContentProvider.java:200)
            at android.content.ContentResolver.query(ContentResolver.java:461)
            at android.content.ContentResolver.query(ContentResolver.java:404)
            at com.android.documentsui.DirectoryLoader.loadInBackground(DirectoryLoader.java:124)
            at com.android.documentsui.DirectoryLoader.loadInBackground(DirectoryLoader.java:65)
            at android.content.AsyncTaskLoader.onLoadInBackground(AsyncTaskLoader.java:312)
            at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:69)
            at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:57)
            at android.os.AsyncTask$2.call(AsyncTask.java:288)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at com.android.documentsui.ProviderExecutor.run(ProviderExecutor.java:107)

content：//com.commonsware.android.documents.provider/thisIsMyRoot/可能是基于queryRoots()实现为我的文档根生成的Uri.但我不知道是什么内容：//com.android.documentsui.recents/state/com.commonsware.android.documents.provider/thisIsMyRoot/或我应该做些什么来防止这个错误.

这是DocumentsProvider实现,旨在提供来自assets /的文件：

/***
  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.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) {
        addDocumentRow(result,child,parentDocumentId+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);

    documentId=fixUpDocumentId(documentId);

    try {
      addDocumentRow(result,Uri.parse(documentId).getLastPathSegment(),documentId);
    }
    catch (IOException e) {
      Log.e(getClass().getSimpleName(),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 {
    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


所以,我的问题是：我哪里错了？


最佳答案
我创建了一个gist,它有工作代码.
问题：
在根目录的情况下,queryDocument实现返回空字符串文档id. RecentProvider尝试将uri与状态/ * / * / *进行匹配,其中最后一个段是文档ID.由于文档id为空字符串,因此uri匹配失败,因此抛出了不受支持的uri异常.
解：
我提供了4个修复程序,使解决方案完全正常工作.我在代码中留下了评论.
修复1：在查询子文档时,如果父文件是root,则assetPath应该只是文件名.如果父级是assets文件夹中的目录,则assetPath应为directory / filename.您还需要在组件之间添加文件分隔符.
更改

addDocumentRow(result,parentDocumentId+child);

至

addDocumentRow(result,parentDocumentId == "" ? child : parentDocumentId + File.separator + child);

修复2：这为不受支持的uri异常提供了修复.文档ID永远不应为null.
删除documentId = fixUpDocumentId(documentId);来自queryDocument.
修复3& 4：确定文件是否是目录.如果是root,则资产目录应为空字符串.非空目录将包含至少1个文件.
变化：

private boolean isDirectory(String assetPath) throws IOException {
    return(assets.list(assetPath).length>1);
}

至

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);
}

这是screenrecord：
 原文链接：https://www.f2er.com/android/431140.html

DocumentsProvider：什么是内容：//com.android.documentsui.recents/state为什么它不喜欢我？

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