如果我们希望自己 APP 的数据也能在 documentsui 中打开，那么就需要写一个自己的 Document provider

Document Provider 自定义

自定义 Document Provider 很简单，短短几步就实现了

1. 要求 API 版本为 19+ ( Android 4.4+ )

2. 自定义个一个 Document Provider，比如 MsCloudProvider

3. 在 AndroidManifest.xml 中注册自定义全限定的 Provider

   1. android:name 为类名加包名，比如

      cn.twle.android.storageprovider.MsCloudProvider
      

   2. android:authority 为 包名 + provider 的类型名 ，如

      cn.twle.android.storageprovider.documents
      

   3. ndroid:exported 属性的值为 true

   下面是 Provider 的写法

   <manifest... >
       ...
       <uses-sdk
           android:minSdkVersion="19"
           android:targetSdkVersion="19" />
           ....
           <provider
               android:name="cn.twle.android.storageprovider.MsCloudProvider"
               android:authorities="cn.twle.android.storageprovider.documents"
               android:grantUriPermissions="true"
               android:exported="true"
               android:permission="android.permission.MANAGE_DOCUMENTS"
               android:enabled="@bool/atLeastKitKat">
               <intent-filter>
                   <action android:name="android.content.action.DOCUMENTS_PROVIDER" />
               </intent-filter>
           </provider>
       </application>
   </manifest>
   

DocumentsProvider 的子类

我们自定义的 DocumentsProvider 至少要实现以下几个方法，其它的按需实现

• queryRoots()
• queryChildDocuments()
• queryDocument()
• openDocument()

比如下面可能是我们的 MsCloudProvider 的大致写法

1. 实现 queryRoots() 方法

   @Override
   public Cursor queryRoots(String[] projection) throws FileNotFoundException {
   
       // Create a cursor with either the requested fields, or the default
       // projection if "projection" is null.
       final MatrixCursor result =
               new MatrixCursor(resolveRootProjection(projection));
   
       // If user is not logged in, return an empty root cursor.  This removes our
       // provider from the list entirely.
       if (!isUserLoggedIn()) {
           return result;
       }
   
       // It's possible to have multiple roots (e.g. for multiple accounts in the
       // same app) -- just add multiple cursor rows.
       // Construct one row for a root called "MyCloud".
       final MatrixCursor.RowBuilder row = result.newRow();
       row.add(Root.COLUMN_ROOT_ID, ROOT);
       row.add(Root.COLUMN_SUMMARY, getContext().getString(R.string.root_summary));
   
       // FLAG_SUPPORTS_CREATE means at least one directory under the root supports
       // creating documents. FLAG_SUPPORTS_RECENTS means your application's most
       // recently used documents will show up in the "Recents" category.
       // FLAG_SUPPORTS_SEARCH allows users to search all documents the application
       // shares.
       row.add(Root.COLUMN_FLAGS, Root.FLAG_SUPPORTS_CREATE |
               Root.FLAG_SUPPORTS_RECENTS |
               Root.FLAG_SUPPORTS_SEARCH);
   
       // COLUMN_TITLE is the root title (e.g. Gallery, Drive).
       row.add(Root.COLUMN_TITLE, getContext().getString(R.string.title));
   
       // This document id cannot change once it's shared.
       row.add(Root.COLUMN_DOCUMENT_ID, getDocIdForFile(mBaseDir));
   
       // The child MIME types are used to filter the roots and only present to the
       //  user roots that contain the desired type somewhere in their file hierarchy.
       row.add(Root.COLUMN_MIME_TYPES, getChildMimeTypes(mBaseDir));
       row.add(Root.COLUMN_AVAILABLE_BYTES, mBaseDir.getFreeSpace());
       row.add(Root.COLUMN_ICON, R.drawable.ic_launcher);
   
       return result;
   }
   

2. 实现 queryChildDocuments() 方法

   public Cursor queryChildDocuments(String parentDocumentId, String[] projection,
                                 String sortOrder) throws FileNotFoundException {
   
       final MatrixCursor result = new
               MatrixCursor(resolveDocumentProjection(projection));
       final File parent = getFileForDocId(parentDocumentId);
       for (File file : parent.listFiles()) {
           // Adds the file's display name, MIME type, size, and so on.
           includeFile(result, null, file);
       }
       return result;
   }
   

3. 实现 queryDocument() 方法

   @Override
   public Cursor queryDocument(String documentId, String[] projection) throws
           FileNotFoundException {
   
       // Create a cursor with the requested projection, or the default projection.
       final MatrixCursor result = new
               MatrixCursor(resolveDocumentProjection(projection));
       includeFile(result, documentId, null);
       return result;
   }