Question

大家好我试图在手机列表视图中显示所有doc，docx，pdf，xls，txt。所以对于初学者，我尝试this在我的应用上实现，但不知何故我在这一行上有错误ContentResolver cr = context.getContentResolver();

编辑：感谢您回答CommonsWare。现在我对这一行newVVI.mimeType = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.MIME_TYPE + "=?"));

有疑问

这是我的代码

 Uri uri = MediaStore.Files.getContentUri("external");

    String[] projection ={ MediaStore.Files.FileColumns._ID,
            MediaStore.Files.FileColumns.DATA, MediaStore.Files.FileColumns.TITLE} ;

    String selectionMimeType = MediaStore.Files.FileColumns.MIME_TYPE + "=?";
    String mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension("pdf");
    String[] selectionArgsPdf = new String[]{ mimeType };
    String sortOrder = null;

    Cursor allPdfFiles = getContentResolver().query(uri, projection, selectionMimeType, selectionArgsPdf, sortOrder);


    if (allPdfFiles.moveToFirst()) {
        do {

            ImageViewInfo newVVI = new ImageViewInfo();
            int id = allPdfFiles.getInt(allPdfFiles.getColumnIndex(MediaStore.Files.FileColumns._ID));


            newVVI.filePath = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATA));
            newVVI.title = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.TITLE));
            newVVI.mimeType = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.MIME_TYPE + "=?"));
            ImageRows.add(newVVI);
        } while (cursor.moveToNext());


        allPdfFiles.close(); }

我做得对吗？请帮帮我。

如何查询多个指定文件，如docs，docx，xls，txt？所以我可以将它与pdf一起列出。

提前谢谢你！

Answer 1

Context context = null;

您的第一行将context设置为null。

ContentResolver cr = context.getContentResolver();

您的第二行会生成NullPointerException，因为您尝试在getContentResolver() null上致电Context。

您需要一个实际的Context，例如Activity或Service。

Answer 2

当您尝试获取投影中列出的返回列时，此语法不正确。确保投影列出了所需的列。可以将其视为电子表格，其中每列代表数据的另一个属性。然后你的do while循环有效地在每一行中运行，同时你要求该行的每个元素。

不正确的：

  allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(Medi‌aStore.Files.FileCol‌umns.MIME_TYPE + "=?"));

正确的：

       String[] projection ={ MediaStore.Files.FileColumns._ID,
        MediaStore.Files.FileColumns.DATA, MediaStore.Files.FileColumns.TITLE, MediaStore.Files.FileColumns.MIME_TYPE} ;

和

  newVVI.filePath = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATA));
        newVVI.title = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.TITLE));
        newVVI.mimeType = allPdfFiles.getString(allPdfFiles.getColumnIndexOrThrow(MediaStore.Files.FileColumns.MIME_TYPE));

Answer 3

感谢您的回答！我的代码得到了一个可行的解决方案并解决了问题！

有效：

private static final String orderBy = MediaStore.Files.FileColumns.DATE_ADDED + " DESC";

ContentResolver contentResolver = getContentResolver();
Uri uri = MediaStore.Files.getContentUri("external");

final String[] columns = {
                    MediaStore.Images.Media.DATA, MediaStore.Images.Media._ID,
                    MediaStore.Images.Media.DATE_ADDED, MediaStore.Images.Media.TITLE,
                    MediaStore.Images.Media.SIZE, MediaStore.Images.Media.DISPLAY_NAME,
                    MediaStore.Images.Media.MIME_TYPE};

        List<String> extensions = new ArrayList<>();
        extensions.add("pdf");
        extensions.add("csv");
        extensions.add("doc");
        extensions.add("docx");
        extensions.add("xls");
        extensions.add("xlsx");

List<String> mimes = new ArrayList<>();
        for (String ext : extensions) {
            mimes.add(MimeTypeMap.getSingleton().getMimeTypeFromExtension(ext));
        }

Cursor cursor;
        cursor = contentResolver.query(uri, columns, null, null, orderBy);
        if (cursor != null) {
            int mimeColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE);
            int pathColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA);

            while (cursor.moveToNext()) {
                String mimeType = cursor.getString(mimeColumnIndex);
                String filePath = cursor.getString(pathColumnIndex);

                if (mimeType != null && mimes.contains(mimeType)) {
                    // handle cursor
                    makeFile(cursor);
                } else {
                    // need to check extension, because the Mime Type is null
                    String extension = getExtensionByPath(filePath);
                    if (extensions.contains(extension)) {
                        // handle cursor
                        makeFile(cursor);
                    }
                }
            }
            cursor.close();
        }

public static String getExtensionByPath(@NonNull String path) {
        String result = "%20";
        int i = path.lastIndexOf('.');
        if (i > 0) {
            result = path.substring(i + 1);
        }
        return result;
    }

private MyCustomFile makeFile(Cursor cursor) {
        int mimeColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE);
        int pathColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA);
        int sizeColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.SIZE);
        int titleColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.TITLE);
        int nameColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME);

        int fileId = cursor.getInt(pathColumnIndex);
        String fileSize = cursor.getString(sizeColumnIndex);
        String fileDisplayName = cursor.getString(nameColumnIndex);
        String fileTitle = cursor.getString(titleColumnIndex);
        String filePath = cursor.getString(pathColumnIndex);
        String mimeType = cursor.getString(mimeColumnIndex);
        String type = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType);
        if (type == null) {
            type = FileUtils.getExtensionByPath(filePath);
            mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(type);
        }

        MyCustomFile result = new MyCustomFile();
        result.setFileId(fileId);
        result.setFilePath(filePath);
        result.setFileSize(fileSize);
        result.setFileTitle(fileTitle);
        result.setFileDisplayName(fileDisplayName);
        result.setMimeType(mimeType);
        result.setFileExtension(type);

        return result;
    }

希望有人帮助我=）

Answer 4

我已经创建了一个这样的查询，它的运行就像一个超级按钮

val mimeTypes = mutableListOf<String>()
val extenstions = mutableListOf("pdf","doc","odt")
extenstions.forEach { mimeType ->
     MimeTypeMap
         .getSingleton()
         .getMimeTypeFromExtension(mimeType)?.let {
             mimeTypes.add("'$it'")
         }
}

val selectionMimeType = MediaStore.Files.FileColumns.MIME_TYPE + " IN (${mimeTypes.joinToString()})"
context.contentResolver.query(
     MediaStore.Files.getContentUri("external"),
     projection,
     selectionMimeType,
     null,
     MediaStore.Video.Media.DATE_ADDED
)

如何在Android的listview中显示doc，docx，pdf，xls，txt

4 个答案: