通过URI获取的文件路径为null的解决方法

今天调用系统自带的FileChooser后，根据Intent返回的uri获取路径的时一直返回null。

这个问题很奇怪，最后发现验证用的华为P7是Android 4.4系统。

先看下4.4之前的uri的形式：

Uri ： content://media/extenral/images/media/17766

是不是很熟悉？再看4.4及以后的Uri形式：

content://com.android.providers.media.documents/document/image%2706

    日志一打印出来我就明白是什么原因啦。这什么东西在Android 4.4前后不一样，4.4之前content后面是文件全路径，4.4之后不再直接表示路径啦。这就好办啦，翻了翻API后发现4.4以后的Uri还不唯一，并不是统一的一种格式，所以就来个通用解决办法好啦：

4.4以前通过Uri获取路径：data是Uri，filename是一个String的字符串，用来保存路径。

public static String getPathByUri(Context context, Uri data) {
		String filename=null;
		if (data.getScheme().toString().compareTo("content") == 0) {
			Cursor cursor = context.getContentResolver().query(data, new String[] { "_data" }, null, null, null);
			if (cursor.moveToFirst()) {
				filename = cursor.getString(0);
			}
		} else if (data.getScheme().toString().compareTo("file") == 0) {// file:///开头的uri
			filename = data.toString();
			filename = data.toString().replace("file://", "");// 替换file://
			if (!filename.startsWith("/mnt")) {// 加上"/mnt"头
				filename += "/mnt";
			}
		}
		return filename;
	}

    4.4以后根据Uri获取路径：

// 专为Android4.4设计的从Uri获取文件绝对路径，以前的方法已不好使
	@SuppressLint("NewApi")
	public static String getPathByUri4kitkat(final Context context, final Uri uri) {
		final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
		// DocumentProvider
		if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
			if (isExternalStorageDocument(uri)) {// ExternalStorageProvider
				final String docId = DocumentsContract.getDocumentId(uri);
				final String[] split = docId.split(":");
				final String type = split[0];
				if ("primary".equalsIgnoreCase(type)) {
					return Environment.getExternalStorageDirectory() + "/" + split[1];
				}
			} else if (isDownloadsDocument(uri)) {// DownloadsProvider
				final String id = DocumentsContract.getDocumentId(uri);
				final Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),
						Long.valueOf(id));
				return getDataColumn(context, contentUri, null, null);
			} else if (isMediaDocument(uri)) {// MediaProvider
				final String docId = DocumentsContract.getDocumentId(uri);
				final String[] split = docId.split(":");
				final String type = split[0];
				Uri contentUri = null;
				if ("image".equals(type)) {
					contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
				} else if ("video".equals(type)) {
					contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
				} else if ("audio".equals(type)) {
					contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
				}
				final String selection = "_id=?";
				final String[] selectionArgs = new String[] { split[1] };
				return getDataColumn(context, contentUri, selection, selectionArgs);
			}
		} else if ("content".equalsIgnoreCase(uri.getScheme())) {// MediaStore
																	// (and
																	// general)
			return getDataColumn(context, uri, null, null);
		} else if ("file".equalsIgnoreCase(uri.getScheme())) {// File
			return uri.getPath();
		}
		return null;
	}

	/**
	 * Get the value of the data column for this Uri. This is useful for
	 * MediaStore Uris, and other file-based ContentProviders.
	 * 
	 * @param context
	 *            The context.
	 * @param uri
	 *            The Uri to query.
	 * @param selection
	 *            (Optional) Filter used in the query.
	 * @param selectionArgs
	 *            (Optional) Selection arguments used in the query.
	 * @return The value of the _data column, which is typically a file path.
	 */
	public static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {
		Cursor cursor = null;
		final String column = "_data";
		final String[] projection = { column };
		try {
			cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
			if (cursor != null && cursor.moveToFirst()) {
				final int column_index = cursor.getColumnIndexOrThrow(column);
				return cursor.getString(column_index);
			}
		} finally {
			if (cursor != null)
				cursor.close();
		}
		return null;
	}

	/**
	 * @param uri
	 *            The Uri to check.
	 * @return Whether the Uri authority is ExternalStorageProvider.
	 */
	public static boolean isExternalStorageDocument(Uri uri) {
		return "com.android.externalstorage.documents".equals(uri.getAuthority());
	}

	/**
	 * @param uri
	 *            The Uri to check.
	 * @return Whether the Uri authority is DownloadsProvider.
	 */
	public static boolean isDownloadsDocument(Uri uri) {
		return "com.android.providers.downloads.documents".equals(uri.getAuthority());
	}

	/**
	 * @param uri
	 *            The Uri to check.
	 * @return Whether the Uri authority is MediaProvider.
	 */
	public static boolean isMediaDocument(Uri uri) {
		return "com.android.providers.media.documents".equals(uri.getAuthority());
	}

    安卓2.3.3 & 4.0.4 & 4.4 & 5.1.1 & 6.0真机亲测都正常，欢迎拷贝！

    最后，附上一个Video项目用到的相关函数供参考：

//return the id of URI
    public static int getVideoUriByPath(Uri resultUri, Activity activity, String path){
    	resultUri= null;
    	int id=-1;
    	if(activity==null || path==null)
    		return id;
    	Uri preUri = Uri.parse("content://media/external/video/media/"); 
    	@SuppressWarnings("deprecation")
		Cursor cursor = activity.managedQuery(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, null, null, null, MediaStore.Video.Media.DEFAULT_SORT_ORDER);
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            String data = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Video.Media.DATA));
            if (path.equals(data)) {
                id = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Video.Media._ID));
                resultUri = Uri.withAppendedPath(preUri, "" + id);
                break;
            }
            cursor.moveToNext();
        }
        return id;
    }