在对我之前的问题的回答中，有人指出 Android 类 UriMatcher 中存在一些固有缺陷(因为没有更好的词)。任何人都可以查明 UriMatcher 的已知问题吗？我正在设计一个依赖 UriMatcher 正确匹配我的 Uris 的内容提供程序(而不是我想的不正确)。已知问题是否有解决方法？还是有更好的匹配 Uris 的策略？

例子:

这是设置我的 UriMatcher 的代码

private static final int MEMBER_COLLECTION_URI = 1;
private static final int MEMBER_SINGLE_URI = 2;
private static final int SUBMATERIAL_COLLECTION_URI = 3;
private static final int SUBMATERIAL_SINGLE_URI = 4;
private static final int JOBNAME_COLLECTION_URI = 5;
private static final int JOBNAME_SINGLE_URI = 6;
private static final int ALL_MEMBERS_URI = 7;
private static final int ALL_SUBMATERIAL_URI = 8;

static
{
        //return the job and fab for anything matching the provided jobName
        // JobNames/jobName
        uriMatcher.addURI(JobMetaData.AUTHORITY, "JobNames/*/",
                          JOBNAME_SINGLE_URI);
        //return a collection of members
        // jobName/member/attribute/value
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/member/*/*/",
                          MEMBER_COLLECTION_URI);
        //return a single member
        // jobName/member/memberNumber
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/member/*/",
                          MEMBER_SINGLE_URI);
        //return a collection of submaterial
        // jobName/submaterial/attribute/value
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/submaterial/*/*",
                          SUBMATERIAL_COLLECTION_URI);
        //return a single piece of submaterial
        // jobName/submaterial/GUID
        //GUID is the only way to uniquely identify a piece of submaterial    
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/submaterial/*",
                          SUBMATERIAL_SINGLE_URI);
        //Return everything in the member and submaterial tables
        //that has the provided attribute that matches the provided value
        // jobName/attribute/value
        //not currently used
        uriMatcher.addURI(JobMetaData.AUTHORITY, "JobNames/",
                          JOBNAME_COLLECTION_URI);
        //return all members in a job
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/members/",
                          ALL_MEMBERS_URI);

}

添加另一个 Uri:

private static final int MEMBER_COLLECTION_URI = 1;
private static final int MEMBER_SINGLE_URI = 2;
private static final int SUBMATERIAL_COLLECTION_URI = 3;
private static final int SUBMATERIAL_SINGLE_URI = 4;
private static final int JOBNAME_COLLECTION_URI = 5;
private static final int JOBNAME_SINGLE_URI = 6;
private static final int ALL_MEMBERS_URI = 7;
private static final int ALL_SUBMATERIAL_URI = 8;
//ADDITIONAL URI
private static final int REVERSE_URI = 9;

static
{
        //return the job and fab for anything matching the provided jobName
        // JobNames/jobName
        uriMatcher.addURI(JobMetaData.AUTHORITY, "JobNames/*/",
                          JOBNAME_SINGLE_URI);
        //return a collection of members
        // jobName/member/attribute/value
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/member/*/*/",
                          MEMBER_COLLECTION_URI);
        //return a single member
        // jobName/member/memberNumber
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/member/*/",
                          MEMBER_SINGLE_URI);
        //return a collection of submaterial
        // jobName/submaterial/attribute/value
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/submaterial/*/*",
                          SUBMATERIAL_COLLECTION_URI);
        //return a single piece of submaterial
        // jobName/submaterial/GUID
        //GUID is the only way to uniquely identify a piece of submaterial    
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/submaterial/*",
                          SUBMATERIAL_SINGLE_URI);
        //Return everything in the member and submaterial tables
        //that has the provided attribute that matches the provided value
        // jobName/attribute/value
        //not currently used
        uriMatcher.addURI(JobMetaData.AUTHORITY, "JobNames/",
                          JOBNAME_COLLECTION_URI);
        //return all members in a job
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/members/",
                          ALL_MEMBERS_URI);
        //ADDITIONAL URI
        uriMatcher.addURI(JobMetaData.AUTHORITY, "*/reverse/*",
                          REVERSE_URI);

}

最后一个 Uri 无法识别: uriMatcher.match(uri)

在上一个问题(前面提到过)中，建议我将有问题的 Uri 移到对 UriMatcher.put(String, int) 的调用的顶部。这解决了之前的问题(让我嘴里的味道不好)。使用此代码尝试相同的解决方案会导致当前的第一个 Uri (JOBNAME_SINGLE_URI) 无法识别。我相当确定问题不在我的代码中(我已经设法使用 Uris 创建了一个工作的 ContentProvider 并在此问题之前调试了它们的所有问题)，而是 Android 中 Uri 匹配的问题.

更新:

public final static String AUTHORITY = "dsndata.sds2mobile.jobprovider";

示例 Uri:
content://dsndata.sds2mobile.jobprovider/SDS2MobileDemo/reverse/C_1

最佳答案

有三个规则没有很好的记录，但对于理解 UriMatcher 的匹配机制至关重要:

1. UriMatcher 尝试将整个 Uri 与模式进行匹配。很像 java.util.regex.Matcher 的 matches() 方法，它仅在整个区域序列与匹配器的模式匹配时才返回 true(与 find() 方法对部分匹配返回 true 相比)。
2. 通配符仅应用于一个路径段，这意味着 * 或 SDS2MobileDemo/* 永远不会匹配 SDS2MobileDemo/reverse/C_1 但 */*/* 或 */*/C_1 会。
3. 一旦找到路径段的匹配项，它就不会找到该特定路径段的任何替代匹配项。

以下是一些使用以下网址的示例:content://dsndata.sds2mobile.jobprovider/SDS2MobileDemo/reverse/C_1

前两条规则很容易理解:

• SDS2MobileDemo/*/* 将匹配
• */reverse/* 将匹配
• */* 不会匹配，因为它只匹配两个路径段
• SDS2MobileDemo 不匹配，因为它只匹配一个路径段

第三条规则有点难以理解。 如果您按此确切顺序添加以下 Uris:

• */错误/C_1
• SDS2MobileDemo/reverse/C_1

然后它将找不到匹配项，因为这会转换为以下(伪)代码:

if ("*".matches("SDS2MobileDemo")) {    
    // tries to match the other parts but fails    
}
else if ("SDS2MobileDemo".matches("SDS2MobileDemo")) {
    // will never be executed
}

如果你颠倒顺序，(伪)代码变成:

if ("SDS2MobileDemo".matches("SDS2MobileDemo")) {    
    // tries to match the other parts and succeeds    
}    
else if ("*".matches("SDS2MobileDemo")) {    
    // will never be executed    
}

现在就最初的问题而言。 SDS2MobileDemo/reverse/C_1 将与 */reverse/* 匹配，但不是例如JobNames/reverse/C_1 因为那个会沿着 JobNames/* 路径... 同样很明显，将 */reverse/* 移到顶部不是解决方案，因为所有其他不以 * 开头的模式将不再匹配。 只要不知道哪个模式应该匹配哪个 Uris，就真的不知道正确的解决方案是什么。

关于android - Android 的 UriMatcher 的问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/5030094/