android.content.UriMatcher的含义 [英] Meaning of android.content.UriMatcher

问题描述

什么是Uri Matcher in android.content.UriMatcher

What is Uri Matcher in android.content.UriMatcher

如何使用它？
有人可以解释以下三行代码的含义吗？

How to use it? Can someone please explain meaning of following three line of code?

  uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
  uriMatcher.addURI(PROVIDER_NAME, "cte", uriCode);
  uriMatcher.addURI(PROVIDER_NAME, "cte/*", uriCode);
  int res = uriMatcher.match(uri);

推荐答案

当您编写ContentProvider时，UriMatcher是一个方便的类或者其他需要响应许多不同URI的类。在您的示例中，用户可以使用URI查询您的提供程序，例如：

UriMatcher is a handy class when you are writing a ContentProvider or some other class that needs to respond to a number of different URIs. In your example, a user could query your provider with URIs such as:

myprovider://cte

或

myprovider://cte/somestring

构建UriMatcher时，需要为每个URI分别设置代码（不只是像你的例子中的uriCode）。我通常将我的UriMatcher实例设置为静态，并在静态构造函数中添加URI：

When you construct a UriMatcher, you need to have separate codes for each URI (not just "uriCode" as in your example). I usually make my UriMatcher instance static, and add the URIs in a static constructor:

private static final int CTE_ALL = 1;
private static final int CTE_FIND = 2;
private static final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
    uriMatcher.addURI(PROVIDER_NAME, "cte", CTE_ALL);
    uriMatcher.addURI(PROVIDER_NAME, "cte/*", CTE_FIND);
}

然后在您的ContentProvider中，您将在查询方法中执行以下操作：

Then in your ContentProvider you would do something like this in your query method:

Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
    int res = uriMatcher.match(uri);
    switch (res) {
        case CTE_ALL:
            //TODO create a results Cursor with all the CTE results
            break;
        case CTE_FIND:
            //TODO create a results Cursor with the single CTE requested
            break;
    }
    return results;
}

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