无法使用FileProvider打开平凡的文本文件 [英] Unable to open trivial text file with FileProvider

问题描述

我快疯了，过去我曾经使用过新的Android FileProvider，但是我无法将其与Download文件夹中的一个(琐碎的)刚刚创建的文件一起使用.

I'm going crazy, I used the new Android FileProvider in the past but I can't get it to work with a (trivial) just-created file in the Download folder.

在我的AsyncTask.onPostExecute我打电话

Intent myIntent = new Intent(Intent.ACTION_VIEW, FileProvider.getUriForFile(mContext, BuildConfig.APPLICATION_ID + ".fileprovider", output));
myIntent.setType("text/plain");
myIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
startActivity(myIntent);

我的FileProvider XML就是这样

My FileProvider XML is like this

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="Download" path="Download"/>
</paths>

在Genymotion模拟器中，我总是选择Amaze Text Editor作为目标应用程序:

In Genymotion emulator I always get, choosing Amaze Text Editor as target app:

虽然我可以使用HTML Viewer查看文件内容:

While I can see the file content with HTML Viewer:

我无法理解这种行为，无法解决琐碎的事情，例如使用所需的文本编辑器打开纯文本文件.

I can't understand this behavior and fix what should be a trivial thing like opening a pure-text file with the desidered text editor.

非常感谢 尼古拉

推荐答案

好的，这里有两个问题.一种是您的代码中的错误会触发Amaze中的错误，另一种是您可以解决的Amaze中的错误.

OK, there are two problems here. One is a bug in your code that triggers a bug in Amaze, and one is a bug in Amaze that you can work around.

setType()有一个令人讨厌的副作用:它会擦掉Intent中的Uri.这等效于调用setDataAndType(null, ...)(其中...是您的MIME类型).这不好.因此，不要将Uri放入构造函数中并调用setType()，而是要调用setDataAndType()并在其中提供Uri. 这使您摆脱了最初的Amaze错误，在该错误中他们无法正确处理null Uri .

setType() has a nasty side effect: it wipes out your Uri in the Intent. It is the equivalent of calling setDataAndType(null, ...) (where ... is your MIME type). That's not good. So, instead of putting the Uri in the constructor and calling setType(), call setDataAndType() and provide the Uri there. This gets you past the initial Amaze bug, where they fail to handle a null Uri correctly.

然后，他们尝试以读写模式打开Uri.您仅授予读取访问权限，因此失败.他们的第二个错误是，当他们无法以读写模式打开文件时，他们以为得到FileNotFoundException，这时他们尝试了只读模式.实际上，至少在Android 8.1上，它们会得到SecurityException .您可以通过提供读写权限来解决此问题.

Then, though, they try to open the Uri in read-write mode. You are only granting read access, so this fails. Their second bug is that they think that they get a FileNotFoundException when they cannot open the file in read-write mode, and at that point they try read-only mode. In reality, at least on Android 8.1, they get a SecurityException. You can work around this by providing both read and write permissions.

因此，除非您特别希望阻止写访问，否则此代码有效:

So, unless you specifically want to block write access, this code works:

Intent myIntent = new Intent(Intent.ACTION_VIEW);
myIntent.setDataAndType(FileProvider.getUriForFile(mContext, BuildConfig.APPLICATION_ID + ".fileprovider", output), "text/plain");
myIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION|Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
startActivity(myIntent);

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