Question

我使用以下代码从文本文件中读取值。但是，始终读取null值（ versionfile 始终为null）。我在代码中遗漏了什么吗？ （注意：文件已存在且值在其中）

String fileversion = Environment.getExternalStorageDirectory() + File.separator + "chk.txt", versionfile = "0";
File chkfile = new File(fileversion);

try {
    BufferedReader br = new BufferedReader(new FileReader(chkfile));
    while ((versionfile = br.readLine()) != null) {

    }
    br.close();
} catch (IOException e) {

}

Answer 1

我认为你提到的文件不存在，因为当我在我的设备中执行此代码时，它完美地工作并在日志中显示输出

String fileversion = Environment.getExternalStorageDirectory() + File.separator + "Links.txt", versionfile = "0";

File chkfile = new File(fileversion);

Log.e("///////////////", "versionfile :: " + versionfile + " : fileversion :: " + fileversion);
try {
    BufferedReader br = new BufferedReader(new FileReader(chkfile));

    while ((versionfile = br.readLine()) != null) {
        Log.e("///////////////", "versionfile ::" + versionfile + ": fileversion :: " + fileversion);
    }
    br.close();
} catch (IOException e) {
    e.printStackTrace();

}

这就是我所做的一切

您的代码非常完美，只需要将版本字符串存储在另一个像

这样的字符串中

newString += versionfile;

Answer 2

这样做：

String fileversion=Environment.getExternalStorageDirectory() + File.separator + "chk.txt", versionfile="0";
FileReader fileReader = new FileReader(fileversion);
try {
    BufferedReader br = new BufferedReader(fileReader);
    while ((versionfile = br.readLine()) != null) {
        System.out.println("versionfile");
    }
    br.close();
} catch (IOException e) {
    System.out.println(e);
}

Answer 3

使用以下代码阅读.txt文件：

// Read text from file
public void ReadBtn() {
    //reading text from file
    try {
        FileInputStream fileIn = openFileInput("mytextfile.txt"); // define your path.
        InputStreamReader InputRead = new InputStreamReader(fileIn);

        char[] inputBuffer = new char[50];
        String s = "";
        int charRead;

        while ((charRead = InputRead.read(inputBuffer)) > 0) {
            // char to string conversion
            String readstring = String.copyValueOf(inputBuffer, 0, charRead);
            s += readstring;
        }
        InputRead.close();
        Log.d("File Data", s);


    } catch (Exception e) {
        e.printStackTrace();
    }
}

我希望您在清单文件中添加以下权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

Answer 4

我发现了问题。

while循环执行了2次，我的文件只有1行，所以第二次将值替换为null。根据要求，文件将始终具有单行内容。所以，我删除了while循环，它运行正常。

String fileversion = Environment.getExternalStorageDirectory() + File.separator + "chk.txt", versionfile = "0";
File chkfile = new File(fileversion);

try {
    BufferedReader br = new BufferedReader(new FileReader(chkfile));
    versionfile = br.readLine();

    }
    br.close();
} catch (IOException e) {

}

在读取txt文件时始终获取空值

4 个答案: