Question

我的应用程序（写入文件）在物理设备上正常工作..但在模拟器中崩溃。我用了

  makeFile = new 
 File(Environment.getExternalStorageDirectory().getAbsolutePath() 
  +  "/" +path);
  if (!makeFile.exists())
        makeFile.mkdirs();
     writeFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" +path + File.separator + file_name + ".txt");

Log cat在这一行说错误

      bufferedWriter = new BufferedWriter(new FileWriter(writeFile, false));

和
引起：java.lang.NullPointerException：尝试调用虚方法＆＃39; void java.io.BufferedWriter.write（java.lang.String）＆＃39;在null对象引用上在这行代码

    bufferedWriter.write(contents);

我自己编写文件

的方法

enter code here
 public void writeSingleFile(String path, String file_name, String contents, boolean append) {
    makeFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" +path);
    if (!makeFile.exists())
        makeFile.mkdirs();
    writeFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" +path + File.separator + file_name + ".txt");
    try {
        if (append)
            bufferedWriter = new BufferedWriter(new FileWriter(writeFile, true));
        else
            bufferedWriter = new BufferedWriter(new FileWriter(writeFile, false));
    } catch (FileNotFoundException e1) {
        e1.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    try {
        if (append)
            bufferedWriter.write(contents + "\n");
        else
            bufferedWriter.write(contents);

    } catch (IOException e1) {
        e1.printStackTrace();
    }
    try {
        bufferedWriter.close();
    } catch (IOException e1) {
        e1.printStackTrace();
    }

}

Answer 1

 <?php
 if( $_POST )
{
   if( empty($_POST['file']) )
 {
   // echo error or do nothing;
   die("Select a file to upload");
     }
   }
 ?>
 <html>
 <body>
 <form action="" method="POST" enctype="multipart/form-data">
 <input type="file" name="image">
 <input type="submit" value="Submit">
 </form>
 </body>
 </html>

首先，只需调用

即可省略第一个

try {
    if (append)
        bufferedWriter = new BufferedWriter(new FileWriter(writeFile, true));
    else
        bufferedWriter = new BufferedWriter(new FileWriter(writeFile, false));
} catch (FileNotFoundException e1) {
    e1.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

语句

if

如果实例化失败并出现异常，则只需在STDERR上输出并继续。在这种情况下，bufferedWriter会bufferedWriter = new BufferedWriter(new FileWriter(writeFile, append));进一步导致null。忽略异常是不好的，并且会导致你亲眼目睹的奇怪行为（充其量）。

应用程序在写入文件时在模拟器中崩溃

1 个答案: