java - 将字符串输出创建到 SD 卡上可访问的文件时出现问题

Question

这是我在这里的第一篇文章，我应该指出我的知识充其量是有限的!

我正在尝试为我的 Android 手机创建一个应用。

我需要最终将用户输入的值输出到一个文件，很可能是一个 txt 文件，当通过 USB 数据线连接时，可以直接从手机中检索该文件。

但是，我正在努力了解如何实现这一目标。

据我所知，我需要确保卡已安装，要获得路径，然后使用 FileOpenStream() 和 FileWriter将字符串“加载”到文件中(抱歉，不确定描述它的正确方法，或与此相关的任何其他内容)

我还在 list 中允许写入 SD 卡的权限。但是，我能找到的所有示例似乎都与 SD 卡无关。非常感谢收到任何建议和/或指向教程。

我现在的代码到处都是，因为我把自己搞糊涂了，抱歉。

boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();

if (Environment.MEDIA_MOUNTED.equals(state)) {
    // We can read and write the media    
    mExternalStorageAvailable = mExternalStorageWriteable = true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
    // We can only read the media   
    mExternalStorageAvailable = true;
    mExternalStorageWriteable = false;
} else {
    // Something else is wrong. It may be one of many other states, but all we need   
    //  to know is we can neither read nor write  
    mExternalStorageAvailable = mExternalStorageWriteable = false;
}

if (mExternalStorageAvailable == true && 
        mExternalStorageAvailable == true) {
    //Environment.getExternalStorageDirectory()  gets root path to SD card
    // FileOutputStream to output somehow
    File path = Environment.getExternalStorageDirectory();
    OutputStream out = null;
    try {
        //File path = Environment.getExternalStorageDirectory();
        //FileOutputStream f = new FileOutputStream(new File(path + "/DCIM", "fileName"));

        out = new BufferedOutputStream(new FileOutputStream(file));

        OutputStreamWriter osw = new OutputStreamWriter(f);

        osw.write("test txt");
        osw.flush();// ensure that everything is really written out and close
        osw.close();
        Toast.makeText(getBaseContext(), "path = " + path, Toast.LENGTH_LONG).show();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        Toast.makeText(getBaseContext(), "File not FOund", Toast.LENGTH_LONG).show();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        Toast.makeText(getBaseContext(), "IOException", Toast.LENGTH_LONG).show();
    }
}

编辑:

这是 XML 文件(希望如此)，看看 FileNotFound 异常是否是由它引起的。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.androidbook.epcsn"
  android:versionCode="1"
  android:versionName="1.0">
<uses-sdk android:minSdkVersion="9" />
<permission></permission>

<application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="true" android:permission="android.permission.WRITE_EXTERNAL_STORAGE">

Answer 1

我稍微清理了您的代码并更改了几行，我认为它现在可以满足您的需求。我使用 BufferedWriter 写入 sdcard。您可以阅读有关我使用的 BufferedWriter 的更多信息 here

    boolean mExternalStorageAvailable = false;
    boolean mExternalStorageWriteable = false;

    String state = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED.equals(state)) {  
        // We can read and write the media    
        mExternalStorageAvailable = mExternalStorageWriteable = true;
    } 
    else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
        // We can only read the media   
        mExternalStorageAvailable = true;    
        mExternalStorageWriteable = false;
    } else {   
        // Something else is wrong. It may be one of many other states, but all we need   
        //  to know is we can neither read nor write  
        mExternalStorageAvailable = mExternalStorageWriteable = false;
    }   

    if ( mExternalStorageAvailable == true && mExternalStorageAvailable == true){

        File mFile = new File(Environment.getExternalStorageDirectory(), "/DCIM/filename.txt");
        try {
            BufferedWriter buf = new BufferedWriter(new FileWriter(mFile, true)); 
            buf.write("test txt");
            buf.close();
            Toast.makeText(getBaseContext(), "path = "+mFile, Toast.LENGTH_LONG).show();


        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(getBaseContext(), "File not FOund", Toast.LENGTH_LONG).show();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(getBaseContext(), "IOException", Toast.LENGTH_LONG).show();
        }
    }