java - 无法打开文件“/mnt/sdcard/test.txt”

Question

由于无法找到文件，我不断收到错误消息。我用android模拟器模拟代码

java.io.FileNotFoundException：/mnt/sdcard/test.txt：打开失败：EACCES（权限被拒绝）打开失败

请帮忙..谢谢

public class TestUpload extends Activity { 

  /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_test_upload); 

        final TextView tmp = (TextView) findViewById(R.id.textView1); 
        tmp.setText("Hi! Click the button!"); 

        Button b = (Button) findViewById(R.id.button1); 
        b.setOnClickListener(new OnClickListener() { 
                public void onClick(View v) { 
                        File f = new File("/mnt/sdcard/test.txt"); 
                        try { 
                                        f.createNewFile(); 
                                        Date d = new Date(); 
                                        PrintWriter writer = new PrintWriter(f);
                                        writer.println(d.toString()); 
                                        writer.close(); 

                                        HttpClient client = new DefaultHttpClient();
                                         httpPostFileUpload(client, "/mnt/sdcard/test.txt", "http://localhost/upload.php", "uploadedfile"); 
                        } catch (Exception e) { 
                                        // TODO Auto-generated catch block 
                                        e.printStackTrace(); 
                                } 
                } 
        }); 
    } 

    public void httpPostFileUpload(HttpClient client,String filePath,String uploadUri,String inputNameAttr) throws ClientProtocolException,IOException { 

            HttpUriRequest         request         = new HttpPost(uploadUri); 
            MultipartEntity        form                = new MultipartEntity(); 
            client.getParams().setBooleanParameter("http.protocol.expect-continue", false); 
            form.addPart(inputNameAttr, new FileBody(new File(filePath))); 

                ((HttpEntityEnclosingRequestBase) request).setEntity(form); 

                try { 
                        client.execute(request); 
                } catch (ClientProtocolException e) { 
                        throw e; 
                } catch (IOException ee) { 
                        throw ee; 
                } 
    } 
} 

Answer 1

使用这种方式：

String file = Environment.getExternalStorageDirectory()+"/test.txt";

File f = new File(file);
if(f.exists()){
   f.createNewFile(); 
}
// your code...

还在android清单文件中添加以下权限

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

Answer 2

在你的 manifest.xml 中添加这一行：

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

然后您将能够在外部存储中写入。