Android的 - 如何從一個parcticular站點下載xls文件

Question

在我的應用程序中，我試圖從一個站點下載xls文件，但我有一個錯誤，如不幸的是，MyApp已停止，當我點擊一個下載按鈕。我不知道爲什麼我有這個問題。

MyActivity.java

 package com.example.mine.myapp; 

    import android.support.v7.app.ActionBarActivity; 
    import android.os.Bundle; 
    import android.view.Menu; 
    import android.view.MenuItem; 
    import android.view.View; 

    import java.io.File; 
    import java.io.FileOutputStream; 
    import java.io.IOException; 
    import java.io.InputStream; 
    import java.net.HttpURLConnection; 
    import java.net.MalformedURLException; 
    import java.net.URL; 

public class MyActivity extends ActionBarActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_my); 
    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.my, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 
     if (id == R.id.action_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    public void button1_Click(View view) throws IOException { 
     downloadFile(); 

    } 

    public void downloadFile() throws IOException { 
     URL url = new URL("https://www.myste.com/myxlsfile.xls"); 

//create the new connection 

     HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 

//set up some things on the connection 

     urlConnection.setRequestMethod("GET"); 

     urlConnection.setDoOutput(true); 

//and connect! 

     urlConnection.connect(); 

//set the path where we want to save the file 

//in this case, going to save it on the root directory of the 

//sd card. 

     File SDCardRoot = new File("/storage/"+"sdcard1/"); 

//create a new file, specifying the path, and the filename 

//which we want to save the file as. 

     File file = new File(SDCardRoot,"name.xls"); 

//this will be used to write the downloaded data into the file we created 

     FileOutputStream fileOutput = new FileOutputStream(file); 

//this will be used in reading the data from the internet 

     InputStream inputStream = urlConnection.getInputStream(); 

//this is the total size of the file 

     int totalSize = urlConnection.getContentLength(); 

//variable to store total downloaded bytes 

     int downloadedSize = 0; 

//create a buffer... 

     byte[] buffer = new byte[1024]; 

     int bufferLength = 0; //used to store a temporary size of the buffer 

//now, read through the input buffer and write the contents to the file 

     while ((bufferLength = inputStream.read(buffer)) > 0) 

     { 

//add the data in the buffer to the file in the file output stream (the file on the sd card 

      fileOutput.write(buffer, 0, bufferLength); 

//add up the size so we know how much is downloaded 

      downloadedSize += bufferLength; 

      int progress=(int)(downloadedSize*100/totalSize); 

//this is where you would do something to report the prgress, like this maybe 

//updateProgress(downloadedSize, totalSize); 

     } 

//close the output stream when done 

     fileOutput.close(); 
    } 
} 

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> 

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

<application 
    android:allowBackup="true" 
    android:icon="@drawable/ic_launcher" 
    android:label="@string/app_name" 
    android:theme="@style/AppTheme" > 
    <activity 
     android:name=".MyActivity" 
     android:label="@string/app_name" > 
     <intent-filter> 
      <action android:name="android.intent.action.MAIN" /> 

      <category android:name="android.intent.category.LAUNCHER" /> 
     </intent-filter> 
    </activity> 
</application> 

Activity_my.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
android:paddingBottom="@dimen/activity_vertical_margin" 
tools:context=".MyActivity"> 


<Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Download" 
    android:id="@+id/button1" 
    android:layout_centerVertical="true" 
    android:layout_centerHorizontal="true" 
    android:onClick="button1_Click"/> 

Answer 1

我認爲你需要開一個線程或異步任務從服務器下載文件。 並在此線程中，使用android.os.Handler將任何進度/結果通知給主UI線程。