上一节介绍了如何把文件存储到内部设备。有的时候，需要把文件存储到外部存储设备，比如SD卡。因为SD卡具有更大的存储空间，同时也可以很容易的和其他用户分享这些文件。
使用上一节的例子，把用户输入的文字保存在SD卡，修改onClick()事件。如下：
public class FilesActivity extends Activity { EditText textBox; static final int READ_BLOCK_SIZE = 100; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); textBox = (EditText) findViewById(R.id.txtText1); InputStream is = this.getResources().openRawResource(R.raw.textfile); BufferedReader br = new BufferedReader(new InputStreamReader(is)); String str = null; try { while ((str = br.readLine()) != null) { Toast.makeText(getBaseContext(), str, Toast.LENGTH_SHORT).show(); } is.close(); br.close(); } catch (IOException e) { e.printStackTrace(); } } public void onClickSave(View view) { String str = textBox.getText().toString(); try { //---SD Card Storage--- File sdCard = Environment.getExternalStorageDirectory(); File directory = new File (sdCard.getAbsolutePath() + "/MyFiles"); directory.mkdirs(); File file = new File(directory, "textfile.txt"); FileOutputStream fOut = new FileOutputStream(file); /* FileOutputStream fOut = openFileOutput("textfile.txt", MODE_WORLD_READABLE); */ OutputStreamWriter osw = new OutputStreamWriter(fOut); //---write the string to the file--- osw.write(str); osw.flush(); osw.close(); //---display file saved message--- Toast.makeText(getBaseContext(), "File saved successfully!", Toast.LENGTH_SHORT).show(); //---clears the EditText--- textBox.setText(""); } catch (IOException ioe) { ioe.printStackTrace(); } }}上面的代码中，使用getExternalStorageDirectory()方法去获取SD卡的路径。通常，在真机上面返回“/sdcard”，在模拟器上面返回"/mnt/sdcard"。但是，不要尝试去写死SD卡的路径，因为手机厂商有可能去给SD卡指定一个路径。因此，确保使用getExternalStorageDirectory()方法去获取SD卡的路径。然后，创建一个MyFiles的文件夹。最终，把文件保存在这个文件夹中。
从外部设备中加载文件，修改onClickLoad()方法：
public void onClickLoad(View view) { try { //---SD Storage--- File sdCard = Environment.getExternalStorageDirectory(); File directory = new File (sdCard.getAbsolutePath() + "/MyFiles"); File file = new File(directory, "textfile.txt"); FileInputStream fIn = new FileInputStream(file); InputStreamReader isr = new InputStreamReader(fIn); /* FileInputStream fIn = openFileInput("textfile.txt"); InputStreamReader isr = new InputStreamReader(fIn); */ char[] inputBuffer = new char[READ_BLOCK_SIZE]; String s = ""; int charRead; while ((charRead = isr.read(inputBuffer))>0) { //---convert the chars to a String--- String readString = String.copyValueOf(inputBuffer, 0, charRead); s += readString; inputBuffer = new char[READ_BLOCK_SIZE]; } //---set the EditText to the text that has been // read--- textBox.setText(s); Toast.makeText(getBaseContext(), "File loaded successfully!", Toast.LENGTH_SHORT).show(); } catch (IOException ioe) { ioe.printStackTrace(); } }请注意，如果想要往SD卡中写入文件，需要在AndroidManifest.xml中加入相关的权限：
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="net.manoel.Files" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="10" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <activity android:label="@string/app_name" android:name=".FilesActivity" > <intent-filter > <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application></manifest>
执行上述代码，查看SD卡：
- 1楼u010239384昨天 13:58
- 支持楼主！
- Re: manoel昨天 16:50
- 回复u010239384n谢谢你。