Android往SD卡上存储文件

 public class DataActivity extends Activity {
    private EditText filenameText;
    private EditText contentText;
    private TextView resultView;
    private static final String TAG = "DataActivity";
    /** Called when the activity is first created. */
    @Override
        public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        filenameText = (EditText) this.findViewById(R.id.filename);
        contentText = (EditText) this.findViewById(R.id.content);
        resultView = (TextView) this.findViewById(R.id.result);
        String filename = filenameText.getText().toString();
        Button button = (Button) this.findViewById(R.id.button);
        Button showButton = (Button) this.findViewById(R.id.showButton);
        button.setOnClickListener(listener);
        showButton.setOnClickListener(listener);
    }  

    private View.OnClickListener listener = new View.OnClickListener() {
        @Override
            public void onClick(View v) {
            Button button = (Button) v;
            String filename = filenameText.getText().toString();
            switch(button.getId()){
            case R.id.button://如果是保存按钮
                int resId = R.string.success;  

                String content = contentText.getText().toString();
                File file = new File(Environment.getExternalStorageDirectory(),filename);
                if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                    try {
                        //OutputStream outStream = DataActivity.this.openFileOutput(filename, Context.MODE_WORLD_WRITEABLE+Context.MODE_WORLD_READABLE);
                        //四中操作模式
                        //Context.MODE_PRIVATE=0 覆盖、私有
                        //Context.MODE_APPEND=32768追加、私有
                        //Context.MODE_WORLD_READABLE=1其他的程序可以访问
                        //Context.MODE_WORLD_WRITEABLE=2
                        //Environment.getExternalStorageDirectory()==new file("/sdcard")  

                        FileOutputStream outStream = new FileOutputStream(file);
                        try {
                            FileService.save(outStream, content);
                        } catch (Exception e) {
                            Log.e(TAG, e.toString());
                            resId = R.string.error;
                        }
                    } catch (FileNotFoundException e) {
                        Log.e(TAG, e.toString());
                        resId = R.string.error;
                    }
                    Toast.makeText(DataActivity.this, resId, Toast.LENGTH_LONG).show();
                }
                else{
                    Toast.makeText(DataActivity.this,"SD卡不存在或者写保护", Toast.LENGTH_LONG).show();
                }
                break;
            case R.id.showButton://如果是显示按钮
                try {
                    InputStream inStream = DataActivity.this.openFileInput(filename);
                    String text = FileService.read(inStream);
                    resultView.setText(text);
                } catch (Exception e) {
                    Log.e(TAG, e.toString());
                    resId = R.string.error;
                    Toast.makeText(DataActivity.this, "读取失败", Toast.LENGTH_LONG).show();
                }  

                break;
            }
        }
    };  

}