Android之再談文件操作和SDcard讀寫

1>讀寫SDCard數據要權限如下。

<!-- 在SDCard中創建與刪除文件權限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!-- 往SDCard寫入數據權限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

2>讀寫service如下

public class FileService {
	private Context context;
	
	public FileService(Context context) {
		this.context = context;
	}
	/**
	 * 以私有文件保存內容
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void saveToSDCard(String filename, String content) throws Exception{
		File file = new File(Environment.getExternalStorageDirectory(), filename);
		FileOutputStream outStream = new FileOutputStream(file);
		outStream.write(content.getBytes());
		outStream.close();
	}
	
	/**
	 * 以私有文件保存內容
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void save(String filename, String content) throws Exception{
		FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_PRIVATE);
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 以追加方式保存內容
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void saveAppend(String filename, String content) throws Exception{// ctrl+shift+y / x
		FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_APPEND);
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 保存內容,注：允許其他應用從該文件中讀取內容
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void saveReadable(String filename, String content) throws Exception{
		FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_READABLE);
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 保存內容,注：允許其他應用往該文件寫入內容
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void saveWriteable(String filename, String content) throws Exception{
		FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_WRITEABLE);
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 保存內容,注：允許其他應用對該文件讀和寫
	 * @param filename 文件名稱
	 * @param content 文件內容
	 * @throws Exception
	 */
	public void saveRW(String filename, String content) throws Exception{
		FileOutputStream outStream = context.openFileOutput(filename, 
				Context.MODE_WORLD_READABLE+ Context.MODE_WORLD_WRITEABLE);
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 讀取文件內容
	 * @param filename 文件名稱
	 * @return
	 * @throws Exception
	 */
	public String readFile(String filename) throws Exception{
		FileInputStream inStream = context.openFileInput(filename);
		byte[] buffer = new byte[1024];
		int len = 0;
		ByteArrayOutputStream outStream = new ByteArrayOutputStream();
		while( (len = inStream.read(buffer))!= -1){
			outStream.write(buffer, 0, len);
		}
		byte[] data = outStream.toByteArray();//得到文件的二進制數據
		outStream.close();
		inStream.close();
		return new String(data);
	}
}

3>控制層如下。要判斷手機是否存在sd卡，並且是否寫保護。

public class MainActivity extends Activity {
	private static final String TAG = "MainActivity";
    private FileService fileService;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
     
        fileService = new FileService(this);
        
        Button button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				EditText filenameText = (EditText) findViewById(R.id.filename);
				EditText contentText = (EditText) findViewById(R.id.filecontent);
				String filename = filenameText.getText().toString();
				String content = contentText.getText().toString();
				try {
					//判斷sdcard是否存在於手機上，並且可以進行讀寫訪問
					if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
						fileService.saveToSDCard(filename, content);
						Toast.makeText(MainActivity.this, R.string.success, 1).show();
					}else{
						Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show();
					}
				} catch (Exception e) {
					Log.e(TAG, e.toString());
					Toast.makeText(MainActivity.this, R.string.error, 1).show();
				}
			}
		});
    }
}