android-向读写sdcard

最新推荐文章于 2019-01-08 19:34:37 发布

原创最新推荐文章于 2019-01-08 19:34:37 发布 · 510 阅读

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本文提供了三种不同的方法来实现从Android设备的SDCard中读取文本文件内容，并介绍了一种向SDCard写入内容的方法。文章详细展示了如何利用Java进行文件操作，包括使用FileInputStream与FileOutputStream进行读写，利用BufferedReader按行读取文件，以及直接通过FileInputStream读取全部内容。

写：

	/**
	 * 向sdcard写入内容
	 * @param fileName 文件的名称
	 * @param content 文件的内容
	 * @return
	 */
	public boolean saveContentToSdcard(String fileName,String content)
	{
		boolean flag = false;
		FileOutputStream fileOutputStream = null;
		//获取sdcard所在的路径
		File file = new File(Environment.getExternalStorageDirectory(),fileName);
		//判断sdcard卡是否可用
		if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()))
		{
			try {
				fileOutputStream = new FileOutputStream(file);
				fileOutputStream.write(content.getBytes());
				System.out.println("HERER");
				flag = true;
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally
			{
				if(fileOutputStream!=null)
					try {
						fileOutputStream.close();
					} catch (Exception e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
			}
		}else
		{
			System.out.println("CAN NOT WRITE");
		}
		return flag;
	}

读：

/**
	 * 从sdcard中读取txt文件内容
	 * @param fileName
	 * @return
	 */
	public String readContentFromSdcard(String fileName)
	{
		String content = "";
		FileInputStream fileInputStream = null;
		//缓存的流，和磁盘无关，不需要关闭
		ByteArrayOutputStream byteArrayOutputStream = new  ByteArrayOutputStream();
		try {
			File file = new File(Environment.getExternalStorageDirectory(),fileName);
			if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
				&&file.isFile()
				&&file.exists())
			{
				fileInputStream = new FileInputStream(file);
				int len = 0;
				byte[] data = new byte[1024];
				while((len = fileInputStream.read(data))!=-1)
				{
					byteArrayOutputStream.write(data,0,len);
				}
				content = new String(byteArrayOutputStream.toByteArray());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally
		{
			if(fileInputStream!=null)
				try {
					fileInputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
		}
		return content;
	}
	
	/**
	 * 从sdcard中读取txt文件内容
	 * @param fileName
	 * @return
	 */
	public String readContentFromSdcard2(String fileName)
	{
		String content = "";
		BufferedReader bufferedReader = null;
		try {
			File file = new File(Environment.getExternalStorageDirectory(),fileName);
			if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
				&&file.isFile()
				&&file.exists())
			{
				bufferedReader = new BufferedReader(new FileReader(file));
				try {
					String s = null;
					while((s = bufferedReader.readLine()) != null){//使用readLine方法，一次读一行
						content = content + "\n" +s;
			        }
					bufferedReader.close();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}finally
		{
			if(bufferedReader!=null)
				try {
					bufferedReader.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
		}
		return content;
	}
	
	/**
	 * 从sdcard中读取txt文件内容
	 * @param fileName
	 * @return
	 */
	public String readContentFromSdcard3(String fileName)
	{
		String content = "";
		FileInputStream fileInputStream = null;
		try {
			File file = new File(Environment.getExternalStorageDirectory(),fileName);
			if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
				&&file.isFile()
				&&file.exists())
			{
				fileInputStream = new FileInputStream(file);
				int len = fileInputStream.available();
				byte[] buffer = new byte[len];
				fileInputStream.read(buffer);
				content = new String(buffer);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally
		{
			if(fileInputStream!=null)
				try {
					fileInputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
		}
		return content;
	}