android之旅——开始

package com.helloword;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;


public class ReadFile {
	private String text = null;
	private StringBuffer strbuf=null;

	public void ReadFile(File file)  {
		// TODO Auto-generated constructor stub
		//获取文件输出流
		FileInputStream fis;
		try {
			fis = new FileInputStream(file);
			//将字节流转换为字符流
			BufferedReader br = new BufferedReader(new InputStreamReader(fis));
			try {
				text = br.readLine();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
		strbuf.append(text);
		
		
		System.out.println(text);
	}

}

public class MainActivity extends Activity {
public Button bt =null;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bt = (Button) findViewById(R.id.btcon);
bt.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
File file = new File("data/data/com.helloword/file");
ReadFile readfile = new ReadFile();
}
});
}

2、SD卡文件的读写操作

　　（1）在manifest.xml中注册，获得SD卡的读写权限

 <!-- SDCard中创建与删除文件权限 --> 
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<!-- 向SDCard写入数据权限 -->  
 <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

　　（2） 接着在使用SDcard进行读写的时候 会用到Environment类下面的几个静态方法  ： 

   　　 1: getDataDirectory() 获取到Android中的data数据目录（sd卡中的data文件夹）
   　　 2:getDownloadCacheDirectory() 获取到下载的缓存目录（sd卡中的download文件夹）
    　　3:getExternalStorageDirectory() 获取到外部存储的目录 一般指SDcard（/storage/sdcard0）
   　　 4:getExternalStorageState() 获取外部设置的当前状态 一般指SDcard，比较常用的应该是 MEDIA_MOUNTED（SDcard存在并且可以进行读写）还有其他的一些状态，可以在文档中进行查找.

	/**
	 * 判断SDCard是否存在 [当没有外挂SD卡时，内置ROM也被识别为存在sd卡]
	 * 
	 * @return
	 */
	public static boolean isSdCardExist() {
		return Environment.getExternalStorageState().equals(
				Environment.MEDIA_MOUNTED);
	}

      * 使用api获得sd卡的真实路径，部分手机品牌会更改sd卡的路径

        Environment.getExternalStorageDirectory();

//读取SD卡内容
	//使用FileInputStream读取文件
	public String ReadFlieInputString(String FileName) throws IOException
	{
		String result = null;
		File file = new File(FileName);
		try {
			FileInputStream isfile = new FileInputStream(file);
			byte[] b = new byte[isfile.available()];
			isfile.read(b);
			result = new String(b);
			System.out.print("读取成功："+ result);
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		return result;
	}
	
	//使用BufferRead 读取文件
	public String FileBufferRead(String FileName) throws IOException {
		String result = null;
		try {
			BufferedReader bReader = new BufferedReader(new FileReader(FileName));
			String oneline = "";
			StringBuffer sb = new  StringBuffer();
			while ((oneline = bReader.readLine()) != null) {
				sb.append(oneline);
			}
			result = sb.toString();
			bReader.close();
			System.out.println("读取成功");
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return result;
		
	}

//写入SD卡
	//使用FileOutputStream写入文件
	public Boolean writeSDFile(String FileName, String content){
		boolean result = false;
		try {
			File file = new File(Environment.getExternalStorageDirectory(), FileName);
			//获得输出流
	        FileOutputStream fos = new FileOutputStream(file);
            fos.write(content.getBytes());
            fos.close();
			System.out.println("写入成功：");
			result = true;
		} catch (Exception e) {
			e.printStackTrace();
		}
		return result;
	}
	
	//使用buffread写入SD卡
	public Boolean BufferWriteFile(String FileName, String content){
		boolean result = false;
		try {
			File file = new File(Environment.getExternalStorageDirectory(),
					FileName);
			//第二个参数意义是说是否以append方式添加内容
			BufferedWriter bw = new BufferedWriter(new FileWriter(file, true));
			bw.write(content);
			bw.flush();
			System.out.println("写入成功");
                        result = true;
		} catch (Exception e) {
			e.printStackTrace();
		}
		return result;
	}