文件操作工具类和字符串判断是否为空

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.media.MediaScannerConnection;
import android.os.Environment;
import android.support.annotation.Nullable;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.FileChannel;

/**
* Created by yanchengmeng on 16/12/9.
*/
public class FileUtil {

/**
* 保存图片到本地
*
* @param bitmap
* @param path
* @param fileName
* @return 保存的路径，如果为null表示保存失败
*/
public static String saveBitMap(Bitmap bitmap, String path, String fileName) {

if (bitmap == null || path == null || fileName == null) {
return null;
}

File storePath = new File(path);

String result = saveBitMap(bitmap, storePath, fileName);

return result;
}

/**
* 保存图片到本地
*
* @param bitmap
* @param path
* @param fileName
* @return
*/
public static String saveBitMap(Bitmap bitmap, File path, String fileName) {

if (bitmap == null || path == null || fileName == null) {
return null;
}

if (!path.exists()) {
if (!path.mkdirs()) {
return null;
}
}

File destFile = new File(path, fileName);
String result = destFile.getAbsolutePath();
OutputStream os = null;
try {
os = new FileOutputStream(destFile);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, os);
os.flush();
os.close();
} catch (IOException e) {
result = null;
} finally {
if (os != null) {
try {
os.close();
} catch (IOException e) {
}
}
}
return result;
}

/**
* 刷新图片到相册中
*
* @param context
* @param path
*/
public static void mediaRefresh(Activity context, File path) {
MediaScannerConnection.scanFile(context, new String[]{path.getAbsolutePath()}, null, null);
}

/**
* 刷新图片到相册中
*
* @param context
* @param path
*/
public static void mediaRefresh(Activity context, String path) {
MediaScannerConnection.scanFile(context, new String[]{path}, null, null);
}

/**
* 从指定文件中读取String
*
* @param fileName
* @return
*/
public static String readFromFile(File fileName) {

StringBuilder sb = new StringBuilder();
BufferedReader reader = null;

try {
reader = new BufferedReader(new FileReader(fileName));

String tempString;

while ((tempString = reader.readLine()) != null) {
sb.append(tempString);
}
} catch (IOException e) {
} finally {
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
}
}

return sb.toString();
}

/**
* 把String写入指定文件
*
* @param fileName
* @param text
*/
public static void writeToFile(File fileName, String text) {

BufferedWriter writer = null;

try {
writer = new BufferedWriter(new FileWriter(fileName));

writer.write(text);
writer.flush();

} catch (IOException e) {
} finally {
try {
if (writer != null) {
writer.close();
}
} catch (IOException e) {
}
}

}

/**
* 复制单个文件
*
* @param oldPath String 原文件路径 如：c:/fqf.txt
* @param newPath String 复制后路径 如：f:/fqf.txt
* @return boolean
*/
public static void copyFile(String oldPath, String newPath) {
try {
int bytesum = 0;
int byteread = 0;
File oldfile = new File(oldPath);
if (oldfile.exists()) { //文件存在时
InputStream inStream = new FileInputStream(oldPath); //读入原文件
FileOutputStream fs = new FileOutputStream(newPath);
byte[] buffer = new byte[1444];
int length;
while ((byteread = inStream.read(buffer)) != -1) {
bytesum += byteread; //字节数 文件大小
System.out.println(bytesum);
fs.write(buffer, 0, byteread);
}
inStream.close();
}
} catch (Exception e) {
System.out.println("复制单个文件操作出错");
e.printStackTrace();
}
}

/**
* 使用文件通道的方式复制文件
*
* @param s 源文件
* @param t 复制到的新文件
*/

public static void copyFile(File s, File t) {

FileInputStream fi = null;

FileOutputStream fo = null;

FileChannel in = null;

FileChannel out = null;

try {

fi = new FileInputStream(s);

fo = new FileOutputStream(t);

in = fi.getChannel();//得到对应的文件通道

out = fo.getChannel();//得到对应的文件通道

in.transferTo(0, in.size(), out);//连接两个通道，并且从in通道读取，然后写入out通道

} catch (IOException e) {

e.printStackTrace();

} finally {

try {
fi.close();

in.close();

fo.close();

out.close();

} catch (IOException e) {
e.printStackTrace();
}
}
}

public static String getCacheDir(Context context) {
String cacheDir = null;
try {
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
|| !Environment.isExternalStorageRemovable()) {
cacheDir = context.getExternalCacheDir().getPath();
if (StringUtil.isEmpty(cacheDir)) {
cacheDir = context.getCacheDir().getPath();
}
} else {
cacheDir = context.getCacheDir().getPath();
}
} catch (Exception e) {

}
if (StringUtil.isEmpty(cacheDir)){
return context.getCacheDir().getPath();
}
return cacheDir;
}

@Nullable
public static File getExternalCacheDir(Context context) {
try {
return context.getExternalFilesDir(null);
} catch (Exception e){
return null;
}
}

public static boolean saveBitmap(Bitmap bm, String picName) {
try {
File f = new File(picName);
if (f.exists()) {
f.delete();
}
FileOutputStream out = new FileOutputStream(f);
bm.compress(Bitmap.CompressFormat.JPEG, 100, out);
out.flush();
out.close();
return true;
} catch (FileNotFoundException e) {
return false;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}

public static boolean fileExist(String path, String fileName) {
File file = new File(path);
if (!file.exists()) {
return false;
}
if (!file.isDirectory()) {
return false;
}

String[] tempList = file.list();
for (int i = 0; i < tempList.length; i++) {
if (fileName.equals(tempList[i])) {
return true;
}
}
return false;

}

public static void delAllFile(String path) {
File file = new File(path);
if (!file.exists()) {
return;
}
if (!file.isDirectory()) {
return;
}
String[] tempList = file.list();
File temp = null;
for (int i = 0; i < tempList.length; i++) {
if (path.endsWith(File.separator)) {
temp = new File(path + tempList[i]);
} else {
temp = new File(path + File.separator + tempList[i]);
}
if (temp.isFile()) {
temp.delete();
}
if (temp.isDirectory()) {
delAllFile(path + "/" + tempList[i]);//先删除文件夹里面的文件
delFolder(path + "/" + tempList[i]);//再删除空文件夹
}
}
}

//删除文件夹
public static void delFolder(String folderPath) {
try {
delAllFile(folderPath); //删除完里面所有内容
String filePath = folderPath;
filePath = filePath.toString();
File myFilePath = new File(filePath);
myFilePath.delete(); //删除空文件夹
} catch (Exception e) {
e.printStackTrace();
}
}

public static boolean isEmpty(String str) {
if (null == str || str.trim().equals("") || str.trim().equalsIgnoreCase("null")) {
return true;
}
return false;
}

}