Android知识点总结－－（三）－－文件读写工具类
1. 创建文件：
/**
* 创建一个文件
* @param FileName 文件名
* @return
*/
public static File createFile(String FileName) {
String path = Environment.getExternalStorageDirectory().toString() + "/1nmpaapp";
File file = new File(path);
/**
*如果文件夹不存在就创建
*/
if (!file.exists()) {
file.mkdirs();
}
return new File(path, FileName);
}2. 写入数据：（FileOutputStream，BufferedOutputStream）
public static void getFile(byte[] bfile, String fileName) {
BufferedOutputStream bos = null;
FileOutputStream fos = null;
File file = null;
try {
file = createFileEm("3",fileName,"");
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos);
bos.write(bfile);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (bos != null) {
try {
bos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
if (fos != null) {
try {
fos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}3. 删除手机中的图片：
public static void deleteFile(Context mContext,String path) {
Log.e(TAG,"deleteFile path="+path);
File file = new File(path);
//删除系统缩略图
mContext.getContentResolver().delete(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, MediaStore.Images.Media.DATA + "=?", new String[]{path});
//删除手机中图片
file.delete();
}有的机型，这样删除后会有残留，需要更新媒体库：
public static void updateMediaStore(final Context context, final String path) {
//版本号的判断 4.4为分水岭，发送广播更新媒体库
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
MediaScannerConnection.scanFile(context, new String[]{path}, null, new MediaScannerConnection.OnScanCompletedListener() {
public void onScanCompleted(String path, Uri uri) {
Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
mediaScanIntent.setData(uri);
context.sendBroadcast(mediaScanIntent);
}
});
} else {
File file = new File(path);
String relationDir = file.getParent();
File file1 = new File(relationDir);
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.fromFile(file1.getAbsoluteFile())));
}
}有的地方更新媒体库时，只有：
Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
intent.setData(Uri.fromFile(new File(imgPath)));
sendBroadcast(intent);4. 在apk中打开某个word文件：
实际应用：从app中下载word文档后自动打开查看文档内容：
public static void openDoc(Context mContext,File file) {
Intent intent = new Intent("android.intent.action.VIEW");
intent.addCategory("android.intent.category.DEFAULT");
Uri data;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
// "net.csdn.blog.ruancoder.fileprovider"即是在清单文件中配置的authorities
data = FileProvider.getUriForFile(mContext, "com.nmpa.nmpaapp.file.provider", file);
// 给目标应用一个临时授权
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
} else {
data = Uri.fromFile(file);
}
intent.addFlags (Intent.FLAG_ACTIVITY_NEW_TASK);
//如果不加判断，直接用Uri.fromFile的形式传参，会报错
intent.setDataAndType(data, "application/msword");
mContext.startActivity(intent);
}5. 获取拍照相片存储文件
/**
* 获取拍照相片存储文件
* @param context
* @return
*/
public static File createFile(Context context){
File file;
String savePath = Environment.getExternalStorageDirectory().toString() + "/photo/";
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
String timeStamp = String.valueOf(new Date().getTime());
file = new File(savePath + timeStamp+".jpg");
}else{
File cacheDir = context.getCacheDir();
String timeStamp = String.valueOf(new Date().getTime());
file = new File(cacheDir, timeStamp+".jpg");
}
return file;
}6. 获取本地图片的路径：
实际应用：从系统文件中选择一个文件，并获取这个文件的实际路径：
public static String handleImageOnKitKat(Context context, Intent data) {
Uri uri = data.getData();
if (DocumentsContract.isDocumentUri(context, uri)) {
String docId = DocumentsContract.getDocumentId(uri);
if ("com.android.providers.media.documents".equals(uri.getAuthority())) {
String id = docId.split(":")[1];
String selection = MediaStore.Images.Media._ID + "=" + id;
String type = docId.split(":")[0];
Uri contentUri = null;
if (type.equalsIgnoreCase("image")) {
contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
} else if (type.equalsIgnoreCase("audio")) {
contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
} else if (type.equalsIgnoreCase("video")) {
contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
}
return getImagePath(context, contentUri, selection);
} else if ("com.android.providers.media.downloads.documents".equals(uri.getAuthority())) {
Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),
Long.valueOf(docId));
return getImagePath(context, contentUri, null);
} else if ("content".equals(uri.getAuthority())) {
return getImagePath(context, uri, null);
} else if ("file".equals(uri.getAuthority())) {
return uri.getPath();
}
}
return "";
}
private static String getImagePath(Context context, Uri uri, String selection) {
String path = null;
Cursor cursor = context.getContentResolver().query(uri, null, selection, null, null);
if (cursor != null) {
if (cursor.moveToFirst()) {
path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
}
cursor.close();
}
return path;
}7. 保存bitmap到本地（FileOutputStream）
public static String saveBitmap(Context context, Bitmap mBitmap) {
String savePath = Environment.getExternalStorageDirectory().toString() + "/1nmpaapp/";
File filePic;
try {
filePic = new File(savePath + System.currentTimeMillis() + ".jpg");
Log.d("LUO", "图片地址====" + filePic);
if (!filePic.exists()) {
filePic.getParentFile().mkdirs();
filePic.createNewFile();
}
FileOutputStream fos = new FileOutputStream(filePic);
//不压缩，保存本地
mBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
fos.flush();
fos.close();
} catch (IOException e) {
e.printStackTrace();
return null;
}
return filePic.getAbsolutePath();
}8. 启动相机程序
public static void takePhoto(Activity mContext, int requestCode) {
// 启动相机程序
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
mContext.startActivityForResult(intent, requestCode);
}9. 从拍照返回的数据中保存图片并返回图片路径（FileOutputStream）
public static String getCameraData(Intent data) {
String path = null;
Bitmap photo = null;
if (data.getData() != null || data.getExtras() != null) { // 防止没有返回结果
Uri uri = data.getData();
if (uri != null) {
photo = BitmapFactory.decodeFile(uri.getPath()); // 拿到图片
}
if (photo == null) {
Bundle bundle = data.getExtras();
if (bundle != null) {
photo = (Bitmap) bundle.get("data");
String saveDir = Environment.getExternalStorageDirectory().toString() + "/nmpaapp/";
String filename = System.currentTimeMillis() + ".jpg";
File file = new File(saveDir, filename);
FileOutputStream fileOutputStream = null;
// 打开文件输出流
try {
fileOutputStream = new FileOutputStream(file);
// 生成图片文件
photo.compress(Bitmap.CompressFormat.JPEG,
100, fileOutputStream);
path = file.getPath();
Log.e("FileLoadUtils", "str=" + path);
} catch (FileNotFoundException e) {
e.printStackTrace();
} finally {
if (fileOutputStream != null) {
try {
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
}
return path;
}10. 获取视频文件的缩略图
public static String getThumnailPath(String fromUser,String videoPath) {
String fileName = "thvideo" + System.currentTimeMillis();
File file = createFileEm("5",fileName,fromUser);
try {
FileOutputStream fos = new FileOutputStream(file);
Bitmap ThumbBitmap = ThumbnailUtils.createVideoThumbnail(videoPath, 3);
ThumbBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
fos.close();
} catch (Exception e) {
e.printStackTrace();
}
return file.getAbsolutePath();
}11. 压缩图片（ByteArrayOutputStream，ByteArrayInputStream）
public static Bitmap compressImage(Bitmap image) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.JPEG, 100, baos);
int options = 90;
int length = baos.toByteArray().length / 1024;
Log.e(TAG,"length="+length);
//循环判断如果压缩后图片是否大于1M,大于继续压缩
while (baos.toByteArray().length / 1024>1024) {
//重置baos即清空baos
baos.reset();
//这里压缩options%，把压缩后的数据存放到baos中
image.compress(Bitmap.CompressFormat.JPEG, options, baos);
//每次都减少10
options -= 10;
}
//把压缩后的数据baos存放到ByteArrayInputStream中
ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());
//把ByteArrayInputStream数据生成图片
Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);
return bitmap;
}12，获取指定文件大小
public static long getFileSize(File file) throws Exception {
long size = 0;
if (file.exists()) {
FileInputStream fis = null;
fis = new FileInputStream(file);
size = fis.available();
} else {
file.createNewFile();
Log.e("获取文件大小", "文件不存在!");
}
return size;
}13. 获取指定文件夹的大小
private static long getFileSizes(File f) throws Exception
{
long size = 0;
File flist[] = f.listFiles();
for (int i = 0; i < flist.length; i++){
if (flist[i].isDirectory()){
size = size + getFileSizes(flist[i]);
}
else{
size =size + getFileSize(flist[i]);
}
}
return size;
}
14. 转换文件大小
private static String FormetFileSize(long fileS)
{
DecimalFormat df = new DecimalFormat("#.00");
String fileSizeString = "";
String wrongSize="0B";
if(fileS==0){
return wrongSize;
}
if (fileS < 1024){
fileSizeString = df.format((double) fileS) + "B";
} else if (fileS < 1048576){
fileSizeString = df.format((double) fileS / 1024) + "KB";
} else if (fileS < 1073741824){
fileSizeString = df.format((double) fileS / 1048576) + "MB";
} else {
fileSizeString = df.format((double) fileS / 1073741824) + "GB";
}
return fileSizeString;
}
15. 转换文件大小,指定转换的类型
private static double FormetFileSize(long fileS,int sizeType)
{
DecimalFormat df = new DecimalFormat("#.00");
double fileSizeLong = 0;
switch (sizeType) {
case SIZETYPE_B:
fileSizeLong=Double.valueOf(df.format((double) fileS));
break;
case SIZETYPE_KB:
fileSizeLong=Double.valueOf(df.format((double) fileS / 1024));
break;
case SIZETYPE_MB:
fileSizeLong=Double.valueOf(df.format((double) fileS / 1048576));
break;
case SIZETYPE_GB:
fileSizeLong=Double.valueOf(df.format((double) fileS / 1073741824));
break;
default:
break;
}
return fileSizeLong;
}
16. 自动计算指定文件或指定文件夹的大小
public static String getAutoFileOrFilesSize(String filePath) {
File file = new File(filePath);
long blockSize = 0;
try {
if (file.isDirectory()) {
blockSize = getFileSizes(file);
} else {
blockSize = getFileSize(file);
}
} catch (Exception e) {
e.printStackTrace();
Log.e("获取文件大小","获取失败!");
}
return FormetFileSize(blockSize);
}
17. 复制单个文件
public static boolean 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];
while ((byteread = inStream.read(buffer)) != -1) {
bytesum += byteread; // 字节数 文件大小
System.out.println(bytesum);
fs.write(buffer, 0, byteread);
}
fs.close();
inStream.close();
}
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
}
}18. 从文件读取数据（FileReader，BufferedReader）
public static String readFromFile(String path) {
try {
File file = new File(path);
if ( !file.exists() ) {
return null;
}
FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
String buffer = "";
String line = null;
while ((line = br.readLine()) != null) {
buffer += line + "\n";
}
br.close();
fr.close();
return buffer;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}19. 写入数据；（FileWriter）
public static void saveToFile(String path, String text) {
try {
File file = new File(path);
if ( !file.exists() ) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file);
fw.write(text);
fw.flush();
fw.close();
} catch (Exception e) {
e.printStackTrace();
}
}