文件读取和写入：打开本地管理器选择txt
拓展：文件管理工具类—FileUtil 实现的功能：获得外部存储绝对路径、创建文件夹、创建文件、遍历文件夹下的所有文件、获得指定文件、删除文件夹里的所有文件、删除文件、向文件中的指定位置添加String内容、修改文件内容（覆盖或者添加String）、读取文件内容String、重命名文件、复制文件夹、复制文件、拷贝图片文件、修改文件内容String（相对路径）。。。
一、功能描述
打开文件管理器，选择本地txt，按行读取内容，按一定格式整理每行内容，显示在界面上，并保存副本txt在同一个文件夹里。
注意：
1.请把txt保存格式修改为utf-8，否则文本会乱码（打开文件，另存为，修改保存格式）
2.动态申请写入权限！！！
二、运行效果
三、技术点讲解
1、声明内存读取权限
2、动态请求内存读取权限
private String[] permissions = {Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE};
/**
* 开始提交请求权限
*/
private void startRequestPermission() {
ActivityCompat.requestPermissions(MainActivity.this, permissions, RESULT_SUCCESS);
}
/**
* 用户权限 申请 的回调方法
*
* @param requestCode
* @param permissions
* @param grantResults
*/
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == RESULT_SUCCESS) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
isGetPermission = true;
}
} else {
isGetPermission = true;
}
}
if (!isGetPermission) {
llMain.setVisibility(View.GONE);
} else {
llMain.setVisibility(View.VISIBLE);
}
}
3、读取txt文本
try {
//1.从assets文件夹里，读取txt
// AssetManager am = getAssets();
// InputStream is = am.open("bbb.txt");
// InputStreamReader reader = new InputStreamReader(is, "UTF-8");
// BufferedReader bufferedReader = new BufferedReader(reader);
//2.打开文件管理区，读取选择的txt文件
BufferedReader bufferedReader = new BufferedReader(new FileReader(readFilePath));
contentStrBuf = new StringBuffer("");
String str;
//按行读取txt
while ((str = bufferedReader.readLine()) != null) {
lineCount++;
contentStrBuf.append(lineCount+"、");
contentStrBuf.append(str);
contentStrBuf.append("\r\n");//追加换行符
}
tvSaveInfo.setText("行数：" + lineCount + "；\n保存路径：" + saveHolderPath + "/" + saveFileName);
tvContent.setText(contentStrBuf.toString());
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
4、写入文本并保存新txt文件
try {
//创建一个带缓冲区的输出流
String state = Environment.getExternalStorageState();
if (state.equals(Environment.MEDIA_MOUNTED)) {
//1.指定存储地址与文件名
// File sdDir = Environment.getExternalStorageDirectory();//外部存储绝对路径
// String fileHoldName = "文件夹";
// File fileDir = new File(savePath + "/" + fileHoldName);
// if (!fileDir.exists()) {
// fileDir.mkdir();
// }
// File file = new File(fileDir.getAbsolutePath(), "data.txt");
//2.自动保存在读取的txt文件夹里
File file = new File(saveHolderPath + "/" + saveFileName);
FileOutputStream fos = new FileOutputStream(file);
OutputStreamWriter writer = new OutputStreamWriter(fos, "utf-8");
writer.write(content);
writer.close();
fos.close();
Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(this, "保存失败,SD卡不可用！", Toast.LENGTH_SHORT).show();
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
5、打开文件管理器
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
//intent.setType(“image/*”);//选择图片
//intent.setType(“audio/*”); //选择音频
//intent.setType(“video/*”); //选择视频 （mp4 3gp 是android支持的视频格式）
//intent.setType(“video/*;image/*”);//同时选择视频和图片
intent.setType("*/*");//无类型限制
intent.addCategory(Intent.CATEGORY_OPENABLE);
startActivityForResult(intent, 1);
url解析
public String getRealPathFromURI(Uri contentUri) {
String res = null;
String[] proj = {MediaStore.Images.Media.DATA};
Cursor cursor = getContentResolver().query(contentUri, proj, null, null, null);
if (null != cursor && cursor.moveToFirst()) {
;
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
res = cursor.getString(column_index);
cursor.close();
}
return res;
}
/**
* 专为Android4.4设计的从Uri获取文件绝对路径，以前的方法已不好使
*/
@SuppressLint("NewApi")
public String getPath(final Context context, final Uri uri) {
final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
// DocumentProvider
if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
// ExternalStorageProvider
if (isExternalStorageDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
if ("primary".equalsIgnoreCase(type)) {
return Environment.getExternalStorageDirectory() + "/" + split[1];
}
}
// DownloadsProvider
else if (isDownloadsDocument(uri)) {
final String id = DocumentsContract.getDocumentId(uri);
final Uri contentUri = ContentUris.withAppendedId(
Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));
return getDataColumn(context, contentUri, null, null);
}
// MediaProvider
else if (isMediaDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
Uri contentUri = null;
if ("image".equals(type)) {
contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
} else if ("video".equals(type)) {
contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
} else if ("audio".equals(type)) {
contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
}
final String selection = "_id=?";
final String[] selectionArgs = new String[]{split[1]};
return getDataColumn(context, contentUri, selection, selectionArgs);
}
}
// MediaStore (and general)
else if ("content".equalsIgnoreCase(uri.getScheme())) {
return getDataColumn(context, uri, null, null);
}
// File
else if ("file".equalsIgnoreCase(uri.getScheme())) {
return uri.getPath();
}
return null;
}
/**
* Get the value of the data column for this Uri. This is useful for
* MediaStore Uris, and other file-based ContentProviders.
*
* @param context The context.
* @param uri The Uri to query.
* @param selection (Optional) Filter used in the query.
* @param selectionArgs (Optional) Selection arguments used in the query.
* @return The value of the _data column, which is typically a file path.
*/
public String getDataColumn(Context context, Uri uri, String selection,
String[] selectionArgs) {
Cursor cursor = null;
final String column = "_data";
final String[] projection = {column};
try {
cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs,
null);
if (cursor != null && cursor.moveToFirst()) {
final int column_index = cursor.getColumnIndexOrThrow(column);
return cursor.getString(column_index);
}
} finally {
if (cursor != null)
cursor.close();
}
return null;
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is ExternalStorageProvider.
*/
public boolean isExternalStorageDocument(Uri uri) {
return "com.android.externalstorage.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is DownloadsProvider.
*/
public boolean isDownloadsDocument(Uri uri) {
return "com.android.providers.downloads.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is MediaProvider.
*/
public boolean isMediaDocument(Uri uri) {
return "com.android.providers.media.documents".equals(uri.getAuthority());
}
6、获取到选择的txt
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK) {
Uri uri = data.getData();
if ("file".equalsIgnoreCase(uri.getScheme())) {//使用第三方应用打开
readFilePath = uri.getPath();
setData();
return;
}
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT) {//4.4以后
readFilePath = getPath(this, uri);
} else {//4.4以下下系统调用方法
readFilePath = getRealPathFromURI(uri);
}
setData();
}
}