深海游弋的鱼 – 第 61 页 – 智障儿童欢乐多

使用AsyncTask防止Memory Leaks(内存泄漏)

1. 合理的使用context–比如我们常使用的Toast,Service,最好使用getApplicationContext(),因为这些在activity结束的时候可能仍在运行
下图展示了一些场景我们该用哪种context(图是盗的,附原文地址https://possiblemobile.com/2013/06/context/ 是国外的大牛写的关于context的使用)

继续阅读使用AsyncTask防止Memory Leaks(内存泄漏)

Android获取存储路径

Android Q(Android 10)之前，需要添加权限，如下：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

1 2	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Android Q(Android 10)开始在App专属目录下本App可以随意操作，无需申请权限，不过App专属目录会在App卸载时跟随删除。看下面几个目录（通过Application的context就可以访问）。

getFilesDir() ：/data/user/0/本应用包名/files

getCacheDir()：/data/user/0/本应用包名/cache

getExternalFilesDir(null)：/storage/emulated/0/Android/data/本应用包名/files

getExternalCacheDir()：/storage/emulated/0/Android/data/本应用包名/cache

getFilesDir和getCacheDir是在手机自带的一块存储区域(internal storage)，通常比较小，SD卡取出也不会影响到，App的sqlite数据库和SharedPreferences都存储在这里。所以这里应该存放特别私密重要的东西。

getExternalFilesDir和getExternalCacheDir是在SD卡下(external storage)，在sdcard/Android/data/包名/files和sdcard/Android/data/包名/cache下，会跟随App卸载被删除。

files和cache下的区别是，在手机设置-找到本应用-在存储中，点击清除缓存，cache下的文件会被删除，files下的文件不会。

谷歌推荐使用getExternalFilesDir。我们项目的下载是个本地功能，下载完成后是存本地数据库的，不是放网络上的，所以下载的音视频都放到了这下面，项目卸载时跟随App都删除了。getExternalFilesDir方法需要传入一个参数，传入null时得到就是sdcard/Android/data/包名/files，传入其他字符串比如"Picture"得到sdcard/Android/data/包名/files/Picture。

参考代码如下：

/**
 * 获取app缓存路径
 *
 * @param context Application Context
 * @return 缓存路径
 */
@NonNull
public static String getCacheDir(Context context) {
    String cacheDir;
    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
            || !Environment.isExternalStorageRemovable()) {
        //外部存储可用
        final File file = context.getExternalCacheDir();
        if (null == file) {
            cacheDir = context.getCacheDir().getPath();
        } else {
            cacheDir = file.getPath();
        }
    } else {
        //外部存储不可用
        cacheDir = context.getCacheDir().getPath();
    }
    return cacheDir;
}

/**
 * 获取app文件路径
 *
 * @param context Application Context
 * @return app文件路径
 */
@NonNull
public static String getFilesDir(Context context) {
    String filesDir;
    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
            || !Environment.isExternalStorageRemovable()) {
        //外部存储可用
        final File file = context.getExternalFilesDir(null);
        if (null == file) {
            filesDir = context.getFilesDir().getPath();
        } else {
            filesDir = file.getPath();
        }
    } else {
        //外部存储不可用
        filesDir = context.getFilesDir().getPath();
    }
    return filesDir;
}

/**

* 获取app缓存路径

* @param context Application Context

* @return 缓存路径

@NonNull

public static String getCacheDir(Context context) {

String cacheDir;

if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())

|| !Environment.isExternalStorageRemovable()) {

//外部存储可用

final File file = context.getExternalCacheDir();

if (null == file) {

cacheDir = context.getCacheDir().getPath();

} else {

cacheDir = file.getPath();

}

} else {

//外部存储不可用

cacheDir = context.getCacheDir().getPath();

}

return cacheDir;

}

/**

* 获取app文件路径

* @param context Application Context

* @return app文件路径

@NonNull

public static String getFilesDir(Context context) {

String filesDir;

if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())

|| !Environment.isExternalStorageRemovable()) {

//外部存储可用

final File file = context.getExternalFilesDir(null);

if (null == file) {

filesDir = context.getFilesDir().getPath();

} else {

filesDir = file.getPath();

}

} else {

//外部存储不可用

filesDir = context.getFilesDir().getPath();

}

return filesDir;

}

参考链接

IntelliJ IDEA 提示 'try' can use automatic resource management Java7新特性

IntelliJ IDEA会提示

'try' can use automatic resource management。

1	'try' can use automatic resource management。

从 Java 7 build 105版本开始，Java 7的编译器和运行环境支持新的try-with-resources语句，称为ARM 块(Automatic Resource Management) ，自动资源管理。

新的语句支持包括流以及任何可关闭的资源。

public static void filyCopy(File one,File two){
    FileInputStream fileInput = null;
    FileOutputStream fileOutput = null;
    try {
        fileInput = new FileInputStream(one);
        fileOutput = new FileOutputStream(two);
        byte[] b = new byte[1024];
        int len = 0;
        while((len = fileInput.read(b)) != -1){
            fileOutput.write(b, 0, len);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {//释放资源
        try {
            if(fileInput != null){
                fileInput.close();
            }
            if(fileOutput != null){
                fileOutput.close();
            }
        } catch (Exception e2) {
            e2.printStackTrace();
        }
    }
}

public static void filyCopy(File one,File two){

FileInputStream fileInput = null;

FileOutputStream fileOutput = null;

try {

fileInput = new FileInputStream(one);

fileOutput = new FileOutputStream(two);

byte[] b = new byte[1024];

int len = 0;

while((len = fileInput.read(b)) != -1){

fileOutput.write(b, 0, len);

}

} catch (Exception e) {

e.printStackTrace();

} finally {//释放资源

try {

if(fileInput != null){

fileInput.close();

}

if(fileOutput != null){

fileOutput.close();

}

} catch (Exception e2) {

e2.printStackTrace();

}

使用try-with-resources语句来简化代码如下：

public static void filyCopy2(File one,File two){
    try (FileInputStream fileInput = new FileInputStream(one);
            FileOutputStream fileOutput = new FileOutputStream(two);){
        byte[] b = new byte[1024];
        int len = 0;
        while((len = fileInput.read(b)) != -1){
            fileOutput.write(b, 0, len);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static void filyCopy2(File one,File two){

try (FileInputStream fileInput = new FileInputStream(one);

FileOutputStream fileOutput = new FileOutputStream(two);){

byte[] b = new byte[1024];

int len = 0;

while((len = fileInput.read(b)) != -1){

fileOutput.write(b, 0, len);

}

} catch (Exception e) {

e.printStackTrace();

}

在这个例子中，数据流会在try执行完毕后自动被关闭，前提是，这些可关闭的资源必须实现java.lang.AutoCloseable接口。

注：目前java.lang.AutoCloseable接口的子接口或实现类如下：

所有已经子接口:

AsynchronousByteChannel, AsynchronousChannel, BaseStream, ByteChannel, CachedRowSet, CallableStatement, Channel, Clip, Closeable, Connection, DataLine, DirectoryStream, DoubleStream, FilteredRowSet, GatheringByteChannel, ImageInputStream, ImageOutputStream, InterruptibleChannel, JavaFileManager, JdbcRowSet, JMXConnector, JoinRowSet, Line, LongStream, MidiDevice, MidiDeviceReceiver, MidiDeviceTransmitter, Mixer, MulticastChannel, NetworkChannel, ObjectInput, ObjectOutput, Port, PreparedStatement, ReadableByteChannel, Receiver, RMIConnection, RowSet, ScatteringByteChannel, SecureDirectoryStream, SeekableByteChannel, Sequencer, SourceDataLine, StandardJavaFileManager, Statement, Stream, SyncResolver, Synthesizer, TargetDataLine, Transmitter, WatchService, WebRowSet, WritableByteChannel

AsynchronousByteChannel, AsynchronousChannel, BaseStream, ByteChannel, CachedRowSet, CallableStatement, Channel, Clip, Closeable, Connection, DataLine, DirectoryStream, DoubleStream, FilteredRowSet, GatheringByteChannel, ImageInputStream, ImageOutputStream, InterruptibleChannel, JavaFileManager, JdbcRowSet, JMXConnector, JoinRowSet, Line, LongStream, MidiDevice, MidiDeviceReceiver, MidiDeviceTransmitter, Mixer, MulticastChannel, NetworkChannel, ObjectInput, ObjectOutput, Port, PreparedStatement, ReadableByteChannel, Receiver, RMIConnection, RowSet, ScatteringByteChannel, SecureDirectoryStream, SeekableByteChannel, Sequencer, SourceDataLine, StandardJavaFileManager, Statement, Stream, SyncResolver, Synthesizer, TargetDataLine, Transmitter, WatchService, WebRowSet, WritableByteChannel

所有已知实现类：

AbstractInterruptibleChannel, AbstractSelectableChannel, AbstractSelector, AsynchronousFileChannel, AsynchronousServerSocketChannel, AsynchronousSocketChannel, AudioInputStream, BufferedInputStream, BufferedOutputStream, BufferedReader, BufferedWriter, ByteArrayInputStream, ByteArrayOutputStream, CharArrayReader,
CharArrayWriter, CheckedInputStream, CheckedOutputStream, CipherInputStream, CipherOutputStream, DatagramChannel, DatagramSocket, DataInputStream, DataOutputStream,
DeflaterInputStream, DeflaterOutputStream, DigestInputStream, DigestOutputStream, FileCacheImageInputStream, FileCacheImageOutputStream, FileChannel, FileImageInputStream, FileImageOutputStream, FileInputStream, FileLock, FileOutputStream, FileReader, FileSystem, FileWriter, FilterInputStream, FilterOutputStream, FilterReader, FilterWriter, Formatter, ForwardingJavaFileManager, GZIPInputStream, GZIPOutputStream, ImageInputStreamImpl, ImageOutputStreamImpl, InflaterInputStream, InflaterOutputStream,
InputStream, InputStream, InputStream, InputStreamReader, JarFile, JarInputStream, JarOutputStream, LineNumberInputStream, LineNumberReader, LogStream, MemoryCacheImageInputStream, MemoryCacheImageOutputStream, MLet, MulticastSocket, ObjectInputStream, ObjectOutputStream, OutputStream, OutputStream, OutputStream, OutputStreamWriter, Pipe.SinkChannel, Pipe.SourceChannel, PipedInputStream, PipedOutputStream, PipedReader, PipedWriter, PrintStream, PrintWriter, PrivateMLet, ProgressMonitorInputStream, PushbackInputStream, PushbackReader, RandomAccessFile, Reader, RMIConnectionImpl, RMIConnectionImpl_Stub, RMIConnector, RMIIIOPServerImpl, RMIJRMPServerImpl, RMIServerImpl, Scanner, SelectableChannel, Selector, ServerSocket, ServerSocketChannel, Socket, SocketChannel, SSLServerSocket, SSLSocket, StringBufferInputStream, StringReader,StringWriter,URLClassLoader, Writer, XMLDecoder, XMLEncoder, ZipFile,ZipInputStream, ZipOutputStream

AbstractInterruptibleChannel, AbstractSelectableChannel, AbstractSelector, AsynchronousFileChannel, AsynchronousServerSocketChannel, AsynchronousSocketChannel, AudioInputStream, BufferedInputStream, BufferedOutputStream, BufferedReader, BufferedWriter, ByteArrayInputStream, ByteArrayOutputStream, CharArrayReader,

CharArrayWriter, CheckedInputStream, CheckedOutputStream, CipherInputStream, CipherOutputStream, DatagramChannel, DatagramSocket, DataInputStream, DataOutputStream,

DeflaterInputStream, DeflaterOutputStream, DigestInputStream, DigestOutputStream, FileCacheImageInputStream, FileCacheImageOutputStream, FileChannel, FileImageInputStream, FileImageOutputStream, FileInputStream, FileLock, FileOutputStream, FileReader, FileSystem, FileWriter, FilterInputStream, FilterOutputStream, FilterReader, FilterWriter, Formatter, ForwardingJavaFileManager, GZIPInputStream, GZIPOutputStream, ImageInputStreamImpl, ImageOutputStreamImpl, InflaterInputStream, InflaterOutputStream,

InputStream, InputStream, InputStream, InputStreamReader, JarFile, JarInputStream, JarOutputStream, LineNumberInputStream, LineNumberReader, LogStream, MemoryCacheImageInputStream, MemoryCacheImageOutputStream, MLet, MulticastSocket, ObjectInputStream, ObjectOutputStream, OutputStream, OutputStream, OutputStream, OutputStreamWriter, Pipe.SinkChannel, Pipe.SourceChannel, PipedInputStream, PipedOutputStream, PipedReader, PipedWriter, PrintStream, PrintWriter, PrivateMLet, ProgressMonitorInputStream, PushbackInputStream, PushbackReader, RandomAccessFile, Reader, RMIConnectionImpl, RMIConnectionImpl_Stub, RMIConnector, RMIIIOPServerImpl, RMIJRMPServerImpl, RMIServerImpl, Scanner, SelectableChannel, Selector, ServerSocket, ServerSocketChannel, Socket, SocketChannel, SSLServerSocket, SSLSocket, StringBufferInputStream, StringReader,StringWriter,URLClassLoader, Writer, XMLDecoder, XMLEncoder, ZipFile,ZipInputStream, ZipOutputStream

对于Android用户来说，只有编译工程的 minSdkVersion大于 19(Android 4.4)的时候才能生效。

try-with-resources is only supported if your minSdkVersion is set to 19 or higher.

1	try-with-resources is only supported if your minSdkVersion is set to 19 or higher.

参考链接

使用HP Service Pack for ProLiant Gen8.1升级HP ProLiant MicroServer Gen8固件

家里使用了HP Gen8作为NAS服务器,对于iLO/BIOS来说，可以直接通过控制台升级。但是网卡/磁盘阵列的固件升级需要使用HP Service Pack for ProLiant(HP SSP)来升级。具体升级过程如下：

继续阅读使用HP Service Pack for ProLiant Gen8.1升级HP ProLiant MicroServer Gen8固件

国密算法

算法分类

国密即国家密码局认定的国产密码算法。主要有SM1，SM2，SM3，SM4。密钥长度和分组长度均为128位。
SM1 为对称加密。其加密强度与AES相当。该算法不公开，调用该算法时，需要通过加密芯片的接口进行调用。
SM2为非对称加密，基于ECC。该算法已公开。由于该算法基于ECC，故其签名速度与秘钥生成速度都快于RSA。ECC 256位（SM2采用的就是ECC 256位的一种）安全强度比RSA 2048位高，但运算速度快于RSA。
SM3 消息摘要。可以用MD5作为对比理解。该算法已公开。校验结果为256位。
SM4 无线局域网标准的分组数据算法。对称加密，密钥长度和分组长度均为128位。

继续阅读国密算法

bash切换zsh后.bashrc文件失效的解决方案

问题

从bash切换到zsh后，发现原先bash下的bashrc文件配置都失效了（显示zsh: command not found字样，当然如果手动通过source FileName加载是可以的），macOS Catalina(10.15.5) 已经默认切换到zsh，那么如何实现不用每次加载.bashrc文件就实现alias等便捷功能呢？

解决方案

使用系统级的/etc/zshrc或/etc/zprofile
使用用户级的~/[X]bashrc或~/[X]profile

鉴于/etc/zshrc里有较多zsh特性配置，而且默认全局加载，因此这里通过编辑用户级的profile并加载原先的bashrc（即Bash Shell下用户文件）来实现我们的需求

详细步骤

复制系统文件并修改权限

mu@xiaomudeMacBook-Pro ~ % cp /etc/zprofile ~/.zprofile

mu@xiaomudeMacBook-Pro ~ % ll ~/.zprofile
-r--r--r--  1 mu  staff  255  9  6 09:35 /Users/mu/.zprofile

mu@xiaomudeMacBook-Pro ~ % chmod u+w ~/.zprofile #要实现自定义必须添加写权限，否则只有只读权限

mu@xiaomudeMacBook-Pro ~ % ll ~/.zprofile
-rw-r--r--  1 mu  staff  255  9  6 09:35 /Users/mu/.zprofile

mu@xiaomudeMacBook-Pro ~ % cp /etc/zprofile ~/.zprofile

mu@xiaomudeMacBook-Pro ~ % ll ~/.zprofile

-r--r--r-- 1 mu staff 255 9 6 09:35 /Users/mu/.zprofile

mu@xiaomudeMacBook-Pro ~ % chmod u+w ~/.zprofile #要实现自定义必须添加写权限，否则只有只读权限

mu@xiaomudeMacBook-Pro ~ % ll ~/.zprofile

-rw-r--r-- 1 mu staff 255 9 6 09:35 /Users/mu/.zprofile

追加自定义配置项，加载Bash Shell的.bashrc文件

mu@xiaomudeMacBook-Pro ~ % cat .bashrc
alias ll='ls -l'

mu@xiaomudeMacBook-Pro ~ % echo "source ~/.bashrc" >> .zprofile

mu@xiaomudeMacBook-Pro ~ % cat .bashrc

alias ll='ls -l'

mu@xiaomudeMacBook-Pro ~ % echo "source ~/.bashrc" >> .zprofile

测试

mu@xiaomudeMacBook-Pro ~ % ll #配置暂未生效
zsh: command not found: ll

mu@xiaomudeMacBook-Pro ~ % source .zprofile #加载配置文件，使其立即生效；下一次打开终端Shell会话，将自动加载

mu@xiaomudeMacBook-Pro ~ % ll
total 16
drwx------   5 mu  staff   160  8 23 14:38 Applications
drwx------@  4 mu  staff   128  1  2  2019 Applications (Parallels)
drwx------@  4 mu  staff   128  9  1 15:23 Desktop
drwx------+ 20 mu  staff   640  8 29 12:14 Documents
drwx------@ 35 mu  staff  1120  9  6 09:29 Downloads
drwx------@ 85 mu  staff  2720  8 30 11:05 Library
drwx------+  4 mu  staff   128  8 20 20:17 Movies
drwx------+  8 mu  staff   256  8 20 20:17 Music
drwx------  26 mu  staff   832  9  6 09:28 Nextcloud
drwx------   3 mu  staff    96  1  2  2019 Parallels
drwx------+  6 mu  staff   192  8 20 20:01 Pictures
drwxr-xr-x+  4 mu  staff   128 11 28  2018 Public
drwxr-xr-x   4 mu  staff   128 12  9  2018 PycharmProjects
-rw-r--r--   1 mu  staff   811 12 15  2018 Untitled.ipynb
-rw-r--r--   1 mu  staff  1578 12 29  2018 Untitled1.ipynb
drwxr-xr-x   3 mu  staff    96  8 25 16:08 VirtualBox VMs
drwxr-xr-x   2 mu  staff    64  1 25  2019 WeChatProjects

mu@xiaomudeMacBook-Pro ~ % ll #配置暂未生效

zsh: command not found: ll

mu@xiaomudeMacBook-Pro ~ % source .zprofile #加载配置文件，使其立即生效；下一次打开终端Shell会话，将自动加载

mu@xiaomudeMacBook-Pro ~ % ll

total 16

drwx------ 5 mu staff 160 8 23 14:38 Applications

drwx------@ 4 mu staff 128 1 2 2019 Applications (Parallels)

drwx------@ 4 mu staff 128 9 1 15:23 Desktop

drwx------+ 20 mu staff 640 8 29 12:14 Documents

drwx------@ 35 mu staff 1120 9 6 09:29 Downloads

drwx------@ 85 mu staff 2720 8 30 11:05 Library

drwx------+ 4 mu staff 128 8 20 20:17 Movies

drwx------+ 8 mu staff 256 8 20 20:17 Music

drwx------ 26 mu staff 832 9 6 09:28 Nextcloud

drwx------ 3 mu staff 96 1 2 2019 Parallels

drwx------+ 6 mu staff 192 8 20 20:01 Pictures

drwxr-xr-x+ 4 mu staff 128 11 28 2018 Public

drwxr-xr-x 4 mu staff 128 12 9 2018 PycharmProjects

-rw-r--r-- 1 mu staff 811 12 15 2018 Untitled.ipynb

-rw-r--r-- 1 mu staff 1578 12 29 2018 Untitled1.ipynb

drwxr-xr-x 3 mu staff 96 8 25 16:08 VirtualBox VMs

drwxr-xr-x 2 mu staff 64 1 25 2019 WeChatProjects

参考链接

Bash切换Zsh后，bashrc文件失效的解决方案

在macOS Catalina(10.15.5)上搭建Flutter开发环境

下载并安装目前最新的Android Studio 4.0，然后通过Android Studio 4.0安装Android SDK。

下载目前最新的flutter

$ cd ~

$ mkdir Android

$ cd Android

$ git clone -b stable https://github.com/flutter/flutter.git

$ cd ~

$ mkdir Android

$ cd Android

$ git clone -b stable https://github.com/flutter/flutter.git

配置环境变量

$ export PATH=/Users/`whoami`/Android/flutter/bin:$PATH

# android sdk目录，替换为你自己的即可，下面是Android Studio安装SDK的默认目录 
$ export ANDROID_HOME="/Users/`whoami`/Library/Android/sdk" 
  
$ export PATH=${PATH}:${ANDROID_HOME}/tools
  
$ export PATH=${PATH}:${ANDROID_HOME}/platform-tools
  
$ export PUB_HOSTED_URL=https://pub.flutter-io.cn
  
$ export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

$ export PATH=/Users/`whoami`/Android/flutter/bin:$PATH

# android sdk目录，替换为你自己的即可，下面是Android Studio安装SDK的默认目录

$ export ANDROID_HOME="/Users/`whoami`/Library/Android/sdk"

$ export PATH=${PATH}:${ANDROID_HOME}/tools

$ export PATH=${PATH}:${ANDROID_HOME}/platform-tools

$ export PUB_HOSTED_URL=https://pub.flutter-io.cn

$ export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

上述环境变量，全部追加到 .bashrc 尾部

export PATH=/Users/`whoami`/Android/flutter/bin:$PATH
# android sdk目录，替换为你自己的即可，下面是Android Studio安装SDK的默认目录
export ANDROID_HOME="/Users/`whoami`/Library/Android/sdk"
export PATH=${PATH}:${ANDROID_HOME}/tools
export PATH=${PATH}:${ANDROID_HOME}/platform-tools
export PUB_HOSTED_URL=https://pub.flutter-io.cn
export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

export PATH=/Users/`whoami`/Android/flutter/bin:$PATH

# android sdk目录，替换为你自己的即可，下面是Android Studio安装SDK的默认目录

export ANDROID_HOME="/Users/`whoami`/Library/Android/sdk"

export PATH=${PATH}:${ANDROID_HOME}/tools

export PATH=${PATH}:${ANDROID_HOME}/platform-tools

export PUB_HOSTED_URL=https://pub.flutter-io.cn

export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

如果不增加到.bashrc 尾部，则在 Android Studio 4.0 创建项目的时候，会非常慢，主要是网络问题。

必要的环境配置，依赖下载

#对于 macOS Catalina 10.15.5 来说，由于Shell被替换成了ZSH,因此环境变量需要重新配置一下

$ cp /etc/zprofile ~/.zprofile

$ chmod u+w ~/.zprofile

$ echo "source ~/.bashrc" >> .zprofile

$ flutter doctor

$ flutter doctor --android-licenses

$ sudo gem install cocoapods

# 杀掉全部的dart进程，否则可能导致长时间无法创建项目的问题
# 任何时候，flutter相关卡住，貌似都可以这样操作

$ killall -9 dart