分类： Java

使用`Robolectric`进行`Android`代码测试的时候，随着测试用例的增多，可能会报告如下错误（`Windows`下常见）：

> Task :biz-h5:testDebugUnitTest

com.xxxx.plugin.face.FaceTest > executeAsync_Success FAILED
    org.mockito.exceptions.base.MockitoException at FaceTest.java:71
        Caused by: java.lang.ClassCastException at FaceTest.java:71

原因为`Mockto`使用了编译缓存导致加载类的时候出现异常。解决方法是禁止`Mockto`缓存测试类的代码。

在`Android`测试项目的`src/test/java`下创建一个名为`org.mockito.configuration`的包,然后实现一个名为`MockitoConfiguration.java`的类，如下：

package org.mockito.configuration;

public class MockitoConfiguration extends DefaultMockitoConfiguration {

  @Override
  public boolean enableClassCache() {
    return false;
  }
}

这样当再次执行测试用例的时候，就已经不使用缓存了。

参考链接

• Mockito with Robolectric: “ClassCastException occurred when creating the proxy”
• java – 使用Robolectric的Mockito：“创建代理时发生了ClassCastException”

目前在对Android的代码进行功能测试的时候，需要服务器返回一个数据来测试整个流程是否正确。不希望引入第三方的JAR包，因此需要一个特别简单的HTTP服务器。

网上查询了一下，找到可用的代码如下：

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
import java.util.StringTokenizer;

// The tutorial can be found just here on the SSaurel's Blog : 
// https://www.ssaurel.com/blog/create-a-simple-http-web-server-in-java
// Each Client Connection will be managed in a dedicated Thread
public class JavaHTTPServer implements Runnable{ 
	
	static final File WEB_ROOT = new File(".");
	static final String DEFAULT_FILE = "index.html";
	static final String FILE_NOT_FOUND = "404.html";
	static final String METHOD_NOT_SUPPORTED = "not_supported.html";
	// port to listen connection
	static final int PORT = 8080;
	
	// verbose mode
	static final boolean verbose = true;
	
	// Client Connection via Socket Class
	private Socket connect;
	
	public JavaHTTPServer(Socket c) {
		connect = c;
	}
	
	public static void main(String[] args) {
		try {
			ServerSocket serverConnect = new ServerSocket(PORT);
			System.out.println("Server started.\nListening for connections on port : " + PORT + " ...\n");
			
			// we listen until user halts server execution
			while (true) {
				JavaHTTPServer myServer = new JavaHTTPServer(serverConnect.accept());
				
				if (verbose) {
					System.out.println("Connecton opened. (" + new Date() + ")");
				}
				
				// create dedicated thread to manage the client connection
				Thread thread = new Thread(myServer);
				thread.start();
			}
			
		} catch (IOException e) {
			System.err.println("Server Connection error : " + e.getMessage());
		}
	}

	@Override
	public void run() {
		// we manage our particular client connection
		BufferedReader in = null; PrintWriter out = null; BufferedOutputStream dataOut = null;
		String fileRequested = null;
		
		try {
			// we read characters from the client via input stream on the socket
			in = new BufferedReader(new InputStreamReader(connect.getInputStream()));
			// we get character output stream to client (for headers)
			out = new PrintWriter(connect.getOutputStream());
			// get binary output stream to client (for requested data)
			dataOut = new BufferedOutputStream(connect.getOutputStream());
			
			// get first line of the request from the client
			String input = in.readLine();
			// we parse the request with a string tokenizer
			StringTokenizer parse = new StringTokenizer(input);
			String method = parse.nextToken().toUpperCase(); // we get the HTTP method of the client
			// we get file requested
			fileRequested = parse.nextToken().toLowerCase();
			
			// we support only GET and HEAD methods, we check
			if (!method.equals("GET")  &&  !method.equals("HEAD")) {
				if (verbose) {
					System.out.println("501 Not Implemented : " + method + " method.");
				}
				
				// we return the not supported file to the client
				File file = new File(WEB_ROOT, METHOD_NOT_SUPPORTED);
				int fileLength = (int) file.length();
				String contentMimeType = "text/html";
				//read content to return to client
				byte[] fileData = readFileData(file, fileLength);
					
				// we send HTTP Headers with data to client
				out.println("HTTP/1.1 501 Not Implemented");
				out.println("Server: Java HTTP Server from SSaurel : 1.0");
				out.println("Date: " + new Date());
				out.println("Content-type: " + contentMimeType);
				out.println("Content-length: " + fileLength);
				out.println(); // blank line between headers and content, very important !
				out.flush(); // flush character output stream buffer
				// file
				dataOut.write(fileData, 0, fileLength);
				dataOut.flush();
				
			} else {
				// GET or HEAD method
				if (fileRequested.endsWith("/")) {
					fileRequested += DEFAULT_FILE;
				}
				
				File file = new File(WEB_ROOT, fileRequested);
				int fileLength = (int) file.length();
				String content = getContentType(fileRequested);
				
				if (method.equals("GET")) { // GET method so we return content
					byte[] fileData = readFileData(file, fileLength);
					
					// send HTTP Headers
					out.println("HTTP/1.1 200 OK");
					out.println("Server: Java HTTP Server from SSaurel : 1.0");
					out.println("Date: " + new Date());
					out.println("Content-type: " + content);
					out.println("Content-length: " + fileLength);
					out.println(); // blank line between headers and content, very important !
					out.flush(); // flush character output stream buffer
					
					dataOut.write(fileData, 0, fileLength);
					dataOut.flush();
				}
				
				if (verbose) {
					System.out.println("File " + fileRequested + " of type " + content + " returned");
				}
				
			}
			
		} catch (FileNotFoundException fnfe) {
			try {
				fileNotFound(out, dataOut, fileRequested);
			} catch (IOException ioe) {
				System.err.println("Error with file not found exception : " + ioe.getMessage());
			}
			
		} catch (IOException ioe) {
			System.err.println("Server error : " + ioe);
		} finally {
			try {
				in.close();
				out.close();
				dataOut.close();
				connect.close(); // we close socket connection
			} catch (Exception e) {
				System.err.println("Error closing stream : " + e.getMessage());
			} 
			
			if (verbose) {
				System.out.println("Connection closed.\n");
			}
		}
		
		
	}
	
	private byte[] readFileData(File file, int fileLength) throws IOException {
		FileInputStream fileIn = null;
		byte[] fileData = new byte[fileLength];
		
		try {
			fileIn = new FileInputStream(file);
			fileIn.read(fileData);
		} finally {
			if (fileIn != null) 
				fileIn.close();
		}
		
		return fileData;
	}
	
	// return supported MIME Types
	private String getContentType(String fileRequested) {
		if (fileRequested.endsWith(".htm")  ||  fileRequested.endsWith(".html"))
			return "text/html";
		else
			return "text/plain";
	}
	
	private void fileNotFound(PrintWriter out, OutputStream dataOut, String fileRequested) throws IOException {
		File file = new File(WEB_ROOT, FILE_NOT_FOUND);
		int fileLength = (int) file.length();
		String content = "text/html";
		byte[] fileData = readFileData(file, fileLength);
		
		out.println("HTTP/1.1 404 File Not Found");
		out.println("Server: Java HTTP Server from SSaurel : 1.0");
		out.println("Date: " + new Date());
		out.println("Content-type: " + content);
		out.println("Content-length: " + fileLength);
		out.println(); // blank line between headers and content, very important !
		out.flush(); // flush character output stream buffer
		
		dataOut.write(fileData, 0, fileLength);
		dataOut.flush();
		
		if (verbose) {
			System.out.println("File " + fileRequested + " not found");
		}
	}
	
}

参考链接

Create a simple HTTP Web Server in Java

`IntelliJ IDEA`会提示

'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();
        }
    }
}

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();
    }
}

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

 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

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.

参考链接

• idea 提示 'try' can use automatic resource management,java7新特性
• Java 7 ARM(Automatic Resource Management，自动资源管理)
• Java 7 新的 try-with-resources 语句，自动资源释放
• try-with-resources are not supported at this language level - Android

最近开发的项目出现界面莫名其秒的卡住，直到发生`ANR`异常退出的问题。
问题排查许久，才发现是由于使用的`ViewPager`导致的。
在`ViewPager`中使用`setCurrentItem`长距离设置当前显示的位置的时候，比如`0->600`,`600->1000`，`1000->500` 这样的长距离跳转。会导致函数卡住在

void populate(int newCurrentItem)

函数中很长时间, 甚至一直不能跳出循环。具体卡住的的循环代码如下：

for(int pos = this.mCurItem + 1; pos < N; ++pos) { 
    if (extraWidthRight >= rightWidthNeeded && pos > endPos) { 
        if (ii == null) {
            break;
        }

        if (pos == ii.position && !ii.scrolling) {
            this.mItems.remove(itemIndex);
            this.mAdapter.destroyItem(this, pos, ii.object);
            ii = itemIndex < this.mItems.size() ? (ViewPager.ItemInfo)this.mItems.get(itemIndex) : null;
        }
    } else if (ii != null && pos == ii.position) {
        extraWidthRight += ii.widthFactor;
        ++itemIndex;
        ii = itemIndex < this.mItems.size() ? (ViewPager.ItemInfo)this.mItems.get(itemIndex) : null;
    } else {
        ii = this.addNewItem(pos, itemIndex);
        ++itemIndex;
        extraWidthRight += ii.widthFactor;
        ii = itemIndex < this.mItems.size() ? (ViewPager.ItemInfo)this.mItems.get(itemIndex) : null;
    }
}

上述代码中循环体会一直循环到`N`结束为止。而这个`N`是通过

int N = this.mAdapter.getCount();

赋值的。恰好，我们的代码中返回的是`Integer.MAX_VALUE`。咨询了同事，当时设置这个数值的目的是为了解决循环滚动展示才设置的。代码是直接抄的 Android无限广告轮播 自定义BannerView / 如何优雅的实现一个可复用的 PagerAdapter。

通过Google搜索关键词 `BannerAdapter extends PagerAdapter` 可以找到类似的代码。

具体的复现`BUG`的例子代码如下：

package com.mobibrw.viewpager;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final ViewPager viewPager = findViewById(R.id.viewPager);
        viewPager.setAdapter(new PagerAdapter() {
            @Override
            public int getCount() {
                return Integer.MAX_VALUE;
            }

            @Override
            public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
                return view == object;
            }

            @Override
            public void destroyItem(ViewGroup container, int position, Object object) {
                container.removeView((View) object);
            }

            @Override
            public Object instantiateItem(ViewGroup container, final int position) {
                final View view = LayoutInflater.from(MainActivity.this).inflate(R.layout.pager_view, null);
                final TextView tv = view.findViewById(R.id.text);
                tv.setText("" + position);
                container.addView(view);
                return view;
            }
        });

        final Button btnCmd = findViewById(R.id.btnCmd);
        btnCmd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Random rdm = new Random(System.currentTimeMillis());
                int rd = Math.abs(rdm.nextInt())%700 + 1;
                viewPager.setCurrentItem(rd);
            }
        });
    }
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clipChildren="false"
        android:clipToPadding="false"/>
    <Button
        android:id="@+id/btnCmd"
        android:text="@string/change_size"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        />

</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.53" />

</android.support.constraint.ConstraintLayout>

完整的项目代码可以点击此处下载 ViewPager / ViewPagerAppCompatV7。项目编译完成之后，多点击几次 `Change Size` 按钮就可以复现界面长时间卡住的情况。第二个项目是支持`appcompat-v7:18.0.0`的版本，目的是观察各个版本的代码是否存在不同，结论是，都一样。

这个问题目前的解决方法就是保证`ViewPager`中的数据不要太多，比如底层分页显示，每页不要太多。另外就是不要大距离跳转，否则会有很多问题。

如果能把`android.support`升级到`androidx`的话，可以试试最新的`ViewPager2`,最新的`ViewPager2`是用`RecyclerView `实现的，应该不会有以前的问题了。

这个问题，我已经向Google提交了BUG，估计最后的答复也是要升级到`androidx`。

参考链接

Android无限广告轮播 - ViewPager源码分析

SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
Date date = sdf.parse(yourdate);      	
Calendar cal=Calendar.getInstance();
if(null!=date) {
	cal.setTime(date);
	if (Calendar.AM == cal.get(Calendar.AM_PM)) {
		return "上午";
	}
}

参考链接

Java Calendar 获取上下午