概述

文件存取的核心就是输入流和输出流。

Android文件的操作模式

文件的相关操作方法

文件读写的实现

openFileOutput和openFileInput方法

  /** * openFIleOutput ,openFileInput * 这两种方法同sp一样只能讲文件保存到手机内存固定的路径中， * 默认为 /data/data/<packageName>/files */    private void save2File() {        try {            //向文件写入内容            FileOutputStream os = openFileOutput("file.txt", Context.MODE_PRIVATE);            String text = "写数据到文件";            os.write(text.getBytes("utf-8"));            //关闭流            os.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (UnsupportedEncodingException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /** * */    private void readFile() {        try {            FileInputStream ins = openFileInput("file.txt");            byte[] buffer = new byte[100];            int byteCount = ins.read(buffer);            String text = new String(buffer,0,byteCount,"utf-8");            Toast.makeText(this,text,Toast.LENGTH_SHORT).show();            ins.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }

文件存储位置

/data/data/<package-name>/files目录下

openFileOutput和openFileInput方法可以获得操作文件的OutputStream以及InputStream对象，而且可以通过流对象处理任何文件的数据，但是这两个方法同SharedPreferences一样，只能在手机内存卡的指定目录建立文件，因此在使用上仍然有一定的局限性。

读取SD卡上的文件

main_activity.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/LinearLayout1"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.jay.example.filedemo2.MainActivity">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="清输入文件名" />    <EditText        android:id="@+id/edittitle"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="文件名" />    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="清输入文件内容" />    <EditText        android:id="@+id/editdetail"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="文件内容" />    <Button        android:id="@+id/btnsave"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="保存到SD卡" />    <Button        android:id="@+id/btnclean"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="清空" />    <Button        android:id="@+id/btnread"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="读取sd卡中的文件" /></LinearLayout>

接着我们来写一个SD操作类： SDFileHelper.java

public class SDFileHelper {    private Context context;    public SDFileHelper() {    }    public SDFileHelper(Context context) {        super();        this.context = context;    }    //往SD卡写入文件的方法    public void savaFileToSD(String filename, String filecontent) throws Exception {        //如果手机已插入sd卡,且app具有读写sd卡的权限        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {            filename = Environment.getExternalStorageDirectory().getCanonicalPath() + "/" + filename;            //这里就不要用openFileOutput了,那个是往手机内存中写数据的            FileOutputStream output = new FileOutputStream(filename);            output.write(filecontent.getBytes());            //将String字符串以字节流的形式写入到输出流中            output.close();            //关闭输出流        } else Toast.makeText(context, "SD卡不存在或者不可读写", Toast.LENGTH_SHORT).show();    }    //读取SD卡中文件的方法    //定义读取文件的方法:    public String readFromSD(String filename) throws IOException {        StringBuilder sb = new StringBuilder("");        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {            filename = Environment.getExternalStorageDirectory().getCanonicalPath() + "/" + filename;            //打开文件输入流            FileInputStream input = new FileInputStream(filename);            byte[] temp = new byte[1024];            int len = 0;            //读取文件内容:            while ((len = input.read(temp)) > 0) {                sb.append(new String(temp, 0, len));            }            //关闭输入流            input.close();        }        return sb.toString();    }}

接着MainActivity.java实现相关逻辑：

public class MainActivity extends AppCompatActivity implements View.OnClickListener{    private EditText editname;    private EditText editdetail;    private Button btnsave;    private Button btnclean;    private Button btnread;    private Context mContext;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mContext = getApplicationContext();        bindViews();    }    private void bindViews() {        editname = (EditText) findViewById(R.id.edittitle);        editdetail = (EditText) findViewById(R.id.editdetail);        btnsave = (Button) findViewById(R.id.btnsave);        btnclean = (Button) findViewById(R.id.btnclean);        btnread = (Button) findViewById(R.id.btnread);        btnsave.setOnClickListener(this);        btnclean.setOnClickListener(this);        btnread.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.btnclean:                editdetail.setText("");                editname.setText("");                break;            case R.id.btnsave:                String filename = editname.getText().toString();                String filedetail = editdetail.getText().toString();                SDFileHelper sdHelper = new SDFileHelper(mContext);                try                {                    sdHelper.savaFileToSD(filename, filedetail);                    Toast.makeText(getApplicationContext(), "数据写入成功", Toast.LENGTH_SHORT).show();                }                catch(Exception e){                    e.printStackTrace();                    Toast.makeText(getApplicationContext(), "数据写入失败", Toast.LENGTH_SHORT).show();                }                break;            case R.id.btnread:                String detail = "";                SDFileHelper sdHelper2 = new SDFileHelper(mContext);                try                {                    String filename2 = editname.getText().toString();                    detail = sdHelper2.readFromSD(filename2);                }                catch(IOException e){e.printStackTrace();}                Toast.makeText(getApplicationContext(), detail, Toast.LENGTH_SHORT).show();                break;        }    }}

最后别忘记在AndroidManifest.xml写上读写SD卡的权限哦！

<!-- 在SDCard中创建与删除文件权限 --><uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/><!-- 往SDCard写入数据权限 --><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

如何判断虚拟和物理两种SDK

在默认情况下，会将一部分存储空间分给虚拟的SD卡使用（一部分用于安装Android操作系统）

android.os.Enviroment.isExternalStorageRemovalbe()

返回true：SD卡是物理的，反之SD卡是虚拟的。

用于适配不同型号手机，反射获取SD卡路径和状态

package com.turing.base.activity.dataStore.fileStore;import android.content.Context;import android.os.Environment;import android.os.StatFs;import android.os.storage.StorageManager;import android.text.TextUtils;import android.util.Log;import java.io.File;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.concurrent.ConcurrentLinkedQueue;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * 用于适配不同型号手机，反射获取SD卡路径和状态 * */public class DevMountInfo {    private final String TAG = DevMountInfo.class.getSimpleName();    private static final int ERROR = -1;    // class name    private final static String CLASS_NAME = "android.os.storage.StorageVolume";    //remained spare memory size    private static final int REMAINED_SPARE_IN_MB = 100;    // method name    private final static String METHOD_GET_VOLUME_LIST = "getVolumeList";    private final static String METHOD_GET_VOLUME_STATE = "getVolumeState";    private final static String METHOD_IS_REMOVABLE = "isRemovable";    private final static String METHOD_GET_PATH = "getPath";    private final static String MOUNTED = "mounted";    private static DevMountInfo INSTANCE;    private String mSDCardPath = null;    // internal file path    private ConcurrentLinkedQueue<String> mInternalPathList = new ConcurrentLinkedQueue<String>();    // external file path    private ConcurrentLinkedQueue<String> mExternalPathList = new ConcurrentLinkedQueue<String>();    private ExecutorService mExecutor = null;    private DevMountInfo() {        mExecutor = Executors.newSingleThreadExecutor();    }    public static DevMountInfo getInstance() {        synchronized (DevMountInfo.class) {            if (null == INSTANCE) {                INSTANCE = new DevMountInfo();            }            return INSTANCE;        }    }    @Override    protected void finalize() throws Throwable {        super.finalize();        synchronized (DevMountInfo.class) {            mInternalPathList.clear();            mExternalPathList.clear();            mExecutor.shutdown();            INSTANCE = null;        }    }    public void init(final Context context) {        mExecutor.execute(new Runnable() {            @Override            public void run() {                executeInit(context);            }        });    }    public boolean isSDCardFull() {        return REMAINED_SPARE_IN_MB > (getSDCardAvailSpace() * 1024);    }    public boolean isSDCardAvaiable() {        return !mExternalPathList.isEmpty() || !mInternalPathList.isEmpty();    }    public String getSDCardPath() {        return mSDCardPath;    }    public long getSDCardTotalSpace() {        long totalSpace = 0;        if (!TextUtils.isEmpty(mSDCardPath)) {            StatFs sf = new StatFs(mSDCardPath);            long blockSize = sf.getBlockSize();            long total = sf.getBlockCount();            totalSpace = total * blockSize / 1024;        }        return totalSpace;    }    public long getSDCardAvailSpace() {        long availSpace = 0;        if (!TextUtils.isEmpty(mSDCardPath)) {            StatFs sf = new StatFs(mSDCardPath);            long blockSize = sf.getBlockSize();            long availCount = sf.getAvailableBlocks();            availSpace = availCount * blockSize / 1024;        }        return availSpace;    }    public String getInternalSDCardPath() {        return mInternalPathList.peek();    }    public String getExternalSDCardPath() {        return mExternalPathList.peek();    }    private void executeInit(Context context) {        StorageManager mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);        if (mStorageManager != null) {            Class<?> mStorageVolume = null;            Method mGetVolumeListMethod = null;            Method mGetVolumeStateMethod = null;            Method mGetPathMethod = null;            Method mIsRemovableMethod = null;            Object[] mStorageVolumeList = null;            try {                mStorageVolume = Class.forName(CLASS_NAME);                mGetVolumeListMethod = mStorageManager.getClass().getMethod(METHOD_GET_VOLUME_LIST, new Class[0]);                mGetVolumeStateMethod = mStorageManager.getClass().getMethod(METHOD_GET_VOLUME_STATE, new Class[]{String.class});                mIsRemovableMethod = mStorageVolume.getMethod(METHOD_IS_REMOVABLE, new Class[0]);                mGetPathMethod = mStorageVolume.getMethod(METHOD_GET_PATH, new Class[0]);                mStorageVolumeList = (Object[]) mGetVolumeListMethod.invoke(mStorageManager, new Object[0]);                boolean mIsRemovable = false;                if (mStorageVolumeList != null && mStorageVolumeList.length > 0) {                    int mStorageVolumeCount = mStorageVolumeList.length;                    Log.i(TAG, "init() === > StorageVolume Count = " + mStorageVolumeCount);                    mInternalPathList.clear();                    mExternalPathList.clear();                    for (int i = 0; i < mStorageVolumeCount; ++i) {                        String mStoragePath = (String) mGetPathMethod.invoke(mStorageVolumeList[i], new Object[0]);                        mIsRemovable = ((Boolean) mIsRemovableMethod.invoke(mStorageVolumeList[i], new Object[0])).booleanValue();                        if (!TextUtils.isEmpty(mStoragePath)) {                            String state = (String) mGetVolumeStateMethod.invoke(mStorageManager, new Object[]{mStoragePath});                            if ((state != null) && (state.equals(MOUNTED))) {                                if (mIsRemovable) {                                    Log.i(TAG, "init() === > external storage path = (" + mStoragePath + ")");                                    mExternalPathList.add(mStoragePath);                                } else {                                    Log.i(TAG, "init() === > internal storage path = (" + mStoragePath + ")");                                    mInternalPathList.add(mStoragePath);                                }                            }                        }                    }                }            } catch (ClassNotFoundException e) {                handleInvalid();                Log.e(TAG, "init() === > Exception:ClassNotFoundException");            } catch (NoSuchMethodException e) {                handleInvalid();                Log.e(TAG, "init() === > Exception:NoSuchMethodException");            } catch (IllegalArgumentException e) {                handleInvalid();                Log.e(TAG, "init() === > Exception:IllegalArgumentException");            } catch (IllegalAccessException e) {                handleInvalid();                Log.e(TAG, "init() === > Exception:IllegalAccessException");            } catch (InvocationTargetException e) {                handleInvalid();                Log.e(TAG, "init() === > Exception:InvocationTargetException");            }        } else {            handleInvalid();            Log.e(TAG, "init() === > can't get storage manager");        }        initSDCardPath();    }    private void handleInvalid() {        mInternalPathList.add(Environment.getExternalStorageDirectory().getPath());    }    private void initSDCardPath() {        if (!mExternalPathList.isEmpty()) {            mSDCardPath = mExternalPathList.peek();        } else if (!mInternalPathList.isEmpty()) {            mSDCardPath = mInternalPathList.peek();        } else {            mSDCardPath = Environment.getExternalStorageDirectory().getPath();        }        Log.i(TAG, "initSDCardPath() === > SDCARD PATH = (" + mSDCardPath + ")");    }    /** * SDCARD是否存 */    public static boolean externalMemoryAvailable() {        return android.os.Environment.getExternalStorageState().equals(                android.os.Environment.MEDIA_MOUNTED);    }    /** * 获取手机内部剩余存储空间 * * @return */    public static long getAvailableInternalMemorySize() {        File path = Environment.getDataDirectory();        StatFs stat = new StatFs(path.getPath());        long blockSize = stat.getBlockSize();        long availableBlocks = stat.getAvailableBlocks();        return availableBlocks * blockSize;    }    /** * 获取手机内部总的存储空间 * * @return */    public static long getTotalInternalMemorySize() {        File path = Environment.getDataDirectory();        StatFs stat = new StatFs(path.getPath());        long blockSize = stat.getBlockSize();        long totalBlocks = stat.getBlockCount();        return totalBlocks * blockSize;    }    /** * 获取手机内置存储剩余存储空间 * * @return */    public static long getAvailableInternalSystemMemorySize() {        File path = Environment.getRootDirectory();        StatFs stat = new StatFs(path.getPath());        long blockSize = stat.getBlockSize();        long availableBlocks = stat.getAvailableBlocks();        return availableBlocks * blockSize;    }    /** * 获取手机内置存储总的存储空间 * * @return */    public static long getTotalInternalSystemMemorySize() {        File path = Environment.getRootDirectory();        StatFs stat = new StatFs(path.getPath());        long blockSize = stat.getBlockSize();        long totalBlocks = stat.getBlockCount();        return totalBlocks * blockSize;    }    /** * 获取SDCARD剩余存储空间 * * @return */    public static long getAvailableExternalMemorySize() {        if (externalMemoryAvailable()) {            File path = Environment.getExternalStorageDirectory();            StatFs stat = new StatFs(path.getPath());            long blockSize = stat.getBlockSize();            long availableBlocks = stat.getAvailableBlocks();            return availableBlocks * blockSize;        } else {            return ERROR;        }    }    /** * 获取SDCARD总的存储空间 * * @return */    public static long getTotalExternalMemorySize() {        if (externalMemoryAvailable()) {            File path = Environment.getExternalStorageDirectory();            StatFs stat = new StatFs(path.getPath());            long blockSize = stat.getBlockSize();            long totalBlocks = stat.getBlockCount();            return totalBlocks * blockSize;        } else {            return ERROR;        }    }    public static long getAvailableMemorySize(String path) {        if (null == path)            return 0;        StatFs stat = new StatFs(path);        long blockSize = stat.getBlockSize();        long availableBlocks = stat.getAvailableBlocks();        return availableBlocks * blockSize;    }}

读取raw和assets文件夹下的文件

相信大家对两个文件夹并不陌生，如果我们不想自己的文件被编译成二进制文件的话，我们可以把文件放到这两个目录下，而两者的区别如下：

res/raw：文件会被映射到R.java文件中，访问的时候直接通过资源ID即可访问，而且他不能有目录结构，就是不能再创建文件夹
assets：不会映射到R.java文件中，通过AssetManager来访问，能有目录结构，即，可以自行创建文件夹。

读取文件资源：

res/raw：

InputStream is =getResources().openRawResource(R.raw.filename);

assets：

AssetManager am =  getAssets();  InputStream is = am.open("filename");

SAX引擎读取XML文件

sax引擎读取xml文件的原理：

sax技术在处理xml文件时并不一次性把xml文件装入内存，而是一边读一般解析。

使用sax处理xml需要一个Handler对象，一般会使用org.xml.sax.helpers.DefaultHandler的子类作为Handler对象

因此,这就需要处理如下5个分析点,也可称为分析事件:

开始分析xml文件。该分析点表示sax引擎刚开始处理xml文件，还没有读取xml文件中的内容。该分析点对应于DefaultHandler类中的startDocument()事件方法，可以在该方法中做一下初始化的工作！
开始处理每一个xml元素，也就是遇到<product>，<item>这样的起始标记，sax引擎每次扫描到新的xml元素的起始标记会触发这个分析事件，对应的事件分析方法是startElement，在该方法中可以获取当前元素的名称和元素属性的相关信息
处理完一个xml元素，也就是遇到</product>，</item>这样的结束标记，该分析点对应的事件方法是endElement，在该事件中可以获得当前处理完的元素的全部信息。
处理完xml文件。如果sax引擎将整个xml文件的内容都扫描完了，就到了这个分析点，该分析点对应的事件方法endDocument()，该事件方法可能不是必需的，如果最后有以下收尾工作，如释放一下资源，可以在该方法中完成！
读取字符分析点。这是最重要的分析点。如果没有这个分析点，前4步的处理相当于白跑一遍，虽然读取了xml文件中的所有内容，但并未保存这些内容，而这个分析点所对应的characters事件方法的主要作用就是保存sax引擎读取的xml文件中的内容。更准确地说是保存xml元素的文本，也就是<product>abc</product>中的abc。

Code

res\raw\product.xml

<?xml version="1.0" encoding="utf-8"?><products>    <product>        <id>10</id>        <name>电脑</name>        <price>2067.25</price>    </product>    <product>        <id>20</id>        <name>微波炉</name>        <price>520</price>    </product>    <product>        <id>30</id>        <name>洗衣机</name>        <price>2400</price>    </product></products>

Product.java

public class Product{    private int id;    private String name;    private float price;    public int getId()    {        return id;    }    public void setId(int id)    {        this.id = id;    }    public String getName()    {        return name;    }    public void setName(String name)    {        this.name = name;    }    public float getPrice()    {        return price;    }    public void setPrice(float price)    {        this.price = price;    }}

XML2Product.java(DefaultHandler子类)

DefaultHandler子类，核心类，负责处理分析点事件。

import org.xml.sax.Attributes;import org.xml.sax.SAXException;import org.xml.sax.helpers.DefaultHandler;import java.util.ArrayList;import java.util.List;public class XML2Product extends DefaultHandler {    private List<Product> products;    private Product product;    private StringBuffer buffer = new StringBuffer();    public List<Product> getProducts() {        return products;    }    @Override    public void characters(char[] ch, int start, int length)            throws SAXException {        buffer.append(ch, start, length);        super.characters(ch, start, length);    }    @Override    public void startDocument() throws SAXException {        // 开始分析xml文件,创建List对象用于保存分析完的Product对象        products = new ArrayList<Product>();    }    @Override    public void startElement(String uri, String localName, String qName,                             Attributes attributes) throws SAXException {        if (localName.equals("product")) {            // 如果分析的是<product>标签，则创建一个Product对象            product = new Product();        }        super.startElement(uri, localName, qName, attributes);    }    @Override    public void endElement(String uri, String localName, String qName)            throws SAXException {        if (localName.equals("product")) {            // 处理完 <product>标签后 将product对象添加到products中            products.add(product);        } else if (localName.equals("id")) {            // 设置id属性的值            product.setId(Integer.parseInt(buffer.toString().trim()));            // 将标签内容的缓存区清空            buffer.setLength(0);        } else if (localName.equals("name")) {            product.setName(buffer.toString().trim());            buffer.setLength(0);        } else if (localName.equals("price")) {            product.setPrice(Float.parseFloat(buffer.toString().trim()));            buffer.setLength(0);        }        super.endElement(uri, localName, qName);    }}

Xml2JavaObjectAct

import android.app.AlertDialog;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.util.Xml;import android.view.View;import com.turing.base.R;import java.io.InputStream;import java.util.List;public class Xml2JavaObjectAct extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_xml2_java_object);    }    public void onClick_XMLToObject(View view) {        try {            // 打开资源文件            InputStream is = getResources().openRawResource(R.raw.products);            XML2Product xml2Product = new XML2Product();            // 开始分析priducts.xml文件            android.util.Xml.parse(is, Xml.Encoding.UTF_8, xml2Product);            // 输出转换后的java对象            List<Product> products = xml2Product.getProducts();            String msg = "共" + products.size() + "个产品\n";            for (Product product : products) {                msg += "id:" + product.getId() + " 产品名：" + product.getName()                        + " 价格：" + product.getPrice() + "\n";            }            // 弹出对话框            new AlertDialog.Builder(this).setTitle("产品信息").setMessage(msg)                    .setPositiveButton("关闭", null).show();        } catch (Exception e) {        }    }}

效果图

文件的压缩（Jar，Zip）

效果图

Code

activity_jar_zip.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" >    <Button  android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="onClick_Jar_Compress" android:text="用jar格式压缩文件" />    <Button  android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="onClick_Jar_Uncompress" android:text="解压jar格式文件" />    <Button  android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="onClick_Zip_Compress" android:text="用zip格式压缩文件" />    <Button  android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="onClick_Zip_Uncompress" android:text="解压zip格式文件" /></LinearLayout>

JarZipAct

import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Toast;import com.turing.base.R;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStream;import java.util.jar.JarEntry;import java.util.jar.JarInputStream;import java.util.jar.JarOutputStream;import java.util.zip.ZipEntry;import java.util.zip.ZipInputStream;import java.util.zip.ZipOutputStream;public class JarZipAct extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_jar_zip);    }    public void onClick_Jar_Compress(View view) {        try {            // 使用FileOutputStream对象指定一个要输出的压缩文件(file.jar)            FileOutputStream fos = new FileOutputStream(                    android.os.Environment.getExternalStorageDirectory()                            + "/file.jar");            // 第一步 创建JarOutputStream对象            JarOutputStream jos = new JarOutputStream(fos);            // 第二步 创建一个JarEntry对象，并指定待压缩文件在压缩包中的文件名            JarEntry jarEntry = new JarEntry("strings.xml");            jos.putNextEntry(jarEntry);            InputStream is = getResources().getAssets().open("strings.xml");            byte[] buffer = new byte[8192];            int count = 0;            // 第四步 写入数据            while ((count = is.read(buffer)) >= 0) {                jos.write(buffer, 0, count);            }            // 第五步 关闭当前的JarEntry等对象            is.close();            jos.closeEntry();            jos.close();            Toast.makeText(this, "成功将strings.xml文件以jar格式压缩.", Toast.LENGTH_LONG)                    .show();        } catch (Exception e) {            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();        }    }    public void onClick_Jar_Uncompress(View view) {        try {            // 定义要解压的文件            String filename = android.os.Environment                    .getExternalStorageDirectory() + "/file.jar";            if (!new File(filename).exists()) {                Toast.makeText(this, "压缩文件不存在.", Toast.LENGTH_LONG).show();                return;            }            // 使用FileInputStream对象指定要解压的对象            FileInputStream fis = new FileInputStream(filename);            // 1 创建JarInputStream对象来读取压缩文件（file.jar）            JarInputStream jis = new JarInputStream(fis);            // 2 调用getNextJarEntry方法打开压缩包中的第一个文件 ，如果有多个，多次调用该方法            JarEntry jarEntry = jis.getNextJarEntry();            // 3 输出已解压的文件            FileOutputStream fos = new FileOutputStream(                    android.os.Environment.getExternalStorageDirectory()                            + "/" + jarEntry.getName());            byte[] buffer = new byte[8192];            int count = 0;            // 4 输出已解压的字节流            while ((count = jis.read(buffer)) >= 0) {                fos.write(buffer, 0, count);            }            // 5 关闭            jis.closeEntry();            jis.close();            fos.close();            Toast.makeText(this, "成功解压jar格式的文件.", Toast.LENGTH_LONG).show();        } catch (Exception e) {            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();        }    }    public void onClick_Zip_Compress(View view) {        try {            // 指定了2个待压缩的w文件，都在assets目录中            String[] filenames = new String[]                    {"main.xml", "strings.xml"};            FileOutputStream fos = new FileOutputStream(                    android.os.Environment.getExternalStorageDirectory()                            + "/file.zip");            ZipOutputStream zos = new ZipOutputStream(fos);            int i = 1;            //枚举filenames中的所有待压缩文件            while (i <= filenames.length) {                // 从filenames数组中取出当前待压缩的温佳明，作为压缩后的文件名,以保持要说前后文件名称一致                ZipEntry zipEntry = new ZipEntry(filenames[i - 1]);                // 打开当前的ZipEntry对象                zos.putNextEntry(zipEntry);                InputStream is = getResources().getAssets().open(                        filenames[i - 1]);                byte[] buffer = new byte[8192];                int count = 0;                // 写入数据                while ((count = is.read(buffer)) >= 0) {                    zos.write(buffer, 0, count);                }                zos.flush();                // 关闭当前的ZipEntry对象                zos.closeEntry();                is.close();                i++;            }            zos.finish();            zos.close();            Toast.makeText(this, "成功将main.xml、strings.xml文件以zip格式压缩.",                    Toast.LENGTH_LONG).show();        } catch (Exception e) {            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();        }    }    public void onClick_Zip_Uncompress(View view) {        try {            // 指定待解压的文件           String filename = android.os.Environment                    .getExternalStorageDirectory() + "/file.zip";            if (!new File(filename).exists()) {                Toast.makeText(this, "压缩文件不存在.", Toast.LENGTH_LONG).show();                return;            }            FileInputStream fis = new FileInputStream(filename);            ZipInputStream zis = new ZipInputStream(fis);            ZipEntry zipEntry = null;            // 通过不断调用getNextEntry方法来解压file.zip中所有的文件            while ((zipEntry = zis.getNextEntry()) != null) {                FileOutputStream fos = new FileOutputStream(                        android.os.Environment.getExternalStorageDirectory()                                + "/" + zipEntry.getName());                byte[] buffer = new byte[8192];                int count = 0;                while ((count = zis.read(buffer)) >= 0) {                    fos.write(buffer, 0, count);                }                zis.closeEntry();                fos.close();            }            zis.close();            Toast.makeText(this, "成功解压jar格式的文件.", Toast.LENGTH_LONG).show();        } catch (Exception e) {            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();        }    }}

数据存储之文件存储

概述

Android文件的操作模式

文件的相关操作方法

文件读写的实现

openFileOutput和openFileInput方法

文件存储位置

读取SD卡上的文件

如何判断虚拟和物理两种SDK

用于适配不同型号手机，反射获取SD卡路径和状态

读取raw和assets文件夹下的文件

SAX引擎读取XML文件

sax引擎读取xml文件的原理：

Code

res\raw\product.xml

Product.java

XML2Product.java(DefaultHandler子类)

Xml2JavaObjectAct

效果图

文件的压缩（Jar，Zip）

效果图

Code

activity_jar_zip.xml

JarZipAct

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