Android实现文件存储并读取的示例代码

要求：

输入文件名，文件内容分别存储在手机内存和外存中，并且都可以读去取出来。

步骤：

1.创建一个名为cdsavefile的android项目

2.编写布局文件activity_main.xml：

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical"
 tools:context="hhh.exercise.cdsavefile.mainactivity" >

 <linearlayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:orientation="horizontal" >

 <textview
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/textview_inputfilename"
  android:textcolor="#00ff00"
  android:textsize="26sp" />

 <edittext
  android:id="@+id/editview_filename"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:gravity="center"
  android:hint="@string/editview_filename"
  android:maxlines="1"
  android:textcolor="#ff0000"
  android:textsize="26sp" />

 <requestfocus />
 </linearlayout>

 <textview
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:text="@string/textview_inputfilecontent"
 android:textcolor="#00ff00"
 android:textsize="26sp" />

 <edittext
 android:id="@+id/editview_filecontent"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:gravity="center"
 android:hint="@string/editview_filecontent"
 android:maxlines="2"
 android:minlines="2"
 android:textcolor="#ff0000"
 android:textsize="26sp" />

 <linearlayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:orientation="horizontal" >

 <button
  android:id="@+id/button_savetophone"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:text="@string/button_savetophone"
  android:textcolor="#ff00ff"
  android:textsize="24sp" />

 <button
  android:id="@+id/button_readfromphone"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:text="@string/button_readfromphone"
  android:textcolor="#00ffff"
  android:textsize="24sp" />
 </linearlayout>

 <linearlayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:orientation="horizontal" >

 <button
  android:id="@+id/button_savetosd"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:text="@string/button_savetosd"
  android:textcolor="#ff00ff"
  android:textsize="24sp" />

 <button
  android:id="@+id/button_readfromsd"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:text="@string/button_readfromsd"
  android:textcolor="#00ffff"
  android:textsize="24sp" />
 </linearlayout>

 <edittext
 android:id="@+id/edittext_showresult"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:gravity="center"
 android:maxlines="3"
 android:minlines="3"
 android:hint="@string/edittext_showresult"
 android:textcolor="#cccc00"
 android:textsize="30sp" />

</linearlayout>

3.编写主活动中代码mainactivity.java：

package hhh.exercise.cdsavefile;

import android.annotation.suppresslint;
import android.annotation.targetapi;
import android.app.activity;
import android.os.build;
import android.os.bundle;
import android.os.environment;
import android.os.statfs;
import android.view.view;
import android.view.window;
import android.view.view.onclicklistener;
import android.widget.button;
import android.widget.edittext;
import android.widget.toast;
import hhh.exercise.service.fileservice;

public class mainactivity extends activity implements onclicklistener {

 private edittext editview_filename;
 private edittext editview_filecontent;
 private edittext edittext_showresult;
 private fileservice service;

 @override
 protected void oncreate(bundle savedinstancestate) {
 super.oncreate(savedinstancestate);
 requestwindowfeature(window.feature_no_title);
 setcontentview(r.layout.activity_main);

 // 实例化 fileservice 类，该类用于处理按钮触发的事件的具体操作
 service = new fileservice(getapplicationcontext());

 // 获取布局中的控件
 editview_filename = (edittext) findviewbyid(r.id.editview_filename);
 editview_filecontent = (edittext) findviewbyid(r.id.editview_filecontent);

 edittext_showresult = (edittext) findviewbyid(r.id.edittext_showresult);

 // 获取按钮并创建触发事件
 ((button) findviewbyid(r.id.button_savetophone)).setonclicklistener(this);
 ((button) findviewbyid(r.id.button_readfromphone)).setonclicklistener(this);
 ((button) findviewbyid(r.id.button_savetosd)).setonclicklistener(this);
 ((button) findviewbyid(r.id.button_readfromsd)).setonclicklistener(this);

 }

 /**
 * 为每一个按钮创建触发的事件
 * 
 * @param v触发事件的view对象
 */
 @override
 public void onclick(view v) {

 string filename = editview_filename.gettext().tostring();
 string filecontent = editview_filecontent.gettext().tostring();

 // 判断文件名，文件名要求不为空
 if (filename == null || "".equals(filename.trim())) {
  toast.maketext(getapplicationcontext(), r.string.toast_missfilename, 0).show();
 } else {
  // 输入的文件名不为空，对每个按钮的触发事件进行处理

  string result = null;

  switch (v.getid()) {
  case r.id.button_savetophone:
  try {
   // 存储文件到手机上
   service.savetophone(filename, filecontent);

   // 清空内容输入框
   editview_filecontent.settext("");

   toast.maketext(getapplicationcontext(), r.string.toast_savetophone_success, 0).show();
  } catch (exception e) {
   toast.maketext(getapplicationcontext(), r.string.toast_savetophone_fail, 0).show();
   e.printstacktrace();
  }
  break;

  case r.id.button_readfromphone:
  try {
   // 读取手机文件中的内容
   result = service.readfromphone(filename);

   // 将内容显示在空间中
   edittext_showresult.settext(result);

  } catch (exception e) {
   toast.maketext(getapplicationcontext(), r.string.toast_readfromphone_fail, 0).show();
   e.printstacktrace();
  }
  break;

  case r.id.button_savetosd:
  // 判断sd卡是否存在，并且可以使用，空间足够
  int flag = judgesd();
  if (flag == 0 || flag == 1) {
   toast.maketext(getapplicationcontext(), r.string.toast_nosd, 0).show();
  } else {
   try {
   service.savetosd(filename, filecontent);
   editview_filecontent.settext("");
   toast.maketext(getapplicationcontext(), r.string.toast_savetosd_success, 0).show();
   } catch (exception e) {
   toast.maketext(getapplicationcontext(), r.string.toast_savetosd_fail, 0).show();
   e.printstacktrace();
   }
  }
  break;

  case r.id.button_readfromsd:
  // 判断sd卡能够读取
  int flag2 = judgesd();
  if (flag2 != 0) {

   try {
   result = service.readfromsd(filename);
   edittext_showresult.settext(result);
   } catch (exception e) {
   toast.maketext(getapplicationcontext(), r.string.toast_readfromsd_fail, 0).show();
   e.printstacktrace();
   }
  } else {
   toast.maketext(getapplicationcontext(), r.string.toast_nosd, 0).show();
  }
  break;

  default:
  break;
  }
 }
 }

 /**
 * 判断sd卡是否存在，并且可以读写，空间足够。
 * 
 * @return
 */
 @targetapi(build.version_codes.jelly_bean_mr2)
 @suppresslint("newapi")
 @suppresswarnings("deprecation")
 private int judgesd() {

 int flag = 0;

 // sd卡存在且可以读取
 if (environment.media_mounted.equals(environment.getexternalstoragestate())) {

  // 获取sd卡的路劲
  string path = environment.getexternalstoragedirectory().getpath();

  // 调用c的类库
  statfs fs = new statfs(path);

  long availabebolocks = 0;
  long bolocksize = 0;

  // 为了兼容低版本，所以获取当前应用所在系统的版本号，进而判断
  // 分为两种。版本低于4.3的和高于等于4.3的(4.3的版本等级为18)
  if (build.version.sdk_int >= 18) {
  // 获取可用的块
  availabebolocks = fs.getavailableblockslong();
  // 获取每个块的大小
  bolocksize = fs.getblocksizelong();

  } else {
  // 获取可用的块
  availabebolocks = fs.getavailableblocks();
  // 获取每个块的大小
  bolocksize = fs.getblocksize();
  }

  // 计算sd卡可用空间的大小（单位用mb）
  long availablebyte = availabebolocks * bolocksize;
  float availablemb = (float) availablebyte / 1024 / 1024;

  // 空间小于1mb，不允许写入数据（实际上时空间小于写入文件的大小，就不允许写入，这里时认为文件大小为1mb）
  if (availablemb < 1) {
  flag = 1;
  } else {
  flag = 2;
  }

  return flag;

 } else {
  return flag;
 }
 }
}

其中主活动中fileservice类是用来处理按钮点击后的事务的具体操作的。代码如下：

package hhh.exercise.service;

import java.io.bufferedreader;
import java.io.bufferedwriter;
import java.io.file;
import java.io.filereader;
import java.io.filewriter;
import java.io.inputstream;
import java.io.inputstreamreader;
import java.io.outputstream;
import java.io.outputstreamwriter;

import android.content.context;
import android.os.environment;

/**
 * @author hhh
 *
 */
public class fileservice {

 public context context;

 public fileservice(context context) {
 super();
 this.context = context;
 }

 /**
 * 保存文件到手机内存中
 * 
 * @param filename
 * @param filecontent
 * @return
 * @throws exception
 */
 public void savetophone(string filename, string filecontent) throws exception {

 outputstream outputstream = context.openfileoutput(filename, context.mode_private);
 bufferedwriter bufferedwriter = new bufferedwriter(new outputstreamwriter(outputstream));
 bufferedwriter.write(filecontent);
 bufferedwriter.close();
 }

 /**
 * 从手机中读取文件
 * 
 * @param filename
 * @return
 * @throws exception
 */
 public string readfromphone(string filename) throws exception {

 stringbuilder sbuilder = new stringbuilder();

 inputstream inputstream = context.openfileinput(filename);
 bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(inputstream));
 string line = null;
 while ((line = bufferedreader.readline()) != null) {
  sbuilder.append(line);
 }
 bufferedreader.close();

 return sbuilder.tostring();
 }

 /**
 * 把输入的内容存入到sd卡中
 * 
 * @param filename
 * @param filecontent
 * @throws exception
 */
 public void savetosd(string filename, string filecontent) throws exception {

 // 获取sd卡的路径
 string path = environment.getexternalstoragedirectory().getpath();

 file file = new file(path, filename);
 bufferedwriter bufferedwriter = new bufferedwriter(new filewriter(file));
 bufferedwriter.write(filecontent);
 bufferedwriter.close();

 }

 /**
 * 从sd卡中读取文件
 * 
 * @param filecontent
 * @return
 * @throws exception
 */
 public string readfromsd(string filename) throws exception {

 stringbuilder sbuilder = new stringbuilder();
 string path = environment.getexternalstoragedirectory().getpath();

 bufferedreader bufferedreader = new bufferedreader(new filereader(new file(path, filename)));
 string line = null;
 while ((line = bufferedreader.readline()) != null) {
  sbuilder.append(line);
 }
 bufferedreader.close();

 return sbuilder.tostring();
 }

}

strings.xml的代码如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>

 <string name="app_name">cdsavefile</string>
 <string name="hello_world">hello world!</string>
 <string name="action_settings">settings</string>
 <string name="textview_inputfilename">请输入文件名</string>
 <string name="editview_filename">filename</string>
 <string name="textview_inputfilecontent">请输入文件内容</string>
 <string name="editview_filecontent">filecontent</string>
 <string name="button_savetophone">存到手机</string>
 <string name="button_savetosd">存到sd卡</string>
 <string name="button_readfromphone">读取手机</string>
 <string name="button_readfromsd">读取sd</string>
 <string name="edittext_showresult">here is the result of the reading</string>
 <string name="toast_missfilename">请输入文件名，文件名不可为空</string>
 <string name="toast_savetophone_success">存储到手机成功</string>
 <string name="toast_savetophone_fail">存储到手机失败啦......</string>
 <string name="toast_savetosd_success">存储到sd成功</string>
 <string name="toast_savetosd_fail">存储到sd失败啦......</string>
 <string name="toast_nosd">sd不存在或空间不足</string>
 <string name="toast_readfromphone_fail">无法读取手机文件</string>
 <string name="toast_readfromsd_fail">无法读取sd文件</string>

</resources>

4.在androidmanifest.xml添加权限

 <uses-permission android:name="android.permission.write_external_storage"/>
 <uses-permission android:name="android.permission.read_external_storage"/>

5.项目部署在模拟器上：

进入程序后：

把文件存储到手机上并读取：

 

把文件存储到sd上并读取：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。