Android中5大数据存储（二）---文件存储

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使用SharedPreferences可以方便的完成数据的存储功能，但是其只能保存一些很简单的数据，如果想存储更多的数据，则需要使用文件存储操作。对于文件的存储操作，在Android中有两种形式：

注意：程序中依然使用前面文章所述的Intent实现Activity的调转显示文件中信息

形式一：直接利用Activity提供的文件操作方法。此类操作的所有文件路径只能是“\data\data\<package name>\files\文件名称”。

跳转Activity（FileOperate--->ShowOperate）

源文件及截图：

activity_save.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="cn.lh.filedata.FileOperate" >    <Button        android:id="@+id/savebtn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/savebtn" />    <Button        android:id="@+id/showbtn"        android:layout_toRightOf="@id/savebtn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/showbtn" />    </RelativeLayout>

activity_load.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="cn.lh.filedata.ShowOperate" >    <TextView        android:id="@+id/msg"        android:textSize="22sp"        android:textColor="#ff00ff"        android:layout_width="match_parent"        android:layout_height="wrap_content"/></RelativeLayout>

FileOperate.java

package cn.lh.filedata;import java.io.FileOutputStream;import java.io.PrintStream;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class FileOperate extends Activity {private static final String FileName = "lh.txt";private Button savebtn = null;private Button showbtn = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_save);        savebtn = (Button)findViewById(R.id.savebtn);        savebtn.setOnClickListener(new saveListener());        showbtn = (Button)findViewById(R.id.showbtn);        showbtn.setOnClickListener(new showListener());            }    public class saveListener implements OnClickListener{@Overridepublic void onClick(View v) {// TODO Auto-generated method stub//文件输出流FileOutputStream output = null;try {output = openFileOutput(FileName, MODE_PRIVATE);} catch (Exception e) {e.printStackTrace();}PrintStream out = new PrintStream(output);out.println("姓名：Norysn;");out.println("年龄：26;");out.println("地址：安徽合肥");out.close();}        }        public class showListener implements OnClickListener{    @Overridepublic void onClick(View v) {//实现Activity的跳转Intent intent = new Intent();intent.setClass(FileOperate.this, ShowOperate.class);startActivity(intent);}        }}

ShowOperate.java

package cn.lh.filedata;import java.io.FileInputStream;import java.util.Scanner;import android.app.Activity;import android.os.Bundle;import android.widget.TextView;public class ShowOperate extends Activity {private static final String FileName = "lh.txt";private TextView msg = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);super.setContentView(R.layout.activity_load);msg = (TextView)findViewById(R.id.msg);//文件输入流FileInputStream input = null;try {//找到指定的文件输入流对象input = openFileInput(FileName);} catch (Exception e) {e.printStackTrace();}//定义ScannerScanner scan = new Scanner(input);while(scan.hasNext()){msg.append(scan.next()+"\n");}//关闭输入流scan.close();}}

形式二：利用JavaIO流执行操作。此类操作的文件可以是任意路径（包括sdcard）下，但是需要为其操作授权。

跳转Activity（FileIoOperate-->ShowData）

源文件及截图

activity_save.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="cn.norysn.iosave.FileIoOperate" >    <Button        android:id="@+id/savebtn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/savebtn" />    <Button        android:id="@+id/showbtn"        android:layout_toRightOf="@id/savebtn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/showbtn" />    </RelativeLayout>

activity_show.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="cn.norysn.iosave.ShowData" >    <TextView        android:id="@+id/msg"        android:textSize="22sp"        android:textColor="#ff00ff"        android:layout_width="match_parent"        android:layout_height="wrap_content"/></RelativeLayout>

FileIoOperate.java

package cn.norysn.iosave;import java.io.File;import java.io.FileOutputStream;import java.io.PrintStream;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.os.Environment;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class FileIoOperate extends Activity {private Button savebtn = null;private Button showbtn = null;//保存文件private static final String FILENAME = "iodata.txt";//保存文件夹private static final String DIR = "/iodata/";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_save);        savebtn = (Button)findViewById(R.id.savebtn);        savebtn.setOnClickListener(new btnListener());        showbtn = (Button)findViewById(R.id.showbtn);        showbtn.setOnClickListener(new btnListener());    }    public class btnListener implements OnClickListener{@Overridepublic void onClick(View v) {// TODO Auto-generated method stubswitch(v.getId()){case R.id.savebtn:save();break;case R.id.showbtn:IntentActivity();break;}}    }    public void save(){    //判断SD卡是否存在    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){    //定义File类对象        File file = new File(Environment.getExternalStorageDirectory().toString()        +DIR+FILENAME);        //判断文件是否存在，如果不存在，则创建        if(!(file.getParentFile().exists())){        //创建文件夹        file.getParentFile().mkdirs();        }        //打印流输入对象        PrintStream out = null;        try {        //追加文件out = new PrintStream(new FileOutputStream(file,true));//String str = "作者：By Norysn";out.println("author：By Norysn");out.println("age：26");        } catch (Exception e) {e.printStackTrace();}finally{if(out != null){//关闭打印流out.close();}}            }else{    Toast.makeText(this, "保存失败，SD卡不存在", Toast.LENGTH_SHORT).show();    }    }    public void IntentActivity(){    //实现Activity调转显示    Intent intent = new Intent();    intent.setClass(FileIoOperate.this, ShowData.class);    startActivity(intent);    }   }

ShowData.java

package cn.norysn.iosave;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStreamReader;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.widget.TextView;import android.widget.Toast;public class ShowData extends Activity {private TextView msg = null;//文本显示//保存文件private static final String FILENAME = "iodata.txt";//保存文件夹private static final String DIR = "/iodata/";@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);super.setContentView(R.layout.activity_show);msg = (TextView)findViewById(R.id.msg);show();} public void show(){    //判断SD卡是否存在,如果不存在则Toast提示    if(Environment.getExternalStorageState().equals(    Environment.MEDIA_MOUNTED)){    //创建File对象    File file = new File(Environment.getExternalStorageDirectory().toString()    +DIR+FILENAME);    //判断文件夹是否存在，不存在则创建文件    if(!(file.getParentFile().exists())){    file.getParentFile().mkdirs();    }    //扫描输入流    //Scanner scan = null;    BufferedReader br = null;    try {    //实例化Scanner//scan = new Scanner(new FileInputStream(file));//while(scan.hasNext()){//循环读取//msg.append(scan.next()+"\n");//}    InputStreamReader in = new InputStreamReader(new FileInputStream(file));    //实例化BufferReader对象    br = new BufferedReader(in);    String str = null;    while((str=br.readLine()) != null){    msg.append(str+"\n");    //msg.setText(str);    }    in.close();} catch (Exception e) {e.printStackTrace();}finally{//关闭输入流//if(scan != null){//scan.close();//}if(br != null){try {br.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}    }else{    Toast.makeText(this, "保存失败，SD卡不存在", Toast.LENGTH_SHORT).show();    }    }}

AndroidManifast.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="cn.norysn.iosave"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="16"        android:targetSdkVersion="16" />    <uses-permission         android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>     <application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name=".FileIoOperate"            android:label="@string/app_name" >            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>        <activity android:name=".ShowData"></activity>    </application></manifest>

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