Android数据存储(2)向机身内存(Internal Storage)和SDcard(External Storage)读写数据实例

总的来说向内存和SDcard中读写数据和java io操作基本差不多    而机身内存读取和SDcard读取数据有少许差别

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机身内存数据读写

 1.机身内存读取主要用个两个类文件输入流(FileInputStream)和文件输出流(FileOutputStream): FileInputStream fileInput = this.openFileInput("test.txt") 第一个参数为 data/此程序包名/data/test.txt 文件下 的文件名 ;

FileOutputStream fileOut = this.openFileOutput("test.txt",this.MODE_APPEND)第一个参数表示文件名 第二个参数表示打开的方式  

2.获取了文件输入输出流之后 其后的文件的读写和基本的IO操作一样

SDcard数据读写

 1.SDcard数据读写需要注定的先要在Androidmainfest.xml文件中注册新建删除和读写的权限 :  

       <!-- 在SD卡上创建与删除权限 -->
       <uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" />
      <!-- 向SD卡上写入权限 -->
       <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

 2.读写的基本流程就是: 

   2. 1  通过Environment类的getExternalStorageState()方法来判断手机是否有SDcard:  Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

   2.2  最通过getExternalStorageDirectory()方法来获取文件目录:File file = new File(Environment.getExternalStorageDirectory().getCanonicalPath() + "/test.txt"); 读写的文件都在sdcrad文件夹中 通过File Explorer可以导出来

   2.3 其后就和基本IO操作相同了

  2.4还有要注意一点的是 在运行的模拟器的时候要附带虚拟的SDcard时  要在Run as->Run Configurations 中要关联一下 如下图

机身内存数据读写实例

 <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:layout_gravity="center_horizontal"
     android:orientation="vertical"
     tools:context=".MainActivity" >
     <EditText
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:id="@+id/ed1"
         android:inputType="textMultiLine"/>
     <Button
         android:id="@+id/write"
         android:text="写入"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"/>
     <Button
         android:id="@+id/read"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="读入"/>
     <EditText
         android:id="@+id/ed2"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:inputType="textMultiLine"/>
     <Button
         android:id="@+id/delete"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="删除指定的文件"
         />
     <EditText
         android:id="@+id/ed3"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         />

 </LinearLayout>

 package com.android.xiong.fileiotest;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStreamReader;
 import java.lang.reflect.Array;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;

 import android.app.Activity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;

 public class MainActivity extends Activity {

     private Button read;
     private Button write;
     private EditText ed1;
     private EditText ed2;
     private EditText ed3;
     private Button delete;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         read = (Button) findViewById(R.id.read);
         write = (Button) findViewById(R.id.write);
         delete = (Button) findViewById(R.id.delete);
         ed3 = (EditText) findViewById(R.id.ed3);
         ed2 = (EditText) findViewById(R.id.ed2);
         ed1 = (EditText) findViewById(R.id.ed1);
         write.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 String str = ed1.getText().toString();
                 if (!str.equals("")) {
                     write(str);
                 }

             }
         });
         read.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 read();

             }
         });
         delete.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 String str = ed3.getText().toString();
                 if (!str.equals("")) {
                     deleteFiles(str);
                 } else {
                     ed3.setText(str + ":该文件输入错误或不存在!");
                 }

             }
         });

     }

     private void write(String content) {
         try {
             // 以追加的方式打开文件输出流
             FileOutputStream fileOut = this.openFileOutput("test.txt",
                     this.MODE_APPEND);
             // 写入数据
             fileOut.write(content.getBytes());
             // 关闭文件输出流
             fileOut.close();

         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     private void read() {
         try {
             ed2.setText("");
             // 打开文件输入流
             FileInputStream fileInput = this.openFileInput("test.txt");
             BufferedReader br = new BufferedReader(new InputStreamReader(
                     fileInput));
             String str = null;
             StringBuilder stb = new StringBuilder();
             while ((str = br.readLine()) !=null ) {
                 stb.append(str);
             }
             ed2.setText(stb);
         } catch (Exception e) {
             e.printStackTrace();
         }

     }

     //删除指定的文件
     private void deleteFiles(String fileName) {
         try {
             // 获取data文件中的所有文件列表
             List<String> name = Arrays.asList(this.fileList());
             if (name.contains(fileName)) {
                 this.deleteFile(fileName);
                 ed3.setText(fileName + ":该文件成功删除！");
             } else
                 ed3.setText(fileName + ":该文件输入错误或不存在!");

         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }

 }

SDcard数据读写实例

 <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:gravity="center_horizontal"
     android:orientation="vertical"
     tools:context=".MainActivity" >
     <EditText
         android:id="@+id/ed1"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:inputType="textMultiLine"/>
     <Button
         android:id="@+id/write"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="写入SD卡中"/>
     <Button
         android:id="@+id/read"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="读取SD文件"/>
     <TextView
         android:id="@+id/txt1"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"/>
 </LinearLayout>

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.android.xiong.sdcardtest"
     android:versionCode="1"
     android:versionName="1.0" >

     <uses-sdk
         android:minSdkVersion="14"
         android:targetSdkVersion="17" />
     <!-- 在SD卡上创建与删除权限 -->
     <uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" />
     <!-- 向SD卡上写入权限 -->
     <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="com.android.xiong.sdcardtest.MainActivity"
             android:label="@string/app_name" >
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
     </application>

 </manifest>

 package com.android.xiong.sdcardtest;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStreamReader;

 import android.app.Activity;
 import android.os.Bundle;
 import android.os.Environment;
 import android.view.Menu;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.TextView;

 public class MainActivity extends Activity {

     private Button write;
     private Button read;

     private EditText ed1;
     private TextView txt1;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         write = (Button) findViewById(R.id.write);
         read = (Button) findViewById(R.id.read);
         ed1 = (EditText) findViewById(R.id.ed1);
         txt1 = (TextView) findViewById(R.id.txt1);
         write.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub
                 writeSDcard(ed1.getText().toString());

             }
         });
         read.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub

                 txt1.setText(readSDcard());
             }
         });
     }

     // 把数据写入SD卡

     private void writeSDcard(String str) {

         try {
             // 判断是否存在SD卡
             if (Environment.getExternalStorageState().equals(
                     Environment.MEDIA_MOUNTED)) {
                 // 获取SD卡的目录
                 File file = Environment.getExternalStorageDirectory();
                 FileOutputStream fileW = new FileOutputStream(file.getCanonicalPath() + "/test.txt");
                 fileW.write(str.getBytes());
                 fileW.close();
             }
         } catch (Exception e) {
             e.printStackTrace();
         }

     }

     // 从SD卡中读取数据
     private String readSDcard() {
         StringBuffer str = new StringBuffer();
         try {
             // 判断是否存在SD
             if (Environment.getExternalStorageState().equals(
                     Environment.MEDIA_MOUNTED)) {
                 File file = new File(Environment.getExternalStorageDirectory()
                         .getCanonicalPath() + "/test.txt");
                 // 判断是否存在该文件
                 if (file.exists()) {
                     // 打开文件输入流
                     FileInputStream fileR = new FileInputStream(file);
                     BufferedReader reads = new BufferedReader(
                             new InputStreamReader(fileR));
                     String st = null;
                     while ((st =reads.readLine())!=null ) {
                         str.append(st);
                     }
                     fileR.close();
                 } else {
                     txt1.setText("该目录下文件不存在");
                 }
             }

         } catch (Exception e) {
             e.printStackTrace();
         }
         return str.toString();
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }

 }