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
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; }}