Android(安卓)SdCard 新建文件夹并在文件夹中读、写文件

首先你要获取SdCard的读写权限：

    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

我们现在SdCard中新建一个文件夹：名字为 datas

File sd = Environment.getExternalStorageDirectory();String mPath = sd.getPath() + "/datas";File file = new File(mPath);if (!file.exists()) {file.mkdir();}

然后定义一个FileService类用于存放那些读写的函数：

首先我们还是要定义一下我们的文件路径：

private String mPath = Environment.getExternalStorageDirectory().getPath()+ "/datas";

接下来是保存文件到 SdCard中某个目录下的函数：保存类型是txt文本

public void write2Path(String fileName, String content) {File f = new File(mPath + "/" + fileName + ".txt");try {FileOutputStream fileOS = new FileOutputStream(f);try {fileOS.write(content.getBytes());fileOS.close();BufferedWriter buf = new BufferedWriter(new OutputStreamWriter(fileOS));buf.write(content, 0, content.length());buf.flush();buf.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}

接着是从保存文件的那个路径读取我们保存的文件的函数：

public String readFromPath(String fileName) {byte[] data = new byte[1024];try {FileInputStream fileIS = new FileInputStream(mPath + "/" + fileName+ ".txt");// BufferedReader buf = new BufferedReader(new// InputStreamReader(in))byte[] buffer = new byte[1024];ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();int len = -1;while ((len = fileIS.read(buffer)) != -1) {// 读取文件到缓冲区byteArrayOutputStream.write(buffer, 0, len);// 写入到内存}data = byteArrayOutputStream.toByteArray();// 将内存中的二进制数据转为数组byteArrayOutputStream.close();fileIS.close();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}return new String(data);}

完整的FileService类如下：

FileService.java：

package com.llp.classdifine;import java.io.BufferedWriter;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.OutputStreamWriter;import android.content.Context;import android.os.Environment;public class FileService {private Context context;private String mPath = Environment.getExternalStorageDirectory().getPath()+ "/datas";public FileService(Context context) {this.context = context;}/** * 保存文件到sdcard中某个路径下 * @param fileName * @param content */public void write2Path(String fileName, String content) {File f = new File(mPath + "/" + fileName + ".txt");try {FileOutputStream fileOS = new FileOutputStream(f);try {fileOS.write(content.getBytes());fileOS.close();BufferedWriter buf = new BufferedWriter(new OutputStreamWriter(fileOS));buf.write(content, 0, content.length());buf.flush();buf.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}/** * 从sdcard中的某个路径下读取文件 * @param fileName * @return */public String readFromPath(String fileName) {byte[] data = new byte[1024];try {FileInputStream fileIS = new FileInputStream(mPath + "/" + fileName+ ".txt");// BufferedReader buf = new BufferedReader(new// InputStreamReader(in))byte[] buffer = new byte[1024];ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();int len = -1;while ((len = fileIS.read(buffer)) != -1) {// 读取文件到缓冲区byteArrayOutputStream.write(buffer, 0, len);// 写入到内存}data = byteArrayOutputStream.toByteArray();// 将内存中的二进制数据转为数组byteArrayOutputStream.close();fileIS.close();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}return new String(data);}}

MainActivity.java代码如下：

package com.example.sdcard;import java.io.File;import com.example.sdcard.FileService;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends Activity {/** Called when the activity is first created. */private static final String TAG = "MainActivity";private FileService fileService;String fileName;String content;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);File sd = Environment.getExternalStorageDirectory();String mPath = sd.getPath() + "/datas";File file = new File(mPath);if (!file.exists()) {file.mkdir();}Log.v("test", "file.getPath()" + file.getPath());Button button = (Button) findViewById(R.id.btnsave);Button read = (Button) findViewById(R.id.btnread);fileService = new FileService(this);// File file = this.getFilesDir();// 快速得到文件夹// this.getCacheDir();// 获得缓存文件夹final EditText fileNameText = (EditText) findViewById(R.id.fileName);final EditText contenText = (EditText) findViewById(R.id.content);final EditText readtext = (EditText) findViewById(R.id.contentread);button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {fileName = fileNameText.getText().toString();content = contenText.getText().toString();try {// 判断sd卡是否存在手机上并且可以进行读写if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {fileService.write2Path(fileName, content);} else {}} catch (Exception e) {Log.e(TAG, e.toString());}}});read.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubtry {// 判断sd卡是否存在手机上并且可以进行读写if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {fileName = fileNameText.getText().toString();Log.v("test", "fileName" + fileName);readtext.setText(fileService.readFromPath(fileName));} else {}} catch (Exception e) {Log.e(TAG, e.toString());}}});}}

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