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;
 }
 }
}

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();
 }

}

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


 CDsaveFile
 Hello world!
 Settings
 请输入文件名
 FileName
 请输入文件内容
 FileContent
 存到手机
 存到SD卡
 读取手机
 读取SD
 Here is the result of the reading
 请输入文件名，文件名不可为空
 存储到手机成功
 存储到手机失败啦......
 存储到SD成功
 存储到SD失败啦......
 sd不存在或空间不足
 无法读取手机文件
 无法读取SD文件