要求：

输入文件名，文件内容分别存储在手机内存和外存中，并且都可以读去取出来。

步骤：

1.创建一个名为CDsaveFile的Android项目

2.编写布局文件activity_main.xml：

<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:orientation="vertical" tools:context="hhh.exercise.cdsavefile.MainActivity" > <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/textView_inputFileName" android:textColor="#00ff00" android:textSize="26sp" /> <EditText android:id="@+id/editView_fileName" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:hint="@string/editView_fileName" android:maxLines="1" android:textColor="#ff0000" android:textSize="26sp" /> <requestFocus /> </LinearLayout> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="@string/textView_inputFileContent" android:textColor="#00ff00" android:textSize="26sp" /> <EditText android:id="@+id/editView_fileContent" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:hint="@string/editView_fileContent" android:maxLines="2" android:minLines="2" android:textColor="#ff0000" android:textSize="26sp" /> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <Button android:id="@+id/button_saveToPhone" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="@string/button_saveToPhone" android:textColor="#ff00ff" android:textSize="24sp" /> <Button android:id="@+id/button_readFromPhone" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="@string/button_readFromPhone" android:textColor="#00ffff" android:textSize="24sp" /> </LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <Button android:id="@+id/button_saveToSD" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="@string/button_saveToSD" android:textColor="#ff00ff" android:textSize="24sp" /> <Button android:id="@+id/button_readFromSD" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="@string/button_readFromSD" android:textColor="#00ffff" android:textSize="24sp" /> </LinearLayout> <EditText android:id="@+id/editText_showResult" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:maxLines="3" android:minLines="3" android:hint="@string/editText_showResult" android:textColor="#cccc00" android:textSize="30sp" /></LinearLayout>

3.编写主活动中代码MainActivity.Java：

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; } }}

其中主活动中FileService类是用来处理按钮点击后的事务的具体操作的。代码如下：

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(); }}

strings.xml的代码如下：

<?xml version="1.0" encoding="utf-8"?><resources> <string name="app_name">CDsaveFile</string> <string name="hello_world">Hello world!</string> <string name="action_settings">Settings</string> <string name="textView_inputFileName">请输入文件名</string> <string name="editView_fileName">FileName</string> <string name="textView_inputFileContent">请输入文件内容</string> <string name="editView_fileContent">FileContent</string> <string name="button_saveToPhone">存到手机</string> <string name="button_saveToSD">存到SD卡</string> <string name="button_readFromPhone">读取手机</string> <string name="button_readFromSD">读取SD</string> <string name="editText_showResult">Here is the result of the reading</string> <string name="toast_missFileName">请输入文件名，文件名不可为空</string> <string name="toast_saveToPhone_success">存储到手机成功</string> <string name="toast_saveToPhone_fail">存储到手机失败啦......</string> <string name="toast_saveToSD_success">存储到SD成功</string> <string name="toast_saveToSD_fail">存储到SD失败啦......</string> <string name="toast_noSD">sd不存在或空间不足</string> <string name="toast_readFromPhone_fail">无法读取手机文件</string> <string name="toast_readFromSD_fail">无法读取SD文件</string></resources>

4.在AndroidManifest.xml添加权限

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

5.项目部署在模拟器上：

进入程序后：

把文件存储到手机上并读取：

把文件存储到SD上并读取：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。