Android 数据存储-内外部存储测试

案例分析：FilePersistenceTest

在EditText中输入文本内容，退出应用程序或者 单击“保存”按钮时

保存EditText中的数据到名 为“data”的文件中。

打开Device File Explorer，该文件应该存于 /data/data/cn.edu.hunnu.filepersistencetest/files/ 目录

MainActivity.java

package cn.edu.hunnu.filepersisttest;import android.content.Context;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;public class MainActivity extends AppCompatActivity {private EditText edit;private Button bt_save_in;private Button bt_read_in;private Button bt_save_out;private Button bt_read_out;private Button bt_clr_edit;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);edit = (EditText)findViewById(R.id.edit);bt_clr_edit = (Button)findViewById(R.id.bt_clr_edit);bt_clr_edit.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {edit.setText("");}});bt_save_in = (Button)findViewById(R.id.bt_save_in);bt_save_in.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {String inputText = edit.getText().toString();saveToInternalStorage(inputText);Toast.makeText(MainActivity.this,"Save to internal storage succeeded",Toast.LENGTH_SHORT).show();}});bt_read_in =(Button)findViewById(R.id.bt_read_in);bt_read_in.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {String inputText = loadFromInternalStorage();if (!TextUtils.isEmpty(inputText)) {edit.setText(inputText);edit.setSelection(inputText.length());Toast.makeText(MainActivity.this, "Restoring from internal storage succeeded", Toast.LENGTH_SHORT).show();}}});bt_save_out = (Button)findViewById(R.id.bt_save_out);bt_save_out.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {String inputText = edit.getText().toString();saveToExternalStorage(inputText);Toast.makeText(MainActivity.this,"Save to external storage succeeded",Toast.LENGTH_SHORT).show();}});bt_read_out = (Button)findViewById(R.id.bt_read_out);bt_read_out.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {String inputText = loadFromExternalStorage();if (!TextUtils.isEmpty(inputText)) {edit.setText(inputText);edit.setSelection(inputText.length());Toast.makeText(MainActivity.this, "Restoring from external storage succeeded", Toast.LENGTH_SHORT).show();}}});}public void saveToInternalStorage(String inputText) {FileOutputStream out = null;BufferedWriter writer = null;try {out = openFileOutput("data", Context.MODE_PRIVATE);writer = new BufferedWriter(new OutputStreamWriter(out));writer.write(inputText);} catch (IOException e) {e.printStackTrace();} finally {try {if (writer != null) {writer.close();}} catch (IOException e) {e.printStackTrace();}}}public String loadFromInternalStorage() {FileInputStream in = null;BufferedReader reader = null;StringBuilder content = new StringBuilder();try {in = openFileInput("data");reader = new BufferedReader(new InputStreamReader(in));String line = "";while ((line = reader.readLine()) != null) {content.append(line);}} catch (IOException e) {e.printStackTrace();} finally {if (reader != null) {try {reader.close();} catch (IOException e) {e.printStackTrace();}}}return content.toString();}public void saveToExternalStorage(String inputText) {String environment = Environment.getExternalStorageState();if(Environment.MEDIA_MOUNTED.equals(environment)) {//外部设备可以进行读写操作//保存在外部存储根目录，卸载应用时不能删除该文件//File sd_path = Environment.getExternalStorageDirectory();
//            Log.e("MainActivity",sd_path.toString());
//            File file = new File(sd_path,"test.txt");//保存在外部私有目录，卸载时会同时删除该文件String sd_path = this.getExternalFilesDir("").getAbsolutePath();Log.e("MainActivity+",sd_path);File file = new File(sd_path);if(!file.exists()){//判断文件目录是否存在file.mkdirs();}file = new File(sd_path,"text.txt");FileOutputStream fos;try{//写入数据fos = new FileOutputStream(file);OutputStreamWriter  osw = new OutputStreamWriter(fos);osw.write(inputText);osw.flush();osw.close();fos.close();}catch(Exception exception){exception.printStackTrace();}}}public String loadFromExternalStorage() {String content = null;String environment = Environment.getExternalStorageState();if(Environment.MEDIA_MOUNTED.equals(environment)) {
//            File sd_path = Environment.getExternalStorageDirectory();
//            Log.e("MainActivity",sd_path.toString());
//            File file = new File(sd_path,"test.txt");String sd_path = this.getExternalFilesDir("").getAbsolutePath();File file = new File(sd_path,"text.txt");Log.e("MainActivity+",file.getPath());FileInputStream fis;try{//读取文件fis = new FileInputStream(file);InputStreamReader  isr = new InputStreamReader(fis,"UTF-8");char[] input = new char[fis.available()];isr.read(input);content = new String(input);isr.close();fis.close();}catch(Exception exception){exception.printStackTrace();}}return content;}@Overrideprotected void onDestroy() {super.onDestroy();String inputText = edit.getText().toString();saveToInternalStorage(inputText);Toast.makeText(MainActivity.this,"Save to internal storage succeeded",Toast.LENGTH_SHORT).show();}
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:padding="5dp"android:orientation="vertical"tools:context=".MainActivity"><EditTextandroid:id="@+id/edit"android:layout_width="match_parent"android:layout_height="wrap_content"android:ems="10"android:hint="Type something here" /><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><Buttonandroid:id="@+id/bt_save_in"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="保存(内部存储)" /><Buttonandroid:id="@+id/bt_read_in"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="读取(内部存储)" /></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><Buttonandroid:id="@+id/bt_save_out"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="保存(外部存储)" /><Buttonandroid:id="@+id/bt_read_out"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="读取(外部存储)" /></LinearLayout><Buttonandroid:id="@+id/bt_clr_edit"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="清空输入框" /></LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.filepersisttest"><uses-permission android:name = "android.permission.WRITE_EXTERNAL_STORAGE"/><uses-permission android:name = "android.permission. READ_EXTERNAL_STORAGE"/><applicationandroid:allowBackup="true"android:icon="@mipmap/ic_launcher"android:label="@string/app_name"android:roundIcon="@mipmap/ic_launcher_round"android:supportsRtl="true"android:theme="@style/AppTheme"><activity android:name=".MainActivity"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity></application></manifest>