Android中实现保存和读取文本文件到内部存储器(实现简易的记事本为例)

场景

在Android应用中需要将某些文本内容保存到存储器中的txt文件中。

在显示时还需要将txt文件的内容读取加载出来。形成一个简单记事本的效果

注：

博客：
https://blog.csdn.net/badao_liumang_qizhi
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实现

首先新建一个Activity并设计页面布局如上，xml布局代码为

<?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:orientation="vertical"
    tools:context=".StoreTextActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:gravity="center_horizontal"
        android:textSize="18sp"
        android:textColor="@android:color/black"
        android:text="记事本"
        />

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="#FFC8C8C8"/>
    <EditText
        android:id="@+id/edit_text"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:gravity="start"
        android:hint="请输入文本"
        android:inputType="textMultiLine"
        />

    <Button
        android:id="@+id/btn_save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="saveFile"
        android:text="保存"
        />
</LinearLayout>

然后在Activity,在保存按钮的点击事件执行的保存到文件的方法中，将editText的文本内容保存到文件

   /***
     * 保存到文件
     * @param str
     */
    public void saveFile(String str)
    {
        FileOutputStream fos = null;
        BufferedWriter writer = null;

        try {
            fos = openFileOutput("badao.txt", Context.MODE_PRIVATE);
            writer = new BufferedWriter(new OutputStreamWriter(fos));
            try {
                writer.write(str);
                Toast.makeText(this,"保存成功",Toast.LENGTH_LONG).show();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }finally {
            if(writer!=null)
            {
                try {
                    writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

保存成功后，文件会在内部存储下data/data/包名/files下找到

然后在onCreate方法中，首先执行从txt加载内容的方法

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_store_text);
        editText = findViewById(R.id.edit_text);
        String str = load();
        if(!(TextUtils.isEmpty(str)))
        {
            editText.setText(str);
            Toast.makeText(this,"加载成功",Toast.LENGTH_LONG).show();
        }
    }

在加载内容的方法load中

   /***
     * 从文件中加载
     * @return
     */
    public String load()
    {
        FileInputStream fis = null;
        BufferedReader reader = null;
        StringBuilder content = new StringBuilder();
        try {
            fis = openFileInput("badao.txt");
            reader = new BufferedReader(new InputStreamReader(fis));
            String str;

            while ((str=reader.readLine())!=null) {
                content.append(str);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(reader!=null)
            {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(fis!=null)
            {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return content.toString();
    }

activity的完整代码

package com.badao.androidstudy;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class StoreTextActivity extends AppCompatActivity {

    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_store_text);
        editText = findViewById(R.id.edit_text);
        String str = load();
        if(!(TextUtils.isEmpty(str)))
        {
            editText.setText(str);
            Toast.makeText(this,"加载成功",Toast.LENGTH_LONG).show();
        }
    }


    public void saveFile(View view)
    {
        saveFile(editText.getText().toString());
    }


    /***
     * 从文件中加载
     * @return
     */
    public String load()
    {
        FileInputStream fis = null;
        BufferedReader reader = null;
        StringBuilder content = new StringBuilder();
        try {
            fis = openFileInput("badao.txt");
            reader = new BufferedReader(new InputStreamReader(fis));
            String str;

            while ((str=reader.readLine())!=null) {
                content.append(str);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(reader!=null)
            {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(fis!=null)
            {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return content.toString();
    }

    /***
     * 保存到文件
     * @param str
     */
    public void saveFile(String str)
    {
        FileOutputStream fos = null;
        BufferedWriter writer = null;

        try {
            fos = openFileOutput("badao.txt", Context.MODE_PRIVATE);
            writer = new BufferedWriter(new OutputStreamWriter(fos));
            try {
                writer.write(str);
                Toast.makeText(this,"保存成功",Toast.LENGTH_LONG).show();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }finally {
            if(writer!=null)
            {
                try {
                    writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

运行之后，输入一些文本内容，点击保存

然后退出app重新启动后