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：
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
