文件操作案例

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将EditText中输入的数据保存下来，点击按钮后再讲文件中的读取出来显示TextView中
这里写图片描述

MainActivity.class

package com.superxingyun.filedemo2;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;import java.io.ByteArrayOutputStream;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;public class MainActivity extends AppCompatActivity {    private EditText edit;    private Button btn;    private TextView text;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //初始化控件        edit = (EditText) findViewById(R.id.edit);        btn = (Button) findViewById(R.id.btn);        text = (TextView) findViewById(R.id.txt);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                WriteFiles(edit.getText().toString());                text.setText(readFiles());            }        });    }    //保存文件的内容    public void WriteFiles(String content){        try {            FileOutputStream fos = openFileOutput("zzzzz.txt", MODE_PRIVATE);//创建文件以及其权限            fos.write(content.getBytes());            fos.close();        }        catch (FileNotFoundException e){            e.printStackTrace();        }        catch (IOException e) {            e.printStackTrace();        }    }    //读取文件的内容    public String readFiles(){        String content = null;        try {            FileInputStream fis = openFileInput("zzzzz.txt");            ByteArrayOutputStream baos = new ByteArrayOutputStream();            byte buffer [] = new byte[1024];            int len = 0;            while ((len = fis.read(buffer)) != -1){                baos.write(buffer, 0 ,len);            }            content = baos.toString();            fis.close();            baos.close();        }        catch (FileNotFoundException e) {            e.printStackTrace();        }catch (IOException e) {            e.printStackTrace();        }        return content;    }}

如要想将文件放入外置SD卡中需要添加权限：

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

<?xml version="1.0" encoding="utf-8"?><RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.superxingyun.filedemo2.MainActivity">    <EditText        android:id="@+id/edit"        android:layout_width="match_parent"        android:layout_height="150dp"        android:layout_marginTop="15dp"/>    <Button        android:id="@+id/btn"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/edit"        android:layout_alignParentRight="true"        android:layout_alignParentEnd="true"        android:layout_marginTop="30dp" />    <TextView        android:id="@+id/txt"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_marginTop="29dp"        android:layout_below="@+id/btn"        android:layout_alignParentRight="true"        android:layout_alignParentEnd="true" /></RelativeLayout>

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