第九篇-新建文件夹和文本文件mkdirs,createNewFile

一、新建一个empty activity的项目

二、修改AndroidMainfest.xml，添加用户权限。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.aimee.test1">
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

    <application
        android: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>

　　三、修改activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginTop="8dp"
        android:text="CreateFile"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

　　四、修改MainActivity.java

package com.example.aimee.test1;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    private final int REQUESTCODE=101;
    private String fileName="test";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    create(fileName);
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        });
    }
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,@NonNull int[] grantResults){
        super.onRequestPermissionsResult(requestCode,permissions,grantResults);
        if(requestCode==REQUESTCODE){
            if (permissions[0].equals(Manifest.permission.WRITE_EXTERNAL_STORAGE) && grantResults[0]== PackageManager.PERMISSION_GRANTED){
                Toast.makeText(MainActivity.this,"111",Toast.LENGTH_LONG).show();

            }else {
                Toast.makeText(MainActivity.this,"222",Toast.LENGTH_LONG).show();
            }
        }
    }

    public void create(String fileName) throws IOException {
        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.M){
            int checkSelfPermission=checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE);
            if(checkSelfPermission==PackageManager.PERMISSION_DENIED){
                requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},REQUESTCODE);
            }
        }
        String path=Environment.getExternalStorageDirectory().getAbsolutePath();
        File file=new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+fileName);
        if(!file.exists()){
            boolean isSuccess=file.mkdirs();
            Toast.makeText(MainActivity.this,"333",Toast.LENGTH_LONG).show();

        }else{
            String file_name=path+"/test.txt";
            File f=new File(file_name);
            if(!f.exists()){
                Toast.makeText(MainActivity.this,"文件不存在",Toast.LENGTH_LONG).show();
                f.createNewFile();
            }
            else{
                Toast.makeText(MainActivity.this,"文件创建成功",Toast.LENGTH_LONG).show();
            }
            Toast.makeText(MainActivity.this,path,Toast.LENGTH_LONG).show();
        }
    }
}

　　如此便可以创建一个文件夹test，在手机的根目录下，同时创建一个text.txt的文件，在test文件夹下。