Android之File内部存储和File外部存储

File内部存储

1. FileOutPutStream FileInputStream

FileActivity 以及对应的xml文件

package com.example.test0508;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileActivity extends AppCompatActivity {

    private EditText mEtName;
    private Button mBtnSave,mBtnShow;
    private TextView mTvContent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_file);
        mEtName = findViewById(R.id.edit_file_name);
        mBtnSave = findViewById(R.id.btn_file_save);
        mBtnShow = findViewById(R.id.btn_file_show);
        mTvContent = findViewById(R.id.tv_file_content);

        mBtnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                save(mEtName.getText().toString());
            }
        });
        mBtnShow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mTvContent.setText(read());
            }
        });
    }


    /**
     * 用来存储数据
     */
    private void save(String content){
        FileOutputStream fileOutputStream = null;
        try {
            fileOutputStream = openFileOutput("test.txt",MODE_PRIVATE);
            fileOutputStream.write(content.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (fileOutputStream != null) {
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    /**
     * 用来读取信息
     */
    private String read(){
        FileInputStream fileInputStream = null;
        try {
            fileInputStream = openFileInput("test.txt");
            byte[] buffer = new byte[1024];
            StringBuffer stringBuffer = new StringBuffer();
            int len = 0;
            while ((len = fileInputStream.read(buffer))>0){
                stringBuffer.append(new String(buffer,0,len));
            }
            return stringBuffer.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "";
    }


}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="15dp"
    >

    <EditText
        android:id="@+id/edit_file_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入内容"
        />

    <Button
        android:id="@+id/btn_file_save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="保存"
        android:layout_marginTop="10dp"
        />

    <Button
        android:id="@+id/btn_file_show"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="显示"
        android:layout_marginTop="10dp"
        />


    <TextView
        android:id="@+id/tv_file_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        />

</LinearLayout>

---

File外部存储

package com.example.test0508;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileActivity extends AppCompatActivity {

    private EditText mEtName;
    private Button mBtnSave,mBtnShow;
    private TextView mTvContent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_file);
        mEtName = findViewById(R.id.edit_file_name);
        mBtnSave = findViewById(R.id.btn_file_save);
        mBtnShow = findViewById(R.id.btn_file_show);
        mTvContent = findViewById(R.id.tv_file_content);

        mBtnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                save(mEtName.getText().toString());
            }
        });
        mBtnShow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mTvContent.setText(read());
            }
        });
    }


    /**
     * 用来存储数据
     */
    private void save(String content){
        FileOutputStream fileOutputStream = null;
        try {
//内部存储     fileOutputStream = openFileOutput("test.txt",MODE_PRIVATE);
            /**
             * 外部存储存储到sd卡
             */
            File dir = new File(Environment.getExternalStorageDirectory(),"skypan");
            if (!dir.exists()){
                dir.mkdirs();
            }
            File file = new File(dir,"test.txt");
            if (!file.exists()){
                file.createNewFile();
            }
            fileOutputStream = new FileOutputStream(file);

            fileOutputStream.write(content.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (fileOutputStream != null) {
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    /**
     * 用来读取信息
     */
    private String read(){
        FileInputStream fileInputStream = null;
        try {

//            fileInputStream = openFileInput("test.txt");
            File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+File.separator+"skypan","test.txt");
            fileInputStream = new FileInputStream(file);

            byte[] buffer = new byte[1024];
            StringBuffer stringBuffer = new StringBuffer();
            int len = 0;
            while ((len = fileInputStream.read(buffer))>0){
                stringBuffer.append(new String(buffer,0,len));
            }
            return stringBuffer.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "";
    }


}