Android文件存储

Android文件读写主要是通过​​openFileInput​​​和​​openFileOutput​​​进行读写，分别返回​​FileInputStream​​​和​​FileOutputStream​​对象。

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.filepersistencetest">

    <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>

activity_main.xml

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

    <EditText
        android:id="@+id/edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="在这儿输入点什么"/>
</LinearLayout>

MainActivity.java

package com.example.filepersistencetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.widget.EditText;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity {
    private EditText edit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit = findViewById(R.id.edit);
        String inputText  = load();
        if (!TextUtils.isEmpty(inputText)) {
            edit.setText(inputText);
            edit.setSelection(inputText.length());
            Toast.makeText(this, "重新加载数据成功！", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        String inputText = edit.getText().toString();
        save(inputText);
        Log.d("Test", inputText);
    }

    /**
     * 保存数据到文件
     * @param inputText
     */
    public void save(String inputText) {
        FileOutputStream out = null;
        BufferedWriter writer = null;
        try {
            out = openFileOutput("data", Context.MODE_PRIVATE);
            writer = new BufferedWriter(new OutputStreamWriter(out));
            writer.write(inputText);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (writer != null) {
                    writer.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 加载文件数据
     * @return String
     */
    public String load() {
        FileInputStream in = null;
        BufferedReader reader = null;
        StringBuffer content = new StringBuffer();
        try {
            in = openFileInput("data");
            reader = new BufferedReader(new InputStreamReader(in));
            String line = "";
            while ((line = reader.readLine()) != null) {
                content.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return content.toString();
    }
}