Android存儲之一利用本地存儲數據

首先創建佈局文件：

<?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=".MainActivity">

    <EditText

        android:id="@+id/et"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:hint="請輸入"
        android:gravity="left|top"
       />
    <Button
        android:id="@+id/bt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="保存"></Button>

</LinearLayout>

數據存儲過程：

  OutputStream outputStream = openFileOutput("geoff", Context.MODE_PRIVATE);
            outputStream.write(s.getBytes());
            outputStream.flush();

解釋下用openFileOutput（）方法獲取outputstream對象，
寫入到geoff文件中，
write（）方法中的s是字符串，之後調用flush（）方法；
這樣保證內存中的數據寫入到本地；
以上是存的過程；

下邊是取數據的過程：

         InputStream inputStream =openFileInput("geoff");
            byte[] bytes =new byte[inputStream.available()];
            inputStream.read(bytes);
            inputStream.close();
            et.setText(new String(bytes));

用openFileInput方法獲取inputstream對象，
inputStream.available()本地數據讀取沒什麼問題，
讀取出來之後給控件設值。

下面代碼的實例：

package com.example.myapplication;

import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class MainActivity extends AppCompatActivity {
    private Button bt;
    private EditText et;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt = findViewById(R.id.bt);
        et = findViewById(R.id.et);
        try {
            showText();
        } catch (IOException e) {
            e.printStackTrace();
        }


        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                saveEdit();
            }
        });
    }

    private void showText() throws IOException {
        try {
            InputStream inputStream =openFileInput("geoff");
            byte[] bytes =new byte[inputStream.available()];
            inputStream.read(bytes);
            inputStream.close();
            et.setText(new String(bytes));

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }

    private void saveEdit() {
        String s = et.getText().toString();
        try {
            OutputStream outputStream = openFileOutput("geoff", Context.MODE_PRIVATE);
            outputStream.write(s.getBytes());
            outputStream.flush();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

這樣就能實現簡單的本地數據存儲。