Android课程---关于数据存储的学习

activity_data1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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.hanqi.test5.DataActivity1"
    android:orientation="vertical">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_1"
        android:hint="key"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_2"
        android:hint="value"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="保存"
            android:layout_weight="1"
            android:onClick="bt1_OnClick"/>

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="读取"
            android:layout_weight="1"
            android:onClick="bt2_OnClick"/>
    </LinearLayout>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_3"
        android:hint="要存储的内容"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_4"
        android:hint="从文件中读取的内容"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="保存"
            android:layout_weight="1"
            android:onClick="bt3_OnClick"/>

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="读取"
            android:layout_weight="1"
            android:onClick="bt4_OnClick"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="保存文件"
            android:layout_weight="1"
            android:onClick="bt5_OnClick"/>

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="读取文件"
            android:layout_weight="1"
            android:onClick="bt6_OnClick"/>
    </LinearLayout>
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/vipflower"
        android:id="@+id/iv_4"/>
</LinearLayout>

DataActivity1.java

package com.hanqi.test5;

import android.content.SharedPreferences;
import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.PrintStream;

public class DataActivity1 extends AppCompatActivity {

    EditText et_1;
    EditText et_2;

    EditText et_3;
    EditText et_4;

    ImageView iv_4;

    SharedPreferences sp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_data1);

        et_1 = (EditText)findViewById(R.id.et_1);
        et_2 = (EditText)findViewById(R.id.et_2);

        et_3 = (EditText)findViewById(R.id.et_3);
        et_4 = (EditText)findViewById(R.id.et_4);

        iv_4 = (ImageView)findViewById(R.id.iv_4);

        //1.获取sp实例，指定了文件名和操作模式
        sp = getSharedPreferences("mydata",MODE_PRIVATE);

    }

    //操作assets内的文件
    public void bt5_OnClick(View v)
    {
      //1.获取AssetManager管理器
        AssetManager am = getAssets();

        try
        {
            //2.打开文件,获取输入流
            InputStream is = am.open("yuantu.png");

            //3.获取输出流
            FileOutputStream fos = openFileOutput("yuantu.png",MODE_PRIVATE);

            //4.边读边写
            byte[] b = new byte[1024];

            int i =0;

            while ((i = is.read(b))>0)
            {
                fos.write(b,0,i);
            }
            fos.close();
            is.close();

            Toast.makeText(DataActivity1.this, "保存成功", Toast.LENGTH_SHORT).show();

        }
        catch (Exception e)
        {
            e.printStackTrace();
            Toast.makeText(DataActivity1.this, "保存失败", Toast.LENGTH_SHORT).show();
        }
    }

    //从手机内部存储读图片文件
    public void bt6_OnClick(View v)
    {
        //改变ImageView的图片来源，指向手机存储空间

        //1.获取文件存储的绝对路径
        String filepath = getFilesDir().getAbsolutePath();

        //2.组合图片文件的完整路径
        filepath += "/yuantu.png";

        //3.生成位图实例
        Bitmap bm = BitmapFactory.decodeFile(filepath);

        //4.改变ImageView的图片来源
        iv_4.setImageBitmap(bm);
    }

    //文件名
    final String FILENAME = "test.txt";
    public void bt3_OnClick(View v)
    {
        //1.获取要存储的内容
        String content = et_3.getText().toString();
        //2.获取输出流
        try
        {
        FileOutputStream fos_1 = openFileOutput(FILENAME,MODE_APPEND);

            //3.构造PrintStream
            PrintStream pm = new PrintStream(fos_1);

            //4.写入内容
            pm.println(content);

            //5.关闭
            pm.close();

            fos_1.close();

            Toast.makeText(DataActivity1.this, "保存成功", Toast.LENGTH_SHORT).show();
        }
        catch (Exception e)
        {
            e.printStackTrace();

            Toast.makeText(DataActivity1.this, "保存失败", Toast.LENGTH_SHORT).show();
        }
    }

    public void bt4_OnClick(View v)
    {
        try
        {
            //1.获取输入流
            FileInputStream fis = openFileInput(FILENAME);

            //2.定义读取的数组
            byte[] b = new byte[1024];

            //3.读出的数据的长度
            int i =0;

            StringBuilder sb_1 = new StringBuilder();

            while ((i=fis.read(b))>0)
            {
                sb_1.append(new String(b,0,i) );
            }
            fis.close();

            //设置显示读出内容
            et_4.setText(sb_1);

            Toast.makeText(DataActivity1.this, "读取成功", Toast.LENGTH_SHORT).show();
        }
        catch (Exception e)
        {
            e.printStackTrace();
            Toast.makeText(DataActivity1.this, "读取失败", Toast.LENGTH_SHORT).show();
        }
    }

    //保存
    public void bt1_OnClick(View v) {
        //1.获取key和value
        String key = et_1.getText().toString();
        String value = et_2.getText().toString();

        if (key.length() == 0 || value.length() == 0) {
            Toast.makeText(DataActivity1.this, "key或value不能为空", Toast.LENGTH_SHORT).show();
        }
        else {
            //2.取得Editor
            SharedPreferences.Editor editor = sp.edit();

            //3.放入键值对
            editor.putString(key, value);

            //4.提交保存
            boolean b = editor.commit();

            if (b) {
                Toast.makeText(DataActivity1.this, "保存成功", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(DataActivity1.this, "保存失败", Toast.LENGTH_SHORT).show();
            }
        }
    }
    //读取
    public void bt2_OnClick(View v)
    {

        //1.获取要读的key
        String key = et_1.getText().toString();

        //2.读并设置文本框
        et_2.setText(sp.getString(key, "没有发现key"));

    }

}

数据存储总结之思维导图：