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：