Android學習之-------SharedPreferences存儲+SD卡存儲

SharedPreferences存儲+SD卡存儲

SharedPreferences

特點:

保存少量的數據，且這些數據的格式非常簡單。 存儲5種原始數據類型: boolean, float, int, long, String
比如應用程序的各種配置信息（如是否打開音效、是否使用震動效果、小遊戲的玩家積分等），記住密碼功能，音樂播放器播放模式。

使用方式

**步驟1：**得到SharedPreferences對象 getSharedPreferences(“文件的名稱”,“文件的類型”);
(1).Context.MODE_PRIVATE:指定該SharedPreferences數據只能被應用程序讀寫
(2)MODE_APPEND：檢查文件是否存在，存在就往文件追加內容，否則就創建新文件。
以下不在建議使用
(3).Context.MODE_WORLD_READABLE:指定該SharedPreferences數據能被其他
應用程序讀，但不能寫。
(4).Context,MODE_WORLD_WRITEABLE:指定該SharedPreferences數據能被其他應用程序寫，但不能讀。
**步驟2：**得到 SharedPreferences.Editor編輯對象
SharedPreferences.Editor editor=sp.edit();
**步驟3：**添加數據
editor.putBoolean(key,value)
editor.putString()
editor.putInt()
editor.putFloat()
editor.putLong()
**步驟4：**提交數據 editor.commit()或者apply()(推薦用這個.異步提交)
Editor其他方法： editor.clear() 清除數據 editor.remove(key) 移除指定key對應的數據

寫數據

//SP寫數據

private void write() {
    //TODO  1:得到SharedPreferences對象
    //參數一 xml文件的名字 參數二 模式 MODE_PRIVATE 指定該SharedPreferences數據只能被本應用程序讀寫
    SharedPreferences preferences = getSharedPreferences("songdingxing", MODE_PRIVATE);
    //TODO 2:獲得編輯對象
    SharedPreferences.Editor editor = preferences.edit();
    //TODO 3:寫數據
    editor.putString("username","送定型");
    editor.putInt("age",18);
    editor.putBoolean("isMan",false);
    editor.putFloat("price",12.4f);
    editor.putLong("id",5425054250l);
    //TODO 4:提交數據
    editor.commit();
}

讀數據

//讀數據

private void read() {
    //TODO  1:得到SharedPreferences對象
    //參數一 xml文件的名字 參數二 模式 MODE_PRIVATE 指定該SharedPreferences數據只能被本應用程序讀寫
    SharedPreferences preferences = getSharedPreferences("sgf", MODE_PRIVATE);
    //TODO 2：直接讀取
    //參數一 鍵  參數二 找不到的時候給默認值
    String username=preferences.getString("username","");
    int age=preferences.getInt("age",0);
    boolean isMan=preferences.getBoolean("isMan",false);
    float price=preferences.getFloat("price",0.0f);
    long id=preferences.getLong("id",0l);
    Toast.makeText(this, username+":"+age+":"+isMan+":"+price+"："+id, Toast.LENGTH_SHORT).show();
}

---

登錄註冊案例

xml佈局

<?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"
    tools:context=".LoginActivity"
    android:orientation="vertical"
    android:gravity="center">
    <EditText
        android:layout_marginLeft="50dp"
        android:layout_marginRight="50dp"
        android:id="@+id/username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <EditText
        android:layout_marginLeft="50dp"
        android:layout_marginRight="50dp"
        android:id="@+id/password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <RelativeLayout
        android:layout_marginLeft="50dp"
        android:layout_marginRight="50dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <CheckBox
            android:layout_alignParentLeft="true"
            android:id="@+id/cb_remember"
            android:text="記住密碼"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
        <Button
            android:layout_alignParentRight="true"
            android:id="@+id/login"
            android:text="登錄"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </RelativeLayout>
</LinearLayout>

java代碼

package com.example.day008;

import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private SharedPreferences sharedPreferences;
    private EditText username;
    private EditText password;
    private CheckBox cb;
    private Button login;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        username = (EditText) findViewById(R.id.username);
        password = (EditText) findViewById(R.id.password);
        cb=(CheckBox)findViewById(R.id.cb_remember);
        login=(Button)findViewById(R.id.login);
        //TODO 讀取
        sharedPreferences=getSharedPreferences("1705A",MODE_PRIVATE);
        boolean ischeck= sharedPreferences.getBoolean("ischeck",false);
        if(ischeck){
            //讀到用戶名和密碼展現在頁面中,複選框被勾選
            String username1=sharedPreferences.getString("username","");
            String password1=sharedPreferences.getString("password","");
            username.setText(username1);
            password.setText(password1);
            cb.setChecked(true);
        }
        //TODO 寫數據
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username2=username.getText().toString().trim();
                String password2=password.getText().toString().trim();
                //用戶名和密碼是否正確
                if("sgf".equals(username2)&&"123456".equals(password2)){
                    //判斷記住密碼是否被選中
                    if(cb.isChecked()){//存
                        SharedPreferences.Editor edit = sharedPreferences.edit();
                        edit.putBoolean("ischeck",true);
                        edit.putString("username",username2);
                        edit.putString("password",password2);
                        edit.commit();

                    }else{//清空
                        SharedPreferences.Editor edit = sharedPreferences.edit();
                        edit.putBoolean("ischeck",false);
                        edit.commit();
                    }
                }
            }
        });
    }
}

輪播圖廣告

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

import com.example.sevenday.Fragments.FourFragment;
import com.example.sevenday.Fragments.oneFragment;
import com.example.sevenday.Fragments.threeFragment;
import com.example.sevenday.Fragments.twoFragment;
import com.example.sevenday.activities.Main2Activity;

import java.sql.Time;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {
    private SharedPreferences preferences;
    private ViewPager vpid;
    private RadioGroup radiogroup;
    private RadioButton b1;
    private RadioButton b2;
    private RadioButton b3;
    private RadioButton b4;
    private Button start;
    private TextView djsId;
    private List<Fragment> list=new ArrayList<>();
    private int item=0;//默認顯示頁面
    private int time=5;
    private Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (msg.what==102){
                djsId.setText("倒計時"+(--time)+"秒");
                if (time==0){
                    Intent intent = new Intent(MainActivity.this, Main2Activity.class);
                    startActivity(intent);
                }
            }else if (msg.what==101){
                vpid.setCurrentItem(++item);
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        preferences = getSharedPreferences("welcome", MODE_PRIVATE);
        boolean flag = preferences.getBoolean("isdone", false);
        if (flag){
            Intent intent = new Intent(MainActivity.this, Main2Activity.class);
            startActivity(intent);
        }

        vpid = (ViewPager) findViewById(R.id.vpid);
        radiogroup = (RadioGroup) findViewById(R.id.radiogroup);
        b1 = (RadioButton) findViewById(R.id.b1);
        b2 = (RadioButton) findViewById(R.id.b2);
        b3 = (RadioButton) findViewById(R.id.b3);
        b4 = (RadioButton) findViewById(R.id.b4);
        start = (Button) findViewById(R.id.start);
        djsId = (TextView) findViewById(R.id.djs_id);

        list.add(new oneFragment());
        list.add(new twoFragment());
        list.add(new threeFragment());
        list.add(new FourFragment());


        final Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                if (item!=list.size()-1){
                    handler.sendEmptyMessage(101);
                }else {
                    timer.cancel();
                }
            }
        },0,1000);
        vpid.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
            @Override
            public Fragment getItem(int i) {
                return list.get(i);
            }

            @Override
            public int getCount() {
                return list.size();
            }
        }) ;

        //滑動事件
        vpid.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int i, float v, int i1) {

            }
            @Override
            public void onPageSelected(int i) {
                if (i==0){
                    b1.setChecked(true);
                }else if (i==1){
                    b2.setChecked(true);
                }else if (i==2){
                    b3.setChecked(true);
                }else if (i==3){
                    b4.setChecked(true);
                }
                if (i==list.size()-1){
                    start.setVisibility(View.VISIBLE);
                    djsId.setVisibility(View.VISIBLE);
                    final Timer timer = new Timer();
                    timer.schedule(new TimerTask() {
                        @Override
                        public void run() {
                            if (time>0){
                                handler.sendEmptyMessage(102);
                            }else {
                                timer.cancel();
                            }
                        }
                    },0,1000);
                }else {
                    start.setVisibility(View.GONE);
                    djsId.setVisibility(View.GONE);
                }
            }
            @Override
            public void onPageScrollStateChanged(int i) {

            }
        });
        //點擊事件
        radiogroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                if (checkedId==R.id.b1){
                    vpid.setCurrentItem(0);
                }else if (checkedId==R.id.b2){
                    vpid.setCurrentItem(1);
                }else if (checkedId==R.id.b3){
                    vpid.setCurrentItem(2);
                }else if (checkedId==R.id.b4){
                    vpid.setCurrentItem(3);
                }
            }
        });
    }
    //開始點擊事件
    public void startclick(View view) {
        Intent intent = new Intent(MainActivity.this, Main2Activity.class);
        startActivity(intent);
    }
}

文件存儲：

內部文件存儲openFileOutput

FileOutputStream fileOutputStream = null;
                try {
                    fileOutputStream = openFileOutput("aa.json", MODE_PRIVATE);
                    fileOutputStream.write("hello".getBytes());
                    fileOutputStream.flush();
                    fileOutputStream.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

openFileInput

 FileInputStream fileInputStream = null;
        try {
            fileInputStream= openFileInput("aa.json");
            byte[] b = new byte[1024];
            int len = 0;
            while((len = fileInputStream.read(b)) != -1){
                Log.i(TAG, "onClick: "+new String(b,0,len));
            }

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

外部文件存儲(SD卡)

必須要添加讀寫SD卡的權限

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
package com.example.day008;

import android.Manifest;
import android.content.SharedPreferences;
import android.content.pm.PackageManager;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Map;

public class MainActivity extends AppCompatActivity {
    private Button login;
    private static final String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String externalStorageState = Environment.getExternalStorageState();
        Log.i(TAG, "onCreate: "+externalStorageState);
        File externalStorageDirectory = Environment.getExternalStorageDirectory();
        Log.i(TAG, "onCreate: "+externalStorageDirectory.toString());
        File externalStoragePublicDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        Log.i(TAG, "onCreate: "+externalStoragePublicDirectory);

        login = findViewById(R.id.login);

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.i(TAG, "onClick: ");
				//運行時權限
                requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},100);
                if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                    //獲取SD卡根路徑：
                    File file = Environment.getExternalStorageDirectory();
                    FileOutputStream out = null;
                    try {
                        //創建輸出流
                        out = new FileOutputStream(new File(file, "json.txt"));
                        out.write("呵呵呵俺哥哥".getBytes());
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if (out != null) {
                            try {
                                out.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode == 100){
            if(grantResults != null && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                Toast.makeText(this, "ok", Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(this, "不行啊", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

改進後的代碼
把文件操作寫到同意授權的回調方法裏.

 @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode == 100 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
            if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                File file = Environment.getExternalStorageDirectory();
                FileOutputStream fileOutputStream = null;
                try {
                    fileOutputStream = new FileOutputStream(new File(file,"aa.json"));
                    fileOutputStream.write("aaa".getBytes());
                    fileOutputStream.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }else{
            Toast.makeText(this, "沒有權限", Toast.LENGTH_SHORT).show();
        }
    }

(1)添加讀寫SD卡的 權限
(2)FileUtils.java:四個方法：實現向SD卡中讀寫Bitmap圖片和json字符串

 public class FileUtils {
    //方法1：向SD卡中寫json串
    public static void write_json(String json)  {
        //判斷是否掛載
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            //獲取SD卡根路徑：mnt/shell/emulated/0
            File file=Environment.getExternalStorageDirectory();
            FileOutputStream out=null;
            try {
                //創建輸出流
                out= new FileOutputStream(new File(file,"json.txt"));
                out.write(json.getBytes());
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally{
                if(out!=null){
                    try {
                        out.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

        }
    }
    //方法2：從SD卡中讀取json串
    public static String read_json() {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File file = Environment.getExternalStorageDirectory();
            FileInputStream inputStream = null;
            StringBuffer sb=new StringBuffer();
            try {
                inputStream=new FileInputStream(new File(file,"json.txt"));
                byte[] b=new byte[1024];
                int len=0;
                while((len=inputStream.read(b))!=-1){
                    sb.append(new String(b,0,len));
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally{
                if(inputStream!=null){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
            return  sb.toString();
        }else{
            return "";
        }
    }

    //方法3:從SD卡中讀取一張圖片
    public  static  Bitmap read_bitmap(String filename) {//filename圖片名字
        Bitmap bitmap=null;
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            File file=Environment.getExternalStorageDirectory();
            File file1 = new File(file, filename);
            //BitmapFactory可以直接根據SD卡圖片路徑轉成一個bitmap對象
             bitmap= BitmapFactory.decodeFile(file1.getAbsolutePath());
        }
        return bitmap;
    }
    //方法4：網絡下載一張圖片存儲到SD卡中
    public  static  void write_bitmap(String url) {//網址
       new MyTask().execute(url);
    }
    static class MyTask extends AsyncTask<String,String,String> {
        @Override
        protected String doInBackground(String... strings) {
            FileOutputStream out=null;
            InputStream inputStream=null;//網絡連接的輸入流
            HttpURLConnection connection=null;//向SD卡寫的輸出流
            try {
                URL url= new URL(strings[0]);
                connection= (HttpURLConnection) url.openConnection();
                connection.setConnectTimeout(5*1000);
                connection.setReadTimeout(5*1000);
                if (connection.getResponseCode()==200){
                    inputStream = connection.getInputStream();
                    //TODO 獲取SD卡的路徑
                    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {//是否掛載
                        File file = Environment.getExternalStorageDirectory();
                        out = new FileOutputStream(new File(file,"xiaoyueyue.jpg"));
                        byte[] bytes=new byte[1024];
                        int len=0;
                        while((len=inputStream.read(bytes))!=-1){
                            out.write(bytes,0,len);
                        }
                    }
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                //關流
                if(out!=null){
                    try {
                        out.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(inputStream!=null){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(connection!=null){
                    connection.disconnect();
                }
            }
            return null;
        }
    }
}

案例備註:

   private void checkAccess(String access,int code){
//Manifest.permission.READ_EXTERNAL_STORAGE
        //檢查當前權限（若沒有該權限，值爲-1；若有該權限，值爲0）
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            int hasAccess = ContextCompat.checkSelfPermission(getApplication(), access);
            Log.e("PERMISION_CODE", hasAccess + "***");
            if (hasAccess == PackageManager.PERMISSION_GRANTED) {
                // TODO: 2019/6/15 獲得授權執行操作
                if (code == 1) {
                    write_json("json");
                }else if(code == 2){
                    read_json();
                }
            } else {
                //若沒有授權，會彈出一個對話框（這個對話框是系統的，開發者不能自己定製），用戶選擇是否授權應用使用系統權限
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, code);
//            第1個參數，當前上下文環境；
//            第2個參數，需要授權的字符串數組；
//            第3個參數，請求碼requestCode，在回調方法中會用到。

            }
        }else{
            // TODO: 2019/6/15 非6.0直接使用
            if (code == 1) {
                write_json("json");
            }else if(code == 2){
                read_json();
            }
        }
    }
    //用戶選擇是否同意授權後，會回調這個方法
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
//        第1個參數，請求碼，對應上述方法的第3個參數；
//        第2個參數，請求權限數組；
//        第3個參數，請求權限的結果數組。
        if(requestCode==1) {
            if (permissions[0].equals(Manifest.permission.READ_EXTERNAL_STORAGE) && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // TODO: 2019/6/15 獲得授權執行操作
//http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=10&page=1
                write_json("json");

            } else {
                // TODO: 2019/6/15 未獲得授權執行的操作 
                finish();

            }
        }else if(requestCode == 2){
            if (permissions[0].equals(Manifest.permission.READ_EXTERNAL_STORAGE) && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // TODO: 2019/6/15 獲得授權執行操作
//http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=10&page=1
                read_json();

            } else {
                // TODO: 2019/6/15 未獲得授權執行的操作
                finish();
            }
        }
    }