您的位置:首页 > Web前端

张萌&韩墨羽——SharedPreferences存储+SD卡存储

2019-07-14 20:10 1206 查看

SharedPreferences存储+SD卡存储

SharedPreferences

特点:

保存少量的数据,且这些数据的格式非常简单。 存储5种原始数据类型: boolean, float, int, long, String
比如应用程序的各种配置信息(如是否打开音效、是否使用震动效果、小游戏的玩家积分等),记住密码功能,音乐播放器播放模式。

使用方式

**步骤1:**得到SharedPreferences对象 getSharedPreferences(“文件的名称”,“文件的类型”);
(1).Context.MODE_PRIVATE:指定该SharedPreferences数据只能被应用程序读写
(2)MODE_APPEND:检查文件是否存在,存在就往文件追加内容,否则就创建新文件。
以下不在建议使用
(3).Context.MODE_WORLD_READABLE:指定该SharedPreferences数据能被其他
应用程序读,但不能写。
(4).Context,MODE_WORLD_WRITEABLE:指定该SharedPreferences数据能被其他应用程序写,但不能读。
**步骤2:**得到 SharedPreferences.Editor编辑对象
SharedPreferences.Editor editor=sp.edit();
**步骤3:**添加数据
editor.putBoolean(key,value)
editor.putString()
editor.putInt()
editor.putFloat()
editor.putLong()
**步骤4:**提交数据 editor.commit()或者apply()(推荐用这个.异步提交)
Editor其他方法: editor.clear() 清除数据 editor.remove(key) 移除指定key对应的数据

写数据

//SP写数据

private void write() {
//TODO  1:得到SharedPreferences对象
//参数一 xml文件的名字 参数二 模式 MODE_PRIVATE 指定该SharedPreferences数据只能被本应用程序读写
SharedPreferences preferences = getSharedPreferences("songdingxing", MODE_PRIVATE);
//TODO 2:获得编辑对象
SharedPreferences.Editor editor = preferences.edit();
//TODO 3:写数据
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:提交数据
editor.commit();
}
读数据

//读数据

private void read() {
//TODO  1:得到SharedPreferences对象
//参数一 xml文件的名字 参数二 模式 MODE_PRIVATE 指定该SharedPreferences数据只能被本应用程序读写
SharedPreferences preferences = getSharedPreferences("sgf", MODE_PRIVATE);
//TODO 2:直接读取
//参数一 键  参数二 找不到的时候给默认值
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();
}
登录注册案例

xml布局

<?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="记住密码"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:layout_alignParentRight="true"
android:id="@+id/login"
android:text="登录"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
</LinearLayout>

java代码

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 读取
sharedPreferences=getSharedPreferences("1705A",MODE_PRIVATE);
boolean ischeck= sharedPreferences.getBoolean("ischeck",false);
if(ischeck){
//读到用户名和密码展现在页面中,复选框被勾选
String username1=sharedPreferences.getString("username","");
String password1=sharedPreferences.getString("password","");
username.setText(username1);
password.setText(password1);
cb.setChecked(true);
}
//TODO 写数据
login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username2=username.getText().toString().trim();
String password2=password.getText().toString().trim();
//用户名和密码是否正确
if("sgf".equals(username2)&&"123456".equals(password2)){
//判断记住密码是否被选中
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();
}
}
}
});
}
}
轮播图广告
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;//默认显示页面
private int time=5;
private Handler handler=new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg.what==102){
djsId.setText("倒计时"+(--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();
}
}) ;

//滑动事件
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) {

}
});
//点击事件
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);
}
}
});
}
//开始点击事件
public void startclick(View view) {
Intent intent = new Intent(MainActivity.this, Main2Activity.class);
startActivity(intent);
}
}
文件存储:
内部文件存储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();
}
外部文件存储(SD卡)

必须要添加读写SD卡的权限

<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: ");
//运行时权限
requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},100);
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
//获取SD卡根路径:
File file = Environment.getExternalStorageDirectory();
FileOutputStream out = null;
try {
//创建输出流
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();
}
}
}
}

改进后的代码
把文件操作写到同意授权的回调方法里.

@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, "没有权限", Toast.LENGTH_SHORT).show();
}
}

(1)添加读写SD卡的 权限
(2)FileUtils.java:四个方法:实现向SD卡中读写Bitmap图片和json字符串

public class FileUtils {
//方法1:向SD卡中写json串
public static void write_json(String json)  {
//判断是否挂载
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
//获取SD卡根路径:mnt/shell/emulated/0
File file=Environment.getExternalStorageDirectory();
FileOutputStream out=null;
try {
//创建输出流
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:从SD卡中读取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:从SD卡中读取一张图片
public  static  Bitmap read_bitmap(String filename) {//filename图片名字
Bitmap bitmap=null;
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
File file=Environment.getExternalStorageDirectory();
File file1 = new File(file, filename);
//BitmapFactory可以直接根据SD卡图片路径转成一个bitmap对象
bitmap= BitmapFactory.decodeFile(file1.getAbsolutePath());
}
return bitmap;
}
//方法4:网络下载一张图片存储到SD卡中
public  static  void write_bitmap(String url) {//网址
new MyTask().execute(url);
}
static class MyTask extends AsyncTask<String,String,String> {
@Override
protected String doInBackground(String... strings) {
FileOutputStream out=null;
InputStream inputStream=null;//网络连接的输入流
HttpURLConnection connection=null;//向SD卡写的输出流
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 获取SD卡的路径
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {//是否挂载
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 {
//关流
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;
}
}
}

案例备注:

private void checkAccess(String access,int code){
//Manifest.permission.READ_EXTERNAL_STORAGE
//检查当前权限(若没有该权限,值为-1;若有该权限,值为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 获得授权执行操作
if (code == 1) {
write_json("json");
}else if(code == 2){
read_json();
}
} else {
//若没有授权,会弹出一个对话框(这个对话框是系统的,开发者不能自己定制),用户选择是否授权应用使用系统权限
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, code);
//            第1个参数,当前上下文环境;
//            第2个参数,需要授权的字符串数组;
//            第3个参数,请求码requestCode,在回调方法中会用到。

}
}else{
// TODO: 2019/6/15 非6.0直接使用
if (code == 1) {
write_json("json");
}else if(code == 2){
read_json();
}
}
}
//用户选择是否同意授权后,会回调这个方法
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
//        第1个参数,请求码,对应上述方法的第3个参数;
//        第2个参数,请求权限数组;
//        第3个参数,请求权限的结果数组。
if(requestCode==1) {
if (permissions[0].equals(Manifest.permission.READ_EXTERNAL_STORAGE) && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// TODO: 2019/6/15 获得授权执行操作
//http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=10&page=1
write_json("json");

} else {
// TODO: 2019/6/15 未获得授权执行的操作
finish();

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

} else {
// TODO: 2019/6/15 未获得授权执行的操作
finish();
}
}
}
内容来自用户分享和网络整理,不保证内容的准确性,如有侵权内容,可联系管理员处理 点击这里给我发消息
标签: