SharedPreferences保存List和对象序列化数据
在Android下做持久化的数据存储，大部分是用到了sqlite数据库或者sharepreference。为了少写sql语句，大部分都是用ORM形式的开源数据库框架，例如greendao和cupboard或者dao4，但是在一般小型存储系统中，我还是比较喜欢用sp来存储，毕竟使用方便，数据量又不大，存储些不是很多的对象数据，用sp来存储还是很方便的。主要有两种方法来存储对象。
1.存储List类型的数据
用于保存各种List数据，最常见的莫过于，ListView、Gridviw中的数据，支持类型有：
(1)List
(2)List
(3)List
处理的方式时用Gson把List转换成json类型，再利用SharedPreferences保存的。
处理工具类如下:
public class ListDataSave {
private SharedPreferences preferences;
private SharedPreferences.Editor editor;
public ListDataSave(Context mContext, String preferenceName) {
preferences = mContext.getSharedPreferences(preferenceName, Context.MODE_PRIVATE);
editor = preferences.edit();
}
/**
* 保存List
* @param tag
* @param datalist
*/
public void setDataList(String tag, List datalist) {
if (null == datalist || datalist.size() <= 0)
return;
Gson gson = new Gson();
//转换成json数据，再保存
String strJson = gson.toJson(datalist);
editor.clear();
editor.putString(tag, strJson);
editor.commit();
}
/**
* 获取List
* @param tag
* @return
*/
public List getDataList(String tag) {
List datalist=new ArrayList();
String strJson = preferences.getString(tag, null);
if (null == strJson) {
return datalist;
}
Gson gson = new Gson();
datalist = gson.fromJson(strJson, new TypeToken>() {
}.getType());
return datalist;
}
} Userbean类如下:
public class Userbean {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
} MainActivity类:
public class MainActivity extends Activity implements OnClickListener {
Context mContext;
ListDataSave dataSave;
private ArrayList listBean;
private ArrayList listString;
private ArrayList> listMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initView();
}
private void initView() {
findViewById(R.id.btn_addString).setOnClickListener(this);
findViewById(R.id.btn_addJavaBean).setOnClickListener(this);
findViewById(R.id.btn_addMap).setOnClickListener(this);
findViewById(R.id.btn_getString).setOnClickListener(this);
findViewById(R.id.btn_getJavaBean).setOnClickListener(this);
findViewById(R.id.btn_getMap).setOnClickListener(this);
mContext = getApplicationContext();
dataSave = new ListDataSave(mContext, "baiyu");
listString = new ArrayList();
listBean = new ArrayList();
listMap = new ArrayList>();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_addString:
String s = "小名";
listString.add(s);
dataSave.setDataList("string", listString);
break;
case R.id.btn_getString:
Toast.makeText(mContext, dataSave.getDataList("string").toString(), Toast.LENGTH_SHORT).show();
break;
case R.id.btn_addJavaBean:
Userbean user = new Userbean();
user.setName("小白");
user.setAge(16);
listBean.add(user);
dataSave.setDataList("javaBean", listBean);
break;
case R.id.btn_getJavaBean:
Toast.makeText(mContext, dataSave.getDataList("javaBean").toString(), Toast.LENGTH_SHORT).show();
break;
case R.id.btn_addMap:
Map map=new HashMap();
map.put("name","大白");
map.put("age", 18);
listMap.add(map);
dataSave.setDataList("listMap", listMap);
break;
case R.id.btn_getMap:
Toast.makeText(mContext, dataSave.getDataList("listMap").toString(), Toast.LENGTH_SHORT).show();
break;
}
}
} 2.存储序列化对象
sharepreference存储对象是利用将对象转化为字节流，然后写入本地xml文件中，下次通过读取设置时的id来实现从xml文件中读取字节流然后再转化为对象
保存对象的工具类:
import android.content.Context;
import android.content.SharedPreferences;
import android.util.Base64;
import android.util.Log;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.StreamCorruptedException;
public class SaveObjectUtils {
private Context context;
private String name;
public SaveObjectUtils(Context context, String name) {
this.context = context;
this.name = name;
}
/**
* 根据key和预期的value类型获取value的值
*
* @param key
* @param clazz
* @return
*/
public T getValue(String key, Class clazz) {
if (context == null) {
throw new RuntimeException("请先调用带有context，name参数的构造！");
}
SharedPreferences sp = this.context.getSharedPreferences(this.name, Context.MODE_PRIVATE);
return getValue(key, clazz, sp);
}
/**
* 针对复杂类型存储<对象>
*
* @param key
* @param object
*/
public void setObject(String key, Object object) {
SharedPreferences sp = this.context.getSharedPreferences(this.name, Context.MODE_PRIVATE);
//创建字节输出流
ByteArrayOutputStream baos = new ByteArrayOutputStream();
//创建字节对象输出流
ObjectOutputStream out = null;
try {
//然后通过将字对象进行64转码，写入key值为key的sp中
out = new ObjectOutputStream(baos);
out.writeObject(object);
String objectVal = new String(Base64.encode(baos.toByteArray(), Base64.DEFAULT));
SharedPreferences.Editor editor = sp.edit();
editor.putString(key, objectVal);
editor.commit();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (baos != null) {
baos.close();
}
if (out != null) {
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
@SuppressWarnings("unchecked")
public T getObject(String key, Class clazz) {
SharedPreferences sp = this.context.getSharedPreferences(this.name, Context.MODE_PRIVATE);
if (sp.contains(key)) {
String objectVal = sp.getString(key, null);
byte[] buffer = Base64.decode(objectVal, Base64.DEFAULT);
//一样通过读取字节流，创建字节流输入流，写入对象并作强制转换
ByteArrayInputStream bais = new ByteArrayInputStream(buffer);
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(bais);
T t = (T) ois.readObject();
return t;
} catch (StreamCorruptedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
try {
if (bais != null) {
bais.close();
}
if (ois != null) {
ois.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
/**
* 对于外部不可见的过渡方法
*
* @param key
* @param clazz
* @param sp
* @return
*/
@SuppressWarnings("unchecked")
private T getValue(String key, Class clazz, SharedPreferences sp) {
T t;
try {
t = clazz.newInstance();
if (t instanceof Integer) {
return (T) Integer.valueOf(sp.getInt(key, 0));
} else if (t instanceof String) {
return (T) sp.getString(key, "");
} else if (t instanceof Boolean) {
return (T) Boolean.valueOf(sp.getBoolean(key, false));
} else if (t instanceof Long) {
return (T) Long.valueOf(sp.getLong(key, 0L));
} else if (t instanceof Float) {
return (T) Float.valueOf(sp.getFloat(key, 0L));
}
} catch (InstantiationException e) {
e.printStackTrace();
Log.e("system", "类型输入错误或者复杂类型无法解析[" + e.getMessage() + "]");
} catch (IllegalAccessException e) {
e.printStackTrace();
Log.e("system", "类型输入错误或者复杂类型无法解析[" + e.getMessage() + "]");
}
Log.e("system", "无法找到" + key + "对应的值");
return null;
}
} import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.nickming.cachedemo.R;
import com.nickming.cachedemo.db.MTStateInfo;
import com.nickming.cachedemo.db.MTStateManager;
import com.nickming.cachedemo.utils.SaveObjectUtils;
public class Main2Activity extends AppCompatActivity {
private Button mSave;
private Button mShow;
private TextView mResult;
SaveObjectUtils utils;
private static final String key=Main2Activity.class.getSimpleName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
mSave= (Button) findViewById(R.id.btn_save1);
mResult= (TextView) findViewById(R.id.tv_result1);
mShow= (Button) findViewById(R.id.btn_show1);
utils=new SaveObjectUtils(this,key);
mSave.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
MTStateManager.getInstance().setTaskId(324444);
MTStateManager.getInstance().setBeginTime("20132003055");
MTStateInfo info=MTStateManager.getInstance().getStateInfo();
utils.setObject(""+info.getTaskId(),info);
}
});
mShow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
MTStateInfo test=utils.getObject("324444",MTStateInfo.class);
MTStateManager.getInstance().clearDatas();
MTStateManager.getInstance().setDatas(test);
mResult.setText(""+MTStateManager.getInstance().getBeginTime());
}
});
}
} 用sp存储对象最大好处就是不要新建好多张表，例如我的stateinfo里还有一个自定义的对象，用greendao时还需要再声明一次，但是用sp就不需要，他不管你是自定义的还是系统的，都能毫无差错的存储。