任何軟件或者app都在一定程度上需要數據存儲,android提供了sharedpreferences用來存儲輕量數據,sharedpreference將數據存儲於xml中,位於/data/data/{包名}/shared_prefs下,仿真機可以通過ddms從中取出,下面就來介紹一下
一、sharedpreferences的基本用法——寫入
1.毫無疑問,首先需要定義sharedpreferences的對象
sharedpreferences share =getsharedpreferences(“包名”,Context.MODE_PRIVATE),第一個參數爲android程序所屬的包的名稱
第二個參數爲存儲模式,
MODE_PRIVATE爲默認參數,設置爲該參數後,寫入形式爲覆蓋式,即新寫入的內容會直接覆蓋掉原本的內容
MODE_APPEND參數,設置爲該參數後,寫入形式爲追加式,如果文件存在,即會在文件末尾添加新內容,而不會覆蓋原本內容,但需注意的是如果tag是相同的,依然會覆蓋掉
MODE_WORLD_READABLE和MODE_WORLD_WRITEABLE這兩個參數設置後,即可允許別的程序訪問本程序的存儲數據,第一個是可讀,第二個是可寫
2.對象創建後,就要獲得對象的編輯器
Editor editor=share.edit();之後就可以通過該編輯器寫入數據了
editor.putString(“name”,”aaa”);第一個參數爲TAG即存儲的數據名稱,第二個參數是存儲的數據,之後用editor.commit()確認即可將數據寫入xml存儲
完整過程如下:
share=getSharedPreferences(“com.example.ui_demo”,mySelected);
Editor editor=share.edit();//獲取編輯器
editor.putString(“name”, name.getText().toString());
editor.putString(“id”,id.getText().toString());
editor.commit();//確認寫入
二、數據讀取
1.創建對象,和上面的一樣
2.直接通過對象獲得數據
share.getString(“name”,”“);第一個參數爲獲取的數據名稱,第二個參數爲缺省值,如果未取得該名稱數據就會返回第二個參數
三、不同應用讀取數據
讀取不同應用,首先要保證存儲模式是MODE_WORLD_READABLE或者MODE_WORLD_WRITEABLE這兩種形式,否則另外的應用是無法讀取的
具體的讀取方法如下
1.定義需要讀取數據所在應用的context
context=createPackageContext(“com.example.ui_demo”,Context.CONTEXT_IGNORE_SECURITY);
2定義sharedPreferences對象,通過1中Context來獲取
SharedPreferences shared=context.getSharedPreferences(“com.example.ui_demo”, Context.MODE_WORLD_READABLE);
之後的讀取過程與同一應用的讀取方式一致
四、DDMS的應用
爲了印證是否正確寫入,如果是仿真機的話就需要用到ddms了,首先點擊windows選項,選擇Open perspective選項中other,即可打開如下界面,選擇DDMS即可
之後會跳轉到如下界面,選擇對應的仿真機後,點擊右側的選項卡到fileExplorer選項卡下,按照之前的目錄找到文件,在導出到電腦上進行查看
導出方法點擊右上角的如下所示圖標即可
四,示例代碼
Shared_prefdemo.java
package com.example.ui_demo;
import java.util.List;
import android.app.Activity;
import android.app.TabActivity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TabHost;
import android.widget.Toast;
import android.widget.TabHost.OnTabChangeListener;
public class SharedP_ref extends Activity {
private String []str={"Mode_Private","Mode_Append","Mode_WorldRead","Mode_WorldWrite"};
private Spinner sp;
private ArrayAdapter<String> arrayAdapter;
private int mySelected=-1;
private Button write;
private Button read;
private SharedPreferences share;
private EditText name;
private EditText id;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shared_p_ref);
sp=(Spinner)this.findViewById(R.id.type);
write=(Button)this.findViewById(R.id.write);
read=(Button)this.findViewById(R.id.read);
name=(EditText)this.findViewById(R.id.editName);
id=(EditText)this.findViewById(R.id.editid);
arrayAdapter=new ArrayAdapter<String>(SharedP_ref.this,android.R.layout.simple_spinner_item, str);
//arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setAdapter(arrayAdapter);
sp.setOnItemSelectedListener(new OnItemSelectedListener(){
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1,
int position, long id) {
// TODO Auto-generated method stub
String str=arg0.getItemAtPosition(position).toString();
if(str=="Mode_Private"){
mySelected=Context.MODE_PRIVATE;
}else if(str=="Mode_Append"){
mySelected=Context.MODE_APPEND;
}else if(str=="Mode_WorldRead"){
mySelected=Context.MODE_WORLD_READABLE;
}else if(str=="Mode_WorldWrite"){
mySelected=Context.MODE_WORLD_WRITEABLE;
}else{
mySelected=-1;
}
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
mySelected=-1;
}
});
Mybutton m=new Mybutton();
write.setOnClickListener(m);
read.setOnClickListener(m);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.shared_p_ref, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class Mybutton implements OnClickListener{
@Override
public void onClick(View vi) {
// TODO Auto-generated method stub
if(vi==write){
if(mySelected!=-1){
share=getSharedPreferences("com.example.ui_demo",mySelected);
Editor editor=share.edit();//獲取編輯器
editor.putString("name", name.getText().toString());
editor.putString("id",id.getText().toString());
editor.commit();//確認寫入
}else{
Toast.makeText(SharedP_ref.this, "未選擇type",Toast.LENGTH_LONG).show();
}
}else if(vi==read){
if(mySelected!=-1){
share=getSharedPreferences("com.example.ui_demo",mySelected);
String names=share.getString("name", "未找到");//若查詢不到會返回第二個參數
String s=share.getString("id", "未找到");//若查詢不到會返回第二個參數
Toast.makeText(SharedP_ref.this, names+s,Toast.LENGTH_LONG).show();
}else{
Toast.makeText(SharedP_ref.this, "未選擇type",Toast.LENGTH_LONG).show();
}
}
}
}
}
xml
<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:orientation="vertical"
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.example.ui_demo.SharedP_ref" >
<TextView
android:id="@+id/Name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Name:" >
</TextView>
<EditText
android:id="@+id/editName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清輸入數值" >
</EditText>
<TextView
android:id="@+id/id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="id:" >
</TextView>
<EditText
android:id="@+id/editid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清輸入數值" >
</EditText>
<Spinner
android:id="@+id/type"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:spinnerMode="dropdown" >
</Spinner>
<Button
android:id="@+id/write"
android:text="寫入"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
<Button
android:id="@+id/read"
android:text="讀取"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
</LinearLayout>
otherActivity.java
package com.example.readothershared;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button mybutton=(Button)this.findViewById(R.id.read);
mybutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Context context;
//創建context
try {
context=createPackageContext("com.example.ui_demo",Context.CONTEXT_IGNORE_SECURITY);
SharedPreferences shared=context.getSharedPreferences("com.example.ui_demo", Context.MODE_WORLD_READABLE);
String name=shared.getString("name", "未獲取到");
TextView myText=(TextView)MainActivity.this.findViewById(R.id.show);
myText.setText(name);
} catch (NameNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}