Android [intermediate tutorial] Chapter 1 Shared Preferences for data storage

 

After reading the Android [basic tutorial], I can finally learn the [intermediate tutorial]. Haha, this time we will learn about data storage in Android development. First, we will learn Shared Preferences, shared Preferences simply stores the Key-Value of the data. I believe anyone who has learned java knows that there is a type of Map, and the data is saved in the form of Key-Value. however, Shared Preferences is essentially different from Map. Map only exists in the program, while Shared Preferences stores data on hardware devices (OK, here the hardware device is the mobile phone ). well, let's not talk about it. We use Shared Preferences to store the number of Goku monsters. You don't want Goku to play monsters again every time it starts a program? Maybe Wukong is looking for you.

 

Main. xml

 

<? Xml version = "1.0" encoding = "UTF-8"?>

<LinearLayout xmlns: android = "http://schemas.android.com/apk/res/android"

Android: orientation = "vertical" android: layout_width = "match_parent"

Android: layout_height = "match_parent">

<TextView android: layout_width = "wrap_content" android: id = "@ + id/textView1"

Android: textAppearance = "? Android: attr/textAppearanceLarge"

Android: layout_height = "wrap_content" android: text = "TextView"> </TextView>

<EditText android: id = "@ + id/editText1" android: layout_width = "match_parent"

Android: layout_height = "wrap_content" android: inputType = "number">

<RequestFocus> </requestFocus>

</EditText>

<LinearLayout android: layout_width = "match_parent"

Android: id = "@ + id/linearLayout2" android: layout_height = "wrap_content">

<Button android: layout_width = "wrap_content"

Android: layout_height = "wrap_content" android: id = "@ + id/addOne"

Android: text = "Wukong killed another monster"> </Button>

<Button android: layout_width = "wrap_content"

Android: layout_height = "wrap_content" android: id = "@ + id/read_edit"

Android: text = "reading data in Edit"> </Button>

</LinearLayout>

<LinearLayout android: layout_width = "match_parent"

Android: id = "@ + id/linearLayout1" android: layout_height = "wrap_content">

<Button android: layout_width = "wrap_content"

Android: layout_height = "wrap_content" android: id = "@ + id/save"

Android: text = "Data Storage"> </Button>

<Button android: layout_width = "wrap_content"

Android: layout_height = "wrap_content" android: id = "@ + id/read"

Android: text = "read data"> </Button>

<Button android: layout_width = "wrap_content"

Android: layout_height = "wrap_content" android: id = "@ + id/clear"

Android: text = "Clear Data"> </Button>

</LinearLayout>

 

</LinearLayout>

 

Here, only an EditText and several buttons are added. Let's take a look at the java source code:

 

Import android. app. Activity;

Import android. content. SharedPreferences;

Import android. content. SharedPreferences. Editor;

Import android. OS. Bundle;

Import android. view. View;

Import android. view. View. OnClickListener;

Import android. widget. Button;

Import android. widget. EditText;

Import android. widget. TextView;

 

Public class Shared_PreferencesDemo extends Activity implements OnClickListener

{

Private int count = 0;

Private String str;

Private TextView text;

Private EditText edit_text;

Private Button add;

Private Button save;

Private Button read;

Private View clear;

Private Button read_edit;

Private SharedPreferences preferences;

Private Editor edit;

@ Override

Protected void onCreate (Bundle savedInstanceState)

{

// TODO Auto-generated method stub

Super. onCreate (savedInstanceState );

SetContentView (R. layout. shared_preferences );

// Obtain the SharedPreferences object that can only be read and written by this program.

Preferences = getSharedPreferences ("shared", 0 );

// Obtain the edit object of SharedPreferences

Edit = preferences. edit ();

Str = "Wukong killed" + count + "only monsters .";

Text = (TextView) findViewById (R. id. textView1 );

Text. setText (str );

Edit_text = (EditText) findViewById (R. id. editText1 );

Edit_text.setText (String. valueOf (count ));

Add = (Button) findViewById (R. id. addOne );

Add. setOnClickListener (this );

Read_edit = (Button) findViewById (R. id. read_edit );

Read_edit.setOnClickListener (this );

Save = (Button) findViewById (R. id. save );

Save. setOnClickListener (this );

Read = (Button) findViewById (R. id. read );

Read. setOnClickListener (this );

Clear = (Button) findViewById (R. id. clear );

Clear. setOnClickListener (this );

}

// Button event monitoring

@ Override

Public void onClick (View v)

{

Switch (v. getId ()){

// Wukong killed another monster button event

Case R. id. addOne:

// Increase the number of monsters by 1

Count ++;

// Refresh the value in the TextView and EditText controls.

Refresh ();

Break;

// Read the data button event in Edit

Case R. id. read_edit:

// Retrieve the value in SharedPreferences

Count = Integer. parseInt (edit_text.getText (). toString ());

Refresh ();

Break;

Case R. id. save:

// Save the number of monsters killed by Wukong to SharedPreferences

Edit. putString ("number", String. valueOf (count ));

Edit. commit ();

Break;

Case R. id. read:

// Retrieve the number of monsters killed by Wukong from SharedPreferences

Count = Integer. valueOf (preferences. getString ("number", "0 "));

Refresh ();

Break;

Case R. id. clear:

// Clear all data in SharedPreferences

Edit. clear ();

Edit. commit ();

Count = 0;

Refresh ();

Break;

}

}

// Custom refresh

Private void refresh ()

{

Str = "Wukong killed" + count + "only monsters .";

Text. setText (str );

Edit_text.setText (String. valueOf (count ));

}

}

Okay. Let's take a look.

 

The data storage location is data/your own package

From: kangkangz4 Column