Android 简明教程

Android - SQLite Database

SQLite 是一个开源 SQL 数据库，它将数据存储到设备上的一个文本文件中。Android 内置了 SQLite 数据库实现。

SQLite is a opensource SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation.

SQLite 支持所有关系数据库功能。要访问此数据库，您不需要为其建立任何类型的连接，如 JDBC、ODBC 等。

SQLite supports all the relational database features. In order to access this database, you don’t need to establish any kind of connections for it like JDBC,ODBC e.t.c

Database - Package

主要包是 android.database.sqlite，它包含用于管理您自己的数据库的类。

The main package is android.database.sqlite that contains the classes to manage your own databases

Database - Creation

要创建一个数据库，您只需调用此方法，并以数据库名称和模式作为参数。openOrCreateDatabase 返回一个 SQLite 数据库实例，您必须在自己的对象中接收它。其语法如下所示：

In order to create a database you just need to call this method openOrCreateDatabase with your database name and mode as a parameter. It returns an instance of SQLite database which you have to receive in your own object.Its syntax is given below

SQLiteDatabase mydatabase = openOrCreateDatabase("your database name",MODE_PRIVATE,null);

除此之外，数据库包中还提供了其他执行此工作的函数。它们列在下面：

Apart from this , there are other functions available in the database package , that does this job. They are listed below

Sr.No

Method & Description

1

openDatabase(String path, SQLiteDatabase.CursorFactory factory, int flags, DatabaseErrorHandler errorHandler) This method only opens the existing database with the appropriate flag mode. The common flags mode could be OPEN_READWRITE OPEN_READONLY

2

openDatabase(String path, SQLiteDatabase.CursorFactory factory, int flags) It is similar to the above method as it also opens the existing database but it does not define any handler to handle the errors of databases

3

openOrCreateDatabase(String path, SQLiteDatabase.CursorFactory factory) It not only opens but create the database if it not exists. This method is equivalent to openDatabase method.

4

openOrCreateDatabase(File file, SQLiteDatabase.CursorFactory factory) This method is similar to above method but it takes the File object as a path rather then a string. It is equivalent to file.getPath()

Database - Insertion

我们可以使用 SQLiteDatabase 类中定义的 execSQL 方法创建表或将数据插入到表中。其语法如下：

we can create table or insert data into table using execSQL method defined in SQLiteDatabase class. Its syntax is given below

mydatabase.execSQL("CREATE TABLE IF NOT EXISTS TutorialsPoint(Username VARCHAR,Password VARCHAR);");
mydatabase.execSQL("INSERT INTO TutorialsPoint VALUES('admin','admin');");

这会将一些值插入到数据库中的表中。另一种也执行相同工作但采用一些附加参数的方法如下：

This will insert some values into our table in our database. Another method that also does the same job but take some additional parameter is given below

Sr.No

Method & Description

1

execSQL(String sql, Object[] bindArgs) This method not only insert data , but also used to update or modify already existing data in database using bind arguments

Database - Fetching

我们可以使用 Cursor 类的一个对象从数据库中检索任何内容。我们将调用此类的一个名为 rawQuery 的方法，它将返回一个结果集，其中光标指向该表。我们可以向前移动光标并检索数据。

We can retrieve anything from database using an object of the Cursor class. We will call a method of this class called rawQuery and it will return a resultset with the cursor pointing to the table. We can move the cursor forward and retrieve the data.

Cursor resultSet = mydatbase.rawQuery("Select * from TutorialsPoint",null);
resultSet.moveToFirst();
String username = resultSet.getString(0);
String password = resultSet.getString(1);

Cursor 类中提供了其他函数，使我们能够有效地检索数据。其中包括：

There are other functions available in the Cursor class that allows us to effectively retrieve the data. That includes

Sr.No

Method & Description

1

getColumnCount() This method return the total number of columns of the table.

2

getColumnIndex(String columnName) This method returns the index number of a column by specifying the name of the column

3

getColumnName(int columnIndex) This method returns the name of the column by specifying the index of the column

4

getColumnNames() This method returns the array of all the column names of the table.

5

getCount() This method returns the total number of rows in the cursor

6

getPosition() This method returns the current position of the cursor in the table

7

isClosed() This method returns true if the cursor is closed and return false otherwise

Database - Helper class

为了管理与数据库相关的所有操作，已给出一个名为 SQLiteOpenHelper 的帮助程序类。它会自动管理数据库的创建和更新。它其语法如下所示

For managing all the operations related to the database , an helper class has been given and is called SQLiteOpenHelper. It automatically manages the creation and update of the database. Its syntax is given below

public class DBHelper extends SQLiteOpenHelper {
   public DBHelper(){
      super(context,DATABASE_NAME,null,1);
   }
   public void onCreate(SQLiteDatabase db) {}
   public void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {}
}

Example

以下是一个展示 SQLite 数据库使用的示例。它创建了一个基本的联系人应用程序，用于允许插入、删除和修改联系人。

Here is an example demonstrating the use of SQLite Database. It creates a basic contacts applications that allows insertion, deletion and modification of contacts.

要试验该示例，您需要在支持相机的实际设备上运行它。

To experiment with this example, you need to run this on an actual device on which camera is supported.

Steps

Description

1

You will use Android studio to create an Android application under a package com.example.sairamkrishna.myapplication.

2

Modify src/MainActivity.java file to get references of all the XML components and populate the contacts on listView.

3

Create new src/DBHelper.java that will manage the database work

4

Create a new Activity as DisplayContact.java that will display the contact on the screen

5

Modify the res/layout/activity_main to add respective XML components

6

Modify the res/layout/activity_display_contact.xml to add respective XML components

7

Modify the res/values/string.xml to add necessary string components

8

Modify the res/menu/display_contact.xml to add necessary menu components

9

Create a new menu as res/menu/mainmenu.xml to add the insert contact option

10

Run the application and choose a running android device and install the application on it and verify the results.

下面是已修改的 MainActivity.java 的内容。

Following is the content of the modified MainActivity.java.

package com.example.sairamkrishna.myapplication;

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;

import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends ActionBarActivity {
   public final static String EXTRA_MESSAGE = "MESSAGE";
   private ListView obj;
   DBHelper mydb;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      mydb = new DBHelper(this);
      ArrayList array_list = mydb.getAllCotacts();
      ArrayAdapter arrayAdapter=new ArrayAdapter(this,android.R.layout.simple_list_item_1, array_list);

      obj = (ListView)findViewById(R.id.listView1);
      obj.setAdapter(arrayAdapter);
      obj.setOnItemClickListener(new OnItemClickListener(){
         @Override
         public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,long arg3) {
            // TODO Auto-generated method stub
            int id_To_Search = arg2 + 1;

            Bundle dataBundle = new Bundle();
            dataBundle.putInt("id", id_To_Search);

            Intent intent = new Intent(getApplicationContext(),DisplayContact.class);

            intent.putExtras(dataBundle);
            startActivity(intent);
         }
      });
   }

   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.menu_main, menu);
      return true;
   }

   @Override
   public boolean onOptionsItemSelected(MenuItem item){
      super.onOptionsItemSelected(item);

      switch(item.getItemId()) {
         case R.id.item1:Bundle dataBundle = new Bundle();
         dataBundle.putInt("id", 0);

         Intent intent = new Intent(getApplicationContext(),DisplayContact.class);
         intent.putExtras(dataBundle);

         startActivity(intent);
         return true;
         default:
         return super.onOptionsItemSelected(item);
      }
   }

   public boolean onKeyDown(int keycode, KeyEvent event) {
      if (keycode == KeyEvent.KEYCODE_BACK) {
         moveTaskToBack(true);
      }
      return super.onKeyDown(keycode, event);
   }
}

以下是对显示联系人活动的修改内容 DisplayContact.java

Following is the modified content of display contact activity DisplayContact.java

package com.example.sairamkrishna.myapplication;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;

import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;

import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class DisplayContact extends Activity {
   int from_Where_I_Am_Coming = 0;
   private DBHelper mydb ;

   TextView name ;
   TextView phone;
   TextView email;
   TextView street;
   TextView place;
   int id_To_Update = 0;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_display_contact);
      name = (TextView) findViewById(R.id.editTextName);
      phone = (TextView) findViewById(R.id.editTextPhone);
      email = (TextView) findViewById(R.id.editTextStreet);
      street = (TextView) findViewById(R.id.editTextEmail);
      place = (TextView) findViewById(R.id.editTextCity);

      mydb = new DBHelper(this);

      Bundle extras = getIntent().getExtras();
      if(extras !=null) {
         int Value = extras.getInt("id");

         if(Value>0){
            //means this is the view part not the add contact part.
            Cursor rs = mydb.getData(Value);
            id_To_Update = Value;
            rs.moveToFirst();

            String nam = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_NAME));
            String phon = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_PHONE));
            String emai = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_EMAIL));
            String stree = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_STREET));
            String plac = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_CITY));

            if (!rs.isClosed())  {
               rs.close();
            }
            Button b = (Button)findViewById(R.id.button1);
            b.setVisibility(View.INVISIBLE);

            name.setText((CharSequence)nam);
            name.setFocusable(false);
            name.setClickable(false);

            phone.setText((CharSequence)phon);
            phone.setFocusable(false);
            phone.setClickable(false);

            email.setText((CharSequence)emai);
            email.setFocusable(false);
            email.setClickable(false);

            street.setText((CharSequence)stree);
            street.setFocusable(false);
            street.setClickable(false);

            place.setText((CharSequence)plac);
            place.setFocusable(false);
            place.setClickable(false);
         }
      }
   }

   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      Bundle extras = getIntent().getExtras();

      if(extras !=null) {
         int Value = extras.getInt("id");
         if(Value>0){
            getMenuInflater().inflate(R.menu.display_contact, menu);
         } else{
            getMenuInflater().inflate(R.menu.menu_main menu);
         }
      }
      return true;
   }

   public boolean onOptionsItemSelected(MenuItem item) {
      super.onOptionsItemSelected(item);
      switch(item.getItemId()) {
         case R.id.Edit_Contact:
         Button b = (Button)findViewById(R.id.button1);
         b.setVisibility(View.VISIBLE);
         name.setEnabled(true);
         name.setFocusableInTouchMode(true);
         name.setClickable(true);

         phone.setEnabled(true);
         phone.setFocusableInTouchMode(true);
         phone.setClickable(true);

         email.setEnabled(true);
         email.setFocusableInTouchMode(true);
         email.setClickable(true);

         street.setEnabled(true);
         street.setFocusableInTouchMode(true);
         street.setClickable(true);

         place.setEnabled(true);
         place.setFocusableInTouchMode(true);
         place.setClickable(true);

         return true;
         case R.id.Delete_Contact:

         AlertDialog.Builder builder = new AlertDialog.Builder(this);
         builder.setMessage(R.string.deleteContact)
            .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {
                  mydb.deleteContact(id_To_Update);
                  Toast.makeText(getApplicationContext(), "Deleted Successfully",
                     Toast.LENGTH_SHORT).show();
                  Intent intent = new Intent(getApplicationContext(),MainActivity.class);
                  startActivity(intent);
               }
         })
         .setNegativeButton(R.string.no, new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
               // User cancelled the dialog
            }
         });

         AlertDialog d = builder.create();
         d.setTitle("Are you sure");
         d.show();

         return true;
         default:
         return super.onOptionsItemSelected(item);

      }
   }

   public void run(View view) {
      Bundle extras = getIntent().getExtras();
      if(extras !=null) {
         int Value = extras.getInt("id");
         if(Value>0){
            if(mydb.updateContact(id_To_Update,name.getText().toString(),
               phone.getText().toString(), email.getText().toString(),
				   street.getText().toString(), place.getText().toString())){
               Toast.makeText(getApplicationContext(), "Updated", Toast.LENGTH_SHORT).show();
               Intent intent = new Intent(getApplicationContext(),MainActivity.class);
               startActivity(intent);
            } else{
               Toast.makeText(getApplicationContext(), "not Updated", Toast.LENGTH_SHORT).show();
            }
         } else{
            if(mydb.insertContact(name.getText().toString(), phone.getText().toString(),
				   email.getText().toString(), street.getText().toString(),
				   place.getText().toString())){
                  Toast.makeText(getApplicationContext(), "done",
						   Toast.LENGTH_SHORT).show();
            } else{
               Toast.makeText(getApplicationContext(), "not done",
					   Toast.LENGTH_SHORT).show();
            }
            Intent intent = new Intent(getApplicationContext(),MainActivity.class);
            startActivity(intent);
         }
      }
   }
}

以下是对数据库类的内容 DBHelper.java

Following is the content of Database class DBHelper.java

package com.example.sairamkrishna.myapplication;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;

public class DBHelper extends SQLiteOpenHelper {

   public static final String DATABASE_NAME = "MyDBName.db";
   public static final String CONTACTS_TABLE_NAME = "contacts";
   public static final String CONTACTS_COLUMN_ID = "id";
   public static final String CONTACTS_COLUMN_NAME = "name";
   public static final String CONTACTS_COLUMN_EMAIL = "email";
   public static final String CONTACTS_COLUMN_STREET = "street";
   public static final String CONTACTS_COLUMN_CITY = "place";
   public static final String CONTACTS_COLUMN_PHONE = "phone";
   private HashMap hp;

   public DBHelper(Context context) {
      super(context, DATABASE_NAME , null, 1);
   }

   @Override
   public void onCreate(SQLiteDatabase db) {
      // TODO Auto-generated method stub
      db.execSQL(
         "create table contacts " +
         "(id integer primary key, name text,phone text,email text, street text,place text)"
      );
   }

   @Override
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      // TODO Auto-generated method stub
      db.execSQL("DROP TABLE IF EXISTS contacts");
      onCreate(db);
   }

   public boolean insertContact (String name, String phone, String email, String street,String place) {
      SQLiteDatabase db = this.getWritableDatabase();
      ContentValues contentValues = new ContentValues();
      contentValues.put("name", name);
      contentValues.put("phone", phone);
      contentValues.put("email", email);
      contentValues.put("street", street);
      contentValues.put("place", place);
      db.insert("contacts", null, contentValues);
      return true;
   }

   public Cursor getData(int id) {
      SQLiteDatabase db = this.getReadableDatabase();
      Cursor res =  db.rawQuery( "select * from contacts where id="+id+"", null );
      return res;
   }

   public int numberOfRows(){
      SQLiteDatabase db = this.getReadableDatabase();
      int numRows = (int) DatabaseUtils.queryNumEntries(db, CONTACTS_TABLE_NAME);
      return numRows;
   }

   public boolean updateContact (Integer id, String name, String phone, String email, String street,String place) {
      SQLiteDatabase db = this.getWritableDatabase();
      ContentValues contentValues = new ContentValues();
      contentValues.put("name", name);
      contentValues.put("phone", phone);
      contentValues.put("email", email);
      contentValues.put("street", street);
      contentValues.put("place", place);
      db.update("contacts", contentValues, "id = ? ", new String[] { Integer.toString(id) } );
      return true;
   }

   public Integer deleteContact (Integer id) {
      SQLiteDatabase db = this.getWritableDatabase();
      return db.delete("contacts",
      "id = ? ",
      new String[] { Integer.toString(id) });
   }

   public ArrayList<String> getAllCotacts() {
      ArrayList<String> array_list = new ArrayList<String>();

      //hp = new HashMap();
      SQLiteDatabase db = this.getReadableDatabase();
      Cursor res =  db.rawQuery( "select * from contacts", null );
      res.moveToFirst();

      while(res.isAfterLast() == false){
         array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_NAME)));
         res.moveToNext();
      }
      return array_list;
   }
}

以下是对 res/layout/activity_main.xml 的内容

Following is the content of the res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/textView"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:textSize="30dp"
      android:text="Data Base" />

   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials Point"
      android:id="@+id/textView2"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true"
      android:textSize="35dp"
      android:textColor="#ff16ff01" />

   <ImageView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageView"
      android:layout_below="@+id/textView2"
      android:layout_centerHorizontal="true"
      android:src="@drawable/logo"/>

   <ScrollView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/scrollView"
      android:layout_below="@+id/imageView"
      android:layout_alignParentLeft="true"
      android:layout_alignParentStart="true"
      android:layout_alignParentBottom="true"
      android:layout_alignParentRight="true"
      android:layout_alignParentEnd="true">

      <ListView
         android:id="@+id/listView1"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:layout_centerVertical="true" >
      </ListView>

   </ScrollView>

</RelativeLayout>

以下是对 res/layout/activity_display_contact.xml 的内容

Following is the content of the res/layout/activity_display_contact.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:id="@+id/scrollView1"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   tools:context=".DisplayContact" >

   <RelativeLayout
      android:layout_width="match_parent"
      android:layout_height="370dp"
      android:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin">

      <EditText
         android:id="@+id/editTextName"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_marginTop="5dp"
         android:layout_marginLeft="82dp"
         android:ems="10"
         android:inputType="text" >
      </EditText>

      <EditText
         android:id="@+id/editTextEmail"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/editTextStreet"
         android:layout_below="@+id/editTextStreet"
         android:layout_marginTop="22dp"
         android:ems="10"
         android:inputType="textEmailAddress" />

      <TextView
         android:id="@+id/textView1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBottom="@+id/editTextName"
         android:layout_alignParentLeft="true"
         android:text="@string/name"
         android:textAppearance="?android:attr/textAppearanceMedium" />

      <Button
         android:id="@+id/button1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/editTextCity"
         android:layout_alignParentBottom="true"
         android:layout_marginBottom="28dp"
         android:onClick="run"
         android:text="@string/save" />

      <TextView
         android:id="@+id/textView2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBottom="@+id/editTextEmail"
         android:layout_alignLeft="@+id/textView1"
         android:text="@string/email"
         android:textAppearance="?android:attr/textAppearanceMedium" />

      <TextView
         android:id="@+id/textView5"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBottom="@+id/editTextPhone"
         android:layout_alignLeft="@+id/textView1"
         android:text="@string/phone"
         android:textAppearance="?android:attr/textAppearanceMedium" />

      <TextView
         android:id="@+id/textView4"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_above="@+id/editTextEmail"
         android:layout_alignLeft="@+id/textView5"
         android:text="@string/street"
         android:textAppearance="?android:attr/textAppearanceMedium" />

      <EditText
         android:id="@+id/editTextCity"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignRight="@+id/editTextName"
         android:layout_below="@+id/editTextEmail"
         android:layout_marginTop="30dp"
         android:ems="10"
         android:inputType="text" />

      <TextView
         android:id="@+id/textView3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignBaseline="@+id/editTextCity"
         android:layout_alignBottom="@+id/editTextCity"
         android:layout_alignParentLeft="true"
         android:layout_toLeftOf="@+id/editTextEmail"
         android:text="@string/country"
         android:textAppearance="?android:attr/textAppearanceMedium" />

      <EditText
         android:id="@+id/editTextStreet"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/editTextName"
         android:layout_below="@+id/editTextPhone"
         android:ems="10"
         android:inputType="text" >

         <requestFocus />
      </EditText>

      <EditText
         android:id="@+id/editTextPhone"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/editTextStreet"
         android:layout_below="@+id/editTextName"
         android:ems="10"
         android:inputType="phone|text" />

   </RelativeLayout>
</ScrollView>

以下是对 res/value/string.xml 的内容

Following is the content of the res/value/string.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <string name="app_name">Address Book</string>
   <string name="action_settings">Settings</string>
   <string name="hello_world">Hello world!</string>
   <string name="Add_New">Add New</string>
   <string name="edit">Edit Contact</string>
   <string name="delete">Delete Contact</string>
   <string name="title_activity_display_contact">DisplayContact</string>
   <string name="name">Name</string>
   <string name="phone">Phone</string>
   <string name="email">Email</string>
   <string name="street">Street</string>
   <string name="country">City/State/Zip</string>
   <string name="save">Save Contact</string>
   <string name="deleteContact">Are you sure, you want to delete it.</string>
   <string name="yes">Yes</string>
   <string name="no">No</string>
</resources>

以下是对 res/menu/main_menu.xml 的内容

Following is the content of the res/menu/main_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >

   <item android:id="@+id/item1"
      android:icon="@drawable/add"
      android:title="@string/Add_New" >
   </item>

</menu>

以下是对 res/menu/display_contact.xml 的内容

Following is the content of the res/menu/display_contact.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
   <item
      android:id="@+id/Edit_Contact"
      android:orderInCategory="100"
      android:title="@string/edit"/>

   <item
      android:id="@+id/Delete_Contact"
      android:orderInCategory="100"
      android:title="@string/delete"/>

</menu>

这是该项目的默认 AndroidManifest.xml

This is the defualt AndroidManifest.xml of this project

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapplication" >

   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >

      <activity
         android:name=".MainActivity"
         android:label="@string/app_name" >

         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>

      </activity>

      <activity android:name=".DisplayContact"/>

   </application>
</manifest>

我们尝试运行该应用程序。我假设您已将实际 Android 计算机设备连接到您的计算机。要从 Android Studio 运行该应用，请打开项目的活动文件之一并从工具栏中单击运行图标。在启动您的应用程序之前，Android Studio 将显示以下窗口以选择您想要运行 Android 应用程序的位置。

Let’s try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Android studio , open one of your project’s activity files and click Run icon from the tool bar. Before starting your application,Android studio will display following window to select an option where you want to run your Android application.

choose device

选择你的移动设备作为选项，然后检查你的移动设备，它将显示以下屏幕 −

Select your mobile device as an option and then check your mobile device which will display following screen −

data base

现在打开您的可选菜单，它将显示如下图像：可选菜单在不同版本中显示的位置不同

Now open your optional menu, it will show as below image:* Optional menu appears different places on different versions*

data base1

点击菜单屏幕的添加按钮以添加新联系人。它将显示以下屏幕 −

Click on the add button of the menu screen to add a new contact. It will display the following screen −

data1

它将显示以下字段。请输入所需的信息，然后点击保存联系人。它将使您返回主屏幕。

It will display the following fields. Please enter the required information and click on save contact. It will bring you back to main screen.

data base2

现在我们的联系人 sai 已被添加。为了了解数据库创建在何处。打开您的 android studio，连接您的移动设备。进入 tools/android/android device monitor 。现在浏览文件管理器选项卡。现在浏览这个文件夹 /data/data/<your.package.name>/databases<database-name>.

Now our contact sai has been added.In order to see that where is your database is created. Open your android studio, connect your mobile. Go tools/android/android device monitor. Now browse the file explorer tab. Now browse this folder /data/data/<your.package.name>/databases<database-name>.