SQLite数据库与Contentprovider（2）

《SQLite数据库与Contentprovider（2）》要点：
本文介绍了SQLite数据库与Contentprovider（2），希望对您有用。如果有疑问，可以联系我们。

ContentProvider：

在创建ContentProvider时,必要首先使用数据库、文件系统或网络实现底层存储功能,

然后在继承ContentProvider的类中实现基本数据操作的接口函数,包含添加、删除、查找和更新等功能.

调用者不能够直接调用ContentProvider的接口函数,而必要使用ContentResolver对象,

通过URI间接调用ContentProvider.下图是ContentProvider调用关系.

URI：

URI是通用资源标志符(Uniform Resource Identifier),用来定位任何远程或当地的可用资源

ContentProvider使用的URI语法布局如下

content://<authority>/<data_path>/<id>

content://是通用前缀,表现该URI用于ContentProvider定位资源,无需修改.

<authority>是授权者名称,用来确定具体由哪一个ContentProvider提供资源.因此,一般<authority>都由类的小写全称组成,以保证唯一性.

<data_path>是数据路径,用来确定哀求的是哪个数据集.

例如：

content://edu.hrbeu.peopleprovider/people/3

可以省略id(/3)部门那么意味着整个数据.

UriMatcher:

在新构造的ContentProvider类中,通过构造一个UriMatcher,判断URI是单条数据还是多条数据.

public void addURI (String authority,String path,int code)

authority表现匹配的授权者名称

path表现数据路径

#可以代表任何数字 (content://<authority>/<data_path>/#)

code表现返回代码(uriMatcher.match(uri))的返回值)

注册ContentProvider ：

<provider android:name = ".PeopleProvider" android:authorities = "edu.hrbeu.peopleprovider"/> 

实例：

ContentProvider一般用于两个分歧的进程之间的数据共享.

1. 假设我们有一个新的工程(app),在此工程中创建一个people.db数据库,然后通过自定义了一个ContentProvider来共享数据库中的data.
2. 我们可以通过注册provider时用到的authority在配合db path之类的来连接(content://<authority>/<data_path>/#)读取内容提供者(分歧进程)的数据.

首先是步骤1:

*只要在AndroidManifast中注册provider就会执行对应的provider类.无需再MainActivity中调用或无需直接调用自定义的new provider.

即系统自动会加载调用PeopleProvider类.

继承ContentProvider时代码如下：

import android.content.*;import android.database.Cursor;import android.net.Uri; public class PeopleProvider extends ContentProvider{    @Override    public int delete(Uri uri,String selection,String[] selectionArgs) {        // TODO Auto-generated method stub        return 0;    }    @Override    public String getType(Uri uri) {        // TODO Auto-generated method stub        return null;    }     @Override    public Uri insert(Uri uri,ContentValues values) {        // TODO Auto-generated method stub        return null;    }     @Override    public boolean onCreate {        // TODO Auto-generated method stub        return false;    }         @Override    public Cursor query(Uri uri,String[] projection,String[] selectionArgs,String sortOrder) {        // TODO Auto-generated method stub        return null;    }     @Override    public int update(Uri uri,ContentValues values,String[] selectionArgs) {        // TODO Auto-generated method stub        return 0;    }}

类似数据库操作.可以这么理解,相对来说好理解.

开始贴代码...

package edu.hrbeu.contentproviderdemo; import android.content.ContentProvider;import android.content.ContentUris;import android.content.ContentValues;import android.content.Context;import android.content.UriMatcher;import android.database.Cursor;import android.database.SQLException;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;import android.database.sqlite.SQLiteQueryBuilder;import android.net.Uri;public class PeopleProvider extends ContentProvider {        private static final String DB_NAME = "people.db";    private static final String DB_TABLE = "peopleinfo";    private static final int DB_VERSION = 1;        private SQLiteDatabase db;    private DBOpenHelper dbOpenHelper;        private static final int MULTIPLE_PEOPLE = 1;    private static final int SINGLE_PEOPLE = 2;    private static final UriMatcher uriMatcher;    static {         uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);         uriMatcher.addURI(People.AUTHORITY,People.PATH_MULTIPLE,MULTIPLE_PEOPLE);         uriMatcher.addURI(People.AUTHORITY,People.PATH_SINGLE,SINGLE_PEOPLE);    }    @Override    public boolean onCreate {        // TODO Auto-generated method stub        Context context = getContext;        dbOpenHelper = new DBOpenHelper(context,DB_NAME,null,DB_VERSION);        db = dbOpenHelper.getWritableDatabase;         if (db == null) return false;        else  return true;        }    @Override    public Cursor query(Uri uri,String sortOrder) {        // TODO Auto-generated method stub        SQLiteQueryBuilder qb = new SQLiteQueryBuilder;        qb.setTables(DB_TABLE);        switch(uriMatcher.match(uri)){ case SINGLE_PEOPLE: qb.appendWhere(People.KEY_ID + "=" + uri.getPathSegments.get(1)); break; default: break;        }        Cursor cursor = qb.query(db,projection,selection,selectionArgs,sortOrder);        cursor.setNotificationUri(getContext.getContentResolver,uri);        return cursor;    }    @Override    public String getType(Uri uri) {        // TODO Auto-generated method stub        switch(uriMatcher.match(uri)){        case MULTIPLE_PEOPLE:    return People.MINE_TYPE_MULTIPLE;        case SINGLE_PEOPLE:    return People.MINE_TYPE_SINGLE;        default: throw new IllegalArgumentException("Unkown uri:"+uri);}    }    @Override    public Uri insert(Uri uri,ContentValues values) {        // TODO Auto-generated method stub        long id = db.insert(DB_TABLE,values);        if ( id > 0 ){ Uri newUri = ContentUris.withAppendedId(People.CONTENT_URI,id); getContext.getContentResolver.notifyChange(newUri,null); return newUri;        }        throw new SQLException("Failed to insert row into " + uri);    }    @Override    public int delete(Uri uri,String[] selectionArgs) {        // TODO Auto-generated method stub        int count = 0;        switch(uriMatcher.match(uri)){    case MULTIPLE_PEOPLE: count = db.delete(DB_TABLE,selectionArgs); break; case SINGLE_PEOPLE: String segment = uri.getPathSegments.get(1); count = db.delete(DB_TABLE,People.KEY_ID + "=" + segment,selectionArgs); break;   default: throw new IllegalArgumentException("Unsupported URI:" + uri);}        getContext.getContentResolver.notifyChange(uri,null);         return count;    }    @Override    public int update(Uri uri,String[] selectionArgs) {        // TODO Auto-generated method stub        int count;        switch(uriMatcher.match(uri)){ case MULTIPLE_PEOPLE: count = db.update(DB_TABLE,values,selectionArgs); break; case SINGLE_PEOPLE: String segment = uri.getPathSegments.get(1); count = db.update(DB_TABLE,People.KEY_ID+"="+segment,selectionArgs); break; default: throw new IllegalArgumentException("Unknow URI:" + uri);             }        getContext.getContentResolver.notifyChange(uri,null);        return count;    }          private static class DBOpenHelper extends SQLiteOpenHelper {  public DBOpenHelper(Context context,String name,CursorFactory factory,int version) { super(context,name,factory,version); } private static final String DB_CREATE = "create table " +  DB_TABLE + " (" + People.KEY_ID + " integer primary key autoincrement," + People.KEY_NAME+ " text not null," + People.KEY_AGE+ " integer," + People.KEY_HEIGHT + " float);";        @Override        public void onCreate(SQLiteDatabase _db) { // TODO Auto-generated method stub _db.execSQL(DB_CREATE);        }        @Override        public void onUpgrade(SQLiteDatabase _db,int oldVersion,int newVersion) { // TODO Auto-generated method stub _db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE); onCreate(_db);        }      }    }

package edu.hrbeu.contentproviderdemo;import android.net.Uri; public class People{        public static final String MIME_DIR_PREFIX = "vnd.android.cursor.dir";    public static final String MIME_ITEM_PREFIX = "vnd.android.cursor.item";    public static final String MINE_ITEM = "vnd.hrbeu.people";        public static final String MINE_TYPE_SINGLE = MIME_ITEM_PREFIX + "/" + MINE_ITEM;    public static final String MINE_TYPE_MULTIPLE = MIME_DIR_PREFIX + "/" + MINE_ITEM;    public static final String AUTHORITY = "edu.hrbeu.peopleprovider";    public static final String PATH_SINGLE = "people/#";    public static final String PATH_MULTIPLE = "people";    public static final String CONTENT_URI_STRING = "content://" + AUTHORITY + "/" + PATH_MULTIPLE;    public static final Uri  CONTENT_URI = Uri.parse(CONTENT_URI_STRING);         public static final String KEY_ID = "_id";    public static final String KEY_NAME = "name";    public static final String KEY_AGE = "age";    public static final String KEY_HEIGHT = "height";}

MainActivity是空的...不贴出来了.

运行成果没有任何内容,因为仅是添加了一个provider.

看一下步调2：

在另一个App中调用此ContentProvider.

无需再AndroidManifast中注册provider.

只需对应步骤1中的People类里的静态变量是完全匹配的便是可以了.

也就是说URI需要与我们自定义的ContentProvider坚持一致.

package edu.hrbeu.contentresolverdemo;import android.net.Uri; public class People{        public static final String MIME_DIR_PREFIX = "vnd.android.cursor.dir";    public static final String MIME_ITEM_PREFIX = "vnd.android.cursor.item";    public static final String MINE_ITEM = "vnd.hrbeu.people";        public static final String MINE_TYPE_SINGLE = MIME_ITEM_PREFIX + "/" + MINE_ITEM;    public static final String MINE_TYPE_MULTIPLE = MIME_DIR_PREFIX + "/" + MINE_ITEM;    public static final String AUTHORITY = "edu.hrbeu.peopleprovider";    public static final String PATH_SINGLE = "people/#";    public static final String PATH_MULTIPLE = "people";    public static final String CONTENT_URI_STRING = "content://" + AUTHORITY + "/" + PATH_MULTIPLE;    public static final Uri  CONTENT_URI = Uri.parse(CONTENT_URI_STRING);         public static final String KEY_ID = "_id";    public static final String KEY_NAME = "name";    public static final String KEY_AGE = "age";    public static final String KEY_HEIGHT = "height";}

操作Contentpriver提供的数据我们必要用到ContentResolver：

package edu.hrbeu.contentresolverdemo;import android.app.Activity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.content.ContentResolver;import android.content.ContentValues;import android.database.Cursor;import android.net.Uri;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class ContentResolverDemo extends Activity {    private EditText nameText;    private EditText ageText;    private EditText heightText;    private EditText idEntry;    private TextView labelView;    private TextView displayView;    private ContentResolver resolver;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_content_resolver_demo);        nameText = (EditText) findViewById(R.id.name);        ageText = (EditText) findViewById(R.id.age);        heightText = (EditText) findViewById(R.id.hight);        idEntry = (EditText) findViewById(R.id.id);        labelView = (TextView) findViewById(R.id.label);        displayView = (TextView) findViewById(R.id.display);        Button addButton = (Button) findViewById(R.id.button1);        Button queryAllButton = (Button) findViewById(R.id.button2);        Button clearButton = (Button) findViewById(R.id.button3);        Button queryButton = (Button) findViewById(R.id.button6);        Button deleteButton = (Button) findViewById(R.id.button5);        Button updateButton = (Button) findViewById(R.id.button7);        resolver = this.getContentResolver;        addButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub ContentValues values = new ContentValues; values.put(People.KEY_NAME,nameText.getText.toString); values.put(People.KEY_AGE,Integer.parseInt(ageText.getText.toString)); values.put(People.KEY_HEIGHT,Float.parseFloat(heightText.getText.toString)); Uri newUri = resolver.insert(People.CONTENT_URI,values); labelView.setText("添加成功,URI:" + newUri); }        });        queryAllButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub Cursor cursor = resolver.query(People.CONTENT_URI,new String[] { People.KEY_ID,People.KEY_NAME,People.KEY_AGE,People.KEY_HEIGHT },null); if (cursor == null) { labelView.setText("数据库中没有数据"); return; } labelView.setText("数据库：" + String.valueOf(cursor.getCount) + "条记录"); String msg = ""; if (cursor.moveToFirst) { do { msg += "ID：" + cursor.getInt(cursor .getColumnIndex(People.KEY_ID)) + ","; msg += "姓名：" + cursor.getString(cursor .getColumnIndex(People.KEY_NAME)) + ","; msg += "年龄：" + cursor.getInt(cursor .getColumnIndex(People.KEY_AGE)) + ","; msg += "身高：" + cursor.getFloat(cursor .getColumnIndex(People.KEY_HEIGHT)) + "n"; } while (cursor.moveToNext); } displayView.setText(msg); }        });        clearButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub displayView.setText(""); }        });        queryButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText.toString); Cursor cursor = resolver.query(uri,null); if (cursor == null) { labelView.setText("数据库中没有数据"); return; } String msg = ""; if (cursor.moveToFirst) { msg += "ID：" + cursor.getInt(cursor .getColumnIndex(People.KEY_ID)) + ","; msg += "身高：" + cursor.getFloat(cursor .getColumnIndex(People.KEY_HEIGHT)) + "n"; } labelView.setText("数据库："); displayView.setText(msg); }        });        deleteButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText.toString); int result = resolver.delete(uri,null); String msg = "删除ID为" + idEntry.getText.toString + "的数据" + (result > 0 ? "成功" : "失败"); labelView.setText(msg); }        });        updateButton.setOnClickListener(new OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub ContentValues values = new ContentValues; values.put(People.KEY_NAME,Float.parseFloat(heightText.getText.toString)); Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText.toString); int result = resolver.update(uri,null); String msg = "更新ID为" + idEntry.getText.toString + "的数据" + (result > 0 ? "成功" : "失败"); labelView.setText(msg); }        });    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater.inflate(R.menu.content_resolver_demo,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);    }}

事成相识的结构文件也附上：

<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: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="edu.hrbeu.contentresolverdemo.ContentResolverDemo" >    <TextView android:id="@+id/Username"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:text="用户名：">    </TextView>    <EditText        android:id="@+id/name"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_below="@id/Username" >    </EditText>    <TextView android:id="@+id/Userage"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/name"        android:text="年龄：">    </TextView>    <EditText android:id="@+id/age"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/Userage">    </EditText>         <TextView android:id="@+id/Userhight"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/age"        android:text="身高：">    </TextView>    <EditText android:id="@+id/hight"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/Userhight">    </EditText>    <Button        android:id="@+id/button2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignBaseline="@+id/button1"        android:layout_alignBottom="@+id/button1"        android:layout_centerHorizontal="true"        android:text="全部显示" />    <Button        android:id="@+id/button3"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignBaseline="@+id/button2"        android:layout_alignBottom="@+id/button2"        android:layout_alignRight="@+id/hight"        android:text="清除显示" />        <TextView android:id="@+id/Userid"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/button1"        android:text="ID：">    </TextView>    <EditText android:id="@+id/id"         android:layout_height="wrap_content"         android:layout_width="fill_parent"         android:layout_below="@id/Userid">    </EditText>    <Button        android:id="@+id/button6"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignBaseline="@+id/button5"        android:layout_alignBottom="@+id/button5"        android:layout_alignLeft="@+id/button2"        android:text="ID查询" />    <Button        android:id="@+id/button7"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignBaseline="@+id/button6"        android:layout_alignBottom="@+id/button6"        android:layout_alignLeft="@+id/button3"        android:text="ID更新" />    <Button        android:id="@+id/button1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_below="@+id/hight"        android:text="添加数据" />    <Button        android:id="@+id/button5"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignLeft="@+id/id"        android:layout_below="@+id/id"        android:text="ID删除" />    <TextView        android:id="@+id/display"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_alignLeft="@+id/label"        android:layout_below="@+id/label"        android:layout_marginTop="23dp" />    <TextView        android:id="@+id/label"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_alignLeft="@+id/button5"        android:layout_below="@+id/button6"        android:layout_marginTop="14dp" /></RelativeLayout>

运行成果：

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（编辑：李大同）

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