Android初试--Android中的ContentProvider(2)

客官°小女子只卖身不卖艺 2022-07-27 15:53 215阅读 0赞

ContentProvider(内容提供者、数据共享)  
创建ContentProvider  
1.创建一个新类继承ContentProvider  
2.重写必要的方法  
public boolean onCreate();  
该方法在ContentProvider创建后就会被调用，Android开机后，ContentProvider在其它应用第一次访问它时才会被创建。  
public Uri insert(Uri uri, ContentValues values);  
该方法用于供外部应用往ContentProvider添加数据。  
public int delete(Uri uri, String selection, String\[\] selectionArgs);  
该方法用于供外部应用从ContentProvider删除数据。  
public int update(Uri uri, ContentValues values, String selection, String\[\] selectionArgs);  
该方法用于供外部应用更新ContentProvider中的数据。  
public Cursor query(Uri uri, String\[\] projection, String selection, String\[\] selectionArgs, String sortOrder);  
该方法用于供外部应用从ContentProvider中获取数据。  
public String getType(Uri uri);  
该方法返回当前Uri所代表数据的MIME类型。  
如果要操作的数据属于集合类型，那么MIME类型字符串应该以vnd.android.cursor.dir/开头  
如果要操作的数据属于非集合类型数据，那么MIME类型字符串应该以vnd.android.cursor.item/开头  
3.配置  
<manifest .... >  
<application android:icon="@drawable/icon" android:label="@string/app\_name">  
...................  
<provider android:name=".PersonContentProvider" android:authorities="com.rxr.providers.personprovider"/>  
</application>  
</manifest>  
android:authorities="com.rxr.providers.personprovider" 的访问方式  
Uri-----访问ContentProvider的路径  
Uri代表了要操作的数据，主要包含两部分信息：  
1、需要操作的ContentProvider。  
2、对ContentProvider中的什么数据进行操作。  
一个Uri由以下几部分组成：  
content://com.rxr.providers.personprovider/person/1  
|————|————————————————|—————|  
schema 主机名或域名 路径  
schema----schema为content://  
主机名或域名-------需要操作的ContentProvider  
路径-------操作 ContentProvider中的数据。  
Uri----访问person表  
content://com.rxr.providers.personprovider/person  
Uri----访问person表第2条数据  
content://com.rxr.providers.personprovider/person/2  
Uri----访问person表第2条数据name值  
content://com.rxr.providers.personprovider/person/2/age  
Uri类中的parse()方法---将字符串转化成Uri对象。  
UriMatcher类---匹配的Uri路径  
addURI（“Uri路径”,"表名称"，返回匹配码）  
match(uri)方法对输入的Uri进行匹配，如果匹配就返回匹配码。  
ContentUris类使用介绍  
ContentUris类用于操作Uri路径后面的ID部分，它有两个比较实用的方法  
withAppendedId(uri, id)用于为路径加上ID部分  
parseId(uri)方法用于从路径中获取ID部分：  
ContentResolver类  
当外部应用需要对ContentProvider中的数据进行添加、删除、修改和查询操作  
监听ContentProvider中数据的变化  
ContentProvider的访问者需要知道ContentProvider中的数据是否发生了变化，则发生数据变化时在ContentProvider中调用getContentResolver().notifyChange(Uri uri, ContentObserver observer)方法通知注册在此Uri上的访问者。  
  
DBOpenHelper.java  
  
package com.example.contentproviderdemo;  
import android.content.Context;  
import android.database.sqlite.SQLiteDatabase;  
import android.database.sqlite.SQLiteOpenHelper;  
public class DBOpenHelper extends SQLiteOpenHelper\{  
private static final String databasename="data\_db";  
private static final int databaseversion=1;  
public DBOpenHelper(Context context) \{  
super(context, databasename, null, databaseversion);  
\}  
@Override  
public void onCreate(SQLiteDatabase database) \{  
database.execSQL("create table person(personid integer primary key autoincrement, name varchar(20), age integer)");  
\}  
@Override  
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) \{  
\}  
\}  
  
PersonContentProvider.java  
  
package com.example.contentproviderdemo;  
import android.content.ContentProvider;  
import android.content.ContentUris;  
import android.content.ContentValues;  
import android.content.UriMatcher;  
import android.database.Cursor;  
import android.database.sqlite.SQLiteDatabase;  
import android.net.Uri;  
public class PersonContentProvider extends ContentProvider\{  
private DBOpenHelper dbOpenHelper=null;  
//常量UriMatcher.NO\_MATCH表示不匹配任何路径时的返回码  
private static final UriMatcher URI\_MATCHER = new UriMatcher(UriMatcher.NO\_MATCH);  
添加需要匹配的uri，如果匹配就会返回匹配码  
static\{  
// content://com.rxr.test.personcontentprovider/person  
URI\_MATCHER.addURI("com.rxr.test.personcontentprovider", "person", 1);  
// content://com.rxr.test.personcontentprovider/person/2  
// content://com.rxr.test.personcontentprovider/person/2/name  
URI\_MATCHER.addURI("com.rxr.test.personcontentprovider", "person/\#", 2);  
\}  
@Override  
public boolean onCreate() \{  
this.dbOpenHelper=new DBOpenHelper(getContext());  
return true;  
\}  
@Override  
public String getType(Uri uri) \{  
String info=null;  
switch(URI\_MATCHER.match(uri))\{  
case 1:  
info="vnd.android.cursor.dir/person"; //集合数据  
break;  
case 2:  
info="vnd.android.cursor.item/person"; //非集合类型  
break;  
 default:throw new IllegalArgumentException("不知道的uri:" + uri);  
\}  
return info;  
\}  
public Uri insert(Uri uri, ContentValues values) \{  
//得到sqliteDatabase对象  
SQLiteDatabase database=dbOpenHelper.getWritableDatabase();  
switch(URI\_MATCHER.match(uri))\{  
case 1:  
long rowid =database.insert("person", null, values);  
Uri insertUri= ContentUris.withAppendedId(uri, rowid);  
this.getContext().getContentResolver().notifyChange(uri, null);  
return insertUri;   
default :throw new IllegalArgumentException("不知道的uri:" + uri);  
\}  
\}  
@Override  
public int delete(Uri uri, String selection, String\[\] selectionargs) \{  
//得到sqliteDatabase对象  
SQLiteDatabase database=dbOpenHelper.getWritableDatabase();  
int count = 0;  
 switch(URI\_MATCHER.match(uri))\{  
//content://com.rxr.test.personcontentprovider/person  
 case 1://删除整张表中的数据  
 count=database.delete("person", selection, selectionargs);  
 return count;  
 case 2://删除整张表中的某一条数据  
 //content://com.rxr.test.personcontentprovider/person/2  
 long id = ContentUris.parseId(uri);  
 //根据id删除数据  
 String whereString = "personid=" + id;  
 if(selection != null && !"".equals(selection))\{  
whereString = selection + " and " + whereString;  
\}  
 count=database.delete("person", whereString, selectionargs);  
 return count;  
 default:  
throw new IllegalArgumentException("不知道的uri:" + uri);  
\}  
\}  
@Override  
public int update(Uri uri, ContentValues values, String selection, String\[\] selectionargs) \{  
//得到sqliteDatabase对象  
SQLiteDatabase database=dbOpenHelper.getWritableDatabase();  
int count = 0;  
switch(URI\_MATCHER.match(uri))\{  
//content://com.rxr.test.personcontentprovider/person  
 case 1://修改整张表中的数据  
 count=database.update("person", values, selection, selectionargs);  
 return count;  
 case 2://修改整张表中的某一条数据  
 //content://com.rxr.test.personcontentprovider/person/2  
 long id = ContentUris.parseId(uri);  
 //根据id修改数据  
 String whereString = "personid=" + id;  
 if(selection != null && !"".equals(selection))\{  
whereString = selection + " and " + whereString;  
\}  
 count=database.update("person",values, whereString, selectionargs);  
 return count;  
 default:  
throw new IllegalArgumentException("不知道的uri:" + uri);  
\}  
\}  
@Override  
public Cursor query(Uri uri, String\[\] projection, String selection, String\[\] selectionargs,String sortOrder) \{  
//得到sqliteDatabase对象  
SQLiteDatabase database=dbOpenHelper.getWritableDatabase();  
Cursor cursor =null;  
switch(URI\_MATCHER.match(uri))\{  
//content://com.rxr.test.personcontentprovider/person  
 case 1://查询整张表中的数据  
 cursor=database.query("person", projection, selection, selectionargs, null, null, sortOrder);  
 return cursor;  
 case 2://查询整张表中的某一条数据  
 //content://com.rxr.test.personcontentprovider/person/2  
 long id = ContentUris.parseId(uri);  
 //根据id修改数据  
 String whereString = "personid=" + id;  
 if(selection != null && !"".equals(selection))\{  
whereString = selection + " and " + whereString;  
\}  
 cursor=database.query("person", projection, whereString, selectionargs, null, null, sortOrder);  
 return cursor;  
 default:  
throw new IllegalArgumentException("不知道的uri:" + uri);  
\}  
\}  
\}

main布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
android:layout\_width="fill\_parent"  
android:layout\_height="fill\_parent"  
android:orientation="vertical" >  
<Button  
android:id="@+id/button1"  
android:layout\_width="match\_parent"  
android:layout\_height="wrap\_content"  
android:text="向ContentProvider添加数据" />  
<Button  
android:id="@+id/button2"  
android:layout\_width="match\_parent"  
android:layout\_height="wrap\_content"  
android:text="修改ContentProvider中的数据" />  
<Button  
android:id="@+id/button3"  
android:layout\_width="match\_parent"  
android:layout\_height="wrap\_content"  
android:text="查询ContentProvider中所有数据" />  
<Button  
android:id="@+id/button4"  
android:layout\_width="match\_parent"  
android:layout\_height="wrap\_content"  
android:text="查询ContentProvider中某一条数据" />  
<Button  
android:id="@+id/button5"  
android:layout\_width="match\_parent"  
android:layout\_height="wrap\_content"  
android:text="删除ContentProvider中某一条数据" />  
<Button  
android:id="@+id/button6"  
android:layout\_width="wrap\_content"  
android:layout\_height="wrap\_content"  
android:text="得到ContentProvider的URI的数据类型" />  
</LinearLayout>  
  
MainActivity.java  
  
package com.example.contentproviderdemo;  
import android.app.Activity;  
import android.content.ContentResolver;  
import android.content.ContentValues;  
import android.database.Cursor;  
import android.net.Uri;  
import android.os.Bundle;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
public class MainActivity extends Activity \{  
private MyClick click=null;  
private Button insertButton=null;  
private Button updateButton=null;  
private Button selectAllButton=null;  
private Button selectAButton=null;  
private Button deleteButton=null;  
private Button typeButton=null;  
@Override  
protected void onCreate(Bundle savedInstanceState) \{  
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity\_main);  
initView();  
\}  
private void initView() \{  
click=new MyClick();  
insertButton=(Button)findViewById(R.id.button1);  
insertButton.setOnClickListener(click);  
updateButton=(Button)findViewById(R.id.button2);  
updateButton.setOnClickListener(click);  
selectAllButton=(Button)findViewById(R.id.button3);  
selectAllButton.setOnClickListener(click);  
selectAButton=(Button)findViewById(R.id.button4);  
selectAButton.setOnClickListener(click);  
deleteButton=(Button)findViewById(R.id.button5);  
deleteButton.setOnClickListener(click);  
typeButton=(Button)findViewById(R.id.button6);  
typeButton.setOnClickListener(click);  
\}  
public class MyClick implements OnClickListener\{  
@Override  
public void onClick(View view) \{  
ContentResolver contentResolver=MainActivity.this.getContentResolver();  
switch(view.getId())\{  
case R.id.button1:  
String insertString="content://com.rxr.test.personcontentprovider/person";  
Uri inserturi=Uri.parse(insertString);  
ContentValues values=new ContentValues();  
values.put("name", "wangwu");  
values.put("age", 23);  
Uri newUri=contentResolver.insert(inserturi, values);  
System.out.println(newUri.toString());  
 break;  
case R.id.button2:  
String updateString="content://com.rxr.test.personcontentprovider/person/1";  
Uri updateuri=Uri.parse(updateString);  
ContentValues updatevalues=new ContentValues();  
updatevalues.put("name", "lisi");  
updatevalues.put("age", 34);  
int temp=contentResolver.update(updateuri, updatevalues, null, null);  
System.out.println(temp);  
break;  
case R.id.button3:  
String selectString="content://com.rxr.test.personcontentprovider/person";  
Uri selecturi=Uri.parse(selectString);  
Cursor cursor=contentResolver.query(selecturi, null, null, null, null);  
while(cursor.moveToNext())\{  
int id=cursor.getInt(cursor.getColumnIndex("personid"));  
String name=cursor.getString(cursor.getColumnIndex("name"));  
int age=cursor.getInt(cursor.getColumnIndex("age"));  
System.out.println(id+" "+name+" "+age);  
\}  
cursor.close();  
break;  
case R.id.button4:  
String selectaString="content://com.rxr.test.personcontentprovider/person/2";  
Uri selectauri=Uri.parse(selectaString);  
Cursor cursor2=contentResolver.query(selectauri, null, null, null, null);  
while(cursor2.moveToNext())\{  
int id=cursor2.getInt(cursor2.getColumnIndex("personid"));  
String name=cursor2.getString(cursor2.getColumnIndex("name"));  
int age=cursor2.getInt(cursor2.getColumnIndex("age"));  
System.out.println(id+" "+name+" "+age);  
\}  
cursor2.close();  
break;  
case R.id.button5:  
String deleteString="content://com.rxr.test.personcontentprovider/person/2";  
Uri deleteuri=Uri.parse(deleteString);  
int temp2=contentResolver.delete(deleteuri, null, null);  
System.out.println(temp2);  
break;  
case R.id.button6:  
String typeString="content://com.rxr.test.personcontentprovider/person";  
Uri typeuri=Uri.parse(typeString);  
String typeinfo=contentResolver.getType(typeuri);  
System.out.println(typeinfo);  
break;   
\}  
\}  
\}  
\}