ContentProvider為Android四大組件之一，主要用來應用程序之間的數(shù)據(jù)共享，也就是說一個應用程序用ContentProvider將自己的數(shù)據(jù)暴露出來，其他應用程序通過ContentResolver來對其暴露出來的數(shù)據(jù)進行增刪改查。
ContenProvider與ContentResolver之間的對話同過Uri(通用資源標識符)，一個不恰當?shù)谋扔骶秃孟駷g覽器要顯示一個網(wǎng)頁要有一個東西發(fā)送請求，這相當于ContentResolver，你要拿東西就要知道去哪里拿，你就得知道服務器的域名或網(wǎng)址，而這個網(wǎng)址就相當于Uri，當?shù)竭_服務器的時候服務器要有個東西來處理，這就相當于ContenProvider。
A程序通過ContenProvider來暴露數(shù)據(jù)的基本步驟：
1、實現(xiàn)一個ContenProvider的子類，并重寫query,insert,update,delete等這幾個方法，
2、在androidmanifest.xml中注冊ContenProvider,指定的android:authorities屬性
B程序通過ContentResolver來操作A程序暴露出來的數(shù)據(jù)的基本步驟
1、通過content的getContentResolver()來獲取ContentResolver對象
2、通過ContentResolver對象來query,insert,update,delete來進行操作
在實現(xiàn)query,insert,update,delete時有一個重要的參數(shù)Uri類,Uri一個中要的方法Uri.parse(String str)用來解析str字符串，而str字符串格式一般都有A程序提供給B程序，B程序按照指定的格式去請求 。比如：content//:com.android.xiong.ConentProviderTestA.firstContentProvider/xiong 其格式一般分為三個部分：content//:這部分是固定不變的 而com.android.xiong.ConentProviderTestA.firstContentProvider表A程序在androidmanifest.xml注冊的android:authorities屬性，xiong則表示資源部分
<provider android:name="com.android.xiong.conentprovidertesta.FirstContentProvider" android:authorities="com.android.xiong.ConentProviderTestA.firstContentProvider" android:exported="true" > </provider>
實例如下
A程序:
UserInfo.java
package com.android.xiong.conentprovidertesta; import android.content.ContentProvider; import android.content.ContentValues; import android.content.UriMatcher; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.net.Uri; public class FirstContentProvider extends ContentProvider { // UriMatcher類主要用來匹配Uri private static final UriMatcher uriMatcher = new UriMatcher( UriMatcher.NO_MATCH); private MySqlite mysqlite; static { // 注冊向外部程序提供的Uri uriMatcher.addURI(UserInfo.AUTOR, "userinfo", 1); uriMatcher.addURI(UserInfo.AUTOR, "userinfoall", 2); } //刪除數(shù)據(jù) @Override public int delete(Uri uri, String selection, String[] selectionArgs) { int number = 0; if (uriMatcher.match(uri) == 1) { // 根據(jù)條件刪除數(shù)據(jù),并獲取刪除的行數(shù) number = mysqlite.getReadableDatabase().delete("user_info", selection, selectionArgs); } // 通知數(shù)據(jù)已經(jīng)改變 getContext().getContentResolver().notifyChange(uri, null); return number; } @Override public String getType(Uri uri) { return null; } //插入數(shù)據(jù) @Override public Uri insert(Uri uri, ContentValues values) { String name = values.getAsString(UserInfo.User.NAME).toString(); String age = values.getAsInteger(UserInfo.User.AGE).toString(); String maxId = "select max(id) id from user_info"; Cursor cursor = mysqlite.getReadableDatabase().rawQuery(maxId, null); cursor.moveToFirst(); int userid = cursor.getInt(0) + 1; if (uriMatcher.match(uri) == 1) { mysqlite.getWritableDatabase().execSQL( "insert into user_info values(?,?,?)", new String[] { String.valueOf(userid), name, age }); } return uri; } // 連接數(shù)據(jù)庫 @Override public boolean onCreate() { mysqlite = new MySqlite(getContext(), "userinfo.db", null, 1); return true; } //查詢數(shù)據(jù) @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { SQLiteDatabase sqlite = mysqlite.getReadableDatabase(); String str = "select name,age from user_info"; if (uriMatcher.match(uri) == 1) { str += " where " + selection; } Cursor cursor = sqlite.rawQuery(str, selectionArgs); return cursor; } //修改數(shù)據(jù) @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { SQLiteDatabase sqlite = mysqlite.getReadableDatabase(); int number = 0; if (uriMatcher.match(uri) == 1) { number = sqlite.update("user_info", values, selection, selectionArgs); } return number; } }
FirstContentProvider.java
package com.android.xiong.conentprovidertesta; import android.content.ContentProvider; import android.content.ContentValues; import android.content.UriMatcher; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.net.Uri; public class FirstContentProvider extends ContentProvider { // UriMatcher類主要用來匹配Uri private static final UriMatcher uriMatcher = new UriMatcher( UriMatcher.NO_MATCH); private MySqlite mysqlite; static { // 注冊向外部程序提供的Uri uriMatcher.addURI(UserInfo.AUTOR, "userinfo", 1); uriMatcher.addURI(UserInfo.AUTOR, "userinfoall", 2); } //刪除數(shù)據(jù) @Override public int delete(Uri uri, String selection, String[] selectionArgs) { int number = 0; if (uriMatcher.match(uri) == 1) { // 根據(jù)條件刪除數(shù)據(jù),并獲取刪除的行數(shù) number = mysqlite.getReadableDatabase().delete("user_info", selection, selectionArgs); } // 通知數(shù)據(jù)已經(jīng)改變 getContext().getContentResolver().notifyChange(uri, null); return number; } @Override public String getType(Uri uri) { return null; } //插入數(shù)據(jù) @Override public Uri insert(Uri uri, ContentValues values) { String name = values.getAsString(UserInfo.User.NAME).toString(); String age = values.getAsInteger(UserInfo.User.AGE).toString(); String maxId = "select max(id) id from user_info"; Cursor cursor = mysqlite.getReadableDatabase().rawQuery(maxId, null); cursor.moveToFirst(); int userid = cursor.getInt(0) + 1; if (uriMatcher.match(uri) == 1) { mysqlite.getWritableDatabase().execSQL( "insert into user_info values(?,?,?)", new String[] { String.valueOf(userid), name, age }); } return uri; } // 連接數(shù)據(jù)庫 @Override public boolean onCreate() { mysqlite = new MySqlite(getContext(), "userinfo.db", null, 1); return true; } //查詢數(shù)據(jù) @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { SQLiteDatabase sqlite = mysqlite.getReadableDatabase(); String str = "select name,age from user_info"; if (uriMatcher.match(uri) == 1) { str += " where " + selection; } Cursor cursor = sqlite.rawQuery(str, selectionArgs); return cursor; } //修改數(shù)據(jù) @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { SQLiteDatabase sqlite = mysqlite.getReadableDatabase(); int number = 0; if (uriMatcher.match(uri) == 1) { number = sqlite.update("user_info", values, selection, selectionArgs); } return number; } } MySqlite.java
package com.android.xiong.conentprovidertesta; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class MySqlite extends SQLiteOpenHelper { static final String sql = "create table user_info(id int,name varchar(30),age int)"; public MySqlite(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { //創(chuàng)建數(shù)據(jù)表 db.execSQL(sql); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub } } MainActivity.java
package com.android.xiong.conentprovidertesta; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class MySqlite extends SQLiteOpenHelper { static final String sql = "create table user_info(id int,name varchar(30),age int)"; public MySqlite(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { //創(chuàng)建數(shù)據(jù)表 db.execSQL(sql); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub } } activity_main.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" tools:context=".MainActivity" > <TextView android:id="@+id/txt1" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center_horizontal" android:text="添加信息" android:textSize="20dp" /> <EditText android:id="@+id/ed1" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="添加name" /> <EditText android:id="@+id/ed2" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="添加age" android:inputType="number" /> <Button android:id="@+id/bt1" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="提交數(shù)據(jù)" /> <ListView android:id="@+id/lists" android:layout_width="match_parent" android:layout_height="wrap_content" > </ListView> </LinearLayout>
item.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:id="@+id/item_txt1" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <TextView android:id="@+id/item_txt2" android:layout_width="wrap_content" android:layout_height="wrap_content"/> </LinearLayout>
B程序
UserInfo.java
package com.android.xiong.contentprovidertestb; //向外部程序提供一個工具類 public class UserInfo { // 獲取ContentProvider的“域名” public static final String AUTOR = "com.android.xiong.ConentProviderTestA.firstContentProvider"; //定義一個靜態(tài)內(nèi)部類，提供ContentProvider可操作的列 public static final class User { public static final String ID="id"; public static final String NAME="name"; public static final String AGE="age"; //定義該content提供服務的一個Uri public static final String uri="content://"+AUTOR+"/userinfo"; public static final String uriall="content://"+AUTOR+"/userinfoall"; } } MainActivity.java
package com.android.xiong.contentprovidertestb; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import android.widget.ScrollView; import android.widget.SimpleAdapter; import android.widget.Toast; public class MainActivity extends Activity { private Button bt1, bt2, bt3, bt4; private EditText ed1, ed2; private ListView list1; private ScrollView sc1; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); bt1 = (Button) findViewById(R.id.bt1); bt2 = (Button) findViewById(R.id.bt2); bt3 = (Button) findViewById(R.id.bt3); bt4 = (Button) findViewById(R.id.bt4); ed1 = (EditText) findViewById(R.id.ed1); ed2 = (EditText) findViewById(R.id.ed2); list1 = (ListView) findViewById(R.id.list); // 顯示所有數(shù)據(jù) list1.setAdapter(adapter(0)); sc1 = (ScrollView) findViewById(R.id.scr1); // 向添加ContentProviderA應用的數(shù)據(jù) bt1.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { String eds1 = ed1.getText().toString(); String eds2 = ed2.getText().toString(); ContentValues content = new ContentValues(); if (!eds1.equals("") && !eds2.equals("")) { content.put(UserInfo.User.NAME, eds1); content.put(UserInfo.User.AGE, eds2); MainActivity.this.getContentResolver().insert( Uri.parse(UserInfo.User.uri), content); Toast.makeText(MainActivity.this, "數(shù)據(jù)插入成功", Toast.LENGTH_LONG).show(); // 刷新ListView界面 list1.setAdapter(adapter(0)); } else { Toast.makeText(MainActivity.this, "name和age不能為空", Toast.LENGTH_LONG).show(); } } }); // 根據(jù)條件刪除ContentProviderA應用的數(shù)據(jù) bt2.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { String eds1 = ed1.getText().toString(); String eds2 = ed2.getText().toString(); if (!eds1.equals("") || !eds2.equals("")) { HashMap<String, String[]> wheres = wheres(eds1, eds2); String sql = wheres.get("sql")[0]; String[] selectags = wheres.get("selectages"); MainActivity.this.getContentResolver().delete( Uri.parse(UserInfo.User.uri), sql, selectags); } else { Toast.makeText(MainActivity.this, "請輸入刪除條件", Toast.LENGTH_LONG).show(); } // 刷新ListView界面 list1.setAdapter(adapter(0)); } }); // 修改數(shù)據(jù) bt3.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { String eds1 = ed1.getText().toString(); String eds2 = ed2.getText().toString(); ContentValues values = new ContentValues(); // 根據(jù)條件將列修改為xiong,23 values.put(UserInfo.User.NAME, "xiong"); values.put(UserInfo.User.AGE, "23"); if (!eds1.equals("") || !eds2.equals("")) { HashMap<String, String[]> wheres = wheres(eds1, eds2); String sql = wheres.get("sql")[0]; String[] selectags = wheres.get("selectages"); int i=MainActivity.this.getContentResolver().update( Uri.parse(UserInfo.User.uri), values, sql, selectags); } else { Toast.makeText(MainActivity.this, "請輸入刪除條件", Toast.LENGTH_LONG).show(); } // 刷新ListView界面 list1.setAdapter(adapter(0)); } }); // 根據(jù)條件查詢ContentProviderA應用的數(shù)據(jù) bt4.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (!ed1.getText().toString().equals("") || !ed2.getText().toString().equals("")) list1.setAdapter(adapter(1)); else list1.setAdapter(adapter(0)); } }); } // 用來判別條件 public HashMap<String, String[]> wheres(String eds1, String eds2) { HashMap<String, String[]> where = new HashMap<String, String[]>(); if (!eds1.equals("") && !eds2.equals("")) { String[] sql = { UserInfo.User.NAME + "=? and " + UserInfo.User.AGE + " =?" }; String[] selectages = { eds1, eds2 }; where.put("sql", sql); where.put("selectages", selectages); } if (!eds1.equals("") && eds2.equals("")) { String[] sql = { UserInfo.User.NAME + "=? " }; String[] selectages = { eds1 }; where.put("sql", sql); where.put("selectages", selectages); } if (eds1.equals("") && !eds2.equals("")) { String[] sql = { UserInfo.User.AGE + " =?" }; String[] selectages = { eds2 }; where.put("sql", sql); where.put("selectages", selectages); } return where; } // 用來顯示數(shù)據(jù) public SimpleAdapter adapter(int i) { Cursor cs = MainActivity.this.getContentResolver().query( Uri.parse(UserInfo.User.uriall), null, null, null, null); String eds1 = ed1.getText().toString(); String eds2 = ed2.getText().toString(); if (i == 1) { if (!eds1.equals("") || !eds2.equals("")) { HashMap<String, String[]> wheres = wheres(eds1, eds2); String sql = wheres.get("sql")[0]; String[] selectags = wheres.get("selectages"); cs = MainActivity.this.getContentResolver().query( Uri.parse(UserInfo.User.uri), null, sql, selectags, null); } } List<Map<String, Object>> lists = new ArrayList<Map<String, Object>>(); while (cs.moveToNext()) { Map<String, Object> map = new HashMap<String, Object>(); map.put("name", cs.getString(0)); map.put("age", cs.getString(1)); lists.add(map); } SimpleAdapter simepl = new SimpleAdapter(MainActivity.this, lists, R.layout.item, new String[] { "name", "age" }, new int[] { R.id.item_txt1, R.id.item_txt2 }); return simepl; } @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; } } activity.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" tools:context=".MainActivity" > <ScrollView android:id="@+id/scr1" android:layout_width="match_parent" android:layout_height="wrap_content" > <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" > <Button android:id="@+id/bt1" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="添加" /> <Button android:id="@+id/bt2" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="刪除" /> <Button android:id="@+id/bt3" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="更改" /> <Button android:id="@+id/bt4" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="查詢" /> <EditText android:id="@+id/ed1" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="輸入name條件進行增刪改查" /> <EditText android:id="@+id/ed2" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="輸age條件進行增刪改查" /> </LinearLayout> </ScrollView> <ListView android:id="@+id/list" android:layout_width="match_parent" android:layout_height="wrap_content" > </ListView> </LinearLayout>
item.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:id="@+id/item_txt1" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <TextView android:id="@+id/item_txt2" android:layout_width="wrap_content" android:layout_height="wrap_content"/> </LinearLayout>
監(jiān)聽ContentProvider數(shù)據(jù)改變
當程序A在執(zhí)行insert、update、delete時，通過getContext().getContentResolver().notifyChange(uri, null)方法來告訴所有注冊在該Uri的監(jiān)聽者數(shù)據(jù)發(fā)生改變
//刪除數(shù)據(jù) @Override public int delete(Uri uri, String selection, String[] selectionArgs) { int number = 0; if (uriMatcher.match(uri) == 1) { // 根據(jù)條件刪除數(shù)據(jù),并獲取刪除的行數(shù) number = mysqlite.getReadableDatabase().delete("user_info", selection, selectionArgs); } // 通知數(shù)據(jù)已經(jīng)改變 getContext().getContentResolver().notifyChange(uri, null); return number; }
在B程序通過registerContentObserver(Uri uri,boolean notifyForDescendents, ContentObserver observer)方法來監(jiān)聽A程序的數(shù)據(jù)改變
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // 為uri的數(shù)據(jù)改變注冊監(jiān)聽器 getContentResolver().registerContentObserver( Uri.parse("content://com.android.xiong.ConentProviderTestA.firstContentProvider/userinfo"), true, new SmsObserver(new Handler())); } registerContentObserver中第三個參數(shù)為監(jiān)聽實例 ，需要通過繼承ContentObserver類，并重寫onChange(booleab selfChange)方法，該方法在監(jiān)聽Uri的ContentProvider的數(shù)據(jù)發(fā)生改變時觸發(fā)該方法
// 提供方自定義的ContentOberver監(jiān)聽器 private final class Observer extends ContentObserver { public SmsObserver(Handler handler) { super(handler); } @Override public void onChange(boolean selfChange, Uri uri) { // 查詢發(fā)送郵箱中的短息(處于正在發(fā)送狀態(tài)的短信放在發(fā)送箱) Cursor cursor = getContentResolver().query( Uri.parse("content://com.android.xiong.ConentProviderTestA.firstContentProvider/userinfo"), null, null, null, null); } } } 新聞熱點
疑難解答
