录播教育系统网站建设费用,佛山省钱网站设计哪家便宜,网站建设什么好,网站开发尾款如何做账本文是我各处东拼西凑加上自己实现一个ContentProvider的使用总结#xff0c;留做后用#xff0c;主要介绍ContentProvider的集成方法。一、综述ContentProvider是Android四大组件之一#xff0c;其核心功能是提供应用间的统一的数据访问方式#xff0c;当然也可以用于应用…本文是我各处东拼西凑加上自己实现一个ContentProvider的使用总结留做后用主要介绍ContentProvider的集成方法。一、综述ContentProvider是Android四大组件之一其核心功能是提供应用间的统一的数据访问方式当然也可以用于应用内的数据封装。ContentProvider类似C/S结构应用A实现ContentProvider向外提供应用内的数据访问应用B使用Context.getContentResolver()来间接与应用A的Provider交互。ContentProvider提供一套类似数据库的query/delete/insert/update的方法来操作数据开发者可以以此来屏蔽管理数据的真正方式 (SharePreference/File/SQLite等)。另外ContentProvider也提供了直接操作文件的方式(覆写openFile)第三方应用可以通过该方式读写当前应用的私有文件(data/data等)。二、相关知识2.1 UriMatcher和ContentUris的使用UriMatcher主要用户判断Uri是否符合特定格式用法如下private static final int TYPE_ALL 1;private static final int TYPE_SINGLE 2;private static UriMatcher mUriMatcher new UriMatcher(UriMatcher.NO_MATCH);static {mUriMatcher.addURI(AUTHORITY, person, TYPE_ALL);mUriMatcher.addURI(AUTHORITY, person/#, TYPE_SINGLE);//#号表示一个数字}以上为其声明与配置下面是使用方法switch (mUriMatcher.match(uri)) {case TYPE_ALL://uri匹配到第一种类型case TYPE_SINGLE://uri匹配到第二种类型default://uri没有匹配到这两种类型}这样我们就可以知道外部传入的Uri的类型了。2.2 ContentUris用法ContentUris用于处理Uri后面的id部分(纯数字)常用函数有parseId(uri) 解析Uri里的最后的idwithAppendedId(uri, id)在路径后面加上id部分三、封装ContentProvider的步骤提供Provider的工程简称应用A。下面是封装ContentProvider的步骤3.1 在Manifest中声明ContentProviderandroid:authoritiesorg.test.authandroid:exportedtrue/声明后应用安装到设备上第三方应用就能通过ContentResolver访问此Provider。3.2 ContentProvider的代码package org.test.auth;import java.io.File;import java.io.FileNotFoundException;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;import android.os.ParcelFileDescriptor;import android.text.TextUtils;import android.util.Log;public class MyDataProvider extends ContentProvider {private static final String AUTHORITY org.test.auth;private static final int TYPE_ALL 1;private static final int TYPE_SINGLE 2;private static final String TAG TEST111_DataProvider;private MyDBHelper mDbHelper;private SQLiteDatabase mDatabase;private static UriMatcher mUriMatcher new UriMatcher(UriMatcher.NO_MATCH);static {mUriMatcher.addURI(AUTHORITY, person, TYPE_ALL);mUriMatcher.addURI(AUTHORITY, person/#, TYPE_SINGLE);}Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {switch (mUriMatcher.match(uri)) {case TYPE_ALL:return mDatabase.delete(MyDBHelper.TABLE_NAME,selection,selectionArgs);case TYPE_SINGLE:long id ContentUris.parseId(uri);String where MyDBHelper.COLUMN_ID id;if(!TextUtils.isEmpty(selection)) {where where and selection;}return mDatabase.delete(MyDBHelper.TABLE_NAME,where,selectionArgs);default:return -1;}}Overridepublic String getType(Uri uri) {switch (mUriMatcher.match(uri)) {case TYPE_ALL:return vnd.android.cursor.dir/person;case TYPE_SINGLE:return vnd.android.cursor.item/person;default:return null;}}Overridepublic Uri insert(Uri uri, ContentValues values) {//由于此时的values中具体是否含有数据是不确定的所以此时需要在第二个参数中添加person表中的非主键的一列long id mDatabase.insert(MyDBHelper.TABLE_NAME, MyDBHelper.COLUMN_NAME, values);return ContentUris.withAppendedId(uri, id);}Overridepublic boolean onCreate() {mDbHelper new MyDBHelper(getContext());mDatabase mDbHelper.getWritableDatabase();return true;}Overridepublic Cursor query(Uri uri, String[] columns,String selection, String[] selectionArgs,String orderBy) {switch (mUriMatcher.match(uri)) {case TYPE_ALL:return mDatabase.query(MyDBHelper.TABLE_NAME, columns, selection, selectionArgs, null, null, orderBy);case TYPE_SINGLE:long id ContentUris.parseId(uri);String where MyDBHelper.COLUMN_ID id;if(!TextUtils.isEmpty(selection)) {where where and selection;}return mDatabase.query(MyDBHelper.TABLE_NAME, columns, where, selectionArgs, null, null, orderBy);default:return null;}}Overridepublic int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {switch (mUriMatcher.match(uri)) {case TYPE_ALL:return mDatabase.update(MyDBHelper.TABLE_NAME, values,selection, selectionArgs);case TYPE_SINGLE:long id ContentUris.parseId(uri);String where MyDBHelper.COLUMN_ID id;if(!TextUtils.isEmpty(selection)) {where where and selection;}return mDatabase.update(MyDBHelper.TABLE_NAME, values,where, selectionArgs);default:return -1;}}Overridepublic ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {File root new File(getContext().getFilesDir() / uri.getPath());root.getParentFile().mkdirs();int imode 0;if (mode.contains(w)) {imode | ParcelFileDescriptor.MODE_WRITE_ONLY;if (!root.exists()) {try {root.createNewFile();} catch (Exception ex) {Log.d(TAG, error happened, ex);}}}if (mode.contains(r)) imode | ParcelFileDescriptor.MODE_READ_ONLY;if (mode.contains()) imode | ParcelFileDescriptor.MODE_APPEND;return ParcelFileDescriptor.open(root, imode);}}此示例中使用的数据操作方式是数据库onCreate执行ContentProvider启动时的初始化操作query/insert/delete/update操作数据getType返回指定Uri对应的数据类型。“vnd.android.cursor.dir”表示cursor集合“vnd.android.cursor.item”表示cursor条目。覆写openFile方法提供私有文件的对外访问在该方法内可以控制是否提供文件读写本例代码来自网络支持读写操作。附上数据库帮助类代码package org.test.auth;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class MyDBHelper extends SQLiteOpenHelper {public static final String DB_NAME test.db;public static final String TABLE_NAME person;public static final String COLUMN_ID _id;public static final String COLUMN_AGE age;public static final String COLUMN_NAME name;public static final int DB_VERSION 1;public MyDBHelper(Context context) {super(context, DB_NAME, null, DB_VERSION);}Overridepublic void onCreate(SQLiteDatabase database) {String sql create table if not exists TABLE_NAME ( COLUMN_ID INTEGER PRIMARY KEY AUTOINCREMENT, COLUMN_NAME varchar(100), COLUMN_AGE integer ) ;database.execSQL(sql);}Overridepublic void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {}}四、测试代码测试代码在另一个工程中简称应用B。package com.example.testcontentprovider;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.FileNotFoundException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.OutputStreamWriter;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.os.ParcelFileDescriptor;import android.util.Log;public class MainActivity extends Activity {private static final String URI content://org.test.auth/person;private static final String TAG TEST111_;Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);doTest();}private void doTest() {ContentResolver cr getContentResolver();String typeAll cr.getType(Uri.parse(URI));Log.d(TAG, get all type typeAll);String typeOne cr.getType(Uri.parse(URI /1));Log.d(TAG, get one type typeOne);insertValue(cr, 张三, 12);insertValue(cr, 李四, 23);//查询所有数据query(cr, -1);//查询单条数据query(cr, 1);//更改id1的数据updateValue(cr, 1, 王五, 20, null, null);//查询所有数据query(cr, -1);//更改name李四的数据updateValue(cr, 2, 哈哈, 34, name?, new String[] {李四});//查询所有数据query(cr, -1);//更改所有数据updateValue(cr, -1, 小明, 15, null, null);//查询所有数据query(cr, -1);//删除id1数据int affectedColumnCountOne cr.delete(Uri.parse(URI /1), null, null);Log.d(TAG, delete one affectedColumnCount affectedColumnCountOne);//查询所有数据query(cr, -1);//删除所有数据int affectedColumnCountAll cr.delete(Uri.parse(URI), null, null);Log.d(TAG, delete all affectedColumnCount affectedColumnCountAll);//查询所有数据query(cr, -1);//测试文件读写try {OutputStream os cr.openOutputStream(Uri.parse(URI/provider_file.txt));BufferedWriter bw new BufferedWriter(new OutputStreamWriter(os));bw.append(think who am I?!);bw.flush();bw.close();InputStream is cr.openInputStream(Uri.parse(URI/provider_file.txt));BufferedReader br new BufferedReader(new InputStreamReader(is));String result br.readLine();br.close();Log.d(TAG, read file result : result);} catch (Exception e) {Log.d(TAG, file op failed, e);}}private void query(ContentResolver cr, int id) {String idCause ;if(id 0) {idCause / id;}Cursor cursorResultAll cr.query(Uri.parse(URI idCause), null, null, null, null);if(null ! cursorResultAll) {while(cursorResultAll.moveToNext()) {int result cursorResultAll.getInt(0);String name cursorResultAll.getString(1);int age cursorResultAll.getInt(2);Log.d(TAG, query()| originid id ; id result name name age age);}}}private void insertValue(ContentResolver cr, String name, int age) {ContentValues value new ContentValues();value.put(name, name);value.put(age, age);Uri insertColumn cr.insert(Uri.parse(URI), value);Log.d(TAG, insertValue() insert at column: insertColumn);}private void updateValue(ContentResolver cr, int id, String name, int age,String selection, String[] selectionArgs) {if (id 0) {ContentValues value new ContentValues();value.put(name, name);value.put(age, age);int affectedColumnCount cr.update(Uri.parse(URI / id), value, selection, selectionArgs);Log.d(TAG, updateValue() affectedColumnCount: affectedColumnCount);} else {ContentValues value new ContentValues();value.put(name, name);value.put(age, age);int affectedColumnCount cr.update(Uri.parse(URI), value,selection, selectionArgs);Log.d(TAG, updateValue() affectedColumnCount: affectedColumnCount);}}}以上就是实现一个ContentProvider的方法后续需要补充ContentProvider的原理部分据说进程间通信是基于共享内存的以后有时间需要分析一下。
