Android四大组件应用系列——使用ContentProvider实现跨进程通讯

一、问题描述

　　如何在Android中实现不同应用之间的通讯（既跨进程进行调用）？Android提供了多种实现方式，使我们可以实现跨进程访问Activity、通过ContentProvider跨进程访问其他应用的数据、通过Broadcast可以向android系统中所有应用程序发送广播、使用AIDL实现跨进程的Service。下面我们就使用ContentProvider实现跨进程访问数据，并可对数据进行增、删、改、查

二、应用实现

　　使用ContentProvider实现数据共享，主要是共享应用的Sqlite数据库，再一个应用中（本例的shareinfo）提供数据源（Sqlite数据库）并创建ContentProvider组件， ContentProvider组件主要对外（其他应用）提供访问数据的接口（Uri信息），其他应用（本例的other）通过这个接口（Uri信息）实现跨进程的方法调用

　　如图所示：



　　本例涉及两个应用shareinfo和other

三、shareinfo应用的核心

　　作为数据的提供者首先是开发对外可访问的数据库（Sqlite）

　　涉及两个组件DbOpenHelper和SQLiteHelper

　　代码如下：

public class DbOpenHelper extends SQLiteOpenHelper {
public DbOpenHelper(Context context) {
super(context, "jereh.db", null, 4);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table person(personid integer primary key " +
" autoincrement,name varchar(20),phone varchar(12) null)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
db.execSQL("drop table person");
onCreate(db);
}
}

public class SQLiteHelper {

private Context context;
private DbOpenHelper  helper = null;
public SQLiteHelper(Context context){
helper = new DbOpenHelper(context);
}

public void save(Person person){//增
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("insert into person(name,phone) values(?,?)",new Object[]{person.getName(),person.getPhone()});
db.close();
}
public void delete(int personid){//删
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("delete from person where personid=?", new Integer[]{personid});
db.close();
}
public void update(Person person){//改
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("update person set name=?,phone=? where personid=?", new Object[]{person.getName(),person.getPhone(),person.getPersonid()});
db.close();
}
public Person find(int personid){//查
SQLiteDatabase db = helper.getReadableDatabase();
//Cursor cursor = db.rawQuery("select * from person where personid=?", new String[]{personid+""});
Cursor cursor=db.rawQuery("select * from person",null);
if(cursor.moveToFirst()){
int id = cursor.getInt(cursor.getColumnIndex("personid"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String phone = cursor.getString(cursor.getColumnIndex("phone"));
return new Person(personid, name, phone);
}
cursor.close();
return null;
}

}

然后编写ContentProvider组件代码如下：

package com.jereh;

public class PersonProvider extends ContentProvider {

private DbOpenHelper openHelper;
private static final UriMatcher MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
private static final int PERSONS = 1;
private static final int PERSON = 2;
static{
MATCHER.addURI("com.jereh.providers.personprovider", "person", PERSONS);
//* 根据pesonid来删除记录
MATCHER.addURI("com.jereh.providers.personprovider", "person/#", PERSON);
}
@Override
public boolean onCreate() {
openHelper = new DbOpenHelper(this.getContext());
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase sqLiteDatabase = openHelper.getReadableDatabase();
switch (MATCHER.match(uri)) {
case 1:
return sqLiteDatabase.query("person", projection, selection, selectionArgs, null, null, sortOrder);
case 2:
long rowid = ContentUris.parseId(uri);
String where = "personid="+rowid;
if(selection != null && "".equals(selection.trim())){
where = selection+"and"+where;
}
return sqLiteDatabase.query("person", projection, where, selectionArgs, null, null, sortOrder);
}
return null;
}

@Override
public String getType(Uri uri) {
switch (MATCHER.match(uri)) {
case 1:
return "vnd.android.cursor.dir/person";
case 2:
return "vnd.android.cursor.item/person";
}
return null;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case 1:
long rowid = sqLiteDatabase.insert("person", "name", values);
return ContentUris.withAppendedId(uri, rowid);

default:
break;
}
return null;
}

//* 删除特定personid行的记录
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case 1:
return sqLiteDatabase.delete("person", selection, selectionArgs);
case 2:
long rowid = ContentUris.parseId(uri);
String where = "personid="+rowid;
if(selection != null && "".equals(selection.trim())){
where = selection+"and"+where;
}
return sqLiteDatabase.delete("person", where, selectionArgs);
}
return 0;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case 1:
return sqLiteDatabase.update("person", values, selection, selectionArgs);
case 2:
long rowid = ContentUris.parseId(uri);
String where = "personid="+rowid;
if(selection != null && "".equals(selection.trim())){
where = selection+"and"+where;
}
return sqLiteDatabase.update("person", values, where, selectionArgs);
}
return 0;
}
}
复制代码
在AndroidManifest.xml中注册provider

<provider android:name="com.jereh.PersonProvider"
android:authorities="com.jereh.providers.personprovider">

shareinfo应用编写完成

四、编写other应用

　　接下来编写other应用，在这个应用中访问shareinfo中数据，我们使用Android JUnit进行测试，开发单元测试组件如下：

public class AccessProvider extends AndroidTestCase {
public void testInsert(){
Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person");
ContentResolver resolver = this.getContext().getContentResolver();
ContentValues values = new ContentValues();
values.put("name", "xiaoli");
values.put("phone", "333333");
resolver.insert(uri, values);
}

public void testDelete(){
Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person/2");
ContentResolver resolver = this.getContext().getContentResolver();
resolver.delete(uri, null, null);
}
public void testUpdate(){
Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person/3");
ContentResolver resolver = this.getContext().getContentResolver();
ContentValues values = new ContentValues();
values.put("name", "ljb");
values.put("phone", "00000000");
resolver.update(uri, values, null, null);
}

public void testQuery(){
Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person");
ContentResolver resolver = this.getContext().getContentResolver();
Cursor cursor = resolver.query(uri, new String[]{"name","phone"}, null, null, null);
while(cursor.moveToNext()){
String name = cursor.getString(cursor.getColumnIndex("name"));
String phone = cursor.getString(cursor.getColumnIndex("phone"));
System.out.println("name="+name+" "+"phone="+phone);
}
}
}

执行单元测试，测试结果如图所示：



　　所有方法均通过了测试，实现了在一个应用（other）中访问另一个应用（shareinfo）中的数据

　　AndroidManifest.xml配置：

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.jereh.other.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>
<uses-library android:name="android.test.runner" />
</application>
<instrumentation
android:name="android.test.InstrumentationTestRunner"
android:targetPackage="com.jereh" android:label="My Test">
</instrumentation>

作者：杰瑞教育

出处：http://blog.csdn.net/jerehedu

版权声明：本文版权归烟台杰瑞教育科技有限公司和CSDN共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

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