1.在同一系统中装载了一个又一个的App，每个App之间有可能需要数据共享，App之间实现数据共享当然可以使用SharedPreferences、文件或数据库等，但是这种方式不仅比较麻烦，而且存在严重的安全漏洞，所以在Android4.2以后不再推荐使用这种方式，而是推荐使用ContentProvider
2.其实ContentProvider和ContentResovler是成对使用，从字面上ContentProvider和ContentResovler可翻译为：内容提供者 和 内容接收者
3.开发ContentProvider子类AlitanContentProvider
步骤1：子类需要实现父类方法query()、inser()、update()和delete()方法;
步骤2：在AndroidManifest中注册ContentProvider并指定android:authorities属性
4.AlitanContentProvider子类代码实现如下
/**
* Created by alitan2014 on 2017/9/8.
*/
public classAlitanContentProviderextendsContentProvider {
privateHandlermHandler;
public voidonMessage(Handler handler){
mHandler= handler;
}
@Override
public booleanonCreate() {
JSONObject object =newJSONObject();
try{
object.put("method","onCreate");
}catch(JSONException e) {
e.printStackTrace();
}
Message message =newMessage();
message.obj= object;
message.what=0x123;
if(mHandler!=null){
mHandler.sendMessage(message);
}
System.out.println("onCreate");
return true;
}
@Nullable
@Override
publicCursorquery(@NonNullUri uri,@NullableString[] projection,@NullableString selection,@NullableString[] selectionArgs,@NullableString sortOrder) {
JSONObject object =newJSONObject();
try{
object.put("method","query");
Message message =newMessage();
message.obj= object;
message.what=0x123;
if(mHandler!=null){
mHandler.sendMessage(message);
}
System.out.println("onCreate");
}catch(JSONException e) {
e.printStackTrace();
}
return null;
}
@Nullable
@Override
publicStringgetType(@NonNullUri uri) {
return null;
}
@Nullable
@Override
publicUriinsert(@NonNullUri uri,@NullableContentValues values) {
JSONObject object =newJSONObject();
try{
object.put("method","insert");
Message message =newMessage();
message.obj= object;
message.what=0x123;
if(mHandler!=null){
mHandler.sendMessage(message);
}
System.out.println("insert");
}catch(JSONException e) {
e.printStackTrace();
}
returnUri.parse("www.baidu.com");
}
@Override
public intdelete(@NonNullUri uri,@NullableString selection,@NullableString[] selectionArgs) {
JSONObject object =newJSONObject();
try{
object.put("method","delete");
Message message =newMessage();
message.obj= object;
message.what=0x123;
if(mHandler!=null){
mHandler.sendMessage(message);
}
System.out.println("delete");
}catch(JSONException e) {
e.printStackTrace();
}
return0;
}
@Override
public intupdate(@NonNullUri uri,@NullableContentValues values,@NullableString selection,@NullableString[] selectionArgs) {
JSONObject object =newJSONObject();
try{
object.put("method","update");
Message message =newMessage();
message.obj= object;
message.what=0x123;
if(mHandler!=null){
mHandler.sendMessage(message);
}
System.out.println("update");
}catch(JSONException e) {
e.printStackTrace();
}
return0;
}
}
5.在Androidmanifest中注册AlitanContentProvoder如下
android:authorities="alitan2014.com.contentprovider.AlitanContentProvider"
android:name=".AlitanContentProvider"
android:exported="true"
/>
6.在另外一个应用获取ContentResovler，并调用query(),insert(),update,delete()方法，实际上是通过ContentProvider暴露在外部的URI，调用到了AlitanContentProvider中的query(),insert(),update,delete()方法，实现方法如下
ublic classMainActivityextendsAppCompatActivity {
privateContentResolverresolver;
privateUriuri= Uri.parse("content://alitan2014.com.contentprovider.AlitanContentProvider/");
@Override
protected voidonCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
resolver= getContentResolver();
}
public voidquery(View view){
Cursor cursor =resolver.query(uri,null,"query_where",null,null);
Toast.makeText(MainActivity.this,"其他应用返回的内容："+cursor,Toast.LENGTH_SHORT).show();
}
public voidinsert(View view){
ContentValues contentValues =newContentValues();
contentValues.put("method","insert");
Uri newUri =resolver.insert(uri,contentValues);
Toast.makeText(MainActivity.this,"新插入的URI为："+newUri,Toast.LENGTH_SHORT).show();
}
public voidupdate(View view){
ContentValues contentValues =newContentValues();
contentValues.put("method","update");
intcount =resolver.update(uri,contentValues,"update_where",null);
Toast.makeText(MainActivity.this,"更新的的URI为："+count,Toast.LENGTH_SHORT).show();
}
public voiddelete(View view){
ContentValues contentValues =newContentValues();
contentValues.put("method","update");
intcount =resolver.delete(uri,"delete_where",null);
Toast.makeText(MainActivity.this,"delete返回值为："+count,Toast.LENGTH_SHORT).show();
}
}