1、什么情况下需要使用ContentProvider
跨进程提供数据访问的接口，如果在同一个App下，没有必要使用此种方式
2、自定义ContentProvider
public class MyContentProvider extends ContentProvider {
private MyDbHelper helper; //Sqlite帮助类
private SQLiteDatabase db;
private static UriMatcher matcher;
private static final String AUTHORITY="com.loo.person";
static {
matcher=new UriMatcher(UriMatcher.NO_MATCH);
matcher.addURI(AUTHORITY,"person",1);
matcher.addURI(AUTHORITY,"person/#",2);
}
@Override
public boolean onCreate() {
helper=new MyDbHelper(getContext());
db=helper.getReadableDatabase();
return false;
}
@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
if( matcher.match(uri)==1){
return db.query("person",null,null,null,null,null,null);
}else if(matcher.match(uri)==2){
long id= ContentUris.parseId(uri);
return db.rawQuery("select * from person where id="+id,null);
}
return null;
}
@Nullable
@Override
public String getType(Uri uri) {
return null;
}
@Nullable
@Override
public Uri insert(Uri uri, ContentValues values) {
if(matcher.match(uri)==1){
long flag= db.insert("person",null,values);
if(flag>0){
getContext().getContentResolver().notifyChange(uri,null);
return uri;
}
}
return null;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
return 0;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
return 0;
}
}
AndroidManifest中注册
<provider
android:authorities="com.loo.person" //主机名
android:name=".MyContentProvider"></provider>
3、如何访问？
访问需要一个Uri content://com.loo.person/person
getContentResolver()即可调用一些相关的增删改查的方法
4、当数据发生更改后如何响应？
当数据发生更改时，调用getContext().getContentResolver().notifyChange(uri,null);
并在获取数据的地方
getContentResolver().registerContentObserver(uri, false, new ContentObserver(handler) {
@Override
public void onChange(boolean selfChange) {
List<Person> list= getData();
adapter=new MyAdapter(MainActivity.this,list);
listview.setAdapter(adapter);
}
});