Androidx学习笔记（82）--- 内容提供者(ContentProvider)-自定义内容提供者

创建数据库

 
public class MyOpenHelper extends SQLiteOpenHelper {
 
public MyOpenHelper(Context context) {
super(context, "people.db", null, 2);
// TODO Auto-generated constructor stub
}
 
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table person(_id integer primary key autoincrement, name char(10), money integer(20))");
 
}
 
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("create table teacher(_id integer primary key autoincrement, name char(10))");
}
 
}

内容提供者

public class PersonProvider extends ContentProvider {
 
private MyOpenHelper oh;
SQLiteDatabase db;
 
//创建uri匹配器对象
static UriMatcher um = new UriMatcher(UriMatcher.NO_MATCH);
//检测其他用户传入的uri与匹配器定义好的uri中，哪条匹配
static {
um.addURI("com.exp.people", "person", 1);//content://com.exp.people/person
um.addURI("com.exp.people", "teacher", 2);//content://com.exp.people/teacher
um.addURI("com.exp.people", "person/#", 3);//content://com.exp.people/person/4
}
//内容提供者创建时调用
@Override
public boolean onCreate() {
oh = new MyOpenHelper(getContext());
db = oh.getWritableDatabase();
return false;
}
 
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
Cursor cursor = null;
if(um.match(uri) == 1){
cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder, null);
}
else if(um.match(uri) == 2){
cursor = db.query("teacher", projection, selection, selectionArgs, null, null, sortOrder, null);
}
else if(um.match(uri) == 3){
//把uri末尾携带的数字取出来
long id = ContentUris.parseId(uri);
cursor = db.query("person", projection, "_id = ?", new String[]{id + ""}, null, null, sortOrder, null);
}
else{
throw new IllegalArgumentException("uri又有问题哟亲么么哒");
}
return cursor;
}
 
@Override
public String getType(Uri uri) {
if(um.match(uri) == 1){
return "vnd.android.cursor.dir/person";
}
else if(um.match(uri) == 3){
return "vnd.android.cursor.item/person";
}
return null;
}
 
//此方法供其他应用调用，用于往people数据库里插数据
//values：由其他应用传入，用于封装要插入的数据
//uri:内容提供者的主机名，也就是地址
@Override
public Uri insert(Uri uri, ContentValues values) {
//使用uri匹配器匹配传入的uri
if(um.match(uri) == 1){
db.insert("person", null, values);
//发送数据改变的通知
//uri:通知发送到哪一个uri上，所有注册在这个uri上的内容观察者都可以收到这个通知
getContext().getContentResolver().notifyChange(uri, null);
}
else if(um.match(uri) == 2){
db.insert("teacher", null, values);
getContext().getContentResolver().notifyChange(uri, null);
}
else{
throw new IllegalArgumentException("uri有问题哟亲么么哒");
}
return uri;
}
 
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
int i = db.delete("person", selection, selectionArgs);
return i;
}
 
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
int i = db.update("person", values, selection, selectionArgs);
return i;
}
 
}

AndroidManifest.xml中对ContentProvider进行注册

       <provider android:name="com.exp.customcontentprovider.provider.PersonProvider"
            android:authorities="com.exp.people"
            android:exported="true"
            ></provider>