ContentProvider使⽤⽰例
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contentProvider是Android中提供的专门⽤于不同应⽤间进⾏数据共享⽅式，作为四⼤组件之⼀的contentProvider，使⽤起来⽐较简单，但是因为使⽤频率不是很⾼，所以经常遗忘其使⽤⽅法，所以在次记录下其基本⽤法的实例。⾸先，有必要对contentProvider的基本原理进⾏⼀个简单的讨论。
contentProvider的底层实现是通过Binder实现，但是他的使⽤⽐aidl要简单很多，因为系统已经为我们做了很多的封装。 系统中也为我们提供了⾮常多的ContentProvider，⽐如通讯录，⽇程表，通话记录等，要跨进程访问这些信息，只需要通过ContentResolver 的query、update、insert、update、insert、delete⽅法即可。 要实现⾃定义ContentProvider，继承ContentProvider类并实现六个抽象⽅法即可，这六个抽象⽅法分别是是：OnCreate、query、update、insert、delete和getType。需要注意的是在这六个⽅法中，除了OnCreate由系统回调并运⾏在主线程⾥，其他五个⽅法均由外界回调并运⾏在Binder线程池中。 下⾯我们⾃定义⼀个BookProvider继承⾃ContentProvider，其代码如下：
public class BookProvider extends ContentProvider {
public static final String TAG = "reoger.hut.hello.word";
public static final String AUTHORLTY = "reoger.hut.hello.word";
public static final Uri BOOK_CONTENT_URI = Uri.parse("content://"+AUTHORLTY+"/book");
public static final Uri USER_CONTENT_URI = Uri.parse("content://"+AUTHORLTY+"/user");
public static final int BOOK_URI_CODE = 0;
public static final int USER_URI_CODE = 1;
private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
private Context mContext;
private SQLiteDatabase mDb;
static {
sUriMatcher.addURI(AUTHORLTY,"book",BOOK_URI_CODE);
sUriMatcher.addURI(AUTHORLTY,"user",USER_URI_CODE);
}
private String getTableName(Uri uri){
String tableName = null;
switch (sUriMatcher.match(uri)){
case BOOK_URI_CODE:
tableName = DbOpenHelper.BOOK_TABLE_NAME;
break;
case USER_URI_CODE:
tableName = DbOpenHelper.USER_TABLE_NAME;
break;
default:
break;
}
return tableName;
}
@Override
public boolean onCreate() {
Log.d(TAG, "onCreate: " + Thread.currentThread());
mContext = getContext();
initProvider();
return true;
}
/**
* 初始化数据库
*/
*/
private void initProvider() {
mDb = new DbOpenHelper(mContext).getWritableDatabase();
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) { Log.d(TAG, "query: " + Thread.currentThread().getName());
String table = getTableName(uri);
if(table == null){
throw new IllegalArgumentException(" UnSupported URL: "+uri);
}
return mDb.query(table,projection,selection,selectionArgs,null,null,sortOrder,null);
}
@Nullable
山核桃采摘机@Override
public String getType(@NonNull Uri uri) {
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
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Log.d(TAG, "insert: ");
String table = getTableName(uri);
if(table == null ){
throw new IllegalArgumentException("UnSupported URI :"+uri);
tm2007}
mDb.insert(table,null,values);
return uri;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "delete: ");
String table = getTableName(uri);
if(table == null ){
throw new IllegalArgumentException("UnSupported URI :"+uri);
}
int count = mDb.delete(table,selection,selectionArgs);
if(count>0){
getContext().getContentResolver().notifyChange(uri,null);
}
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}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "update: ");
String table = getTableName(uri);
if(table == null ){
throw new IllegalArgumentException("UnSupported URI :"+uri);
}
int row = mDb.update(table,values,selection,selectionArgs);
if(row >0 ){
getContext().getContentResolver().notifyChange(uri,null);
}
return row;
}
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}
public static final Creator<Book> CREATOR = new Creator<Book>() { @Override
public Book createFromParcel(Parcel in) {
return new Book(in);
}
@Override
public Book[] newArray(int size) {
return new Book[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(id);
dest.writeString(name);
}
@Override
public String toString() {
String result = "book = ["+id+
","+name+"];";
return result;
}
}
public class User implements Parcelable {
private int id;
private String name;
private int sex;
public User(int id, String name, int sex) {
this.id = id;
this.name = name;
this.sex = sex;
}
@Override
public String toString() {
return "id= "+id+" ,name ="+name+" ,sex= "+sex;
}
protected User(Parcel in) {
id = in.readInt();
name = in.readString();
sex = in.readInt();
}
public static final Creator<User> CREATOR = new Creator<User>() { @Override
public User createFromParcel(Parcel in) {
return new User(in);
}
@Override
public User[] newArray(int size) {
return new User[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
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