Android(安卓)ContentProvider简介
16lz
2021-01-25
前言
ContentProvider为存储和获取数据提供统一的接口，可以在不同的应用程序之间共享数据。
1. 读取通讯录
常通过ContentProvider来读取通讯录的信息。
Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null);while (cursor.moveToNext()) { int id = cursor.getInt(cursor.getColumnIndex( ContactsContract.Contacts._ID)); String name = cursor.getString(cursor.getColumnIndex( ContactsContract.Contacts.DISPLAY_NAME));}cursor.close();需要在AndroidManifest.xml中添加权限。
2. 自定义ContentProvider
自定义ContentProvider利用数据库提供了数据，并对数据进行查询和修改操作。可查看Android SQLite应用。
用户数据库
利用SQLiteOpenHelper创建，数据库包含ID、姓名、地址和年龄。
public class PeopleSQLiteOpenHelper extends SQLiteOpenHelper { public final static String LOGTAG = "PeopleSQLiteOpenHelper"; public final static String DB_NAME = "people.db"; public final static String TABLE_NAME = "people"; public final static int VERSION = 1; public final static String COL_ID = "_id"; public final static String COL_NAME = "name"; public final static String COL_ADDR = "addr"; public final static String COL_AGE = "age"; public final static String TABLE_CREATE = "create table if not exists " + TABLE_NAME + "(" + COL_ID + " integer primary key autoincrement not null," + COL_NAME + " text not null, " + COL_ADDR + " text not null, " + COL_AGE + " integer " + ")"; public PeopleSQLiteOpenHelper(Context context) { super(context, DB_NAME, null, VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(TABLE_CREATE); }}自定义ContentProvider
在自定义ContentProvider之前，为了安全需要添加自定义权限。
同时也要添加ContentProvider声明，指定读取和写入权限。
自定义PeopleContentProvider继承ContentProvider，实现了查询、插入、删除和修改四类操作。
定义people和people/#两种不同uri请求，并利用UriMatcher来解析。people代表所有用户，people/#代表某个用户。
public class PeopleContentProvider extends ContentProvider { private static final String AUTHORITY = "com.blog.demo.people"; private static final String TABLE_NAME = PeopleSQLiteOpenHelper.TABLE_NAME; private static final int PEOPLE = 1; private static final int PEOPLE_ID = 2; private static final UriMatcher uriMatcher; static { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI(AUTHORITY, "people", PEOPLE); uriMatcher.addURI(AUTHORITY, "people/#", PEOPLE_ID); } private PeopleSQLiteOpenHelper helper; @Nullable @Override public String getType(@NonNull Uri uri) { switch(uriMatcher.match(uri)) { case PEOPLE: // 集合类型 vnd.android.cursor.dir return "vnd.android.cursor.dir/com.blog.demo.people"; case PEOPLE_ID: // 非集合类型 vnd.android.cursor.item return "vnd.android.cursor.item/com.blog.demo.people"; default: throw new IllegalArgumentException("Unsupported URI: " + uri); } } @Override public boolean onCreate() { helper = new PeopleSQLiteOpenHelper(getContext()); return true; } @Nullable @Override public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) { if (uriMatcher.match(uri) == PEOPLE) { // 查询所有people数据 return helper.getReadableDatabase().query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder); } else if (uriMatcher.match(uri) == PEOPLE_ID) { // 查询所有指定id的people数据 String id = uri.getPathSegments().get(1); return helper.getReadableDatabase().query(TABLE_NAME, projection, PeopleSQLiteOpenHelper.COL_ID +"=?", new String[]{id}, null, null, sortOrder); } throw new IllegalArgumentException("Unsupported URI: " + uri); } @Nullable @Override public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) { if (uriMatcher.match(uri) == PEOPLE) { SQLiteDatabase db = helper.getWritableDatabase(); try { db.beginTransaction(); long id = db.insert(TABLE_NAME, null, values); if (id > 0) { db.setTransactionSuccessful(); return ContentUris.withAppendedId(uri, id); } } finally { db.endTransaction(); } } throw new IllegalArgumentException("Unsupported URI: " + uri); } @Override public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) { if (uriMatcher.match(uri) == PEOPLE_ID) { String id = uri.getPathSegments().get(1); SQLiteDatabase db = helper.getWritableDatabase(); try { db.beginTransaction(); int result = db.delete(TABLE_NAME, PeopleSQLiteOpenHelper.COL_ID +"=?", new String[]{id}); db.setTransactionSuccessful(); return result; } finally { db.endTransaction(); } } throw new IllegalArgumentException("Unsupported URI: " + uri); } @Override public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) { if (uriMatcher.match(uri) == PEOPLE_ID) { String id = uri.getPathSegments().get(1); SQLiteDatabase db = helper.getWritableDatabase(); try { db.beginTransaction(); int result = db.update(TABLE_NAME, values, PeopleSQLiteOpenHelper.COL_ID +"=?", new String[]{id}); db.setTransactionSuccessful(); return result; } finally { db.endTransaction(); } } throw new IllegalArgumentException("Unsupported URI: " + uri); }}3. 读取用户数据
需要添加读取权限。
查询操作，查询所有用户信息和根据ID查询某个用户信息。
private void query() { List list = new ArrayList<>(); Cursor cursor = getContentResolver().query(PeopleConstant.CONTENT_URI, null, null, null, null); if (cursor != null) { while (cursor.moveToNext()) { int id = cursor.getInt(cursor.getColumnIndex(PeopleColumns.ID)); String name = cursor.getString(cursor.getColumnIndex(PeopleColumns.NAME)); String addr = cursor.getString(cursor.getColumnIndex(PeopleColumns.ADDR)); int age = cursor.getInt(cursor.getColumnIndex(PeopleColumns.AGE)); list.add(new People(id, name, addr, age)); } cursor.close(); }}private void query(int id) { Cursor cursor = getContentResolver().query( ContentUris.withAppendedId(PeopleConstant.CONTENT_URI, id), null, null, null, null); if (cursor != null) { People people = null; if (cursor.moveToNext()) { int rid = cursor.getInt(cursor.getColumnIndex(PeopleColumns.ID)); String name = cursor.getString(cursor.getColumnIndex(PeopleColumns.NAME)); String addr = cursor.getString(cursor.getColumnIndex(PeopleColumns.ADDR)); int age = cursor.getInt(cursor.getColumnIndex(PeopleColumns.AGE)); people = new People(rid, name, addr, age); } cursor.close(); }} 添加、修改和删除操作。
private void insert(String name, String addr, int age) { ContentValues insertValues = new ContentValues(); insertValues.put(PeopleColumns.NAME, name); insertValues.put(PeopleColumns.ADDR, addr); insertValues.put(PeopleColumns.AGE, age); getContentResolver().insert(PeopleConstant.CONTENT_URI, insertValues);}private void update(int id, String name, String addr, int age) { ContentValues updateValues = new ContentValues(); updateValues.put(PeopleColumns.NAME, name); updateValues.put(PeopleColumns.ADDR, addr); updateValues.put(PeopleColumns.AGE, age); getContentResolver().update(ContentUris.withAppendedId(PeopleConstant.CONTENT_URI, id), updateValues, null, null);}private void delete(int id) { getContentResolver().delete(ContentUris.withAppendedId(PeopleConstant.CONTENT_URI, id), null, null); }辅助类PeopleConstant。
public class PeopleConstant { public final static Uri CONTENT_URI = Uri.parse("content://com.blog.demo.people/people"); public final static class PeopleColumns { public final static String ID = "_id"; public final static String NAME = "name"; public final static String ADDR = "addr"; public final static String AGE = "age"; }}相关文章
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