android-db-commons

WARNING: This library is under heavy development. We can't guarantee both stability of the library itself and the API. However, if you'll find some troubles, bugs, problems please submit an issue here so we can fix it!

Some common utilities for ContentProvider/ContentResolver/Cursor and other db-related android stuff

Currently it's just a builder for ContentResolver-related crap. If you feel tired of this:

getContentResolver().query(uri, 
  new String[] { People.NAME, People.AGE }, 
  People.NAME + "=? AND " + People.AGE + ">?", 
  new String[] { "Ian", "18" }, 
  null
);

or:

getContentResolver().query(uri, null, null, null, null);

Using this lib you can replace it with something like:

ProviderAction.newQuery(uri)
  .projection(People.NAME, People.AGE)
  .where(People.NAME + "=?", "Ian")
  .where(People.AGE + ">?", 18)
  .perform(getContentResolver());

What's next? You may want to transform your Cursor to some collection of something. Using this util you can easily do:

ProviderAction.newQuery(uri)
  .projection(People.NAME, People.AGE)
  .where(People.NAME + "=?", "Ian")
  .where(People.AGE + ">?", 18)
  .perform(getContentResolver());
  .transform(new Function<Cursor, String>() {
    @Override public String apply(Cursor cursor) {
      return cursor.getString(cursor.getColumnIndexOrThrow(People.NAME));
    }
  })
  .filter(new Predicate<String>() {
    @Override public boolean apply(String string) {
      return string.length()%2 == 0;
    }
  });

Loaders

Loaders are fine. They do some hard work for you which otherwise you would need to do manually. But maybe they can be even funnier?

This is a standard way of creating CursorLoader.

long age = 18L;
final CursorLoader loader = new CursorLoader(getActivity());
loader.setUri(uri);
loader.setProjection(new String[] { People.NAME });
loader.setSelection(People.AGE + ">?");
loader.setSelectionArgs(new String[] { String.valueOf(age) });

Using android-db-commons you can build it using this builder:

CursorLoaderBuilder.forUri(uri)
  .projection(People.NAME)
  .where(People.AGE + ">?", 18)
  .build(getActivity());

Looks nice, isn't it? Yeah, but it's still not a big change. Anyway, all of us know this:

@Override public void onLoadFinished(Loader<Cursor> loader, Cursor result) {
  RealResult result = ReaulResult.veryExpensiveOperationOnMainUiThread(result);
  myFancyView.setResult(result);
}

Using this library you are able to perform additional operations inside Loader's doInBackground().

CursorLoaderBuilder.forUri(uri)
  .projection(People.NAME)
  .where(People.AGE + ">?", 18)
  .wrap(new Function<Cursor, RealResult>() {
    @Override public RealResult apply(Cursor cursor) {
      return RealResult.veryExpensiveOperationOnMainUiThread(result);
    }
  })
  .build(getActivity());

Wanna transform your Cursor into a collection of something? Easy.

CursorLoaderBuilder.forUri(uri)
  .projection(People.NAME)
  .where(People.AGE + ">?", 18)
  .transform(new Function<Cursor, String>() {
    @Override public RealResult apply(Cursor cursor) {
      return cursor.getString(0);
    }
  })
  .build(getActivity());

Your Loader will return List as a result in this case. It's lazy list. We do not iterate through your 100K-rows Cursor. Every row's transformation is calculated at its access time.

Sure, you can still wrap() your transformed() result.

CursorLoaderBuilder.forUri(uri)
  .projection(People.NAME)
  .where(People.AGE + ">?", 18)
  .transform(new Function<Cursor, String>() {
    @Override public RealResult apply(Cursor cursor) {
      return cursor.getString(0);
    }
  })
  .transform(new Function<String, Integer>() {
    @Override public Integer apply(String name) {
      return name.length();
    }
  })
  .wrap(new Function<List<Integer>, RealResult>() {
    @Override public RealResult apply(List<Integer> list) {
      return RealResult.factoryFactory(lazyList);
    }
  })
  .build(getActivity());

Wrap function is applyied in Loader's doInBackground() so you don't have to worry about ANRs in case you want to do something more complex in there.

Building

This is standard maven project. To build it just execute:

mvn clean package

in directory with pom.xml.

License

Copyright (C) 2013 Mateusz Herych

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

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