AnderWeb

AppCompat-v7:21 provides a very useful way of dealing with pressed/focused/activated states maintaining backwards compatibility downto API-7, but there's a small issue (big for some) with the default selectableItemBackground: It uses some PNGs and/or default values for API<21.

The main reason is that android drawable resource definitions (prior API 21) CANNOT use theme attributes at all, so there's no way of making something like:
<shape android:shape="rectangle">
        <solid android:color="?attr/colorControlHighlight" />
</shape>

For this, I've put this simple mockup on how to give your app better drawables that the appcompat defaults.

fesago90

package com.dopplerlabs.hereactivelistening.hacks;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;

neworld

#!/bin/sh

# Copy templates to Android Studio in default location

TMP_PATH=`pwd`
TEMPLATES_PATH="/Applications/Android Studio.app/Contents/plugins/android/lib/templates/other"

DIRS=`find $TMP_PATH -type d -maxdepth 1 -not -name '.*' -not -path $TMP_PATH`

for f in $DIRS

d4rkc0de

inside onCreate() : 

Transition fade = new Fade();
fade.excludeTarget(android.R.id.statusBarBackground, true);
fade.excludeTarget(android.R.id.navigationBarBackground, true);
getWindow().setEnterTransition(fade);

or via xml : 

<?xml version="1.0" encoding="utf-8"?>

Augusent

/* Attributes

 <declare-styleable name="DateTimePickerView">
        <attr name="timeHourOfDay" format="integer"/>
        <attr name="timeMinute" format="integer"/>
        <attr name="timeFormat" format="string"/>
        <attr name="timeType" format="enum">
            <enum name="time" value="0"/>
            <enum name="date" value="1"/>
        </attr>

chrisbanes

package kotterknife

import android.app.Activity
import android.app.Dialog
import android.app.DialogFragment
import android.app.Fragment
import android.arch.lifecycle.Lifecycle
import android.arch.lifecycle.LifecycleObserver
import android.arch.lifecycle.LifecycleOwner
import android.arch.lifecycle.OnLifecycleEvent

elizarov

// https://akarnokd.blogspot.ru/2017/09/rxjava-vs-kotlin-coroutines-quick-look.html
import kotlinx.coroutines.experimental.*

suspend fun f1(i: Int): Int {
    Thread.sleep(if (i != 2) 2000L else 200L)
    return 1
}

suspend fun f2(i: Int): Int {
    Thread.sleep(if (i != 2) 2000L else 200L)

Augusent

public class TicketsPresenter extends BasePresenter<TicketsView, TicketsModel> {

    private final DisplayErrorUsecase displayErrorUsecase;
    private final LoadTicketsPageUsecase loadTicketsPageUsecase;
    private final ArchiveTicketUsecase archiveTicketUsecase;
    private final RenewTicketUsecase renewTicketUsecase;
    private final DeleteTicketUsecase deleteTicketUsecase;
    private final DeleteAllArchivedTicketsUsecase deleteAllArchivedTicketsUsecase;

ArthurNagy

package com.your.package

import android.app.Dialog
import android.os.Bundle
import com.your.package.R
import com.google.android.material.bottomsheet.BottomSheetDialog
import com.google.android.material.bottomsheet.BottomSheetDialogFragment

/**
 * BottomSheetDialog fragment that uses a custom 

rharter

package com.pixite.pigment.testing

import android.app.Activity
import android.app.Application
import android.content.Context
import android.content.Intent
import android.os.Bundle
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentActivity
import androidx.fragment.app.FragmentManager