Swipe View + Animations - Coding in Flow

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In this video we will learn, how we can swipe between Fragments with an animation by creating classes that implement the PageTransformer interface and then creating the animation in the transformPage method. Finally we set this animation to our ViewPager by using the setPageTransformer method.

PageTransformer guide:
developer.android.com/training/animation/screen-slide#pagetransformer

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DepthPageTransformerZoomOutPageTransformerMainActivity.javafragment_main.xml

package com.example.application.swipeexample;

import android.support.v4.view.ViewPager;
import android.view.View;

public class DepthPageTransformer implements ViewPager.PageTransformer {
    private static final float MIN_SCALE = 0.75f;

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();

        if (position < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.setAlpha(0);

        } else if (position <= 0) { // [-1,0]
            // Use the default slide transition when moving to the left page
            view.setAlpha(1);
            view.setTranslationX(0);
            view.setScaleX(1);
            view.setScaleY(1);

        } else if (position <= 1) { // (0,1]
            // Fade the page out.
            view.setAlpha(1 - position);

            // Counteract the default slide transition
            view.setTranslationX(pageWidth * -position);

            // Scale the page down (between MIN_SCALE and 1)
            float scaleFactor = MIN_SCALE
                    + (1 - MIN_SCALE) * (1 - Math.abs(position));
            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.setAlpha(0);
        }
    }
}

package com.example.application.swipeexample;

import android.support.v4.view.ViewPager;

import android.view.View;

public class DepthPageTransformer implements ViewPager.PageTransformer {

private static final float MIN_SCALE = 0.75f;

public void transformPage(View view, float position) {

int pageWidth = view.getWidth();

if (position < -1) { // [-Infinity,-1)

// This page is way off-screen to the left.

view.setAlpha(0);

} else if (position <= 0) { // [-1,0]

// Use the default slide transition when moving to the left page

view.setAlpha(1);

view.setTranslationX(0);

view.setScaleX(1);

view.setScaleY(1);

} else if (position <= 1) { // (0,1]

// Fade the page out.

view.setAlpha(1 - position);

// Counteract the default slide transition

view.setTranslationX(pageWidth * -position);

// Scale the page down (between MIN_SCALE and 1)

float scaleFactor = MIN_SCALE

+ (1 - MIN_SCALE) * (1 - Math.abs(position));

view.setScaleX(scaleFactor);

view.setScaleY(scaleFactor);

} else { // (1,+Infinity]

// This page is way off-screen to the right.

view.setAlpha(0);

}

package com.example.application.swipeexample;

import android.support.v4.view.ViewPager;
import android.view.View;

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
    private static final float MIN_SCALE = 0.85f;
    private static final float MIN_ALPHA = 0.5f;

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();
        int pageHeight = view.getHeight();

        if (position < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.setAlpha(0);

        } else if (position <= 1) { // [-1,1]
            // Modify the default slide transition to shrink the page as well
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            float vertMargin = pageHeight * (1 - scaleFactor) / 2;
            float horzMargin = pageWidth * (1 - scaleFactor) / 2;
            if (position < 0) {
                view.setTranslationX(horzMargin - vertMargin / 2);
            } else {
                view.setTranslationX(-horzMargin + vertMargin / 2);
            }

            // Scale the page down (between MIN_SCALE and 1)
            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);

            // Fade the page relative to its size.
            view.setAlpha(MIN_ALPHA +
                    (scaleFactor - MIN_SCALE) /
                            (1 - MIN_SCALE) * (1 - MIN_ALPHA));

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.setAlpha(0);
        }
    }
}

package com.example.application.swipeexample;

import android.support.v4.view.ViewPager;

import android.view.View;

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {

private static final float MIN_SCALE = 0.85f;

private static final float MIN_ALPHA = 0.5f;

public void transformPage(View view, float position) {

int pageWidth = view.getWidth();

int pageHeight = view.getHeight();

if (position < -1) { // [-Infinity,-1)

// This page is way off-screen to the left.

view.setAlpha(0);

} else if (position <= 1) { // [-1,1]

// Modify the default slide transition to shrink the page as well

float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));

float vertMargin = pageHeight * (1 - scaleFactor) / 2;

float horzMargin = pageWidth * (1 - scaleFactor) / 2;

if (position < 0) {

view.setTranslationX(horzMargin - vertMargin / 2);

} else {

view.setTranslationX(-horzMargin + vertMargin / 2);

}

// Scale the page down (between MIN_SCALE and 1)

view.setScaleX(scaleFactor);

view.setScaleY(scaleFactor);

// Fade the page relative to its size.

view.setAlpha(MIN_ALPHA +

(scaleFactor - MIN_SCALE) /

(1 - MIN_SCALE) * (1 - MIN_ALPHA));

} else { // (1,+Infinity]

// This page is way off-screen to the right.

view.setAlpha(0);

}

package com.example.application.swipeexample;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setPageTransformer(true, new ZoomOutPageTransformer());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        public PlaceholderFragment() {
        }

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            TextView textView = (TextView) rootView.findViewById(R.id.section_label);
            textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            return PlaceholderFragment.newInstance(position + 1);
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "SECTION 1";
                case 1:
                    return "SECTION 2";
                case 2:
                    return "SECTION 3";
            }
            return null;
        }
    }

    @Override
    public void onBackPressed() {
        if (mViewPager.getCurrentItem() == 0) {
            super.onBackPressed();
        } else {
            mViewPager.setCurrentItem(mViewPager.getCurrentItem() - 1);
        }
    }
}

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package com.example.application.swipeexample;

import android.os.Bundle;

import android.support.design.widget.FloatingActionButton;

import android.support.design.widget.Snackbar;

import android.support.v4.app.Fragment;

import android.support.v4.app.FragmentManager;

import android.support.v4.app.FragmentPagerAdapter;

import android.support.v4.view.ViewPager;

import android.support.v7.app.AppCompatActivity;

import android.support.v7.widget.Toolbar;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.ViewGroup;

import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

/**

* The {@link android.support.v4.view.PagerAdapter} that will provide

* fragments for each of the sections. We use a

* {@link FragmentPagerAdapter} derivative, which will keep every

* loaded fragment in memory. If this becomes too memory intensive, it

* may be best to switch to a

* {@link android.support.v4.app.FragmentStatePagerAdapter}.

private SectionsPagerAdapter mSectionsPagerAdapter;

/**

* The {@link ViewPager} that will host the section contents.

private ViewPager mViewPager;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

setSupportActionBar(toolbar);

// Create the adapter that will return a fragment for each of the three

// primary sections of the activity.

mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

// Set up the ViewPager with the sections adapter.

mViewPager = (ViewPager) findViewById(R.id.container);

mViewPager.setPageTransformer(true, new ZoomOutPageTransformer());

mViewPager.setAdapter(mSectionsPagerAdapter);

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

fab.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)

.setAction("Action", null).show();

}

});

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.menu_main, menu);

return true;

}

@Override

public boolean onOptionsItemSelected(MenuItem item) {

// Handle action bar item clicks here. The action bar will

// automatically handle clicks on the Home/Up button, so long

// as you specify a parent activity in AndroidManifest.xml.

int id = item.getItemId();

//noinspection SimplifiableIfStatement

if (id == R.id.action_settings) {

return true;

}

return super.onOptionsItemSelected(item);

}

/**

* A placeholder fragment containing a simple view.

public static class PlaceholderFragment extends Fragment {

/**

* The fragment argument representing the section number for this

* fragment.

private static final String ARG_SECTION_NUMBER = "section_number";

public PlaceholderFragment() {

}

/**

* Returns a new instance of this fragment for the given section

* number.

public static PlaceholderFragment newInstance(int sectionNumber) {

PlaceholderFragment fragment = new PlaceholderFragment();

Bundle args = new Bundle();

args.putInt(ARG_SECTION_NUMBER, sectionNumber);

fragment.setArguments(args);

return fragment;

}

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) {

View rootView = inflater.inflate(R.layout.fragment_main, container, false);

TextView textView = (TextView) rootView.findViewById(R.id.section_label);

textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));

return rootView;

}

/**

* A {@link FragmentPagerAdapter} that returns a fragment corresponding to

* one of the sections/tabs/pages.

public class SectionsPagerAdapter extends FragmentPagerAdapter {

public SectionsPagerAdapter(FragmentManager fm) {

super(fm);

}

@Override

public Fragment getItem(int position) {

// getItem is called to instantiate the fragment for the given page.

// Return a PlaceholderFragment (defined as a static inner class below).

return PlaceholderFragment.newInstance(position + 1);

}

@Override

public int getCount() {

// Show 3 total pages.

return 3;

}

@Override

public CharSequence getPageTitle(int position) {

switch (position) {

case 0:

return "SECTION 1";

case 1:

return "SECTION 2";

case 2:

return "SECTION 3";

}

return null;

}

@Override

public void onBackPressed() {

if (mViewPager.getCurrentItem() == 0) {

super.onBackPressed();

} else {

mViewPager.setCurrentItem(mViewPager.getCurrentItem() - 1);

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_blue_dark"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.example.application.swipeexample.MainActivity$PlaceholderFragment">

    <TextView
        android:id="@+id/section_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="@android:color/holo_blue_dark"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingBottom="@dimen/activity_vertical_margin"

tools:context="com.example.application.swipeexample.MainActivity$PlaceholderFragment">

<TextView

android:id="@+id/section_label"

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

</RelativeLayout>