gitignore file for Android Studio projects

This is the .gitignore file I use in my projects.

build/
local.properties
.gradle/
.idea/
*.iml
.DS_Store
.gitignore

I keep track of this files:

'your_application'/src/*
'your_application'/app/build.gradle
'your_application'/app/proguard-rules.pro
build.gradle
gradle.properties
gradle/
gradlew
gradlew.bat
settings.gradle

This way I can easily import the project as graddle projects in Android Studio.
I’ve been using this .gitignore from version 0.5.2 to 0.6.1.

Edit:

As David Wursteisen commented here:

gitignore.io can help you! example: http://www.gitignore.io/api/android,intellij,osx,windows,linux,gradle,java

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Custom ImageView with Zoom and Drag

I have made a custom ImageView that allows you to zoom in and out, and drag the window. The code is hosted in bitbucket: https://bitbucket.org/jewinaruto/zoomimage

Download  the apk corresponding to the video.

I tried to allow the user to customize the image as much as possible, so there are several custom parameters to configure in the xml. This are the things you can configure:

  • Adjust the image fit. If you disable this you can move or zoom the image as you want (Attr: adjustToBounds).
  • Block the image in the middle when it’s not occupying all the view (Google Pictures like). (Attr: blockImageInTheMidleWhileIsSmallerThanView)
  • Not allow the image never surpass the limits. If you let the image surpass the limits it will be like QuickPick (like the top video), if not it will be like Google Pictures or Google+ (like the video below). (Attr: allowExcedLimitsWhenMovingImage)
  • Double click to adjust image to center, or zoom in. You can enable it or no (Attr: doubleClickAdjust), set the maximum time to make a double click (Attr: doubleClickTimeInMillis), or set the zoom level double clicking by second time (Attr: doubleClickZoomLevel).
  • Configure the zoom levels. They are relative to the initial position of the view.(Attr: mininumZoomLevel & maximumZoomLevel). You can make this values relative to the size of the Image (Attr: isMinimumZoomLevelRelativeToView && isMaximumZoomLevelRelativeToView)

Download  the apk corresponding to the video.

Here is the code for the parameters:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ZoomImageView">
        <attr name="doubleClickTimeInMillis" format="integer"/>
        <attr name="mininumZoomLevel" format="float" />
        <attr name="maximumZoomLevel" format="float"/>
        <attr name="doubleClickZoomLevel" format="float" />
        <attr name="isMinimumZoomLevelRelativeToView" format="boolean" />
        <attr name="isMaximumZoomLevelRelativeToView" format="boolean"/>
        <attr name="adjustToBounds" format="boolean"/>
        <attr name="doubleClickAdjust" format="boolean"/>
        <attr name="allowExcedLimitsWhenMovingImage" format="boolean"/>
        <attr name="blockImageInTheMidleWhileIsSmallerThanView" format="boolean"/>
    </declare-styleable>
</resources>

Parsing the attributes:

private void parseAttributes(Context context, AttributeSet attrs) {
    TypedArray a = context.getTheme().obtainStyledAttributes(
            attrs, R.styleable.ZoomImageView, 0, 0);
    try {
        maxZoomLevel = a.getFloat(R.styleable.ZoomImageView_maximumZoomLevel, 3f);
        minZoomLevel = a.getFloat(R.styleable.ZoomImageView_mininumZoomLevel, 1f);
        doubleClickZoomLevel = a.getFloat(R.styleable.ZoomImageView_doubleClickZoomLevel, 2f);
        isMaxZoomLevelRelative = a.getBoolean(R.styleable.ZoomImageView_isMaximumZoomLevelRelativeToView, true);
        isMinZoomLevelRelative = a.getBoolean(R.styleable.ZoomImageView_isMinimumZoomLevelRelativeToView, true);
        adjustToBounds = a.getBoolean(R.styleable.ZoomImageView_adjustToBounds, true);
        doubleClickAdjust = a.getBoolean(R.styleable.ZoomImageView_doubleClickAdjust, true);
        allowExcedLimitsWhenMovingImage = a.getBoolean(R.styleable.ZoomImageView_allowExcedLimitsWhenMovingImage, false);
        blockImageInTheMiddle = a.getBoolean(R.styleable.ZoomImageView_blockImageInTheMidleWhileIsSmallerThanView, true);
        doubleClickTimeInMillis = a.getInteger(R.styleable.ZoomImageView_doubleClickTimeInMillis, 250);
    } finally {
        a.recycle();
    }
}

And here we have an example of how to configure the image view (this was the configuration for the second video).

<es.slothdevelopers.zoomimages.views.ZoomImageView
    android:id="@+id/image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/picture_01"
    custom:allowExcedLimitsWhenMovingImage="false"
    custom:blockImageInTheMidleWhileIsSmallerThanView="true"
    custom:doubleClickTimeInMillis="275"
    custom:doubleClickZoomLevel="3"
    custom:maximumZoomLevel="3"
    />

The code is too extend to put it in the post, but bassically you have to extend an ImageView and set it an onTouch listener.

Here you have the code for the custom imageview. This fragment shows you the onTouch method.

@Override
public boolean onTouch(View view, MotionEvent event) {
    if (!areValuesInitialized){
        initializeValues();
    }
    if (mode == CENTERING_IMAGE){
        return true;
    }

    switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            savedMatrix.set(matrix);
            start.set(event.getX(), event.getY());
            mode = DRAG;
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            oldDistance = spacing(event);
            if (oldDistance > 10f) {
                savedMatrix.set(matrix);
                midPoint(mid, event);
                mode = ZOOM;
            }
            break;
        case MotionEvent.ACTION_UP:
            checkClick(event);
            if (mode != CENTERING_IMAGE){
                postAdjust();
            }
        case MotionEvent.ACTION_POINTER_UP:
            setModeToNoneIfNotAdjustingOrCenteringView();
            break;
        case MotionEvent.ACTION_MOVE:
            if (mode == DRAG) {
                moveImage(event);
            } else if (mode == ZOOM) {
                scaleImage(event);
            }
            preAdjust();
            break;
    }

    return true;
}

To move and scale the images we use matrix.

In this case we use a 3×3 matrix, for this example we can use this as a reference:

|f0 f1 f2|
|f3 f4 f5|
|f6 f7 f8|

This are the corresponding values:

  • f0 -> x scale value
  • f2 -> x position value
  • f4 -> y scale value
  • f5 -> y position value

For this example the x scale value will always be equal to y scale value.

To adjust the image with an animation I use a Runnable and an Interpolator, I took the idea from here.

private void interpolateMatrixToValue(final float destinyMatrixValues[]){
    final float originMatrixValues[] = new float[9];
    matrix.getValues(originMatrixValues);

    final Interpolator interpolator = new AccelerateDecelerateInterpolator();
    final long startTime = System.currentTimeMillis();
    final long duration = 400;
    post(new Runnable() {
        @Override
        public void run() {
            float tempMatrix[] = new float[9];

            float t = (float) (System.currentTimeMillis() - startTime) / duration;
            t = t > 1.0f ? 1.0f : t;
            float interpolatedRatio = interpolator.getInterpolation(t);

            for (int i = 0; i < 9; i++){
                tempMatrix[i] =
                        originMatrixValues[i] +
                                interpolatedRatio * (destinyMatrixValues[i] - originMatrixValues[i]);
            }

            matrix.setValues(tempMatrix);
            setImageMatrix(matrix);
            if ((t < 1f) && ((mode == ADJUSTING) || mode == CENTERING_IMAGE)) {
                post(this);
            } else {
                if ((mode == CENTERING_IMAGE) || (mode == ADJUSTING)) {
                    mode = NONE;
                }
            }
        }
    });
}

In the future I want to add kinetic scrolling and transform this code into a library.

Image slider with parallax effect (FlickR style)

In this post we will see how to make an image slider with parallax effect. You can download the code, and the apk: normal, flickR style.

First I will explain how to achieve this effect without copying the FlickR layout. This is what we will make:

ParallaxImageSliderSimple

Fast resume: we will create a ViewPager in the MainActivity and attach it an OnPageChangeListener, then in the onPageScrolled method add the parallax effect.

These are the elements of our project:

Layout

Main activity layout

<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"
    tools:context="es.slothdevelopers.parallaximageslider.MainActivity">

    <android.support.v4.view.ViewPager
        android:id="@+id/parallaxSlider"
        android:layout_width="match_parent"
        android:layout_height="250dp"
        android:layout_centerInParent="true"/>

</RelativeLayout>

Page adapter element layout:

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

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"
        android:layout_gravity="center"/>

</FrameLayout>

We define the ImageView in a FrameLayout to keep the image inside and not to overlap the other images when applying the parallax effect.

Code

We will start defining the ViewPage adapter. Inside it we will override the intantiateItem method to inflate our layout and attach the image.

public class ImagePageAdapter extends PagerAdapter {
    private final Activity activity;
    private int[] imagesId;
    Map<Integer, View> imageViews = new HashMap<Integer, View>();

    public ImagePageAdapter(Activity activity, int[] imagesId) {
        this.activity = activity;
        this.imagesId = imagesId;
    }

    public Map<Integer, View> getImageViews() {
        return imageViews;
    }

    @Override
    public int getCount() {
        return imagesId.length;
    }

    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        LayoutInflater inflater = activity.getLayoutInflater();

        View view = inflater.inflate(R.layout.page_adapter_element, null);
        ImageView imageView = (ImageView) view.findViewById(R.id.image);
        imageView.setImageResource(imagesId[position]);
        container.addView(view);
        imageViews.put(position, imageView);
        return view;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((FrameLayout) object);
    }

}

We have defined the field imageViews that saves the position and the view of the image. We will access this field later from the MainActivity to get the views and apply the parallax effect.

Saving the views at this point improves the performance due to we don’t have to search for them lather.

Now we will analyze the MainActivity code:

public class MainActivity extends ActionBarActivity implements ViewPager.OnPageChangeListener {
    int[] pictures = new int[]{
            R.drawable.picture_1,
            R.drawable.picture_2,
            R.drawable.picture_3,
            R.drawable.picture_4,
            R.drawable.picture_5,
            R.drawable.picture_6
    };

    private int width;
    ViewPager viewPager;
    private ImagePageAdapter adapter;

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

        initViewPagerAndSetAdapter();
        calculateWidth();
    }

    private void initViewPagerAndSetAdapter(){
        viewPager = (ViewPager) findViewById(R.id.parallaxSlider);
        adapter = new ImagePageAdapter(this, pictures);
        viewPager.setAdapter(adapter);

        addPageChangeListenerIfSDKAbove11();
    }

    private void addPageChangeListenerIfSDKAbove11() {
        if (Build.VERSION.SDK_INT >11) {
            viewPager.setOnPageChangeListener(this);
        }
    }

    private void calculateWidth() {
        Display display = getWindowManager().getDefaultDisplay();
        Point size = new Point();
        viewPager.getWidth();

        if (Build.VERSION.SDK_INT <13) {
            width = display.getWidth();
        } else {
            display.getSize(size);
            width = size.x;
        }
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        parallaxImages(position, positionOffsetPixels);
    }

    private void parallaxImages(int position, int positionOffsetPixels) {
        Map<Integer, View> imageViews = adapter.getImageViews();

        for (Map.Entry<Integer, View> entry: imageViews.entrySet()){
            int imagePosition = entry.getKey();
            int correctedPosition = imagePosition - position;
            int displace = -(correctedPosition * width/2)+ (positionOffsetPixels / 2);

            View view = entry.getValue();
            view.setX(displace);
        }
    }

    @Override
    public void onPageSelected(int position) {

    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }
}

We set the content view, init the view pager, set the onPageChangeListener and finally calculate the width of the screen (because we will need it to make the parallax effect).

As we can see we don’t do nothing to complicated, all the “magic” its done in the parallaxImages method.

The parallax effect

First we will see how is the effect we want to achieve, and later we will recheck the code again.

In an view pager the positions of the views are assigned from 0 to N in order. In the onPageScrolled method the position parameter indicates the view that is more to the left in the Screen. Here we can see the values for that parameter in function of the screen position (the black rectangle). The orange squares are the views.

Position in viewpager

In this image (click to full size) we can see the starting and end position of the first images (position 0 and 1), and its correlation with the code.

Parallax Effect Explained

private void parallaxImages(int position, int positionOffsetPixels) {
    Map<Integer, View> imageViews = adapter.getImageViews();
    for (Map.Entry<Integer, View> entry: imageViews.entrySet()){
        int imagePosition = entry.getKey();
        int correctedPosition = imagePosition - position;
        int displace = -(correctedPosition * width/2)+ (positionOffsetPixels / 2);

        View view = entry.getValue();
        view.setX(displace);
    }
}

On this method we process all the views we saved (in the instantiate method) adjusting the X.

Custom layouts, FlickR like layout example

Once you get this point is easy to customize your layouts. For example I will change the layout to have the slider similar to the flickR.

FlickR like layout

Here are the new layout files:

Lets see the viewpager layout first:

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

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingRight="0.5dp"
    android:paddingLeft="0.5dp">

    <ImageView
        android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerInside"
        android:layout_gravity="center"/>

</FrameLayout>

The only differences are that now we want to match the parent size, and we add a small padding to the sides to the FrameLayout.

Now lets see the MainActivity layout:

<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="#1f1f21"
    tools:context="es.slothdevelopers.parallaximageslider.MainActivity">

    <android.support.v4.view.ViewPager
        android:id="@+id/parallaxSlider"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerInParent="true"/>
    <View
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:background="@drawable/header_background">
    </View>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Parallax Image Slider"
        android:textColor="@android:color/white"
        android:textSize="20sp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"/>

</RelativeLayout>

In this case:

  • I set the height of the ViewPager to match parent height.
  • I added a view on top of the view pager with a gradient from grey to transparent and white text in top. This way we can read the text even with a bright images.

Parallax Image Slider FlickR like landscape

Here is the code for the gradient:

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

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <gradient android:angle="270" android:startColor="#99000000" android:endColor="#00000000">
            </gradient>
        </shape>
    </item>
</selector>

You can check the code at bitbucket, in the flickRLike branch.