What is RecyclerView and How to use it?
Ans:-The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. Use the RecyclerView widget when you have data collections whose elements change at runtime based on user action or network events.
The RecyclerView class simplifies the display and handling of large data sets by providing:
1.Layout managers for positioning items
2.Default animations for common item operations, such as removal or addition of items
You also have the flexibility to define custom layout managers and animations for RecyclerView widgets.
To use the RecyclerView widget, you have to specify an adapter and a layout manager. To create an adapter, extend the RecyclerView.Adapter class. The details of the implementation depend on the specifics of your dataset and the type of views.
A layout manager positions item views inside a RecyclerView and determines when to reuse item views that are no longer visible to the user. To reuse (or recycle) a view, a layout manager may ask the adapter to replace the contents of the view with a different element from the dataset. Recycling views in this manner improves performance by avoiding the creation of unnecessary views or performing expensive findViewById() lookups.
RecyclerView provides these built-in layout managers:
build.gradle:
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion "21.1.2"
defaultConfig {
applicationId "recyclerviewexample.ram.com.recyclerviewexample"
minSdkVersion 10
targetSdkVersion 21
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.+'
compile 'com.android.support:cardview-v7:21.0.+'
}
drawable files:
back_select.xml:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@android:color/darker_gray" />
<item android:drawable="@android:color/transparent" />
</selector>
back_select.xml(v14):
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@android:color/holo_blue_bright" />
<item android:drawable="@android:color/transparent" />
</selector>
Layout files:
activity_main.xml:
<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=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clickable="true"
android:background="#ffcccc"
/>
</RelativeLayout>
list_cardview_layout.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@drawable/back_select">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/info_text"
android:layout_gravity="center" />
</LinearLayout>
</android.support.v7.widget.CardView>
java code:
MyDataAdapter:
package recyclerviewexample.ram.com.recyclerviewexample;
import android.app.Activity;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
/**
* Created by Ram-Roots on 30-01-2015.
*/
public class MyDataAdapter extends RecyclerView.Adapter<MyDataAdapter.ViewHolder> {
public String[] NAMES_DATA;
static Activity activity;
public MyDataAdapter(Activity activity, String[] NAMES_DATA) {
this.NAMES_DATA = NAMES_DATA;
this.activity = activity;
}
// Create new views (invoked by the layout manager)
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
// create a new view
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_cardview_layout, parent, false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.info_textView.setText(NAMES_DATA[position]);
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return NAMES_DATA.length;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
TextView info_textView;
public ViewHolder(View view) {
super(view);
this.info_textView = (TextView) view.findViewById(R.id.info_text);
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, info_textView.getText().toString(), Toast.LENGTH_LONG).show();
}
});
}
}}
MainActivity.java:
package recyclerviewexample.ram.com.recyclerviewexample;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.MotionEvent;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity {
RecyclerView recyclerView;
private RecyclerView.LayoutManager mLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
recyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(mLayoutManager);
MyDataAdapter myDataAdapter = new MyDataAdapter(MainActivity.this, COUNTRIES);
recyclerView.setAdapter(myDataAdapter);
}
static final String[] COUNTRIES = new String[]{"Afghanistan", "Albania",
"Algeria", "American Samoa", "Andorra", "Angola", "Anguilla",
"Antarctica", "Antigua and Barbuda", "Argentina", "Armenia",
"Aruba", "Australia", "Austria", "Azerbaijan", "Bahrain",
"Bangladesh", "Barbados", "Belarus", "Belgium", "Belize", "Benin",
"Bermuda", "Bhutan", "Bolivia", "Bosnia and Herzegovina",
"Botswana", "Bouvet Island", "Brazil",
"British Indian Ocean Territory", "British Virgin Islands",
"Brunei", "Bulgaria", "Burkina Faso", "Burundi", "Cote d'Ivoire"
};
}
Ans:-The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. Use the RecyclerView widget when you have data collections whose elements change at runtime based on user action or network events.
The RecyclerView class simplifies the display and handling of large data sets by providing:
1.Layout managers for positioning items
2.Default animations for common item operations, such as removal or addition of items
You also have the flexibility to define custom layout managers and animations for RecyclerView widgets.
A layout manager positions item views inside a RecyclerView and determines when to reuse item views that are no longer visible to the user. To reuse (or recycle) a view, a layout manager may ask the adapter to replace the contents of the view with a different element from the dataset. Recycling views in this manner improves performance by avoiding the creation of unnecessary views or performing expensive findViewById() lookups.
RecyclerView provides these built-in layout managers:
- LinearLayoutManager shows items in a vertical or horizontal scrolling list.
- GridLayoutManager shows items in a grid.
- StaggeredGridLayoutManager shows items in a staggered grid.
To create a custom layout manager, extend the RecyclerView.LayoutManager class.
Animations:
Animations for adding and removing items are enabled by default in RecyclerView. To customize these animations, extend the RecyclerView.ItemAnimator class and use the RecyclerView.setItemAnimator() method.
Example:coming soon....
Screen Shots:build.gradle:
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion "21.1.2"
defaultConfig {
applicationId "recyclerviewexample.ram.com.recyclerviewexample"
minSdkVersion 10
targetSdkVersion 21
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.+'
compile 'com.android.support:cardview-v7:21.0.+'
}
drawable files:
back_select.xml:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@android:color/darker_gray" />
<item android:drawable="@android:color/transparent" />
</selector>
back_select.xml(v14):
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@android:color/holo_blue_bright" />
<item android:drawable="@android:color/transparent" />
</selector>
Layout files:
activity_main.xml:
<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=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clickable="true"
android:background="#ffcccc"
/>
</RelativeLayout>
list_cardview_layout.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@drawable/back_select">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/info_text"
android:layout_gravity="center" />
</LinearLayout>
</android.support.v7.widget.CardView>
java code:
MyDataAdapter:
package recyclerviewexample.ram.com.recyclerviewexample;
import android.app.Activity;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
/**
* Created by Ram-Roots on 30-01-2015.
*/
public class MyDataAdapter extends RecyclerView.Adapter<MyDataAdapter.ViewHolder> {
public String[] NAMES_DATA;
static Activity activity;
public MyDataAdapter(Activity activity, String[] NAMES_DATA) {
this.NAMES_DATA = NAMES_DATA;
this.activity = activity;
}
// Create new views (invoked by the layout manager)
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
// create a new view
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_cardview_layout, parent, false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.info_textView.setText(NAMES_DATA[position]);
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return NAMES_DATA.length;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
TextView info_textView;
public ViewHolder(View view) {
super(view);
this.info_textView = (TextView) view.findViewById(R.id.info_text);
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, info_textView.getText().toString(), Toast.LENGTH_LONG).show();
}
});
}
}}
MainActivity.java:
package recyclerviewexample.ram.com.recyclerviewexample;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.MotionEvent;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity {
RecyclerView recyclerView;
private RecyclerView.LayoutManager mLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
recyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(mLayoutManager);
MyDataAdapter myDataAdapter = new MyDataAdapter(MainActivity.this, COUNTRIES);
recyclerView.setAdapter(myDataAdapter);
}
static final String[] COUNTRIES = new String[]{"Afghanistan", "Albania",
"Algeria", "American Samoa", "Andorra", "Angola", "Anguilla",
"Antarctica", "Antigua and Barbuda", "Argentina", "Armenia",
"Aruba", "Australia", "Austria", "Azerbaijan", "Bahrain",
"Bangladesh", "Barbados", "Belarus", "Belgium", "Belize", "Benin",
"Bermuda", "Bhutan", "Bolivia", "Bosnia and Herzegovina",
"Botswana", "Bouvet Island", "Brazil",
"British Indian Ocean Territory", "British Virgin Islands",
"Brunei", "Bulgaria", "Burkina Faso", "Burundi", "Cote d'Ivoire"
};
}
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