4 August 2015

Making Intents in Listview

We will learn to navigate to a new page by clicking on list item. I will consider a Custom List from the one of the previous post.

What we will do?
-> We will make a list with some items. When we click on a list-item we will traverse to a specific page.

What we will need?
  • activity_jaguar.xml (newly added)
  • MainActivity.java (changes required)
  • Jaguar.java (newly added)
  • AndroidManifest.xml (changes required)
Note : we will edit the project from one of the previous post of Custom List.

Step 1 : Add a android xml file in res->layout folder and name it as activity_jaguar.xml. Right Click on layout->New->Android XML Layout.

activity_jaguar.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Jaguar's business was founded as the Swallow Sidecar Company in 1922, originally making motorcycle sidecars before developing bodies for passenger cars." />

</LinearLayout>

Step 2 : Add a class under src->com.mia.customlistdemo folder by  name it as Jaguar.java. Right Click on com.mia.customlistdemo under src->New->Class

Jaguar.java
package com.mia.customlistdemo;

import android.app.Activity;
import android.os.Bundle;

public class Jaguar extends Activity{
public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_jaguar);
 }
}
The Project Skeleton is shown as below:

Step 3 : Go to MainActivity.java from the previous post. Remove the toast at the end lines and replace it with Intents. Right now I will connect only the second list item(Jaguar) with one page (Jaguar.java), the other list items will return a toast as before.
The modified MainActivity.java is shown below
package com.mia.customlistdemo;

import java.util.ArrayList;
import java.util.HashMap;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends ListActivity {
  
   //ArrayList thats going to hold the search results
          ArrayList<HashMap<String, Object>> searchResults;

   //ArrayList that will hold the original Data
          ArrayList<HashMap<String, Object>> originalValues;
   LayoutInflater inflater;
 @Override
   public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
   
  setContentView(R.layout.activity_main);
  final EditText searchBox=(EditText) findViewById(R.id.searchBox);
  ListView playersListView=(ListView) findViewById(android.R.id.list);
  
  //get the LayoutInflater for inflating the customomView
  //this will be used in the custom adapter
  inflater=(LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
  
  //these arrays are just the data that 
  //I'll be using to populate the ArrayList
  //You can use our own methods to get the data
  String names[]={"FIESTA","XJ","BOXSTER"}; 
  
  String teams[]={"Ford","Jaguar","Porsche"};
  Integer[] photos={R.drawable.picford,R.drawable.picjaguar,R.drawable.picporsche};
         originalValues=new ArrayList<HashMap<String,Object>>();
         
         //temporary HashMap for populating the 
  //Items in the ListView
  HashMap<String , Object> temp;
  
  //total number of rows in the ListView
  int noOfPlayers=names.length;
  
  //now populate the ArrayList players
  for(int i=0;i<noOfPlayers;i++)
  {
   temp=new HashMap<String, Object>();
  
   temp.put("name", names[i]);
   temp.put("team", teams[i]);    
   temp.put("photo", photos[i]);
  
   //add the row to the ArrayList
   originalValues.add(temp);        
  }
  //searchResults=OriginalValues initially
  searchResults=new ArrayList<HashMap<String,Object>>(originalValues);
  
  //create the adapter
  //first param-the context
  //second param-the id of the layout file 
  //you will be using to fill a row
  //third param-the set of values that
  //will populate the ListView
  final CustomAdapter adapter=new CustomAdapter(this, R.layout.activity_item,searchResults); 
  
  //finally,set the adapter to the default ListView
  playersListView.setAdapter(adapter);
  searchBox.addTextChangedListener(new TextWatcher() {
  
  public void onTextChanged(CharSequence s, int start, int before, int count) {
    //get the text in the EditText
    String searchString=searchBox.getText().toString();
    int textLength=searchString.length();
    searchResults.clear();
  
           for(int i=0;i<originalValues.size();i++)
    {
   String playerName=originalValues.get(i).get("name").toString();
          if(textLength<=playerName.length()){
   //compare the String in EditText with Names in the ArrayList
     if(searchString.equalsIgnoreCase(playerName.substring(0,textLength)))
     searchResults.add(originalValues.get(i));
   }}
    adapter.notifyDataSetChanged();
  }
  
  public void beforeTextChanged(CharSequence s, int start, int count,
      int after) {}
    
  public void afterTextChanged(Editable s) {}
   });
  }
  
  //define your custom adapter
  private class CustomAdapter extends ArrayAdapter<HashMap<String, Object>>
  {
   public CustomAdapter(Context context, int textViewResourceId,
     ArrayList<HashMap<String, Object>> Strings) {
  
    //let android do the initializing :)
    super(context, textViewResourceId, Strings);
   }
  
   //class for caching the views in a row  
   private class ViewHolder
   {
    ImageView photo;
    TextView name,team;
   }
  
   ViewHolder viewHolder;
  
   @Override
   public View getView(int position, View convertView, ViewGroup parent) {
  
    if(convertView==null)
    {
     convertView=inflater.inflate(R.layout.activity_item, null);
     viewHolder=new ViewHolder();
  
      //cache the views
      viewHolder.photo=(ImageView) convertView.findViewById(R.id.photo);
      viewHolder.name=(TextView) convertView.findViewById(R.id.name);
      viewHolder.team=(TextView) convertView.findViewById(R.id.team);
  
       //link the cached views to the convertview
       convertView.setTag(viewHolder);
    }
    else
     viewHolder=(ViewHolder) convertView.getTag();
    int photoId=(Integer) searchResults.get(position).get("photo");
  
    //set the data to be displayed
    viewHolder.photo.setImageDrawable(getResources().getDrawable(photoId));
    viewHolder.name.setText(searchResults.get(position).get("name").toString());
    viewHolder.team.setText(searchResults.get(position).get("team").toString());
    //return the view to be displayed
    return convertView;
   }
  }
  protected void onListItemClick(ListView l, View v, int position, long id) {
   // TODO Auto-generated method stub
   super.onListItemClick(l, v, position, id);
   String str = searchResults.get(position).get("name").toString();
   try{
    if(str=="XJ"){
     Class jClass = Class.forName("com.mia.customlistdemo.Jaguar");
     Intent jIntent = new Intent(this, jClass);
     startActivity(jIntent);
     }
    if(str=="FIESTA"){
     Toast.makeText(getApplicationContext(), "FIESTA\nFORD", Toast.LENGTH_SHORT).show();
    }
    if(str=="BOXSTER"){
     Toast.makeText(getApplicationContext(), "BOXSTER\nPORSCHE", Toast.LENGTH_SHORT).show();
    }
   }
    catch(Exception e){
     e.printStackTrace();
    }
   
}
}
MainActivity.java



Step 4 : Open AndroidManifest.xml and add activity of Jaguar class as shown below.

Android Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mia.customlistdemo"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <activity
            android:name=".Jaguar"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

Step 5 : Run the Project.

Explanation of the code :

Explanation from MainActivity.java :
  • At line 162 we have made a variable jClass of type Class and stored location of Jaguar Class there.
  • Then we made use of Intent to reference this(MainActivity) class with Jaguar class.
Explanation from AndroidManifest.xml :
  • We have just added a new Activity of Jaguar class.

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