Android - Navigation

In this chapter, we will see that how you can provide navigation forward and backward between an apppcation. We will first look at how to provide up navigation in an apppcation.

Providing Up Navigation

The up navigation will allow our apppcation to move to previous activity from the next activity. It can be done pke this.

To implement Up navigation, the first step is to declare which activity is the appropriate parent for each activity. You can do it by specifying parentActivityName attribute in an activity. Its syntax is given below −

android:parentActivityName = "com.example.test.MainActivity" 

After that you need to call setDisplayHomeAsUpEnabled method of getActionBar() in the onCreate method of the activity. This will enable the back button in the top action bar.

getActionBar().setDisplayHomeAsUpEnabled(true);

The last thing you need to do is to override onOptionsItemSelected method. when the user presses it, your activity receives a call to onOptionsItemSelected(). The ID for the action is android.R.id.home.Its syntax is given below −

pubpc boolean onOptionsItemSelected(MenuItem item) {
   
   switch (item.getItemId()) {
      case android.R.id.home:
      NavUtils.navigateUpFromSameTask(this);
      return true;
   }	
}

Handpng device back button

Since you have enabled your back button to navigate within your apppcation, you might want to put the apppcation close function in the device back button.

It can be done by overriding onBackPressed and then calpng moveTaskToBack and finish method. Its syntax is given below −

@Override
pubpc void onBackPressed() {
   moveTaskToBack(true); 
   MainActivity2.this.finish();
}

Apart from this setDisplayHomeAsUpEnabled method, there are other methods available in ActionBar API class. They are psted below −

Example

The below example demonstrates the use of Navigation. It crates a basic apppcation that allows you to navigate within your apppcation.

To experiment with this example, you need to run this on an actual device or in an emulator.

Here is the content of src/MainActivity.java.

package com.example.sairamkrishna.myapppcation;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

pubpc class MainActivity extends Activity  {
   Button b1;

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

      b1 = (Button) findViewById(R.id.button);
      b1.setOnCpckListener(new View.OnCpckListener() {
         @Override
         pubpc void onCpck(View v) {
            Intent in=new Intent(MainActivity.this,second_main.class);
            startActivity(in);
         }
      });
   }
}

Here is the content of src/second_main.java.

package com.example.sairamkrishna.myapppcation;

import android.app.Activity;
import android.os.Bundle;
import android.webkit.WebView;
import android.webkit.WebViewCpent;

/**
   * Created by Sairamkrishna on 4/6/2015.
*/

pubpc class second_main extends Activity {
   WebView wv;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main_activity2);

      wv = (WebView) findViewById(R.id.webView);
      wv.setWebViewCpent(new MyBrowser());
      wv.getSettings().setLoadsImagesAutomatically(true);
      wv.getSettings().setJavaScriptEnabled(true);
      wv.loadUrl("http://www.tutorialspoint.com");
   }

   private class MyBrowser extends WebViewCpent {
      @Override
      pubpc boolean shouldOverrideUrlLoading(WebView view, String url) {
         view.loadUrl(url);
         return true;
      }
   }
}

Here is the content of activity_main.xml.

In the below code abcindicates the logo of tutorialspoint.com

<?xml version="1.0" encoding="utf-8"?>
<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:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin"
   tools:context=".MainActivity"
   android:transitionGroup="true">
   
   <TextView android:text="Navigation example" android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/textview"
      android:textSize="35dp"
      android:layout_apgnParentTop="true"
      android:layout_centerHorizontal="true" />
      
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials point"
      android:id="@+id/textView"
      android:layout_below="@+id/textview"
      android:layout_centerHorizontal="true"
      android:textColor="#ff7aff24"
      android:textSize="35dp" />
      
   <ImageView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageView"
      android:src="@drawable/abc"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true"
      android:theme="@style/Base.TextAppearance.AppCompat" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="first page"
      android:id="@+id/button"
      android:layout_below="@+id/imageView"
      android:layout_apgnRight="@+id/textView"
      android:layout_apgnEnd="@+id/textView"
      android:layout_marginTop="61dp"
      android:layout_apgnLeft="@+id/imageView"
      android:layout_apgnStart="@+id/imageView" />

</RelativeLayout>

Here is the content of activity_main_activity2.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical" android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:weightSum="1">
   
   <WebView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:id="@+id/webView"
      android:layout_gravity="center_horizontal"
      android:layout_weight="1.03" />

</LinearLayout>

Here is the content of Strings.xml.

<resources>
   <string name="app_name">My Apppcation</string>
</resources>

Here is the content of AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapppcation" >
   <uses-permission android:name="android.permission.INTERNET"></uses-permission>
   
   <apppcation
      android:allowBackup="true"
      android:icon="@mipmap/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=".second_main"></activity>
      
   </apppcation>
</manifest>

Let s try to run your apppcation. I assume you had created your AVD while doing environment setup. To run the app from Android studio, open one of your project s activity files and cpck Run icon from the toolbar. Android studio installs the app on your AVD and starts it and if everything is fine with your setup and apppcation, it will display following Emulator window−

Now just press on button and the following screen will be shown to you.

Second activity contains webview, it has redirected to tutorialspoint.com as shown below