android: how to change layout on button click?

Question

I have to following code for selecting layout on button click.

View.OnClickListener handler = new View.OnClickListener(){
    public void onClick(View v) {

        switch (v.getId()) {

            case R.id.DownloadView: 
                // doStuff
                setContentView(R.layout.main);
                break;
            case R.id.AppView: 
                // doStuff
                setContentView(R.layout.app);
                break;
        }
    }
};

findViewById(R.id.DownloadView).setOnClickListener(handler);
findViewById(R.id.AppView).setOnClickListener(handler);

When I click the "AppView" button, the layout changes, but when I click the "DownloadView "button, nothing happens.

This link says that I have to start a new activity.

But I don't know how to use the code there of intent to start new activity, will a new file be added?

EDIT: I have my code on the new activity:

package com.example.engagiasync;

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

public class AppView extends Activity implements OnClickListener{


    @Override
    public void onCreate(Bundle savedInstanceState){

        setContentView(R.layout.app);

        TextView tv = (TextView) this.findViewById(R.id.thetext);
        tv.setText("App View yo!?\n");
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

    }
}

but it does not work, it force closes, the logcat says:

Answer 1

  Button btnDownload = (Button) findViewById(R.id.DownloadView);
  Button btnApp = (Button) findViewById(R.id.AppView);

  btnDownload.setOnClickListener(handler);
  btnApp.setOnClickListener(handler);

  View.OnClickListener handler = new View.OnClickListener(){

  public void onClick(View v) {

    if(v==btnDownload){ 
            // doStuff
            Intent intentMain = new Intent(CurrentActivity.this , 
                                           SecondActivity.class);
            CurrentActivity.this.startActivity(intentMain);
            Log.i("Content "," Main layout ");
    }

    if(v==btnApp){ 
            // doStuff
            Intent intentApp = new Intent(CurrentActivity.this, 
                                          ThirdActivity.class);

            CurrentActivity.this.startActivity(intentApp);

            Log.i("Content "," App layout ");

    }
   }
  };

Note : and then you should declare all your activities in the manifest .xml file like this :

<activity android:name=".SecondActivity" ></activity>
<activity android:name=".ThirdActivity" ></activity>

EDIT : update this part of Code :) :

@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);// Add THIS LINE

    setContentView(R.layout.app);

    TextView tv = (TextView) this.findViewById(R.id.thetext);
    tv.setText("App View yo!?\n");
}

NB : check this (Broken link) Tutorial About How To Switch Between Activities.

Answer 2

I would add an android:onClick to the layout and then change the layout in the activity.

So in the layout

<ImageView
(Other things like source etc.)
android:onClick="changelayout"
/>

Then in the activity add the following:

public void changelayout(View view){
    setContentView(R.layout.second_layout);
}