Platform 2 Code: Understanding activities in Android

Platform 2 Code: Understanding activities in Android: To create an activity,you create a java class that extends the activity class package com.firstactivity; import android.os.Bundle...

Understanding activities in Android

1. To create an activity,you create a java class that extends the activity class

package com.firstactivity;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.activity_main, menu);

return true;

}

}

Your activity class would the load its UI component using the XML file defined in your res/layout folder.In this example you would load the UI from the main.xml file:

setContentView(R.layout.activity_main);

Every activity you have in your application must be declared in your AndroidManifest.xml file like this:


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

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.firstactivity.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>
    </application>

</manifest>

Progress Bar in Android

Creating Prograss Bar in Android
-------------------------------------

Activity File

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".ProgBar" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/prog_msg" />
    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/b1"
        android:text="@string/msg"
        />

</LinearLayout>





Java Code
-------------
package com.progbar;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class ProgBar extends Activity {

ProgressDialog pb;
int value=0;
Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.progbar_activity);
        Button b=(Button) findViewById(R.id.b1);
        b.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
showDialog(1);
pb.setProgress(0);
handler.sendEmptyMessage(0);
}
});
        handler=new Handler()
        {
        public void handleMessage(Message msg)
        {
        super.handleMessage(msg);
        if(value>=100)
        {
        pb.dismiss();
        }
        else
        {
        value++;
        pb.incrementProgressBy(1);
        handler.sendEmptyMessageDelayed(0,100);
        }
        }
        };
    }
protected Dialog onCreateDialog(int id)
{
switch(id)
{
case 0:
return new AlertDialog.Builder(this).create();
case 1:
pb=new ProgressDialog(this);
pb.setIcon(R.drawable.ic_launcher);
pb.setTitle("Download files...");
pb.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pb.setButton(DialogInterface.BUTTON_POSITIVE,"Hide",new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog,int whichButton)
{
Toast.makeText(getBaseContext(), "Hide Clicked !",Toast.LENGTH_LONG).show();
}

});
return pb;
}
return null;
}
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.progbar_activity, menu);
        return true;
    }
 
}