Android Activity Quick Start

Android Activity Quick Start

Declaring Activity

 

1.       In Eclipse click File->New->Android Application Project

2.       Specify all  required infrmation as shown below

 

3.       Click Next antil you reached activity creation step, and specify activity information as shown below

 

4.Click finish, your project will be created as shown below.

 

4.       Open up the manifest file from the Package Explorer, and then click on the AndroidManifest.xml tab at the bottom to display the code that the IDE has produced.

Within the <activity> element, find the following attributes:

android:name=".MainActivity"

android:label="@string/app_name"

5.       Edit the code so that it matches the following snippet:

<activity

android:name=".MainActivity"

android:label="Welcome to Android Introduction"

android:screenOrientation="portrait">

...

</activity>

6.       To run your application you need to create android virtual device , to do so click “Android Virtual Device Manager” from task bar as shown in the figure below.

7.       You will be presented with virtual device manager as shown below

8.       Click New and create new emulator and start .

9.       Now close all the dialog except the emulator , and return to your Eclipse IDE

10.   To run your application click Run ->Run

Starting a new activity with an intent object

 

1.       Now from package explorer go to res->layout and open main.xml 

2.       Next  to </TextView>  Insert button as shown below

<Button

        android:id="@+id/callButton"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:text="Call Log" />

3.       Save and close

4.       From package explorer got src and open MainActivity.java and put the following method at the end inside the class               

                void startCallButton () {

       Intent myIntent = new Intent();

       myIntent.setAction(Intent.ACTION_CALL_BUTTON);

       startActivity(myIntent);

5.       Insert button click event listener  code show bellow in to onCreate() method  next setContentView()

                                Button cButton=(Button)findViewById(R.id.callButton);

              cButton.setOnClickListener(new View.OnClickListener() {

                    

                     @Override

                     public void onClick(View arg0) {

                           // TODO Auto-generated method stub

                           startCallButton();

                          

                     }

              });

 

6.       Save the project and run,and click the button

7.       If this generates an error message, it may be that the correct libraries have not been imported. To use intents we have to import the relevant library, which can be done with import android.content.Intent; however it's easy to get Eclipse to import any missing libraries simply by pressing Shift + Ctrl + O.

 

 

Switching between activities

 

Often we will want to activate one activity from within another. Although this is not a difficult task, it will require more setting up than the previous two recipes as it will need two activities to be declared in the Manifest, a new Class to serve as our second activity, and a button along with a click listener to perform the switch.

1.       Create a new activity in the same location as the original activity subclass to do so:

                Right Click on your project->click New->click other

                You will be presented with the following dialog box.

2.       Select Android Activity and click next ->next until you reach new activity dialog box and

    Activity Name-  MySubActivity

   Layout Name – mysub

And leave everything as it is and click finish.

 

3.       Next, we must add a button that the user can click on to switch activities. This is set up through the main.xml file which resides in the res/layout folder in the Package Explorer.

4.       Open the main.xml file and click on the XML tab at the bottom so that the code can be edited.

5.       Add the following <Button> element just after the  call button from previous example y:

   <Button

       android:text="click to switch activities"

       android:id="@+id/main_activity_button"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content">

       </Button>

6.       Now open the original Java activity class,.

7.       Add the following code to the onCreate() method after the setContentView(R. layout.main); statement, making sure to replace the package and class parameters in the setClassName() call with your own, as they will most likely be different:

             Button switchButton = (Button) findViewById(R.id.main_activity_button);

              switchButton.setOnClickListener(new View.OnClickListener() {

                     @Override

                     public void onClick(View v) {

                           Intent intent = new Intent();

                           String packageName =

                           "com.example.mysimpleapp ";

                           String className =

                           "com.example.mysimpleapp.MySubActivity";

                           intent.setClassName(packageName, className);

                           startActivity(intent);

                     }

              });

8.       Run the application on a device or emulator. Clicking on the button will now start the sub activity.

Passing Data from one activity to another

 

1.       Create a new project with these project name PassDataActivity. Leave everything else as it is by default and click finish.

2.        Open activity_main.xml and put EditText  and Button as shown below.

 

<EditText

        android:id="@+id/messageText"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:ems="10" >

 

        <requestFocus />

    </EditText>

 

    <Button

        android:id="@+id/sendButton"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Send" />

 

 

 

 

 

 

 

 

 

3.       In the package explorer open MainActivity.java and add the following code to the onCreate() method after the setContentView(R. layout.main);

 

Button mSendButton=(Button)findViewById(R.id.sendButton);

          mSendButton.setOnClickListener(new View.OnClickListener() {

                

                 @Override

                 public void onClick(View arg0) {

                        // TODO Auto-generated method stub

EditText    MessageText=(EditText)findViewById(R.id.messageText);

                        Intent intent= new Intent();

                    intent.setClassName("com.example.passdataactivity","com.example.passdataactivity.SecondActivity");

                        intent.putExtra("com_example_passdataactivity_id", mMessageText.getText().toString());

                        startActivity(intent);

                       

                 }

          });

 

4.       Now time to create our second activity, add new activity and name it SecondActivity. Leave everything as it and click finish.

 

5.       From package explorer Open SecondActivity.java and add the following code to the onCreate() method after the setContentView(R. layout.main);

 

String msg=getIntent().getExtras().getString("com_example_passdataactivity_id ");

              EditText msgView=new EditText(this);

              msgView.setText(msg);

          setContentView(msgView);

 

6.       Run the application on a device or an emulator.