App Development

Table of Contents

• App Development
  • Table of Contents
  • 1. Intents (Explicit)
  • 2. Handler
  • 3. AsynTask
  • 4. TCP Communication
  • 5. Others
  • Appendix and FAQ

1. Intents (Explicit)

Link: Javapoint Android Explicit Intents

• Simple Intent

Intent i = new Intent(getApplicationContext(), ActivityTwo.class);  
startActivity(i);  

• Adding Extras to intent
  Code in Main Activity

public void callSecondActivity(View view){  
    Intent i = new Intent(getApplicationContext(), SecondActivity.class);  
    i.putExtra("Value1", "Android By Javatpoint");  
    i.putExtra("Value2", "Simple Tutorial");   
    startActivity(i);  
}   

Code in Second Activity

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity_second);  
    Intent intent = getIntent();  
    String value1 = intent.getStringExtra("Value1");  
    String value2 = intent.getStringExtra("Value2");  
    Toast.makeText(getApplicationContext(),"Values are:\n First value: "+value1+  
            "\n Second Value: "+value2, Toast.LENGTH_LONG).show();  
}  

• Intent Activity for result

There are two variants of startActivityForResult() method.

public void startActivityForResult (Intent intent, int requestCode)  
public void startActivityForResult (Intent intent, int requestCode, Bundle options)  

Code in Main Activity

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity_main);  
    textView1=(TextView)findViewById(R.id.textView1);  
    button1=(Button)findViewById(R.id.button1);  
    button1.setOnClickListener(new OnClickListener() {  
        @Override  
        public void onClick(View arg0) {  
            Intent intent=new Intent(MainActivity.this,SecondActivity.class);  
            startActivityForResult(intent, 2);// Activity is started with requestCode 2  
        }  
    });  
}  
// Call Back method  to get the Message form other Activity  
@Override  
   protected void onActivityResult(int requestCode, int resultCode, Intent data)  
   {  
             super.onActivityResult(requestCode, resultCode, data);  
              // check if the request code is same as what is passed  here it is 2  
               if(requestCode==2)  
                     {  
                        String message=data.getStringExtra("MESSAGE");   
                        textView1.setText(message);  
                     }  
 }  

Code in Second Activity

@Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_second);  
        editText1=(EditText)findViewById(R.id.editText1);  
            button1=(Button)findViewById(R.id.button1);  
            button1.setOnClickListener(new OnClickListener() {  
                @Override  
                public void onClick(View arg0) {  
                    String message=editText1.getText().toString();  
                    Intent intent=new Intent();  
                    intent.putExtra("MESSAGE",message);  
                    setResult(2,intent);  
                    finish();//finishing activity  
                }  
            });  
    }  

2. Handler

Link: Android Developer Handler Class
There are two main uses for a Handler: (1) to schedule messages and runnables to be executed at some point in the future; and (2) to enqueue an action to be performed on a different thread than your own.

• postDelayed(Runnable r, long delayMillis)

  Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses.

3. AsynTask

Link: Android Developer AsyncTask Class
Link: Stackoverflow AsyncTask Example
Android AsyncTask going to do background operation on background thread and update on main thread.

4. TCP Communication

Link: Tutorialspoint sending and recieving using Sockets in Android

5. Others

• Making TextView Scrollable

  ​​​​<TextView
  ​​​​android:scrollbars=”vertical” />
  

  ​​​​textView.setMovementMethod(newScrollingMovementMethod());
  

Appendix and FAQ

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