Novice under eclipse ADT advice on how to add visual environment in response to a button event

eclipse adt java

I wrote Mainactivity.java in a openDialog () used to do incident response, but added openDialog in button OnClick property () no effect, suggesting openDialog () can not find

 
public class MainActivity extends Activity {
private TextView txtView; 
@ Override 
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState); 
setContentView (R.layout.activity_main); 
this.txtView = (TextView) findViewById (R.id.textView1); 

if (this.txtView! = null) {

this.txtView.setText ("Hello World"); 
} 
} 
public void openDialog () {
AlertDialog.Builder builder = new AlertDialog.Builder (this); 
builder.setTitle ("Hello"); 
builder.setMessage ("Hello World \ n"); 
builder.setNegativeButton ("OK", null); 
builder.show (); 
} 

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

} 

Add Button's On Click property

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Reply:
Visual design interface only provides property settings, trigger events with a code on it:

 public class MainActivity extends Activity {
private TextView txtView; 
@ Override 
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState); 
setContentView (R.layout.activity_main); 
this.txtView = (TextView) findViewById (R.id.textView1); 

if (this.txtView! = null) {

this.txtView.setText ("Hello World"); 
} 

Button button = (Button) findViewById (R.id.button_id); 
button.setOnClickListener (new View.OnClickListener () {
public void onClick (View v) {
openDialog (); 
} 
}); 
} 
public void openDialog () {
AlertDialog.Builder builder = new AlertDialog.Builder (this); 
builder.setTitle ("Hello"); 
builder.setMessage ("Hello World \ n"); 
builder.setNegativeButton ("OK", null); 
builder.show (); 
} 

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

} 

Reply:
Think of ways to define onClick in xml in the case, be sure to use this format:

 public void openDialog (View view) {
/ / ... 
} 

To be defined as public, and to accept a View as parameters, this parameter is less here, you is not enough.
Or use the second floor of the method, using code.