add onclick listener to predefined button?

I've got the following button in my xml layout file...

<Button
    android:layout_width="150dip"
    android:id="@+id/button1"
    android:layout_height="50dip"
    android:text="@string/l开发者_如何学Googin"
    android:layout_marginRight="10dip">
</Button>

I'd like to programmatically add an onclick() listener in it's Java file. How would I do this?

You just need something like this:

Button buttonOne = (Button) findViewById(R.id.button1);
buttonOne.setOnClickListener(new Button.OnClickListener() {
    public void onClick(View v) {
            //Do stuff here
    }
});

This answer comes from Five Ways to Wire Up an Event Listener. Please read that blog post for a fuller explanation from the author. See my other answer for these five ways reworked to add multiple onClick listeners.

1. Member Class

public class main extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //attach an instance of HandleClick to the Button
        findViewById(R.id.button1).setOnClickListener(new HandleClick());
    }    
    private class HandleClick implements OnClickListener{
        public void onClick(View arg0) {
            Button btn = (Button)arg0;  //cast view to a button
            // get a reference to the TextView
            TextView tv = (TextView) findViewById(R.id.textview1);
            // update the TextView text
            tv.setText("You pressed " + btn.getText());
        }
    }
}

2. Interface Type

public class main extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //use the handleClick variable to attach the event listener
        findViewById(R.id.button1).setOnClickListener(handleClick);
    }    
    private OnClickListener handleClick = new OnClickListener(){
        public void onClick(View arg0) {
            Button btn = (Button)arg0;
            TextView tv = (TextView) findViewById(R.id.textview1);
            tv.setText("You pressed " + btn.getText());
        }
    };
}

3. Anonymous Inner Class

public class main extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        findViewById(R.id.button1).setOnClickListener(new OnClickListener(){
            public void onClick(View arg0) {
            Button btn = (Button)arg0;
            TextView tv = (TextView) findViewById(R.id.textview1);
            tv.setText("You pressed " + btn.getText());
            }
        });
    }     
}

4. Implementation in Activity

public class main extends Activity implements OnClickListener{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        findViewById(R.id.button1).setOnClickListener(this);
    }    
    public void onClick(View arg0) {
        Button btn = (Button)arg0;
        TextView tv = (TextView) findViewById(R.id.textview1);
        tv.setText("You pressed " + btn.getText());
    }
}

5. Attribute in View Layout for OnClick Events

public class main extends Activity{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }    
    public void HandleClick(View arg0) {
        Button btn = (Button)arg0;
        TextView tv = (TextView) findViewById(R.id.textview1);
        tv.setText("You pressed " + btn.getText());
    }
}

xml:

<Button android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 1"
        android:onClick="HandleClick"/>

You can try this.

public class myNewClass extends Activity implements OnClickListener {
    ................... 
    ...................       

    Button button = (Button)findViewById(R.id.button1);
    button.setOnClickListener(this);

        public void onClick(View v) {
                Intent i = new Intent();
                Bundle extras = new Bundle();

        // This will catch the button click 
        // Now do what you wanted to do as a 
        // result of the onClick
        }
 }

You can apply onClicklistner in Two way : 1. Under onCreate Method
2. Out side onCreate Method

if we will use under onCreate method then we will use like this:-

protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_graphics1);

        textview1 = (TextView) findViewById(R.id.textview1);
        circleBtn = (Button) findViewById(R.id.circleBtn);

        // Click Listner Under on Create Method
        circleBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

}

if You want out side to onCreate Method then first register the onClickListner in onCreate Method like this :-

@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_graphics1);

        circleBtn = (Button) findViewById(R.id.circleBtn);

        **// Register on click on button
        circleBtn.setOnClickListener(new ClickMe());**

    }

and then implement clicklistner outside of onCreate Method so full code will be like this :-

public class ActiononBtn extends AppCompatActivity {

    private TextView textview1;
    private Button circleBtn;




    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_graphics1);

        textview1 = (TextView) findViewById(R.id.textview1);
        circleBtn = (Button) findViewById(R.id.circleBtn);

        // Register on click on button
        circleBtn.setOnClickListener(new ClickMe());

    } // Close onCreate Method


    private class ClickMe implements View.OnClickListener {
        public void onClick(View v) {

        }
    }

}//Close main Activity Class

1.use findViewById(R.id.button1).setOnClickListener(this);

2.and activty implements OnClickListener

<Button
    android:id="@+id/btnOk"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Ok"
    android:layout_marginRight="50dp"
    android:layout_marginLeft="50dp"/>

public class MainActivity extends AppCompatActivity {

    Button btnOk;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnOk = findViewById(R.id.btnOk);
        btnOk.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "This button ok click.", Toast.LENGTH_SHORT).show();
            }
        });
    }
}