1.onClick方法：在Xml中添加onClick属性

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/mybutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Press Me"
        android:onClick="buttonClick"/>
</RelativeLayout>

在代码中添加对应的函数buttonClick，注意要添加到当前Activity对应的java类中。

public class MainActivity extends AppCompatActivity {

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

    public void buttonClick(View view) {
        Toast.makeText(this, "Button was clicked", Toast.LENGTH_SHORT).show();
    }
    
    // ....
}

2.setOnClickListener方法

public class MainActivity extends AppCompatActivity {

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

        Button button = (Button)findViewById(R.id.mybutton);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "Button was clicked", Toast.LENGTH_SHORT).show();
            }
        });
    }
}