Button btn = new Button(this);
    btn.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        
      }
    });

 package com.xqx.InterfaceDemo;
 public interface ChangeTitle {
   void onChangeTitle(String title);
 }

package com.xqx.InterfaceDemo;
import android.content.Context;
import android.os.AsyncTask;
public class MyTask extends AsyncTask<String,Void,String>{
  private ChangeTitle changeTitle;
  public MyTask(ChangeTitle changeTitle) {
    this.changeTitle = changeTitle;
  }
  @Override
  protected String doInBackground(String... strings) {
    if (strings[0]!=null){
      changeTitle.onChangeTitle(strings[0]);
    }
    return null;
  }
}

package com.xqx.InterfaceDemo;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends Activity implements ChangeTitle {
  private TextView textView;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    textView = (TextView) findViewById(R.id.textView);
    new MyTask(this).execute("我是标题");
  }
　　// 重写接口方法，执行相应操作
  @Override
  public void onChangeTitle(String title) {
    textView.setText(title);
  }
}