这对我很管用。

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment, container, false);
    getActivity().setTitle("My Title");
//...
}

试试setTitle本身，像这样:

setTitle("Hello StackOverflow");

如果你想改变活动标题时，你改变活动点击按钮。在MainActivity中声明必要的变量:

    private static final String TITLE_SIGN = "title_sign";
    ImageButton mAriesButton;

在onCreate()中添加onClickListener，并为另一个活动创建新意图:

    mTitleButton = (ImageButton) findViewById(R.id.title_button);
    mTitleButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent intent = new Intent(MainActivity.this, 
        SignActivity.class);
        String title_act = getText(R.string.simple_text).toString();
        intent.putExtra("title_act", title_act);
        startActivity(intent);
        finish();
        }
    });

onCreate()中的SecondActivity代码:

    String txtTitle = getIntent().getStringExtra("title_act");
    this.setTitle(txtTitle);

setTitle(“欢迎活动”);

MainActivity内部:

public class act1 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.act1);

    setTitle("First Activity");

}

}

setTitle(“应用程序”); 在MainActivity.java中更简单 我会说。