我有一个工具栏在我的活动和基础活动，覆盖所有的标题。所以我必须在onResume()在活动中使用setTitle，就像这样:

@Override
  protected void onResume() {
    super.onResume();
    toolbar.setTitle(R.string.title);
  }

setTitle(getResources().getText(R.string.MyTitle));

如果你有多个活动，你可以在AndroidManifest.xml中这样设置

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".NumbersActivity"
        android:label="@string/category_numbers"
        android:theme="@style/category_numbers" />
    <activity
        android:name=".FamilyActivity"
        android:label="@string/category_family"
        android:theme="@style/category_family" />
    <activity
        android:name=".ColorsActivity"
        android:label="@string/category_colors"
        android:theme="@style/category_colors" />
    <activity
        android:name=".PhrasesActivity"
        android:label="@string/category_phrases"
        android:theme="@style/category_phrases" />
    <activity
        android:name=".ExperimentActivity"
        android:label="@string/category_experiment"
        android:theme="@style/category_experiment" />
</application>

代码帮助我更改了标题。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_name);
    ActivityName.this.setTitle("Your Activity Title");}

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");
//...
}

如果你正在使用onCreateOptionsMenu，你也可以在onCreateOptionsMenu中添加setTitle代码。

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);

    setTitle("Neue Aktivität");
    return true;
}