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);

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>

仅供参考，您可以选择从XML执行此操作。

在AndroidManifest.xml中，你可以用

android:label="My Activity Title"

Or

android:label="@string/my_activity_label"

例子:

    <activity
        android:name=".Splash"
        android:label="@string/splash_activity_title" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

如果你想要它一次，让系统处理剩下的(不是动态的)，那么在你的manifest文件中这样做:

<application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name_full" > //This is my custom title name on activity. <- The question is about this one.
            <intent-filter android:label="@string/app_launcher_name" > //This is my custom Icon title name (launcher name that you see in android apps/homescreen)
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.Main_Activity);
    this.setTitle("Title name");
}

setTitle(“欢迎活动”);