Android webview全屏显示视频不起作用

webView.setWebChromeClient(new WebChromeClient() {
    @Override
    public void onShowCustomView(View view, CustomViewCallback callback) {
        super.onShowCustomView(view, callback);
        // 切换为全屏模式
        setFullScreen();
        // 在全屏的Activity中展示视频
        showVideoInFullScreen(view);
    }

    @Override
    public void onHideCustomView() {
        super.onHideCustomView();
        // 退出全屏模式
        exitFullScreen();
    }
});

public class FullScreenActivity extends AppCompatActivity {
    private VideoView videoView;

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

        videoView = findViewById(R.id.video_view);
        // 设置视频路径
        videoView.setVideoPath("视频路径");
        // 开始播放视频
        videoView.start();
    }
}

<activity
    android:name=".FullScreenActivity"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen" />