java - 使用帖子的线程问题

Question

我对 Android 和线程总体来说是新手。我目前正在制作一款游戏，其中渲染和逻辑发生在与 UI 不同的线程上。我的问题是我似乎无法使用工作线程中的帖子更新用户界面。

这是我的主要 Activity :

private GameScene gameScene;
private Handler uiHandler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    super.onCreate(savedInstanceState);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.game);
    uiHandler = new Handler(Looper.getMainLooper());

    gameScene = new GameScene(getApplicationContext(), uiHandler);
    LinearLayout gameHolder = (LinearLayout)findViewById(R.id.game_view);
    gameHolder.addView(gameScene);
    gameScene.resume();
}

这是实现 runnable 的类:

public abstract class Scene extends SurfaceView implements Runnable {

    Handler uiHandler;
    Thread thread = null;
    public Scene(Context context, Handler uiHandler) {
        super(context);
        this.uiHandler = uiHandler;
    }

    @Override
    public void run() {
        uiHandler.post(() -> {
            TextView textView = findViewById(R.id.fps_counter);
            textView.setText("hello");
        });
    }

    public void resume() {
        thread = new Thread(this);
        thread.start();
    }

xml:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/game_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:visibility="visible">

        <TextView
            android:id="@+id/fps_counter"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="0"
            android:textColor="@color/colorAccent"
            android:textSize="24sp" />
    </LinearLayout>

</FrameLayout>

post里面的代码应该在ui线程上运行，对吗？但是当我尝试设置文本时，我得到了一个空对象引用。是的，ID 为 fps_counter 的文本存在。

Answer 1

由于 Gamescene 不包含 fps_counter TextView ，因此请修改抽象场景和类扩展，以便可以传递对 TextView 的引用。

public abstract class Scene extends SurfaceView implements Runnable {

    Handler uiHandler;
    Thread thread = null;
    TextView textView;
    public Scene(Context context, Handler uiHandler, TextView textView) {
        super(context);
        this.uiHandler = uiHandler;
        this.textView = textView;
    }

    @Override
    public void run() {
        uiHandler.post(() -> {
            textView.setText("hello");
        });
    }

    public void resume() {
        thread = new Thread(this);
        thread.start();
    }

然后使用 TextView 的第三个参数创建 GameScene :

TextView textView = findViewById(R.id.fps_counter);
// no need to use getApplicationContext(), you may use this (a reference to "mainActivity")
gameScene = new GameScene(this, uiHandler, textView);