如何以编程方式设置视图的LayoutParams？

Question

您从http://code.google.com/p/mobile-anarchy-widgets/wiki/JoystickView知道此JoystickView吗？ 好吧，我试图实现它。 没问题。 我无法更改其大小，因为我以编程方式添加了它。 我以某种方式找到了更改大小的方法，但是现在它卡在了左上角，我发现三个小时的所有内容都使我在我创建或被拒绝的LayoutParams参数上出现了NullPointerException异常，因为它不可铸造或其他首先。

public class GameActivity extends Activity implements JoystickMovedListener{

private GraphicsHolder mGraphicsHolder;
private String TAG = "GameActivity";

/*
 * creates a new GraphicsHolder and sets it its ContentView
 * the GraphicsThread is being included in the GraphicsHolder
 */
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    Log.d(TAG, "created");

    FrameLayout gameScreen = new FrameLayout(this);

    mGraphicsHolder = new GraphicsHolder(this);

    JoystickView Joystick = new JoystickView(this);


    // I need to set the Gravity HERE


    Joystick.setLayoutParams(new RelativeLayout.MarginLayoutParams(500,500));

    gameScreen.addView(mGraphicsHolder);
    gameScreen.addView(Joystick);

    setContentView(gameScreen);
}
}

现在这是我的问题：您能以编程方式设置此视图的重力吗？

Answer 1

你可以试试这个

RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(500,500);
params.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);

Joystick.setLayoutParams(params);

Answer 2

尝试将重心设置为FrameLayout并使用ViewGroup.LayoutParams设置Joystick LayoutParams：

FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT,FrameLayout.LayoutParams.MATCH_PARENT);
params.gravity = Gravity.CENTER;
gameScreen.setLayoutParams(params);

Joystick.setLayoutParams(new ViewGroup.LayoutParams(500,500));

Answer 3

尝试这个。

FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) Joystick.getLayoutParams();
params.gravity = Gravity.TOP;// desired gravity

Joystick.setLayoutParams(params);

不要更改您的代码，只需在setContentView(gameScreen);之后添加此代码setContentView(gameScreen); 希望它能工作

Answer 4

好吧，我找到了答案，但这是一种完全不同的方法，因为以上内容或我在其他地方发现的内容都不适合我。

我在onCreate方法中做了以下更改：

    mGraphicsHolder = new GraphicsHolder(this);

    LayoutInflater inflate = (LayoutInflater)
            getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    setContentView(mGraphicsHolder);

    getWindow().addContentView(inflate.inflate(
        R.layout.controllayout, null), new ViewGroup.LayoutParams(
        ViewGroup.LayoutParams.FILL_PARENT, 
        ViewGroup.LayoutParams.FILL_PARENT));

    Joystick = (JoystickView) getWindow().findViewById(R.id.joystickView1);
    Joystick.setOnJostickMovedListener(this);

现在，我将操纵杆安装在XML布局上，但是它实际上可以工作（至少在我没有其他工作的情况下），并且可以很容易地对Layout等进行更改。