How do getHeight () not return 0 before the Draw method?

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How do getHeight () not return 0 before the Draw method?

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#1 by (4 votes)

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I have a problem where I need to make a ball appear in the middle of the getHeight () / 2 screen, the real problem is in the init () function where the value of getHeight () return me 0, which should return me the height value of the screen of my device consequently the ball appears at the top when I draw it ...

The question is, How do I get the Value of getHeight () before starting the draw () method ??

public class GameView extends View implements Runnable {

    private static final int INTERVALO = 10;
    private boolean running = true;
    private Paint paint;
    Ball bola;

    public GameView(Context context) {
        super(context);


        paint = new Paint();
        Thread MinhaThread = new Thread(this);
        MinhaThread.setPriority(Thread.MIN_PRIORITY);
        MinhaThread.start();
        init();
    }

    private void init() {

        bola = new Ball(20,getHeight()/2,5,0,0);  //Ball(x,y,size,forca,speed) x e y sao as coordenadas para desenhar na tela.
        Log.e("daniel","Inicializando "+getHeight()); // <-- aqui me retorna0
    }

    public void draw(Canvas canvas){
        super.draw(canvas);

        canvas.drawColor(Color.rgb(100, 190, 230));
        paint.setColor(Color.GREEN);
        canvas.drawRect(0,getHeight()-25,getWidth(),getHeight(),paint); //desenha o chao

        bola.draw(canvas); //AQUI eu desenho meu objeto no topo da tela, deveria ser no meio
        bola.gravidade();  //simulo a gravidade... nada de importante aqui!
    }

    @Override
    public void run() {
        while(running){
            try{
                Thread.sleep(INTERVALO);
            }catch (Exception e){
                Log.e("ERRO", e.getMessage());
            }

            update();
        }
    }

    private void update() {
        //bola.gravidade();
        //dispara o metodo draw (p/desenhar a tela)
        postInvalidate();
    }

    public void release(){
        running = false;
    }

}

PS: I know I could write the getHeight () / 2 method in draw () but I really I need to do this OUTSIDE the draw method . Is there any possibility of doing this? Thank you all.

java android

asked by anonymous 25.05.2014 / 22:20

1 answer

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score 4 · Accepted Answer

There is a way to get the values of getHeight() correctly, and I usually do it this way, but using Activity, not inside your View:

public class ExampleActivity extends Activity {
    //... Código

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

        View view = findViewById(android.R.id.content);
        //Qualquer forma de pegar o ViewRoot
        //ou uma view que ocupe a tela inteira

        view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                // Nesse momento a view já esta com o seu layout renderizado.
                // Os métodos getHeight() e getWidth() da view irão retornar valores corretos.
                view.getViewTreeObserver().removeGlobalOnLayoutListener(this);
            }
        });
    }

    //... Código
}

The other way inside the View is:

public class GameView extends View implements Runnable {
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        // Nesse momento, getWidth() e getHeight() estão com os valores corretos.
    }
}

These are two ways I know of getting the size of the View out of the draw method.