Question

我需要一些帮助，因为当我想应用display.getWidth()和display.getHeight()时，Eclipse中没有错误，但是当我想在虚拟设备上启动时，应用程序崩溃（应用程序已经崩溃）意外停止......）

public class GameState extends Activity {

//Largeur et hauteur de l'écran
Display display = getWindowManager().getDefaultDisplay(); 
int _screenWidth = display.getWidth();
int _screenHeight = display.getHeight();


//La balle
final int _ballSize = 10;
int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
int _ballVelocityX = 2;     int _ballVelocityY = 4;

//Les barres
final int _batLength = 75;  final int _batHeight = 10;
int _topBatX = (_screenWidth/2) - (_batLength / 2);
final int _topBatY = 10;
int _bottomBatX = (_screenWidth/2) - (_batLength / 2);  
final int _bottomBatY = _screenHeight - 20;

等

提前致谢（我是法国人所以请用简单的词语）

编辑1

喜欢这个吗？

public class GameState extends Activity {
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Display display = getWindowManager().getDefaultDisplay(); 
    setContentView(display);}

//Largeur et hauteur de l'écran
int _screenWidth = display.getWidth();
int _screenHeight = display.getHeight();


//La balle
final int _ballSize = 10;
int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
int _ballVelocityX = 2;     int _ballVelocityY = 4;

这里我得到3个错误：类型为Activity的方法setContentView（int）不适用于参数（显示）

并且2次：显示无法解析

    03-14 16:29:44.655: E/AndroidRuntime(538): FATAL EXCEPTION: main
03-14 16:29:44.655: E/AndroidRuntime(538): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nicmer.pong/com.salocincreations.pong.P1_vs_P1}: android.view.InflateException: Binary XML file line #8: Error inflating class com.salocincreations.pong.GameView
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.os.Looper.loop(Looper.java:123)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-14 16:29:44.655: E/AndroidRuntime(538):  at java.lang.reflect.Method.invokeNative(Native Method)
03-14 16:29:44.655: E/AndroidRuntime(538):  at java.lang.reflect.Method.invoke(Method.java:507)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-14 16:29:44.655: E/AndroidRuntime(538):  at dalvik.system.NativeStart.main(Native Method)
03-14 16:29:44.655: E/AndroidRuntime(538): Caused by: android.view.InflateException: Binary XML file line #8: Error inflating class com.salocincreations.pong.GameView
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.createView(LayoutInflater.java:518)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:570)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.rInflate(LayoutInflater.java:623)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.inflate(LayoutInflater.java:408)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.inflate(LayoutInflater.java:320)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:207)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.Activity.setContentView(Activity.java:1657)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.salocincreations.pong.P1_vs_P1.onCreate(P1_vs_P1.java:20)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
03-14 16:29:44.655: E/AndroidRuntime(538):  ... 11 more
03-14 16:29:44.655: E/AndroidRuntime(538): Caused by: java.lang.reflect.InvocationTargetException
03-14 16:29:44.655: E/AndroidRuntime(538):  at java.lang.reflect.Constructor.constructNative(Native Method)
03-14 16:29:44.655: E/AndroidRuntime(538):  at java.lang.reflect.Constructor.newInstance(Constructor.java:415)
03-14 16:29:44.655: E/AndroidRuntime(538):  at android.view.LayoutInflater.createView(LayoutInflater.java:505)
03-14 16:29:44.655: E/AndroidRuntime(538):  ... 21 more
03-14 16:29:44.655: E/AndroidRuntime(538): Caused by: java.lang.NullPointerException
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.salocincreations.pong.GameState.<init>(GameState.java:12)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.salocincreations.pong.GameThread.<init>(GameThread.java:19)
03-14 16:29:44.655: E/AndroidRuntime(538):  at com.salocincreations.pong.GameView.<init>(GameView.java:23)
03-14 16:29:44.655: E/AndroidRuntime(538):  ... 24 more

编辑2

package com.salocincreations.pong;

import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Bundle;

public class GameState extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.p1_vs_p1);

    Display display = getWindowManager().getDefaultDisplay(); 
    int _screenWidth = display.getWidth();
    int _screenHeight = display.getHeight();


    //La balle
    final int _ballSize = 10;
    int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
    int _ballVelocityX = 2;     int _ballVelocityY = 4;

    //Les barres
    final int _batLength = 75;  final int _batHeight = 10;
    int _topBatX = (_screenWidth/2) - (_batLength / 2);
    final int _topBatY = 10;
    int _bottomBatX = (_screenWidth/2) - (_batLength / 2);  
    final int _bottomBatY = _screenHeight - 20;

    public GameState()
    {
    }

    //The update method
    public void update() {

    _ballX += _ballVelocityX;
    _ballY += _ballVelocityY;

    //DEATH!
    if(_ballY > _bottomBatY + 10 || _ballY < 0)         
    {_ballX = 100;  _ballY = 100;}//Collisions with the goals

    if(_ballX > _screenWidth || _ballX < 0)
                _ballVelocityX *= -1;   //Collisions with the sides     

    if(_ballX > _topBatX && _ballX < _topBatX+_batLength && _ballY - 16 < _topBatY)         
                     _ballVelocityY *= -1;  //Collisions with the bats      

    if(_ballX > _bottomBatX && _ballX < _bottomBatX+_batLength 
                    && _ballY + 16 > _bottomBatY)
                           _ballVelocityY *= -1;
    }

    public boolean surfaceTouched(float posX, float posY) {
        _topBatX = (int) posX;
        _bottomBatX = (int) posX;

        return true;
        }


    //the draw method
    public void draw(Canvas canvas, Paint paint) {

    //Clear the screen
    canvas.drawRGB(0, 0, 0);

    //set the colour
    paint.setARGB(200, 0, 200, 700);

    //draw the ball
    canvas.drawRect(new Rect(_ballX,_ballY,_ballX + _ballSize,_ballY + _ballSize),
                                 paint);

    //draw the bats
    canvas.drawRect(new Rect(_topBatX, _topBatY, _topBatX + _batLength,
                                          _topBatY + _batHeight), paint); //top bat
    canvas.drawRect(new Rect(_bottomBatX, _bottomBatY, _bottomBatX + _batLength, 
                                          _bottomBatY + _batHeight), paint); //bottom bat

        // Nous allons dessiner nos points par rapport à la résolution de l'écran
        int iWidth = canvas.getWidth(); // Largeur
        int iHeight = canvas.getHeight(); // Hauteur

        // Affecter une couleur de manière aléatoire
            paint.setARGB(255, 500, 500, 500);
            // Définir l'épaisseur du segment
            paint.setStrokeWidth (2);
            // Puis dessiner nos points dans le cavenas
            canvas.drawLine(0, iHeight/2, iWidth, iHeight/2, paint);    
            canvas.drawCircle(iWidth/2, iHeight/2, 50, paint);
        }            
    }

编辑3

package com.salocincreations.pong;

import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;

public class GameState extends Activity {
    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
     super.onWindowFocusChanged(hasFocus);
     Display display = getWindowManager().getDefaultDisplay(); 
    int _screenWidth = display.getWidth();
    int _screenHeight = display.getHeight();;


    //La balle
    final int _ballSize = 10;
    int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
    int _ballVelocityX = 2;     int _ballVelocityY = 4;

    //Les barres
    final int _batLength = 75;  final int _batHeight = 10;
    int _topBatX = (_screenWidth/2) - (_batLength / 2);
    final int _topBatY = 10;
    int _bottomBatX = (_screenWidth/2) - (_batLength / 2);  
    final int _bottomBatY = _screenHeight - 20;

    public GameState()
    {
    }

    //The update method
    public void update() {

    _ballX += _ballVelocityX;
    _ballY += _ballVelocityY;

    //DEATH!
    if(_ballY > _bottomBatY + 10 || _ballY < 0)         
    {_ballX = 100;  _ballY = 100;}//Collisions with the goals

    if(_ballX > _screenWidth || _ballX < 0)
                _ballVelocityX *= -1;   //Collisions with the sides     

    if(_ballX > _topBatX && _ballX < _topBatX+_batLength && _ballY - 16 < _topBatY)         
                     _ballVelocityY *= -1;  //Collisions with the bats      

    if(_ballX > _bottomBatX && _ballX < _bottomBatX+_batLength 
                    && _ballY + 16 > _bottomBatY)
                           _ballVelocityY *= -1;
    }

    public boolean surfaceTouched(float posX, float posY) {
        _topBatX = (int) posX;
        _bottomBatX = (int) posX;

        return true;
        }


    //the draw method
    public void draw(Canvas canvas, Paint paint) {

    //Clear the screen
    canvas.drawRGB(0, 0, 0);

    //set the colour
    paint.setARGB(200, 0, 200, 700);

    //draw the ball
    canvas.drawRect(new Rect(_ballX,_ballY,_ballX + _ballSize,_ballY + _ballSize),
                                 paint);

    //draw the bats
    canvas.drawRect(new Rect(_topBatX, _topBatY, _topBatX + _batLength,
                                          _topBatY + _batHeight), paint); //top bat
    canvas.drawRect(new Rect(_bottomBatX, _bottomBatY, _bottomBatX + _batLength, 
                                          _bottomBatY + _batHeight), paint); //bottom bat

        // Nous allons dessiner nos points par rapport à la résolution de l'écran
        int iWidth = canvas.getWidth(); // Largeur
        int iHeight = canvas.getHeight(); // Hauteur

        // Affecter une couleur de manière aléatoire
            paint.setARGB(255, 500, 500, 500);
            // Définir l'épaisseur du segment
            paint.setStrokeWidth (2);
            // Puis dessiner nos points dans le cavenas
            canvas.drawLine(0, iHeight/2, iWidth, iHeight/2, paint);    
            canvas.drawCircle(iWidth/2, iHeight/2, 50, paint);
        }            
    }

Answer 1

在创建DisplayManager之前，您无法使用Activity获取所需的任何信息。

public class GameState extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.your_layout);

    Display display = getWindowManager().getDefaultDisplay(); 
    int _screenWidth = display.getWidth();
    int _screenHeight = display.getHeight();


    //La balle
    final int _ballSize = 10;
    int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
    int _ballVelocityX = 2;     int _ballVelocityY = 4;

    //Les barres
    final int _batLength = 75;  final int _batHeight = 10;
    int _topBatX = (_screenWidth/2) - (_batLength / 2);
    final int _topBatY = 10;
    int _bottomBatX = (_screenWidth/2) - (_batLength / 2);  
    final int _bottomBatY = _screenHeight - 20;

    }

Answer 2

在屏幕有焦点之前，你不会得到宽度和高度。试试这个：

@Override
    public void onWindowFocusChanged(boolean hasFocus) {
     super.onWindowFocusChanged(hasFocus);
Display display = getWindowManager().getDefaultDisplay(); 
    int _screenWidth = display.getWidth();
    int _screenHeight = display.getHeight();


    //La balle
    final int _ballSize = 10;
    int _ballX = _screenWidth/2;    int _ballY = _screenHeight/2;
    int _ballVelocityX = 2;     int _ballVelocityY = 4;

    //Les barres
    final int _batLength = 75;  final int _batHeight = 10;
    int _topBatX = (_screenWidth/2) - (_batLength / 2);
    final int _topBatY = 10;
    int _bottomBatX = (_screenWidth/2) - (_batLength / 2);  
    final int _bottomBatY = _screenHeight - 20;
}

应用程序崩溃在getHeight和getWidth上

2 个答案: