我是一个关于android（和Java）的完整新手，并从拖放教程中获得了一些示例代码，以便尝试理解。做得很好，但是这段代码会生成java.lang.ArrayIndexOutOfBoundsException错误，并且会在应用程序启动时每秒关闭一次。
我猜测应用程序没有清除其资源可能是一件简单的事情，如果有人知道代码的哪一部分导致它以及原因，我将不胜感激。 试过1.5和2.2。
Main.java：
package eas.org;
import android.app.Activity;
import android.os.Bundle;
public class Main extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// draw the view
setContentView(new DrawView(this));
}
}
DrawView.java：
package eas.org;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Point;
import android.view.MotionEvent;
import android.view.View;
public class DrawView extends View {
private ColorBall[] colorballs = new ColorBall[3]; // array that holds the balls
private int balID = 0; // variable to know what ball is being dragged
public DrawView(Context context) {
super(context);
setFocusable(true); //necessary for getting the touch events
// setting the start point for the balls
Point point1 = new Point();
point1.x = 50;
point1.y = 20;
Point point2 = new Point();
point2.x = 100;
point2.y = 20;
Point point3 = new Point();
point3.x = 150;
point3.y = 20;
// declare each ball with the ColorBall class
colorballs[0] = new ColorBall(context,R.drawable.bol_groen, point1);
colorballs[1] = new ColorBall(context,R.drawable.bol_rood, point2);
colorballs[2] = new ColorBall(context,R.drawable.bol_blauw, point3);
}
// the method that draws the balls
@Override protected void onDraw(Canvas canvas) {
//canvas.drawColor(0xFFCCCCCC); //if you want another background color
//draw the balls on the canvas
for (ColorBall ball : colorballs) {
canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null);
}
}
// events when touching the screen
public boolean onTouchEvent(MotionEvent event) {
int eventaction = event.getAction();
int X = (int)event.getX();
int Y = (int)event.getY();
switch (eventaction ) {
case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball
balID = 0;
for (ColorBall ball : colorballs) {
// check if inside the bounds of the ball (circle)
// get the center for the ball
int centerX = ball.getX() + 25;
int centerY = ball.getY() + 25;
// calculate the radius from the touch to the center of the ball
double radCircle = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y)));
// if the radius is smaller then 23 (radius of a ball is 22), then it must be on the ball
if (radCircle < 23){
balID = ball.getID();
break;
}
// check all the bounds of the ball (square)
//if (X > ball.getX() && X < ball.getX()+50 && Y > ball.getY() && Y < ball.getY()+50){
// balID = ball.getID();
// break;
//}
}
break;
case MotionEvent.ACTION_MOVE: // touch drag with the ball
// move the balls the same as the finger
if (balID > 0) {
colorballs[balID-1].setX(X-25);
colorballs[balID-1].setY(Y-25);
}
break;
case MotionEvent.ACTION_UP:
// touch drop - just do things here after dropping
break;
}
// redraw the canvas
invalidate();
return true;
}
}
ColorBall.java：
package eas.org;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Point;
public class ColorBall {
private Bitmap img; // the image of the ball
private int coordX = 0; // the x coordinate at the canvas
private int coordY = 0; // the y coordinate at the canvas
private int id; // gives every ball his own id, for now not necessary
private static int count = 1;
private boolean goRight = true;
private boolean goDown = true;
public ColorBall(Context context, int drawable) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
img = BitmapFactory.decodeResource(context.getResources(), drawable);
id=count;
count++;
}
public ColorBall(Context context, int drawable, Point point) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
img = BitmapFactory.decodeResource(context.getResources(), drawable);
id=count;
count++;
coordX= point.x;
coordY = point.y;
}
public static int getCount() {
return count;
}
void setX(int newValue) {
coordX = newValue;
}
public int getX() {
return coordX;
}
void setY(int newValue) {
coordY = newValue;
}
public int getY() {
return coordY;
}
public int getID() {
return id;
}
public Bitmap getBitmap() {
return img;
}
public void moveBall(int goX, int goY) {
// check the borders, and set the direction if a border has reached
if (coordX > 270){
goRight = false;
}
if (coordX < 0){
goRight = true;
}
if (coordY > 400){
goDown = false;
}
if (coordY < 0){
goDown = true;
}
// move the x and y
if (goRight){
coordX += goX;
}else
{
coordX -= goX;
}
if (goDown){
coordY += goY;
}else
{
coordY -= goY;
}
}
}
崩溃日志：
10-13 15:15:15.038: ERROR/AndroidRuntime(492): FATAL EXCEPTION: main
10-13 15:15:15.038: ERROR/AndroidRuntime(492): java.lang.ArrayIndexOutOfBoundsException
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at eas.org.DrawView.onTouchEvent(DrawView.java:112)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.view.View.dispatchTouchEvent(View.java:3766)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1671)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.app.Activity.dispatchTouchEvent(Activity.java:2086)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1655)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.view.ViewRoot.handleMessage(ViewRoot.java:1785)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.os.Handler.dispatchMessage(Handler.java:99)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.os.Looper.loop(Looper.java:123)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at java.lang.reflect.Method.invokeNative(Native Method)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at java.lang.reflect.Method.invoke(Method.java:521)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-13 15:15:15.038: ERROR/AndroidRuntime(492): at dalvik.system.NativeStart.main(Native Method)
感谢我能得到任何帮助！
答案 0 :(得分：1)
ArrayIndexOutOfBoundsException表示您正在尝试访问不存在的数组中的项目。例如，您有一个长度为3的数组。
private ColorBall[] colorballs = new ColorBall[3];
数组从0开始编入索引，因此要获得第一个彩色球，您需要colorballs[0]，第二个彩弹将colorballs[1]最终collorbals[2]。
如果您要求colorballs[3]，您应该获得执行，因为索引3超出了正确的范围，0到2（包括0和2）。
我不确定代码中的哪一行112，但是看一下该行，看看你是否试图访问数字不在0到2之间的数组。
答案 1 :(得分：1)
我似乎找到了问题，虽然我不太确定它为什么会发生。
“count”变量在通过后退按钮退出应用程序后显然没有重置，因此它使阵列成为香蕉。
我现在更改了代码，以确保每次调用ColorBall（）时计数不高于3（我当前的对象数）（临时丑陋的解决方法）：
public ColorBall(Context context, int drawable) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
img = BitmapFactory.decodeResource(context.getResources(), drawable);
if (count > 3) count=1;
id=count;
count++;
}
public ColorBall(Context context, int drawable, Point point) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
img = BitmapFactory.decodeResource(context.getResources(), drawable);
if (count > 3) count=1;
id=count;
count++;
coordX= point.x;
coordY = point.y;
}
答案 2 :(得分：0)
尝试设置
public static int count = 0
看看是否有帮助。