我想对超声波传感器的距离数据进行图形表示（尚未实现）
我想绘制一个代表gokart的矩形，前面有6行，后面有6行。 由于我的新手java知识，代码似乎被严重屠杀。 在测试线条绘制方法时，程序将无法启动。有什么想法吗？
package com.example.gokartdst;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class GameView extends SurfaceView implements SurfaceHolder.Callback
{
private RefreshThread drawThread;
public static int screenWidth;
public static int screenHeight;
private float density;
public static float tX;
public static float tY;
public int i;
public int j;
private GoKart[][] detectors;
public GameView(Context context, float density) {
super(context);
this.density = density;
detectors=new GoKart[1][5];
for(i=0;i<=1;i++)
{
for(j=0;j<=5;j++)
{
detectors[i][j]=new GoKart(i,j);
}
}
//detectors = new GoKart(Color.WHITE, 15.0, dpTodx(30));
getHolder().addCallback(this);
drawThread = new RefreshThread(getHolder(), this);
}
/*public GameView(Context context, AttributeSet attrs) {
super(context, attrs);
}
*/
// Itt számolja újra a szükséges pozíciókat
public void update(Canvas c) {
if (c != null) {
screenWidth = c.getWidth();
screenHeight = c.getHeight();
}
//detectors.BallPosUpdate();
}
//Újrarajzolás
@Override
public void onDraw(Canvas canvas) {
if (canvas != null) {
canvas.drawColor(Color.BLACK);
for(i=0;i<=1;i++)
for(j=0;j<=5;j++)
{
detectors[i][j].BallDraw(canvas);
}
//Log.i("onDraw", "onDraw");
}
}
public int dpTodx(int dp) {
int px = (int) (dp*density);
return px;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
if(drawThread!=null)
{
drawThread.setRunning(true);
drawThread.start();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
if(drawThread!=null)
{
drawThread.setRunning(false);
while (retry) {
try {
drawThread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}
}
// A RefreshThread a fő szál, hogy ne az UI szálon fusson. Így gyorsabb.
class RefreshThread extends Thread {
private SurfaceHolder mSurfaceHolder;
private GameView gameView;
private boolean enabled = false;
public RefreshThread(SurfaceHolder surfaceHolder, GameView panel) {
mSurfaceHolder = surfaceHolder;
gameView = panel;
}
public void setRunning(boolean run) {
enabled = run;
}
@Override
public void run() {
long lastTime = System.nanoTime();
long timer = System.currentTimeMillis();
final double ns = 1000000000.0 / 60.0;
double delta = 0;
int frames = 0;
int updates = 0;
Canvas c;
while (enabled) {
c = null;
long now = System.nanoTime();
delta += (now - lastTime) / ns;
//Log.i("DELTA", Double.toString(delta));
lastTime = now;
try {
c = mSurfaceHolder.lockCanvas(null);
while (delta >= 1) {
synchronized (mSurfaceHolder) {
if (gameView != null) {
gameView.update(c);
updates++;
delta--;
}
}
}
gameView.onDraw(c);
frames++;
if (System.currentTimeMillis() - timer > 1000) {
timer += 1000;
Log.i("Frames", "Frames: " + frames + " | Updates: " + updates);
updates = 0;
frames = 0;
}
} finally {
// igy biztos nem hagyjuk
// inkonzisztens állapotban a Surface-t
if (c != null) {
mSurfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
}
Gokart对象：
package com.example.gokartdst;
import android.graphics.Canvas;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.graphics.drawable.shapes.RectShape;
import android.graphics.Paint;
public class GoKart {
private int i;
private double j;
private int dst;
ShapeDrawable mLinesDrawable;
Paint paint= new Paint();
public GoKart(int ix, double jx) {
this.i = ix;
this.j = jx;
mLinesDrawable = new ShapeDrawable(new RectShape());
}
public void BallDraw(Canvas canvas) {
/*mLinesDrawable.setBounds(X - diameter / 2, Y - diameter / 2, X + diameter / 2, Y + diameter / 2);
mLinesDrawable.getPaint().setColor(color);
mLinesDrawable.draw(canvas);
*/
if(i==0)
{
if(j==1)
{
canvas.drawLine(30, 30, 40, 30, paint);
}
if(j==2)
{
canvas.drawLine(40, 30, 50, 30, paint);
}
}
}
和Logkat：
09-20 11:01:29.320: W/dalvikvm(5277): threadid=1: thread exiting with uncaught exception (group=0x415efba8)
09-20 11:01:29.320: E/AndroidRuntime(5277): FATAL EXCEPTION: main
09-20 11:01:29.320: E/AndroidRuntime(5277): Process: com.example.soccergame, PID: 5277
09-20 11:01:29.320: E/AndroidRuntime(5277): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.soccergame/com.example.gokartdst.GameActivity}: java.lang.ArrayIndexOutOfBoundsException: length=5; index=5
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.os.Handler.dispatchMessage(Handler.java:102)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.os.Looper.loop(Looper.java:136)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread.main(ActivityThread.java:5017)
09-20 11:01:29.320: E/AndroidRuntime(5277): at java.lang.reflect.Method.invokeNative(Native Method)
09-20 11:01:29.320: E/AndroidRuntime(5277): at java.lang.reflect.Method.invoke(Method.java:515)
09-20 11:01:29.320: E/AndroidRuntime(5277): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-20 11:01:29.320: E/AndroidRuntime(5277): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-20 11:01:29.320: E/AndroidRuntime(5277): at dalvik.system.NativeStart.main(Native Method)
09-20 11:01:29.320: E/AndroidRuntime(5277): Caused by: java.lang.ArrayIndexOutOfBoundsException: length=5; index=5
09-20 11:01:29.320: E/AndroidRuntime(5277): at com.example.gokartdst.GameView.<init>(GameView.java:36)
09-20 11:01:29.320: E/AndroidRuntime(5277): at com.example.gokartdst.GameActivity.onCreate(GameActivity.java:17)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.Activity.performCreate(Activity.java:5231)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-20 11:01:29.320: E/AndroidRuntime(5277): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
09-20 11:01:29.320: E/AndroidRuntime(5277): ... 11 more
答案 0 :(得分：1)
因为你的for循环，它应该是
for(i=0;i<1;i++)
{
for(j=0;j<5;j++)
{
detectors[i][j]=new GoKart(i,j);
}
}
注意我改变了外部和内部循环。两种停止条件都应该使用＆lt;运算符不是＆lt; =
每当你创建一个大小为N的数组（或者在这种情况下是2D数组）时，只要i（或j）小于N，你就应该迭代，因为如果你在i <= N时继续它也将继续i = N + 1，这将导致ArrayIndexOutOfBoundsException，它基本上表示你要求的值超出数组的范围。
答案 1 :(得分：1)
您的数组detectors长度为5
for(j = 0; j <= 5; j++) {
detectors[i][j] = new GoKart(i, j);
}
当您将值分配到第6个索引时，for循环中的条件为j <= 5，使其为j < 5
应该是
for(j = 0; j < 5; j++) {
detectors[i][j] = new GoKart(i, j);
}