Android的多点触控我试图教程 http://www.vogella.com/tutorials/AndroidTouch/article.html上vogella教程不工作
给予多点触控色点的这个代码，我要放置在触摸点，当我将我的手指一个点shuold留在那里，另一个应该移动就像操纵杆一样。
所以弹出点出现并停留在那里，直到我举起我的手指，如果将我的手指相同颜色的另一点应该移动
我想这个代码
public class MultitouchView extends View {
private static final int SIZE = 150;
float xx;
float yy;
float[] abcisa;
float[] ordinate;
private SparseArray<PointF> mActivePointers;
private Paint mPaint;
private int[] colors = { Color.BLUE, Color.GREEN, Color.MAGENTA,
Color.BLACK, Color.CYAN, Color.GRAY, Color.RED, Color.DKGRAY,
Color.LTGRAY, Color.YELLOW };
private Paint textPaint;
public MultitouchView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
private void initView() {
mActivePointers = new SparseArray<PointF>();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
// set painter color to a color you like
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
textPaint.setTextSize(20);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// get pointer index from the event object
int pointerIndex = event.getActionIndex();
// get pointer ID
int pointerId = event.getPointerId(pointerIndex);
// get masked (not specific to a pointer) action
int maskedAction = event.getActionMasked();
switch (maskedAction) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_POINTER_DOWN: {
// We have a new pointer. Lets add it to the list of pointers
PointF f = new PointF();
xx = f.x = event.getX(pointerIndex);
yy = f.y = event.getY(pointerIndex);
canvas.drawCircle(xx, yy, SIZE, mPaint);
mActivePointers.put(pointerId, f);
break;
}
case MotionEvent.ACTION_MOVE: { // a pointer was moved
for (int size = event.getPointerCount(), i = 0; i < size; i++) {
PointF point = mActivePointers.get(event.getPointerId(i));
if (point != null) {
point.x = event.getX(i);
point.y = event.getY(i);
}
}
break;
}
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
case MotionEvent.ACTION_CANCEL: {
mActivePointers.remove(pointerId);
break;
}
}
invalidate();
return true;
}
@Override
protected void onDraw(Canvas canvas) {
// draw all pointers
for (int size = mActivePointers.size(), i = 0; i < size; i++) {
PointF point = mActivePointers.valueAt(i);
if (point != null)
mPaint.setColor(colors[i % 9]);
canvas.drawCircle(xx, yy, SIZE, mPaint);
canvas.drawCircle(point.x, point.y, SIZE, mPaint);
}
canvas.drawText("Total pointers: " + mActivePointers.size(), 10, 40 , textPaint);
}
}
我也试图存储XX和在阵列中作为YY XX [pointerID]以及访问上canvas.drawCircle但应用程序崩溃
它的代码是这样
public class MultitouchView extends View {
private static final int SIZE = 150;
float[] xx;
float[] yy;
private SparseArray<PointF> mActivePointers;
private Paint mPaint;
private int[] colors = { Color.BLUE, Color.GREEN, Color.MAGENTA,
Color.BLACK, Color.CYAN, Color.GRAY, Color.RED, Color.DKGRAY,
Color.LTGRAY, Color.YELLOW };
private Paint textPaint;
public MultitouchView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
private void initView() {
mActivePointers = new SparseArray<PointF>();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
// set painter color to a color you like
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
textPaint.setTextSize(20);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// get pointer index from the event object
int pointerIndex = event.getActionIndex();
// get pointer ID
int pointerId = event.getPointerId(pointerIndex);
// get masked (not specific to a pointer) action
int maskedAction = event.getActionMasked();
switch (maskedAction) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_POINTER_DOWN: {
// We have a new pointer. Lets add it to the list of pointers
PointF f = new PointF();
xx[pointerId] = f.x = event.getX(pointerIndex);
yy[pointerId] = f.y = event.getY(pointerIndex);
mActivePointers.put(pointerId, f);
break;
}
case MotionEvent.ACTION_MOVE: { // a pointer was moved
for (int size = event.getPointerCount(), i = 0; i < size; i++) {
PointF point = mActivePointers.get(event.getPointerId(i));
if (point != null) {
point.x = event.getX(i);
point.y = event.getY(i);
}
}
break;
}
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
case MotionEvent.ACTION_CANCEL: {
mActivePointers.remove(pointerId);
break;
}
}
invalidate();
return true;
}
@Override
protected void onDraw(Canvas canvas) {
// draw all pointers
for (int size = mActivePointers.size(), i = 0; i < size; i++) {
PointF point = mActivePointers.valueAt(i);
if (point != null)
mPaint.setColor(colors[i % 9]);
canvas.drawCircle(xx[i], yy[i], SIZE, mPaint);
canvas.drawCircle(point.x, point.y, SIZE, mPaint);
}
canvas.drawText("Total pointers: " + mActivePointers.size(), 10, 40 , textPaint);
}
}
请帮忙。
崩溃日志
06-01 16：48：42.781 10922-10922/com.example.nimishmaravikd.colourmtouch E/AndroidRuntime：致命异常：主 工艺：com.example.nimishmaravikd.colourmtouch， PID：10922 java.lang.NullPointerException：尝试写入空数组 at com.example.nimishmaravikd.colourmtouch.MultitouchView.onTouchEvent（MultitouchView.java:73） at android.view.View.dispatchTouchEvent（View.java： 9323） at android.view.ViewGroup .dispatchTransformedTouchEvent（ViewGroup.java:2554） 在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2198） 在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2554） 在android.view.ViewGroup.dispatchTouchEvent （ViewGroup.java:2198） 在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2554） 在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2198） 在android.view.ViewGroup.dispatchTransformedTouchEvent（的ViewGroup .java：2554） at android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2198） at co在android.app.Activity.dispatchTouchEvent（）中， （android.view.java:9543） at android.view。 ViewRootImpl $ ViewPostImeInputStage.processPointerEvent（ViewRootImpl.java:4619） at android.view.ViewRootImpl $ ViewPostImeInputStage.onProcess（ViewRootImpl.java:4480） at android.view.ViewRootImp升$ InputStage.deliver（ViewRootImpl.java:4010） 在android.view.ViewRootImpl $ InputStage.onDeliverToNext（ViewRootImpl.java:4063） 在android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java:4029） 在android.view。ViewRootImpl $ AsyncInputStage.forward（ViewRootImpl.java:4155） 在android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:4037） 在android.view.ViewRootImpl $ AsyncInputStage.apply（ViewRootImpl.java:4212） 在（ViewRootImpl.java:4010） at android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java： 4029） at android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:4037） at android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:4010） 在android.view.ViewRootImpl.deliverInputEvent（ViewRootImpl.java:6397） 在android.view.ViewRootImpl.doProcessInputEvents（ViewRootImpl.java:6371） 在android.view.ViewRootImpl.enqueueInputEvent（ViewRootImpl.java:6318） 在机器人.view.ViewRootImpl $ WindowInputEventReceiver.onInputEvent（ViewRootImpl.java:6576） 在android.view.InputEventReceiver.dispatchInputEvent（InputEventReceiver.java:185） 在android.os.MessageQueue.nativePollOnce（本机方法） 在android.os。 MessageQueue.next（MessageQueue.java:324） at android.os.Looper.loop（Looper.java:135） 在android.app.ActivityThread.main（ActivityThread.java:5582） at java.lang.reflect.Method.invoke（Native Method） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java： 726） at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616） 06-01 16：48：42.791 10922-10933/com.example.nimishmaravikd.colourmtouch I/ActivityThreadEui：schedulePauseActivity com.example .nimishmaravikd.colourmtouch.MainActivity完成=真userLeaving =假configChanges = 0 dontReport =假
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