在这个应用程序中，我已经为用户启用了长按以显示警报的选项。此警报有2个按钮，用户可以从中选择。第一个允许使用在地图上长时间点击的位置放置标记，第二个获取长时间点击的位置的地址。地址按钮有效，但标记按钮强制关闭我的应用程序。我不确定我做错了什么。它可能是愚蠢的。
以下是我的主要课程的方法：
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
/*
* We want to capture the place the user long pressed on the map and add
* a marker (pin) on the map at that lat/long. This solution: 1. Allows
* you to set the time threshold for what constitutes a long press 2.
* Doesn't get fooled by scrolling, multi-touch, or non-multi-touch
* events
*
* Thank you Roger Kind Kristiansen for the main idea
*/
// get the action from the MotionEvent: down, move, or up
int actionType = ev.getAction();
if (actionType == MotionEvent.ACTION_DOWN) {
// user pressed the button down so let's initialize the main
// variables that we care about:
// later on when the "Action Up" event fires, the "DownTime" should
// match the "startTimeForLongClick" that we set here
// the coordinate on the screen should not change much during the
// long press
startTimeForLongClick = ev.getEventTime();
xScreenCoordinateForLongClick = ev.getX();
yScreenCoordinateForLongClick = ev.getY();
} else if (actionType == MotionEvent.ACTION_MOVE) {
// For non-long press actions, the move action can happen a lot
// between ACTION_DOWN and ACTION_UP
if (ev.getPointerCount() > 1) {
// easiest way to detect a multi-touch even is if the pointer
// count is greater than 1
// next thing to look at is if the x and y coordinates of the
// person's finger change.
startTimeForLongClick = 0; // instead of a timer, just reset
// this class variable and in our
// ACTION_UP event, the DownTime
// value will not match and so we
// can reset.
} else {
// I know that I am getting to the same action as above,
// startTimeForLongClick=0, but I want the processor
// to quickly skip over this step if it detects the pointer
// count > 1 above
float xmove = ev.getX(); // where is their finger now?
float ymove = ev.getY();
// these next four values allow you set a tiny box around their
// finger in case
// they don't perfectly keep their finger still on a long click.
xlow = xScreenCoordinateForLongClick - xtolerance;
xhigh = xScreenCoordinateForLongClick + xtolerance;
ylow = yScreenCoordinateForLongClick - ytolerance;
yhigh = yScreenCoordinateForLongClick + ytolerance;
if ((xmove < xlow || xmove > xhigh)
|| (ymove < ylow || ymove > yhigh)) {
// out of the range of an acceptable long press, reset the
// whole process
startTimeForLongClick = 0;
}
}
} else if (actionType == MotionEvent.ACTION_UP) {
// determine if this was a long click:
long eventTime = ev.getEventTime();
long downTime = ev.getDownTime(); // this value will match the
// startTimeForLongClick
// variable as long as we didn't
// reset the
// startTimeForLongClick
// variable because we detected
// nonsense that invalidated a
// long press in the ACTION_MOVE
// block
// make sure the start time for the original "down event" is the
// same as this event's "downTime"
if (startTimeForLongClick == downTime) {
// see if the event time minus the start time is within the
// threshold
if ((eventTime - startTimeForLongClick) > minMillisecondThresholdForLongClick) {
// make sure we are at the same spot where we started the
// long click
float xup = ev.getX();
float yup = ev.getY();
// I don't want the overhead of a function call:
xlow = xScreenCoordinateForLongClick - xtolerance;
xhigh = xScreenCoordinateForLongClick + xtolerance;
ylow = yScreenCoordinateForLongClick - ytolerance;
yhigh = yScreenCoordinateForLongClick + ytolerance;
if ((xup > xlow && xup < xhigh)
&& (yup > ylow && yup < yhigh)) {
// **** safe to process your code for an actual long
// press ****
// comment out these next rows after you confirm in
// logcat that the long press works
long totaltime = eventTime - startTimeForLongClick;
String strtotaltime = Long.toString(totaltime);
Log.d("long press detected: ", strtotaltime);
// Below is code from my touchy class
x = (int) ev.getX();
y = (int) ev.getY();
touchPoint = mapView.getProjection().fromPixels(x, y);
Builder alert = new AlertDialog.Builder(Map.this);
alert.setTitle("Pick an option.");
alert.setNeutralButton("Place a marker",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
OverlayItem overlayItem = new OverlayItem(
touchPoint, "What's up", "2nd String");
Mark custom = new Mark(d, Map.this);
custom.dropMarker(overlayItem);
mapoverlays.add(custom);
}
});
alert.setPositiveButton("Get Address",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
Geocoder geocoder = new Geocoder(
getBaseContext(), Locale.getDefault());
try {
List<Address> address = geocoder.getFromLocation(
touchPoint.getLatitudeE6() / 1E6,
touchPoint.getLongitudeE6() / 1E6,
1);
if (address.size() > 0) {
String display = "";
for (int i = 0; i < address.get(0)
.getMaxAddressLineIndex(); i++) {
display += address.get(0)
.getAddressLine(i) + "\n";
}
Toast t = Toast.makeText(
getBaseContext(), display,
Toast.LENGTH_LONG);
t.show();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
}
}
});
alert.show();
}
}
}
}
return super.dispatchTouchEvent(ev);
}
这是我的Mark课程：
package com.almyz125.stamp.overlay;
import java.util.ArrayList;
import android.content.Context;
import android.graphics.drawable.Drawable;
import com.google.android.maps.ItemizedOverlay;
import com.google.android.maps.OverlayItem;
public class Mark extends ItemizedOverlay<OverlayItem>{
private ArrayList<OverlayItem> markers = new ArrayList<OverlayItem>();
private Context c;
public Mark(Drawable defaultMarker) {
super(boundCenter(defaultMarker));
// TODO Auto-generated constructor stub
}
public Mark(Drawable m, Context context){
this(m);
c = context;
}
@Override
protected OverlayItem createItem(int i) {
// TODO Auto-generated method stub
return markers.get(i);
}
@Override
public int size() {
// TODO Auto-generated method stub
return markers.size();
}
public void dropMarker(OverlayItem item){
markers.add(item);
this.populate();
}
}
当应用程序遇到FC时，这是我的logcat：
10-30 13:51:25.548: W/dalvikvm(17616): threadid=1: thread exiting with uncaught exception (group=0x40dd11f8)
10-30 13:51:25.548: E/AndroidRuntime(17616): FATAL EXCEPTION: main
10-30 13:51:25.548: E/AndroidRuntime(17616): java.lang.NullPointerException
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.google.android.maps.ItemizedOverlay.boundCenter(ItemizedOverlay.java:173)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.almyz125.stamp.overlay.Mark. <init>(Mark.java:19)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.almyz125.stamp.overlay.Mark.<init>(Mark.java:24)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.almyz125.stamp.Map$2.onClick(Map.java:255)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:167)
10-30 13:51:25.548: E/AndroidRuntime(17616): at android.os.Handler.dispatchMessage(Handler.java:99)
10-30 13:51:25.548: E/AndroidRuntime(17616): at android.os.Looper.loop(Looper.java:137)
10-30 13:51:25.548: E/AndroidRuntime(17616): at android.app.ActivityThread.main(ActivityThread.java:4499)
10-30 13:51:25.548: E/AndroidRuntime(17616): at java.lang.reflect.Method.invokeNative(Native Method)
10-30 13:51:25.548: E/AndroidRuntime(17616): at java.lang.reflect.Method.invoke(Method.java:511)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
10-30 13:51:25.548: E/AndroidRuntime(17616): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:561)
10-30 13:51:25.548: E/AndroidRuntime(17616): at dalvik.system.NativeStart.main(Native Method)
如果我发布更多代码，请告诉我，我们将不胜感激任何帮助！
答案 0 :(得分：0)
看起来你传递给Mark构造函数的drawable d是null