java - 以前可以启动的应用程序现在没有

Question

我不确定这里发生了什么。我正在添加一个声明，让手机在长按时振动。我把声明放在了错误的位置，电话一直在振动。所以我拔下电话并关闭电源。然后我删除了导致我的手机执行此操作的代码。然后尝试重新启动应用程序，就像我添加代码之前一样，现在我明白了。我不确定发生了什么，因为代码与它工作时完全一样。缓存文件是否会导致此问题？

这是我的日志:

10-28 17:34:51.381: W/dalvikvm(718): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
10-28 17:34:51.389: E/AndroidRuntime(718): FATAL EXCEPTION: main
10-28 17:34:51.389: E/AndroidRuntime(718): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.almyz125.stamp/com.almyz125.stamp.Map}: java.lang.NullPointerException
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.os.Looper.loop(Looper.java:137)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread.main(ActivityThread.java:4745)
10-28 17:34:51.389: E/AndroidRuntime(718):  at java.lang.reflect.Method.invokeNative(Native Method)
10-28 17:34:51.389: E/AndroidRuntime(718):  at java.lang.reflect.Method.invoke(Method.java:511)
10-28 17:34:51.389: E/AndroidRuntime(718):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-28 17:34:51.389: E/AndroidRuntime(718):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-28 17:34:51.389: E/AndroidRuntime(718):  at dalvik.system.NativeStart.main(Native Method)
10-28 17:34:51.389: E/AndroidRuntime(718): Caused by: java.lang.NullPointerException
10-28 17:34:51.389: E/AndroidRuntime(718):  at com.almyz125.stamp.Map.onCreate(Map.java:88)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.Activity.performCreate(Activity.java:5008)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
10-28 17:34:51.389: E/AndroidRuntime(718):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
10-28 17:34:51.389: E/AndroidRuntime(718):  ... 11 more

这也是我的代码:

public class Map extends MapActivity implements LocationListener {

// variable for determining long press and then automatically adding a pin
// to the map
private int minMillisecondThresholdForLongClick = 800;
private long startTimeForLongClick = 0;
private float xScreenCoordinateForLongClick;
private float yScreenCoordinateForLongClick;
private float xtolerance = 10;// x pixels that your finger can be off but
                                // still constitute    a long press
private float ytolerance = 10;// y pixels that your finger can be off but
                                // still constitute a long press
private float xlow; // actual screen coordinate when you subtract the
                    // tolerance
private float xhigh; // actual screen coordinate when you add the tolerance
private float ylow; // actual screen coordinate when you subtract the
                    // tolerance
private float yhigh; // actual screen coordinate when you add the tolerance

// Variables
MapView mapView;
MapController mc;
long start;
long stop;
int x, y, longTemp, latTemp;
GeoPoint touchPoint;
LocationManager lm;
Drawable d;
Location lastKnownLoc;
List<Overlay> mapoverlays;
GeoPoint gp;
private MyLocationOverlay myLocOverlay, compass;

// Auto Generated Methods
@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    // sets view to map
    setContentView(R.layout.main);
    mapView = (MapView) findViewById(R.id.mvMain);
    mc = mapView.getController();
    compass = new MyLocationOverlay(Map.this, mapView);
    d = getResources().getDrawable(R.drawable.icon);
    mapoverlays = mapView.getOverlays();
    myLocOverlay = new MyLocationOverlay(this, mapView);

    mapoverlays = mapView.getOverlays();

    lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    lastKnownLoc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

    longTemp = (int) (lastKnownLoc.getLongitude() * 1e6);
    latTemp = (int) (lastKnownLoc.getLatitude() * 1e6);
    gp = new GeoPoint(latTemp, longTemp);

    // enables on screen zoom buttons
    mapView.setBuiltInZoomControls(true);

    // create overlay that shows our location

    // add this overlay to the map and refresh it
    mapView.getOverlays().add(myLocOverlay);
    mapView.invalidate();

    mapoverlays.add(compass);
    compass.enableMyLocation();
    compass.enableCompass();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // TODO Auto-generated method stub
    // return super.onCreateOptionsMenu(menu);
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.options, menu);
    return true;
}

@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
    // handle on menu item selected here
    super.onMenuItemSelected(featureId, item);

    // if item is selected satellite view is toggled
    if (item.getItemId() == R.id.opt_tog_view) {
        toggleSat();
    }

    return true;
}

// method to toggles satellite view called in option menu
public void toggleSat() {
    if (mapView.isSatellite()) {

        mapView.setSatellite(false);
    } else {
        mapView.setSatellite(true);
    }
}

// Volume keys zoom in and out.
public boolean onKeyDown(int keyCode, KeyEvent event) {

    mc = mapView.getController();
    switch (keyCode) {
    case KeyEvent.KEYCODE_VOLUME_UP:
        mc.zoomIn();
        break;
    case KeyEvent.KEYCODE_VOLUME_DOWN:
        mc.zoomOut();
        break;
    }
    return super.onKeyDown(keyCode, event);
}

@Override
protected boolean isRouteDisplayed() {
    // TODO Auto-generated method stub
    return false;
}

@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    compass.disableMyLocation();
    compass.disableCompass();
    myLocOverlay.disableMyLocation();

}

@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
    gp = new GeoPoint(latTemp, longTemp);
    myLocOverlay.enableMyLocation();
    compass.enableMyLocation();
    compass.enableCompass();
    mapoverlays.add(compass);
}

@Override
public void onLocationChanged(Location location) {
    // TODO Auto-generated method stub

}

@Override
public void onProviderDisabled(String arg0) {
    // TODO Auto-generated method stub

}

@Override
public void onProviderEnabled(String arg0) {
    // TODO Auto-generated method stub

}

@Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
    // TODO Auto-generated method stub

}

@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) && true;
}
}

这是我的 list :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.almyz125.stamp" >

<uses-permission android:name="android.permission.INTERNET" />

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="16" />

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<application
    android:icon="@drawable/icon"
    android:label="@string/activity_main_map" >
    <uses-library android:name="com.google.android.maps" />

    <activity
        android:name="com.almyz125.stamp.Map"
        android:label="STAMP" >
        <intent-filter>
            <category android:name="android.intent.category.LAUNCHER" >
            </category>

            <action android:name="android.intent.action.MAIN" >
            </action>
        </intent-filter>
    </activity>
    </application>

</manifest>

Answer 1

在创建包含 MyLocationOverlay 的 Activity 时，您无法确定 getLastKnownLocation 不会为 null，因此您必须像下面的代码 fragment 一样考虑它:

if(lastKnownLoc != null){
    longTemp = (int) (lastKnownLoc.getLongitude() * 1e6);
    latTemp = (int) (lastKnownLoc.getLatitude() * 1e6);
    gp = new GeoPoint(latTemp, longTemp);
}

它在您重新启动手机之前就可以正常工作的事实仅仅是因为 android 先前已对您的位置进行了修复，但情况可能并非总是如此。

您可能还想尝试使用 runOnFirstFix 方法来更好地解决您的问题。

compass.runOnFirstFix(new Runnable() {

        @Override
        public void run() {
            Location location = compass.getLastFix();
            //do your location code here
        }
    });