我是android的新手。我跟着一个关于使用地方api寻找附近地方的尝试，并尝试将其集成到我的应用程序中。我在我的应用程序的主页活动中传递了一个意图，例如，“Intent i1 = new Intent（this，NearbyPlaces.class）; startactivity（i1）;”但它不起作用，当我点击调用附近活动意图的按钮时，应用程序意外关闭。不知道wat是错的，因为代码与教程中提到的几乎相同。以下是我的代码。如果有人可以提供帮助，我将非常感激......
//code for NearbyPlaces.java
package com.example.travelplanner;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.Html;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class NearbyPlacesActivity extends Activity {
// flag for Internet connection status
Boolean isInternetPresent = false;
// Connection detector class
ConnectionDetector cd;
// Alert Dialog Manager
AlertDialogManager alert = new AlertDialogManager();
// Google Places
GooglePlaces googlePlaces;
// Places List
PlacesList nearPlaces;
// GPS Location
GPSTracker gps;
// Button
Button btnShowOnMap;
// Progress dialog
ProgressDialog pDialog;
// Places Listview
ListView lv;
// ListItems data
ArrayList<HashMap<String, String>> placesListItems = new ArrayList<HashMap<String,String>>();
// KEY Strings
public static String KEY_REFERENCE = "reference"; // id of the place
public static String KEY_NAME = "name"; // name of the place
public static String KEY_VICINITY = "vicinity"; // Place area name
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cd = new ConnectionDetector(getApplicationContext());
// Check if Internet present
isInternetPresent = cd.isConnectingToInternet();
if (!isInternetPresent) {
// Internet Connection is not present
alert.showAlertDialog(NearbyPlacesActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// creating GPS Class object
gps = new GPSTracker(this);
// check if GPS location can get
if (gps.canGetLocation()) {
Log.d("Your Location", "latitude:" + gps.getLatitude() + ", longitude: " + gps.getLongitude());
} else {
// Can't get user's current location
alert.showAlertDialog(NearbyPlacesActivity.this, "GPS Status",
"Couldn't get location information. Please enable GPS",
false);
// stop executing code by return
return;
}
// Getting listview
lv = (ListView) findViewById(R.id.list);
// button show on map
btnShowOnMap = (Button) findViewById(R.id.btn_show_map);
// calling background Async task to load Google Places
// After getting places from Google all the data is shown in listview
new LoadPlaces().execute();
/** Button click event for shown on map */
btnShowOnMap.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent i = new Intent(getApplicationContext(),
PlacesMapActivity.class);
// Sending user current geo location
i.putExtra("user_latitude", Double.toString(gps.getLatitude()));
i.putExtra("user_longitude", Double.toString(gps.getLongitude()));
// passing near places to map activity
i.putExtra("near_places", nearPlaces);
// staring activity
startActivity(i);
}
});
/**
* ListItem click event
* On selecting a listitem SinglePlaceActivity is launched
* */
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String reference = ((TextView) view.findViewById(R.id.reference)).getText().toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),
SinglePlaceActivity.class);
// Sending place refrence id to single place activity
// place refrence id used to get "Place full details"
in.putExtra(KEY_REFERENCE, reference);
startActivity(in);
}
});
}
/**
* Background Async Task to Load Google places
* */
class LoadPlaces extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(NearbyPlacesActivity.this);
pDialog.setMessage(Html.fromHtml("<b>Search</b><br/>Loading Places..."));
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting Places JSON
* */
protected String doInBackground(String... args) {
// creating Places class object
googlePlaces = new GooglePlaces();
try {
// Separeate your place types by PIPE symbol "|"
// If you want all types places make it as null
// Check list of types supported by google
//
String types = "cafe|restaurant"; // Listing places only cafes, restaurants
// Radius in meters - increase this value if you don't find any places
double radius = 1000; // 1000 meters
// get nearest places
nearPlaces = googlePlaces.search(gps.getLatitude(),
gps.getLongitude(), radius, types);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* and show the data in UI
* Always use runOnUiThread(new Runnable()) to update UI from background
* thread, otherwise you will get error
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed Places into LISTVIEW
* */
// Get json response status
String status = nearPlaces.status;
// Check for all possible status
if(status.equals("OK")){
// Successfully got places details
if (nearPlaces.results != null) {
// loop through each place
for (Place p : nearPlaces.results) {
HashMap<String, String> map = new HashMap<String, String>();
// Place reference won't display in listview - it will be hidden
// Place reference is used to get "place full details"
map.put(KEY_REFERENCE, p.reference);
// Place name
map.put(KEY_NAME, p.name);
// adding HashMap to ArrayList
placesListItems.add(map);
}
// list adapter
ListAdapter adapter = new SimpleAdapter(NearbyPlacesActivity.this, placesListItems,
R.layout.list_item,
new String[] { KEY_REFERENCE, KEY_NAME}, new int[] {
R.id.reference, R.id.name });
// Adding data into listview
lv.setAdapter(adapter);
}
}
else if(status.equals("ZERO_RESULTS")){
// Zero results found
alert.showAlertDialog(NearbyPlacesActivity.this, "Near Places",
"Sorry no places found. Try to change the types of places",
false);
}
else if(status.equals("UNKNOWN_ERROR"))
{
alert.showAlertDialog(NearbyPlacesActivity.this, "Places Error",
"Sorry unknown error occured.",
false);
}
else if(status.equals("OVER_QUERY_LIMIT"))
{
alert.showAlertDialog(NearbyPlacesActivity.this, "Places Error",
"Sorry query limit to google places is reached",
false);
}
else if(status.equals("REQUEST_DENIED"))
{
alert.showAlertDialog(NearbyPlacesActivity.this, "Places Error",
"Sorry error occured. Request is denied",
false);
}
else if(status.equals("INVALID_REQUEST"))
{
alert.showAlertDialog(NearbyPlacesActivity.this, "Places Error",
"Sorry error occured. Invalid Request",
false);
}
else
{
alert.showAlertDialog(NearbyPlacesActivity.this, "Places Error",
"Sorry error occured.",
false);
}
}
});
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.nearby_places, menu);
return true;
}
}
下面是我的logcat：
06-30 05:25:55.315: D/dalvikvm(1045): GC_FOR_ALLOC freed 34K, 7% free 2424K/2580K, paused 87ms, total 91ms
06-30 05:25:55.415: I/dalvikvm-heap(1045): Grow heap (frag case) to 7.125MB for 4869136-byte allocation
06-30 05:25:55.507: D/dalvikvm(1045): GC_FOR_ALLOC freed 1K, 3% free 7178K/7336K, paused 84ms, total 84ms
06-30 05:25:55.635: D/dalvikvm(1045): GC_CONCURRENT freed <1K, 3% free 7178K/7336K, paused 12ms+31ms, total 133ms
06-30 05:25:56.575: D/gralloc_goldfish(1045): Emulator without GPU emulation detected.
06-30 05:25:57.526: I/Choreographer(1045): Skipped 184 frames! The application may be doing too much work on its main thread.
06-30 05:25:58.025: I/Choreographer(1045): Skipped 130 frames! The application may be doing too much work on its main thread.
06-30 05:25:58.825: I/Choreographer(1045): Skipped 31 frames! The application may be doing too much work on its main thread.
06-30 05:26:00.065: I/Choreographer(1045): Skipped 31 frames! The application may be doing too much work on its main thread.
06-30 05:26:00.735: I/Choreographer(1045): Skipped 30 frames! The application may be doing too much work on its main thread.
06-30 05:26:00.965: I/Choreographer(1045): Skipped 44 frames! The application may be doing too much work on its main thread.
06-30 05:26:01.105: I/Choreographer(1045): Skipped 36 frames! The application may be doing too much work on its main thread.
06-30 05:26:01.426: I/Choreographer(1045): Skipped 34 frames! The application may be doing too much work on its main thread.
06-30 05:26:01.605: I/Choreographer(1045): Skipped 46 frames! The application may be doing too much work on its main thread.
06-30 05:26:02.434: D/dalvikvm(1045): GC_FOR_ALLOC freed 15K, 2% free 7591K/7728K, paused 325ms, total 343ms
06-30 05:26:03.665: D/dalvikvm(1045): GC_CONCURRENT freed 2K, 2% free 9210K/9348K, paused 75ms+61ms, total 402ms
06-30 05:26:03.675: D/dalvikvm(1045): WAIT_FOR_CONCURRENT_GC blocked 330ms
06-30 05:26:04.235: I/Choreographer(1045): Skipped 685 frames! The application may be doing too much work on its main thread.
06-30 05:26:06.815: I/Choreographer(1045): Skipped 669 frames! The application may be doing too much work on its main thread.
06-30 05:26:08.095: I/Choreographer(1045): Skipped 333 frames! The application may be doing too much work on its main thread.
06-30 05:26:08.835: I/Choreographer(1045): Skipped 103 frames! The application may be doing too much work on its main thread.
06-30 05:26:09.045: I/Choreographer(1045): Skipped 37 frames! The application may be doing too much work on its main thread.
06-30 05:26:09.494: D/dalvikvm(1045): GC_FOR_ALLOC freed 1605K, 18% free 8393K/10120K, paused 89ms, total 105ms
06-30 05:26:09.694: I/Choreographer(1045): Skipped 86 frames! The application may be doing too much work on its main thread.
06-30 05:26:13.365: D/dalvikvm(1045): GC_FOR_ALLOC freed 1569K, 18% free 8389K/10120K, paused 147ms, total 191ms
06-30 05:26:13.485: I/dalvikvm-heap(1045): Grow heap (frag case) to 10.092MB for 1872016-byte allocation
06-30 05:26:13.666: D/dalvikvm(1045): GC_FOR_ALLOC freed 5137K, 58% free 5079K/11952K, paused 177ms, total 177ms
06-30 05:26:17.095: I/Choreographer(1045): Skipped 56 frames! The application may be doing too much work on its main thread.
06-30 05:26:17.695: D/dalvikvm(1045): GC_FOR_ALLOC freed 1831K, 73% free 3261K/11952K, paused 356ms, total 389ms
06-30 05:26:17.704: I/dalvikvm-heap(1045): Grow heap (frag case) to 4.794MB for 1568016-byte allocation
06-30 05:26:18.304: D/dalvikvm(1045): GC_CONCURRENT freed <1K, 60% free 4791K/11952K, paused 78ms+73ms, total 601ms
06-30 05:26:20.645: I/Choreographer(1045): Skipped 544 frames! The application may be doing too much work on its main thread.
06-30 05:26:22.796: I/Choreographer(1045): Skipped 444 frames! The application may be doing too much work on its main thread.
06-30 05:26:23.715: D/dalvikvm(1045): GC_FOR_ALLOC freed 1556K, 66% free 3456K/10120K, paused 196ms, total 224ms
06-30 05:26:23.755: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.015MB for 1600016-byte allocation
06-30 05:26:24.015: D/dalvikvm(1045): GC_CONCURRENT freed 10K, 51% free 5008K/10120K, paused 78ms+25ms, total 254ms
06-30 05:26:24.125: I/Choreographer(1045): Skipped 247 frames! The application may be doing too much work on its main thread.
06-30 05:26:25.358: D/dalvikvm(1045): GC_FOR_ALLOC freed 1567K, 66% free 3447K/10120K, paused 154ms, total 173ms
06-30 05:26:25.386: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.007MB for 1600016-byte allocation
06-30 05:26:25.804: D/dalvikvm(1045): GC_CONCURRENT freed 1K, 51% free 5008K/10120K, paused 97ms+42ms, total 421ms
06-30 05:26:29.347: D/dalvikvm(1045): GC_FOR_ALLOC freed 1563K, 66% free 3447K/10120K, paused 164ms, total 174ms
06-30 05:26:29.435: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.266MB for 1872016-byte allocation
06-30 05:26:29.767: D/dalvikvm(1045): GC_CONCURRENT freed <1K, 48% free 5274K/10120K, paused 84ms+35ms, total 330ms
06-30 05:26:33.317: D/dalvikvm(1045): GC_FOR_ALLOC freed 1830K, 66% free 3452K/10120K, paused 153ms, total 158ms
06-30 05:26:33.344: I/dalvikvm-heap(1045): Grow heap (frag case) to 4.981MB for 1568016-byte allocation
06-30 05:26:33.784: D/dalvikvm(1045): GC_CONCURRENT freed <1K, 51% free 4982K/10120K, paused 117ms+26ms, total 437ms
06-30 05:26:37.675: D/dalvikvm(1045): GC_FOR_ALLOC freed 1534K, 66% free 3473K/10120K, paused 171ms, total 178ms
06-30 05:26:37.725: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.033MB for 1600016-byte allocation
06-30 05:26:38.015: D/dalvikvm(1045): GC_CONCURRENT freed 1K, 51% free 5034K/10120K, paused 80ms+24ms, total 293ms
06-30 05:26:41.355: D/dalvikvm(1045): GC_FOR_ALLOC freed 1564K, 66% free 3473K/10120K, paused 156ms, total 160ms
06-30 05:26:41.385: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.033MB for 1600016-byte allocation
06-30 05:26:41.774: D/dalvikvm(1045): GC_CONCURRENT freed <1K, 51% free 5035K/10120K, paused 104ms+23ms, total 388ms
06-30 05:26:44.245: I/Choreographer(1045): Skipped 49 frames! The application may be doing too much work on its main thread.
06-30 05:26:45.255: I/Choreographer(1045): Skipped 164 frames! The application may be doing too much work on its main thread.
06-30 05:26:46.315: D/dalvikvm(1045): GC_FOR_ALLOC freed 1565K, 66% free 3475K/10120K, paused 176ms, total 181ms
06-30 05:26:46.335: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.293MB for 1872016-byte allocation
06-30 05:26:46.595: D/dalvikvm(1045): GC_CONCURRENT freed 1K, 48% free 5302K/10120K, paused 78ms+25ms, total 258ms
06-30 05:26:46.697: I/Choreographer(1045): Skipped 281 frames! The application may be doing too much work on its main thread.
06-30 05:26:47.116: I/Choreographer(1045): Skipped 62 frames! The application may be doing too much work on its main thread.
06-30 05:26:47.490: I/Choreographer(1045): Skipped 38 frames! The application may be doing too much work on its main thread.
06-30 05:26:48.515: I/Choreographer(1045): Skipped 39 frames! The application may be doing too much work on its main thread.
06-30 05:26:49.365: D/dalvikvm(1045): GC_FOR_ALLOC freed 1844K, 60% free 4132K/10120K, paused 109ms, total 129ms
06-30 05:26:49.385: I/dalvikvm-heap(1045): Grow heap (frag case) to 5.645MB for 1568016-byte allocation
06-30 05:26:49.717: D/dalvikvm(1045): GC_CONCURRENT freed 188K, 46% free 5474K/10120K, paused 82ms+15ms, total 326ms
06-30 05:26:49.755: I/Choreographer(1045): Skipped 145 frames! The application may be doing too much work on its main thread.
06-30 05:26:53.785: D/dalvikvm(1045): GC_FOR_ALLOC freed 14K, 44% free 5698K/10120K, paused 370ms, total 378ms
06-30 05:26:54.406: I/dalvikvm-heap(1045): Grow heap (frag case) to 10.323MB for 4869136-byte allocation
06-30 05:26:55.017: D/dalvikvm(1045): GC_CONCURRENT freed 4K, 30% free 10448K/14876K, paused 16ms+113ms, total 606ms
06-30 05:26:57.294: D/GPS(1045): GPS Enabled
06-30 05:26:57.336: D/Your Location(1045): latitude:0.0, longitude: 0.0
06-30 05:26:58.475: D/AndroidRuntime(1045): Shutting down VM
06-30 05:26:58.475: W/dalvikvm(1045): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
06-30 05:26:58.555: E/AndroidRuntime(1045): FATAL EXCEPTION: main
06-30 05:26:58.555: E/AndroidRuntime(1045): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.travelplanner/com.example.travelplanner.NearbyPlacesActivity}: java.lang.NullPointerException
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.os.Handler.dispatchMessage(Handler.java:99)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.os.Looper.loop(Looper.java:137)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread.main(ActivityThread.java:5041)
06-30 05:26:58.555: E/AndroidRuntime(1045): at java.lang.reflect.Method.invokeNative(Native Method)
06-30 05:26:58.555: E/AndroidRuntime(1045): at java.lang.reflect.Method.invoke(Method.java:511)
06-30 05:26:58.555: E/AndroidRuntime(1045): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-30 05:26:58.555: E/AndroidRuntime(1045): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-30 05:26:58.555: E/AndroidRuntime(1045): at dalvik.system.NativeStart.main(Native Method)
06-30 05:26:58.555: E/AndroidRuntime(1045): Caused by: java.lang.NullPointerException
06-30 05:26:58.555: E/AndroidRuntime(1045): at com.example.travelplanner.NearbyPlacesActivity.onCreate(NearbyPlacesActivity.java:109)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.Activity.performCreate(Activity.java:5104)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
06-30 05:26:58.555: E/AndroidRuntime(1045): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
06-30 05:26:58.555: E/AndroidRuntime(1045): ... 11 more
06-30 05:26:59.336: I/dalvikvm(1045): Could not find method com.google.common.base.Preconditions.checkNotNull, referenced from method com.google.api.client.http.GenericUrl.setHost
06-30 05:26:59.385: W/dalvikvm(1045): VFY: unable to resolve static method 8238: Lcom/google/common/base/Preconditions;.checkNotNull (Ljava/lang/Object;)Ljava/lang/Object;
06-30 05:26:59.415: D/dalvikvm(1045): VFY: replacing opcode 0x71 at 0x0000
06-30 05:26:59.455: I/dalvikvm(1045): Could not find method com.google.common.base.Preconditions.checkArgument, referenced from method com.google.api.client.http.GenericUrl.setPort
06-30 05:26:59.475: W/dalvikvm(1045): VFY: unable to resolve static method 8236: Lcom/google/common/base/Preconditions;.checkArgument (ZLjava/lang/Object;)V
06-30 05:26:59.475: D/dalvikvm(1045): VFY: replacing opcode 0x71 at 0x0006
06-30 05:26:59.546: I/dalvikvm(1045): Could not find method com.google.common.base.Preconditions.checkNotNull, referenced from method com.google.api.client.http.GenericUrl.setScheme
06-30 05:26:59.632: W/dalvikvm(1045): VFY: unable to resolve static method 8238: Lcom/google/common/base/Preconditions;.checkNotNull (Ljava/lang/Object;)Ljava/lang/Object;
06-30 05:26:59.632: D/dalvikvm(1045): VFY: replacing opcode 0x71 at 0x0000
06-30 05:27:02.425: I/Process(1045): Sending signal. PID: 1045 SIG: 9
我是否应该指定用于查找附近地点的其他类代码？ 并且请作为一个新手，我期待一些更简单的解释......我不太了解Android世界..