Question

我感觉它是一个愚蠢的错误，但我无法找到它。我试图在此代码上面添加一个GPS处理。

日志文件：

04-28 01:14:59.266: E/AndroidRuntime(5940): FATAL EXCEPTION: main
04-28 01:14:59.266: E/AndroidRuntime(5940): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.wazeresturant/com.example.wazeresturant.MainActivity}: java.lang.NullPointerException
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.os.Looper.loop(Looper.java:137)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread.main(ActivityThread.java:5419)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at java.lang.reflect.Method.invokeNative(Native Method)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at java.lang.reflect.Method.invoke(Method.java:525)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at dalvik.system.NativeStart.main(Native Method)
04-28 01:14:59.266: E/AndroidRuntime(5940): Caused by: java.lang.NullPointerException
04-28 01:14:59.266: E/AndroidRuntime(5940):     at com.example.wazeresturant.MainActivity.onCreate(MainActivity.java:42)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.Activity.performCreate(Activity.java:5372)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-28 01:14:59.266: E/AndroidRuntime(5940):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
04-28 01:14:59.266: E/AndroidRuntime(5940):     ... 11 more

Java文件：

import android.app.Activity;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;

import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MainActivity extends Activity {

     private GoogleMap map;
     private final LatLng LOCATION_TA = new LatLng(32.066667, 34.766667);// תל אביב
     private final LatLng LOCATION_BY = new LatLng(32.023056, 34.750278);// בת ים
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        // יצרת מפה

        map=((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
        //  לאפשר למצוא מקום נוכחי
        map.setMyLocationEnabled(true);
        LocationManager lm=(LocationManager)getSystemService(LOCATION_SERVICE);

        Criteria criteria= new Criteria();

        String provider =lm.getBestProvider(criteria, true);

        Location myLocation=lm.getLastKnownLocation(provider);

        map.setMapType(GoogleMap.MAP_TYPE_HYBRID);  
        // השגת מיקום נוכחי
        double latitude = myLocation.getLatitude();
        double longitude = myLocation.getLongitude();
        // 
        LatLng latlng = new LatLng(latitude,longitude);
        //למקם אוטמטי למיקום הנוכחי
        map.moveCamera(CameraUpdateFactory.newLatLng(latlng));
        // כמה זום יהיה על המפה 
        map.animateCamera(CameraUpdateFactory.zoomTo(20));
        // יצירת חץ במפה במיקום הנוכחי
        map.addMarker(new MarkerOptions().position(new LatLng(latitude,longitude)).title("You Are Here"));


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


    // כל כפתור מציג או את בתים או ת"א בסוג מפה אחר
    public void OnClick_City(View v)
    {
        map.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_TA, 9);
        map.animateCamera(update);
    }
    public void OnClick_pepep_A(View v)
    {// רגיל
        map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_TA, 16);
        map.animateCamera(update);
    }
    public void OnClick_pepep_B(View v)
    {// רגיל
        map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_BY, 10);
        map.animateCamera(update);
    }

}

主XML文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/btcity"
        android:layout_centerHorizontal="true"
        android:onClick="OnClick_pepep_A"
        android:text="@string/pepe_a" />

    <fragment
          android:id="@+id/map"
          android:name="com.google.android.gms.maps.MapFragment"
          class="com.google.android.gms.maps.MapFragment"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_below="@+id/button2"   
          />

    <Button
        android:id="@+id/btcity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/map"
        android:layout_alignParentTop="true"
        android:onClick="OnClick_City"
        android:text="@string/City"/>

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/button2"
        android:layout_alignRight="@+id/map"
        android:onClick="OnClick_pepep_B"
        android:text="@string/pepe_b"/>

</RelativeLayout>

和清单文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.wazeresturant"
    android:versionCode="1"
    android:versionName="1.0" >

    <permission
        android:name="com.example.wazeresturant.premission.MAPS_RECEIVE"
        android:protectionLevel="signature" />

    <uses-permission android:name="com.example.wazeresturant.premission.MAPS_RECEIVE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <!-- Google Maps Android API v2, but are recommended. -->
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <uses-sdk
        android:minSdkVersion="11"
        android:targetSdkVersion="19" />

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="XXXX" />
        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />

        <activity
            android:name="com.example.wazeresturant.MainActivity"
            android:label="@string/app_name" >
        </activity>
        <activity
            android:name="com.example.wazeresturant.LoginActivity"
            android:label="@string/title_activity_login" >
        </activity>
        <activity
            android:name="com.example.wazeresturant.RegisterActivity"
            android:label="@string/title_activity_register" >
        </activity>
        <activity
            android:name="com.example.wazeresturant.FirstScreenActivity"
            android:label="@string/title_activity_first_screen" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <uses-library android:name="com.google.android.maps" />

        <activity
            android:name="com.example.wazeresturant.MainActivity"
            android:label="@string/title_activity_amain" >
        </activity>
    </application>

</manifest>

Answer 1

这里的地图为空：

map.setMapType(GoogleMap.MAP_TYPE_SATELLITE);

将其初始化为onCreate（）。

Answer 2

您已声明private GoogleMap map;，但您已注释了初始化此变量的代码。

我建议您在onCreate（）方法的下面注释。

setContentView(R.layout.main);
map=((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

这肯定会解决您的NullPointerException错误。

Answer 3

使用 MapActivity 代替活动。

AndroidRuntime（5940）：java.lang.RuntimeException：无法启动活动ComponentInfo

3 个答案: