我最近开始用android开发一些东西。 我正在尝试使用抽屉导航和谷歌地图创建一个活动。
我已经阅读了如何操作，我搜索了一个解决方案，但一直无法解决问题。
这是主要活动。并且＆＃39;也对错误负责：
package it.kytech.linkess;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
public class MainActivity extends ActionBarActivity
implements NavigationDrawerFragment.NavigationDrawerCallbacks {
/**
* Fragment managing the behaviors, interactions and presentation of the navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in {@link #restoreActionBar()}.
*/
private CharSequence mTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
@Override
public void onNavigationDrawerItemSelected(int position) {
}
public void restoreActionBar() {
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setTitle(mTitle);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!mNavigationDrawerFragment.isDrawerOpen()) {
// Only show items in the action bar relevant to this screen
// if the drawer is not showing. Otherwise, let the drawer
// decide what to show in the action bar.
getMenuInflater().inflate(R.menu.main, menu);
restoreActionBar();
return true;
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
static final LatLng HAMBURG = new LatLng(53.558, 9.927);
static final LatLng KIEL = new LatLng(53.551, 9.993);
private GoogleMap map;
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_main, null, false);
FragmentTransaction ft = getFragmentManager().beginTransaction();
map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
SupportMapFragment fmap = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);
if (fmap == null) {
fmap = SupportMapFragment.newInstance();
ft.add(R.id.map, fmap);
}
ft.commit();
Marker hamburg = map.addMarker(new MarkerOptions().position(HAMBURG)
.title("Hamburg"));
Marker kiel = map.addMarker(new MarkerOptions()
.position(KIEL)
.title("Kiel")
.snippet("Kiel is cool"));
// Move the camera instantly to hamburg with a zoom of 15.
map.moveCamera(CameraUpdateFactory.newLatLngZoom(HAMBURG, 15));
// Zoom in, animating the camera.
map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);
return v;
}
}
}
这是主要的xml。
<!-- A DrawerLayout is intended to be used as the top-level content view using match_parent for both width and height to consume the full space available. -->
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="it.kytech.linkess.MainActivity">
<!-- As the main content view, the view below consumes the entire
space available using match_parent in both dimensions. -->
<FrameLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- android:layout_gravity="start" tells DrawerLayout to treat
this as a sliding drawer on the left side for left-to-right
languages and on the right side for right-to-left languages.
If you're not building against API 17 or higher, use
android:layout_gravity="left" instead. -->
<!-- The drawer is given a fixed width in dp and extends the full height of
the container. -->
<fragment android:id="@+id/navigation_drawer"
android:layout_width="@dimen/navigation_drawer_width"
android:layout_height="match_parent"
android:layout_gravity="start"
android:name="it.kytech.linkess.NavigationDrawerFragment" />
</android.support.v4.widget.DrawerLayout>
这是地图的xml：
<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"
tools:context="it.kytech.linkess.MainActivity$PlaceholderFragment">
<fragment
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:name="com.google.android.gms.maps.MapFragment"/>
</RelativeLayout>
这是抽屉的xml：
<ListView 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:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#cccc"
tools:context="it.kytech.myapplication2.app.NavigationDrawerFragment" />
我还附上我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="it.kytech.linkess" >
<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"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<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="my hidden key"/>
<meta-data android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<activity
android:name="it.kytech.linkess.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
此行发生错误：
map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
完整日志：
04-15 22:21:08.325 30251-30251/it.kytech.linkess E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: it.kytech.linkess, PID: 30251
java.lang.RuntimeException: Unable to start activity ComponentInfo{it.kytech.linkess/it.kytech.linkess.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
at android.app.ActivityThread.access$800(ActivityThread.java:145)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5149)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at it.kytech.linkess.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:110)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:938)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1115)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
at android.app.Activity.performStart(Activity.java:5241)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
at android.app.ActivityThread.access$800(ActivityThread.java:145)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5149)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
at dalvik.system.NativeStart.main(Native Method)
显然，隐藏了生成代码的关键。 我希望你能帮助我。
答案 0 :(得分：0)
问题是你在初始化你的sopportmapfragment之前得到了地图，这就是你的地图为空的原因..尝试切换它首先初始化地图片段并获取地图。
答案 1 :(得分：0)
您的空指针可能是因为它无法在当前布局（activity_main.xml）中找到R.id.map。
查看完代码后，我看不到您在哪里充气地图xml文件并将其添加到您的布局中。
也许您打算添加一个include语句
<include layout="@layout/map"/>
而不是框架布局，以便实际实例化？
或者，或者将map.xml文件膨胀，将其附加到您的布局，然后调用findViewById。