我是android程序员的新手 . 最近,我试图制作在Android应用程序中使用谷歌 Map v2的项目,但我收到了很多错误(我已经将谷歌播放服务添加到我的库并在这里找到类似的主题,但没有解决我的问题) . 请看我的日志猫吼叫:
更新
03-22 13:52:29.331: E/AndroidRuntime(17708): FATAL EXCEPTION: main
03-22 13:52:29.331: E/AndroidRuntime(17708): java.lang.RuntimeException: Unable to resume activity {com.yai.testmap/com.yai.testmap.MainActivity}: java.lang.NullPointerException
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2613)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2641)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2127)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.access$600(ActivityThread.java:140)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1228)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.os.Handler.dispatchMessage(Handler.java:99)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.os.Looper.loop(Looper.java:137)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.main(ActivityThread.java:4895)
03-22 13:52:29.331: E/AndroidRuntime(17708): at java.lang.reflect.Method.invokeNative(Native Method)
03-22 13:52:29.331: E/AndroidRuntime(17708): at java.lang.reflect.Method.invoke(Method.java:511)
03-22 13:52:29.331: E/AndroidRuntime(17708): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
03-22 13:52:29.331: E/AndroidRuntime(17708): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
03-22 13:52:29.331: E/AndroidRuntime(17708): at dalvik.system.NativeStart.main(Native Method)
03-22 13:52:29.331: E/AndroidRuntime(17708): Caused by: java.lang.NullPointerException
03-22 13:52:29.331: E/AndroidRuntime(17708): at com.yai.testmap.MainActivity.setUpMapIfNeeded(MainActivity.java:93)
03-22 13:52:29.331: E/AndroidRuntime(17708): at com.yai.testmap.MainActivity.onResume(MainActivity.java:187)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1199)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.Activity.performResume(Activity.java:5237)
03-22 13:52:29.331: E/AndroidRuntime(17708): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2603)
03-22 13:52:29.331: E/AndroidRuntime(17708): ... 12 more
更新
我的MainActivity.java:
package com.yai.testmap;
import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
/* FOR ERROR REPPORT */
import android.util.Log;
/* IMPORT FOR DROPDOWNLIST USED THIS PROJECT */
import android.widget.CheckBox;
import android.widget.Spinner;
import android.widget.Toast;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.AdapterView.OnItemSelectedListener;
/* IMPORT FOR GOOGLE MAP */
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
/* FOR GOOGLE MAP TYPE */
import static com.google.android.gms.maps.GoogleMap.MAP_TYPE_HYBRID;
import static com.google.android.gms.maps.GoogleMap.MAP_TYPE_NONE;
import static com.google.android.gms.maps.GoogleMap.MAP_TYPE_NORMAL;
import static com.google.android.gms.maps.GoogleMap.MAP_TYPE_SATELLITE;
import static com.google.android.gms.maps.GoogleMap.MAP_TYPE_TERRAIN;
class PlaceholderFragment extends Fragment implements OnItemSelectedListener{
private GoogleMap mGoogleMap;
private CheckBox mTrafficCheckbox, mLocationCheckbox, mBuildingCheckbox, mIndoorCheckbox;
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Spinner spinner = (Spinner) rootView.findViewById(R.id.spinnerOption);
ArrayAdapter adapter = ArrayAdapter.createFromResource(getActivity(), R.array.spinner_option_string, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener((OnItemSelectedListener) getActivity());
mTrafficCheckbox = (CheckBox) rootView.findViewById(R.id.checkbox_traffic);
mLocationCheckbox = (CheckBox) rootView.findViewById(R.id.checkbox_location);
mBuildingCheckbox = (CheckBox) rootView.findViewById(R.id.checkbox_building);
mIndoorCheckbox = (CheckBox) rootView.findViewById(R.id.checkbox_indoor);
return rootView;
}
@Override
public void onItemSelected(AdapterView parent, View view, int position,
long id) {
// TODO Auto-generated method stub
}
@Override
public void onNothingSelected(AdapterView parent) {
// TODO Auto-generated method stub
}
}
public class MainActivity extends ActionBarActivity implements OnItemSelectedListener {
private GoogleMap mGoogleMap;
private CheckBox mTrafficCheckbox, mLocationCheckbox, mBuildingCheckbox, mIndoorCheckbox;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
private void setUpMapIfNeeded(){
if(mGoogleMap == null){
mGoogleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
}
}
private boolean checkReady(){
if(mGoogleMap == null){
Toast.makeText(this, R.string.map_not_ready, Toast.LENGTH_SHORT).show();
return false;
}
return true;
}
private void updateTraffic(){
if(!checkReady()){
return;
}
mGoogleMap.setTrafficEnabled(mTrafficCheckbox.isChecked());
}
public void onTrafficToggled(View view){
updateTraffic();
}
private void updateLocation(){
if(!checkReady()){
return;
}
mGoogleMap.setMyLocationEnabled(mLocationCheckbox.isChecked());
}
public void onLocationToggled(View view){
updateLocation();
}
private void updateBuilding(){
if(!checkReady()){
return;
}
mGoogleMap.setBuildingsEnabled(mBuildingCheckbox.isChecked());
}
public void onBuildingToggled(View view){
updateBuilding();
}
private void updateIndoor(){
if(!checkReady()){
return;
}
mGoogleMap.setIndoorEnabled(mIndoorCheckbox.isChecked());
}
public void onIndoorToggled(View view){
updateIndoor();
}
@Override
public void onItemSelected(AdapterView parent, View view, int position, long id){
setLayer((String) parent.getItemAtPosition(position));
}
private void setLayer(String layerName){
if(!checkReady()){
return;
}
if(layerName.equals(getString(R.string.normal))){
mGoogleMap.setMapType(MAP_TYPE_NORMAL);
}
else if(layerName.equals(getString(R.string.hybrid))){
mGoogleMap.setMapType(MAP_TYPE_HYBRID);
}
else if(layerName.equals(getString(R.string.satellite))){
mGoogleMap.setMapType(MAP_TYPE_SATELLITE);
}
else if(layerName.equals(getString(R.string.terrain))){
mGoogleMap.setMapType(MAP_TYPE_TERRAIN);
}
else if(layerName.equals(getString(R.string.none_map))){
mGoogleMap.setMapType(MAP_TYPE_NONE);
}
else{
Log.i("LDA", "Error setting layer with name " + layerName);
}
}
@Override
public void onNothingSelected(AdapterView parent){
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
if (mGoogleMap != null) {
updateTraffic();
updateLocation();
updateBuilding();
updateIndoor();
}
}
@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;
}
@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 {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}
我在这里使用片段,所以这里是fragment_main.xml:
<?xml version="1.0" encoding="utf-8" ?>
<Spinner
android:id="@+id/spinnerOption"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<CheckBox
android:id="@+id/checkbox_traffic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onTrafficToggled"
android:text="@string/traffic" />
<CheckBox
android:id="@+id/checkbox_location"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onLocationToggled"
android:text="@string/location" />
<CheckBox
android:id="@+id/checkbox_building"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onBuildingsToggled"
android:checked="true"
android:text="@string/building" />
<CheckBox
android:id="@+id/checkbox_indoor"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onIndoorToggled"
android:checked="true"
android:text="@string/indoor" />
</LinearLayout>
</RelativeLayout>
和我的清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.yai.testmap"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="9"
android:targetSdkVersion="17" />
<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.gms.version"
android:value="@integer/google_play_services_version"
/>
<activity
android:name="com.yai.testmap.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>
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="SUPER SCREET CODE"
/>
</application>
</manifest>
这里是我的activity_main.xml:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.yai.testmap.MainActivity"
tools:ignore="MergeRootFrame" />
我很好奇我的Spinner和函数setUpMapIfNeeded(),因为当我评论那部分代码时,我的app工作 . 我想念的是什么?任何的想法?非常感谢 .
3 回答
试试这个..
将
Spinner
和所有CheckBox
从MainActivity
删除到PlaceholderFragment
,如下所示和
你的所有
View
都不属于activity_main.xml
. 他们是你PlaceHolderFragment
的一部分 . 因此,当您调用findViewById()
(如findViewById(R.id.spinnerOption)
)时,它们只返回null
,因为它们不属于Activity
视图层次结构...首先将
PlaceHolderFragment
添加到Activity
,然后调用findViewById()
,否则将View
的所有声明及其实现移到PlaceHolderFragment
中 .您可以先添加
Fragment
添加,然后在您的视图上调用findViewById()
s ...问题是因为Spinner和复选框以及所有其他视图都在
文件 . 您正在尝试在MainActivity中找到该视图的ID,因此每次它都会为您提供Null Poniter异常,因为它位于_1141739中 . 因此,首先将PlaceHolderFragment添加到您的Activity并查找视图的ID . 看到这个