-1
...我已經尋找這個錯誤，並發現了許多解決方案，但我不能夠解決問題，因爲在我的Android無法啓動活動ComponentInfo：顯示java.lang.NullPointerException
這裏是初學者是我的主要活動
package ***.***.greytrix.test;
import android.app.LauncherActivity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.AsyncTask;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import android.widget.TextView;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.gcm.GoogleCloudMessaging;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import android.webkit.CookieManager;
public class MainActivity extends ActionBarActivity {
private WebView mWebView;
private Context context;
public static final String EXTRA_MESSAGE = "message";
public static final String PROPERTY_REG_ID = "registration_id";
private static final String PROPERTY_APP_VERSION = "appVersion";
private final static int PLAY_SERVICES_RESOLUTION_REQUEST = 9000;
// please enter your sender id
String SENDER_ID = "11111111";
static final String TAG = "Pocket ";
GoogleCloudMessaging gcm;
TextView mDisplay;
String regid;
String fileurl="https://neel.test.com/";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = getApplicationContext();
if(checkPlayServices()){
gcm = GoogleCloudMessaging.getInstance(this);
regid = getRegistrationId(context);
//For Testing Purpose
new RegisterBackground().execute();
}
Bundle extras = getIntent().getExtras();
String url;
if (extras != null) {
url = extras.getString("url");
mWebView = (WebView) findViewById(R.id.activity_main_webview);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setDomStorageEnabled(true);
mWebView.getSettings().setDatabaseEnabled(true);
if (extras.getString("url").isEmpty()) {
mWebView.loadUrl("https://neel.test.com/");
} else {
mWebView.loadUrl(url);
}
mWebView.setWebViewClient(new MyAppWebViewClient());
} else {
mWebView = (WebView) findViewById(R.id.activity_main_webview);
WebSettings webSettings = mWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setDomStorageEnabled(true);
webSettings.setDatabaseEnabled(true);
fileurl = ReadFile();
if (fileurl == "") {
fileurl="https://neel.test.com/";
mWebView.loadUrl("https://neel.test.com/");
} else {
mWebView.loadUrl(fileurl);
}
mWebView.setWebViewClient(new MyAppWebViewClient());
}
}
private String ReadFile() {
String aBuffer = "";
try {
File myFile = new File(getFilesDir() + "/mysdfile.txt");
if (myFile.exists()) {
FileInputStream fIn = new FileInputStream(myFile);
BufferedReader myReader = new BufferedReader(
new InputStreamReader(fIn));
String aDataRow = "";
while ((aDataRow = myReader.readLine()) != null) {
aBuffer += aDataRow + "\n";
}
myReader.close();
}
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_SHORT).show();
}
return aBuffer.trim();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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();
//noinspection SimplifiableIfStatement
if (id == R.id.SetURL) {
Intent nextscreen = new Intent(PayrollApplication.getContext(), SecondScreenActivity.class);
startActivity(nextscreen);
//setContentView(R.layout.seturl);
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onBackPressed() {
if (mWebView.canGoBack()) {
mWebView.goBack();
} else {
super.onBackPressed();
}
}
@Override
protected void onResume(){
super.onResume();
checkPlayServices();
}
//New Code developed by Nilesh Gajare on 10th July 2015
class RegisterBackground extends AsyncTask<String,String,String> {
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
String msg = "";
try {
if (gcm == null) {
gcm = GoogleCloudMessaging.getInstance(context);
}
regid = gcm.register(SENDER_ID);
msg = "Device registered, registration ID=" + regid;
Log.d("111", msg);
sendRegistrationIdToBackend();
// Persist the regID - no need to register again.
storeRegistrationId(context, regid);
} catch (IOException ex) {
msg = "Error :" + ex.getMessage();
}
return msg;
}
@Override
protected void onPostExecute(String msg) {
//mDisplay.append(msg + "\n");
}
private void sendRegistrationIdToBackend() {
// Set Server URL for Storing Android Device Registration ID.
String CompanyCode= getCookie(fileurl,"CompanyId");
String UserName= getCookie(fileurl,"UserName");
String Password= getCookie(fileurl,"Password");
String url = "https://neel.test.com//api/v1.0/SaveAndroidRegId?RegId="+regid+"&CompanyId="+CompanyCode+"&UserName="+UserName+"&Password="+Password ;
try {
HttpResponse httpResponse = httpClient.execute(httpPost);
Log.i(TAG,httpResponse.getStatusLine().toString());
Log.i(TAG,httpResponse.getEntity().toString());
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void storeRegistrationId(Context context, String regId) {
final SharedPreferences prefs = getGCMPreferences(context);
int appVersion = getAppVersion(context);
Log.i(TAG, "Saving regId on app version " + appVersion);
SharedPreferences.Editor editor = prefs.edit();
editor.putString(PROPERTY_REG_ID, regId);
editor.putInt(PROPERTY_APP_VERSION, appVersion);
editor.commit();
}
}
private boolean checkPlayServices() {
int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
if (resultCode != ConnectionResult.SUCCESS) {
if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
GooglePlayServicesUtil.getErrorDialog(resultCode, this,
PLAY_SERVICES_RESOLUTION_REQUEST).show();
} else {
Log.i(TAG, "This device is not supported.");
finish();
}
return false;
}
return true;
}
private String getRegistrationId(Context context) {
final SharedPreferences prefs = getGCMPreferences(context);
String registrationId = prefs.getString(PROPERTY_REG_ID, "");
if (registrationId.isEmpty()) {
Log.i(TAG, "Registration not found.");
return "";
}
int registeredVersion = prefs.getInt(PROPERTY_APP_VERSION, Integer.MIN_VALUE);
int currentVersion = getAppVersion(context);
if (registeredVersion != currentVersion) {
Log.i(TAG, "App version changed.");
return "";
}
return registrationId;
}
private SharedPreferences getGCMPreferences(Context context) {
return getSharedPreferences(MainActivity.class.getSimpleName(),
Context.MODE_PRIVATE);
}
private static int getAppVersion(Context context) {
try {
PackageInfo packageInfo = context.getPackageManager()
.getPackageInfo(context.getPackageName(), 0);
return packageInfo.versionCode;
} catch (PackageManager.NameNotFoundException e) {
// should never happen
throw new RuntimeException("Could not get package name: " + e);
}
}
public String getCookie(String siteName,String CookieName){
String CookieValue = null;
CookieManager cookieManager = CookieManager.getInstance();
String cookies = cookieManager.getCookie(siteName);
if(cookies != null) {
String[] temp = cookies.split(";");
for (String ar1 : temp) {
if (ar1.contains(CookieName)) {
String[] temp1 = ar1.split("=");
CookieValue = temp1[1];
}
}
}
return CookieValue;
}
}
在MainActivy.xml，我得到了下面的代碼：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity">
<WebView
android:id="@+id/activity_main_webview"
android:layout_width="fill_parent"
android:layout_height= "fill_parent"
android:layout_weight="1.0" />
</RelativeLayout>
堆棧跟蹤爲
過程：com.pockethcm.xxx.test，PID：2347 了java.lang.RuntimeException：無法啓動活動ComponentInfo {xxx.xxx.xxx.test/xxx.xxx.xxx.test.MainActivity}： java.lang.NullPointerException：嘗試調用虛擬方法 'boolean java.lang.String.isEmpty（）'null對象引用 at android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2298） at android.app .ActivityThread.handleLaunchActivity（ActivityThread.java:2360） 在android.app.ActivityThread.access $ 800（ActivityThread.java:144） 在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1278） 的機器人。 os.Handler.dispatchMessage（手在android.app.ActivityThread.main（ActivityThread.java:5221）處使用android.os.Looper.loop（Looper.java:135） （在java.lang.reflect.Method.invoke處使用 ）本地方法） at java.lang.reflect.Method.invoke（Method.java:372） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899） at com.android.internal .os.ZygoteInit.main（ZygoteInit.java:694） 引起：java.lang.NullPointerException：試圖在空對象 參考 自助服務調用虛擬方法'布爾java.lang.String.isEmpty（）'。 pokethcm.greytrix.test.MainActivity.onCreate（MainActivity.java:106） at android.app.Activity.performCreate（Activity.java:5937） 在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1105） 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2251） 在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2360） 在android.app.ActivityThread.access $ 800（ActivityThread.java:144） at android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1278） at android.os.Handler.dispatchMessage（Handler.java:102） at android.os.Looper.loop（Looper.java:135） at android.app.ActivityThread.main（ActivityThread.java:5221） at java.lang方法.invoke（本地方法） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899） at com.android.internal.os.ZygoteInit.main（ZygoteInit。Java的：694）設備 離線
而且明顯是在這裏下面
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="selfservice.xxx.xxx.test"
android:versionCode="2"
android:versionName="1.1">
<uses-sdk
android:minSdkVersion="16"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
<uses-permission android:name="android.permission.ACCESS_DOWNLOAD_MANAGER"/>
<permission
android:name="selfservice.xxx.xxx.test.permission.C2D_MESSAGE"
android:protectionLevel="signature" />
<uses-permission android:name="selfservice.xxx.xxx.test.gcm.permission.C2D_MESSAGE" />
<application
android:name="selfservice.xxx.xxx.test.PayrollApplication"
android:allowBackup="true"
android:icon="@mipmap/icon_pocket"
android:label="Pocket HCM"
android:theme="@style/AppTheme">
<activity
android:name="selfservice.xxx.xxx.test.MainActivity"
android:label="Pocket HCM"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="selfservice.xxx.xxx.test.SecondScreenActivity"
android:screenOrientation="portrait"></activity>
<receiver
android:name="selfservice.xxx.xxx.test.GcmBroadcastReceiver"
android:permission="com.google.android.c2dm.permission.SEND" >
<intent-filter>
<!-- Receives the actual messages. -->
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<category android:name="selfservice.xxx.xxx.test" />
</intent-filter>
</receiver>
<service android:name="selfservice.xxx.xxx.test.GcmIntentService" />
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<activity
android:name="selfservice.pockethcm.greytrix.test.ReceiveActivity">
</activity>
</application>
</manifest>
它正在爲第一次安裝應用程序後，但是當我們關閉並重新打開它崩潰不幸的是應用程序已經關閉 你有什麼想法，這將不勝感激:)
謝謝！
作爲日誌'String.isEmpty（）上的」空對象引用...' –
哪一行是＃106？ if（extras.getString（「url」）。isEmpty（））{ –
檢查'registrationId！= null'在檢查'registrationId.isEmpty（）' – Rustam