I got this error while the running the app:
05-10 01：44：39.243 11047-11047 / com.efe.efeAlumni E / AndroidRuntime：FATAL EXCEPTION：main进程：com.efe.efeAlumni，PID：11047 java.lang.RuntimeException：无法启动活动ComponentInfo {com . efe.efeAlumni / com.efe.efeAlumni.ui.MainActivity}：java.lang.NullPointerException：尝试在android.app.ActivityThread的android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2325）获取null数组的长度 . android.app.Handler.dispatchMessage上android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1303）的android.app.ActivityThread.access $ 800（ActivityThread.java:151）上的handleLaunchActivity（ActivityThread.java:2387） Handler.java:102）在android.app.Looper.loop（Looper.java:135）的android.app.ActivityThread.main（ActivityThread.java:5254）at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）的com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:903）at com.android.internal.os.ZygoteInit.main （ZY goteInit.java:698）引起：java.lang.NullPointerException：尝试在android.widget.ListView.setAdapter的com.efe.efeAlumni.Adaptors.JobAdaptor.getCount（JobAdaptor.java:28）获取null数组的长度（ ListView.java:487）在android.app.A活动中，comAfe.efeAlumni.ui.MainActivity.onCreate（MainActivity.java:74）上的android.app.ListActivity.setListAdapter（ListActivity.java:265），来自android.app.Activity.performCreate（Activity .java：5990）在Android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2387）的android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1106）android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2278）在android.app.ActivityThread.access $ 800（ActivityThread.java:151）android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1303）在android.os.Handler.dispatchMessage（Handler.java:102）在android .os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5254）java.lang.reflect.Method.invoke（Native Method）a t.android.internal.os.ZygoteInit.main中的com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:903）中的java.lang.reflect.Method.invoke（Method.java:372） （ZygoteInit.java:698）
主要活动：
import android.app.ListActivity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListView;
package com.efe.efeAlumni.ui;
import android.app.ListActivity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.util.Log;
import com.efe.efeAlumni.Adaptors.JobAdaptor;
import com.efe.efeAlumni.Model.Config;
import com.efe.efeAlumni.Model.JobDetails;
import com.efe.efeAlumni.Model.Jobs;
import com.efe.efeAlumni.R;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
public class MainActivity extends ListActivity {
public static final String TAG = MainActivity.class.getSimpleName();
private Jobs mJobs;
private JobDetails[] mJobDetails;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getJobsDetails();
JobAdaptor adaptor = new JobAdaptor(this, mJobDetails);
setListAdapter(adaptor);
Log.d(TAG," OkHttp success ");
}
private void getJobsDetails() {
if(isNetworkAvailable()) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(Config.jobsURL)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}
@Override
public void onResponse(Response response) throws IOException {
try {
String jsonData = response.body().string();
Log.v(TAG, jsonData);
if (response.isSuccessful()) {
mJobs = parseJobsDetails(jsonData);
} else {
AlertUserAboutError();
}
} catch (IOException e) {
Log.v(TAG, "Exception caught: ", e);
} catch (JSONException e) {
Log.v(TAG, "Exception caught: ", e);
}
}
});
}else {
AlertUserAboutError();
}
}
private Jobs parseJobsDetails (String jsonData) throws JSONException{
Jobs jobs = new Jobs();
jobs.setJobDetailses(getCurrentJobDetails(jsonData));
return jobs;
}
private JobDetails[] getCurrentJobDetails(String jsonData) throws JSONException {
JSONObject jsonObject = new JSONObject(jsonData);
JSONArray result = jsonObject.getJSONArray("result");
JobDetails[] jobDetails = new JobDetails[result.length()];
for (int i = 0; i < result.length(); i++) {
JSONObject jsonDetail = result.getJSONObject(i);
JobDetails jobDetail = new JobDetails();
jobDetail.setIds(jsonDetail.getString("id"));
jobDetail.setSalary(jsonDetail.getString("title"));
jobDetail.setTitles(jsonDetail.getString("salary"));
jobDetails[i] = jobDetail;
Log.d(TAG, jobDetail.getIds());
}
return jobDetails;
}
private boolean isNetworkAvailable() {
ConnectivityManager manger = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manger.getActiveNetworkInfo();
boolean isAvailable = false;
if(networkInfo != null && networkInfo.isConnected()){
isAvailable = true;
}
return isAvailable;
}
private void AlertUserAboutError() {
AlertDialogFragment dialog = new AlertDialogFragment();
dialog.show(getFragmentManager(),"error_dailog");
}
}
JobAdaptor类：
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.efe.efeAlumni.Model.JobDetails;
import com.efe.efeAlumni.R;
public class JobAdaptor extends BaseAdapter {
private JobDetails[] mJobs;
private Context mContext;
public JobAdaptor(Context context, JobDetails[] jobs) {
mContext = context;
mJobs = jobs;
}
@Override
public int getCount() {
return mJobs.length;
}
@Override
public Object getItem(int i) {
return mJobs[i];
}
@Override
public long getItemId(int i) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = LayoutInflater.from(mContext).inflate(R.layout.job_list_items, null);
holder = new ViewHolder();
holder.titleLabel = (TextView) convertView.findViewById(R.id.titleTextView);
holder.salaryLabel = (TextView) convertView.findViewById(R.id.salaryTextView);
convertView.setTag(holder);
}
else {
holder = (ViewHolder) convertView.getTag();
}
JobDetails job = mJobs[position];
holder.titleLabel.setText(job.getTitles() + "");
holder.salaryLabel.setText(job.getSalary() + "");
if (position == 0) {
holder.titleLabel.setText("Noting to show ");
holder.titleLabel.setText(" ");
}
return convertView;
}
private static class ViewHolder {
TextView titleLabel;
TextView salaryLabel;
}
}
JobDetails类：
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.efe.efeAlumni.Model.JobDetails;
import com.efe.efeAlumni.R;
public class JobAdaptor extends BaseAdapter {
private JobDetails[] mJobs;
private Context mContext;
public JobAdaptor(Context context, JobDetails[] jobs) {
mContext = context;
mJobs = jobs;
}
@Override
public int getCount() {
return mJobs.length;
}
@Override
public Object getItem(int i) {
return mJobs[i];
}
@Override
public long getItemId(int i) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
// brand new
convertView = LayoutInflater.from(mContext).inflate(R.layout.job_list_items, null);
holder = new ViewHolder();
holder.titleLabel = (TextView) convertView.findViewById(R.id.titleTextView);
holder.salaryLabel = (TextView) convertView.findViewById(R.id.salaryTextView);
convertView.setTag(holder);
}
else {
holder = (ViewHolder) convertView.getTag();
}
JobDetails job = mJobs[position];
holder.titleLabel.setText(job.getTitles() + "");
holder.salaryLabel.setText(job.getSalary() + "");
if (position == 0) {
holder.titleLabel.setText("Noting to show ");
holder.titleLabel.setText(" ");
}
return convertView;
}
private static class ViewHolder {
TextView titleLabel;
TextView salaryLabel;
}
}