我在Android Studio上开发的应用程序android发生崩溃，在日志中，我收到此错误消息(logs):
04-26 16:58:12.393 31024-31024/com.example.nicol.etablissement43 D/AbsListView: checkAbsListViewlLogProperty get invalid command
04-26 16:58:12.394 31024-31024/com.example.nicol.etablissement43 D/AndroidRuntime: Shutting down VM
04-26 16:58:12.395 31024-31024/com.example.nicol.etablissement43 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nicol.etablissement43, PID: 31024
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.nicol.etablissement43/com.example.nicol.etablissement43.recherche_2}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2521)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2595)
at android.app.ActivityThread.access$800(ActivityThread.java:178)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5631)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.example.nicol.etablissement43.recherche_2.onCreate(recherche_2.java:74)
at android.app.Activity.performCreate(Activity.java:6092)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1112)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2468)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2595)
at android.app.ActivityThread.access$800(ActivityThread.java:178)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5631)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)
这是我的课:
package com.example.nicol.etablissement43;
import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.params.HttpConnectionParams;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
/**
* Created by nicol on 25/04/2017.
*/
public class recherche_2 extends AppCompatActivity {
private static final String LOG_TAG = "Selection Ville";
private ListView Ville;
private ArrayAdapter<String> listAdapter ;
private AdapterClient adapterClient ;
private TextView SQLData;
@Override/*
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.recherche_2);
}*/
protected void onCreate(Bundle savedInstanceState) {
{
if (Build.VERSION.SDK_INT > 8) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
super.onCreate(savedInstanceState);
String page = this.getPage("http://appec43.890m.com/connectionbddandroid/config.inc.php");
Log.i("ContenuPost", page);
setContentView(R.layout.recherche_2);
Ville = (ListView) findViewById(R.id.Ville);
SQLData.setText("Les villes");
SQLData.setText("Les villes");
//String[] planets = new String[] {""};
// ArrayList<String> planetList = new ArrayList<String>();
// planetList.addAll( Arrays.asList(planets) );
//listAdapter = new ArrayAdapter<String>(this, R.layout.simplerow, planetList);
adapterClient = new AdapterClient(this, R.layout.recherche_2);
try {
JSONArray jsonArray = new JSONArray(page);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
client clientobj = new client();
clientobj.setIdVille(jsonObject.getString("Ville"));
clientobj.setCodepostal(jsonObject.getString("codepostal"));
adapterClient.add(clientobj);
}
} catch (JSONException e) {
e.printStackTrace();
}
/*
String[] split = page.split(",");
for (int i = 0; i < split.length; i++) {
listAdapter.add( split[i] );
if (i != split.length - 1) {
listAdapter.add(" ");
}
}
*/
Ville.setAdapter(adapterClient);
}
}
public String getPage(String adresse){
StringBuffer stringBuffer = new StringBuffer("");
BufferedReader bufferedReader = null;
try {
HttpClient httpClient = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(httpClient.getParams(), 15000);
HttpPost httpPost = new HttpPost();
URI uri = new URI(adresse);
httpPost.setURI(uri);
List<NameValuePair> parametres = new ArrayList<NameValuePair>();
parametres.add(new BasicNameValuePair("login", "u265740438_root2"));
parametres.add(new BasicNameValuePair("pass", "nicolas"));
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parametres);
httpPost.setEntity(formEntity);
HttpResponse httpResponse = httpClient.execute(httpPost);
InputStream inputStream = httpResponse.getEntity().getContent();
bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
String ligneLue = bufferedReader.readLine();
while (ligneLue != null) {
Log.i("Valeur", ligneLue);
stringBuffer.append(ligneLue);
stringBuffer.append("\n");
ligneLue = bufferedReader.readLine();
}
}
catch(Exception e) {
Log.e("Erreur", e.getMessage());
}
finally{
if(bufferedReader != null){
try{
bufferedReader.close();
}
catch (IOException e){
}
}
}
return stringBuffer.toString();
}
}
这是我的布局:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="Villes"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/SQLData"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginLeft="52dp"
android:layout_marginStart="52dp" />
<ListView
android:id="@+id/Ville"
style="@style/Widget.AppCompat.Light.ListView.DropDown"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_below="@+id/textView"
android:layout_marginTop="24dp" />
有人会找到解决方案，因为我一直在寻找答案已经有一段时间了
先感谢您
最佳答案
您需要初始化SQLData textView。
像这样SQLData = (TextView)findViewById(R.id.SQLData)方法中的onCreate。