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\問題は、ベストシグナルを検出しているときにWifiScannerクラスに表示されるNullPointerExceptionに関するものです。NullPointerException
java.lang.RuntimeException: Unable to start activity
ComponentInfo{project.e.wifiactivity/project.e.wifiactivity.WifiConnector}:
java.lang.NullPointerException: Attempt to invoke virtual method
'java.lang.String android.net.wifi.ScanResult.toString()'
\
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method
'java.lang.String android.net.wifi.ScanResult.toString()' on a null object reference
at
project.e.wifiactivity.WifiScanner.bestReturn(WifiScanner.java:46)
at
project.e.wifiactivity.WifiConnector.onCreate(WifiConnector.java:23)
Logcat MainActivityクラス /パッケージproject.e.wifiactivity \
03-30 04:26:07.351 26037-26037/? I/art﹕ Late-enabling -Xcheck:jni
03-30 04:26:07.522 26037-26059/project.e.wifiactivity D/OpenGLRenderer﹕ Use EGL_SWAP_BEHAVIOR_PRESERVED: true
03-30 04:26:07.525 26037-26037/project.e.wifiactivity D/﹕ HostConnection::get() New Host Connection established 0xf3e5c7b0, tid 26037
03-30 04:26:07.536 26037-26037/project.e.wifiactivity D/Atlas﹕ Validating map...
03-30 04:26:07.573 26037-26059/project.e.wifiactivity D/libEGL﹕ loaded /system/lib/egl/libEGL_emulation.so
03-30 04:26:07.574 26037-26059/project.e.wifiactivity D/libEGL﹕ loaded /system/lib/egl/libGLESv1_CM_emulation.so
03-30 04:26:07.596 26037-26059/project.e.wifiactivity D/libEGL﹕ loaded /system/lib/egl/libGLESv2_emulation.so
03-30 04:26:07.607 26037-26059/project.e.wifiactivity D/﹕ HostConnection::get() New Host Connection established 0xeec393f0, tid 26059
03-30 04:26:07.628 26037-26059/project.e.wifiactivity I/OpenGLRenderer﹕ Initialized EGL, version 1.4
03-30 04:26:07.672 26037-26059/project.e.wifiactivity D/OpenGLRenderer﹕ Enabling debug mode 0
03-30 04:26:07.692 26037-26059/project.e.wifiactivity W/EGL_emulation﹕ eglSurfaceAttrib not implemented
03-30 04:26:07.692 26037-26059/project.e.wifiactivity W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xeec38740, error=EGL_SUCCESS
03-30 04:26:09.662 26037-26059/project.e.wifiactivity W/EGL_emulation﹕ eglSurfaceAttrib not implemented
03-30 04:26:09.662 26037-26059/project.e.wifiactivity W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xf3d0cc60, error=EGL_SUCCESS
03-30 04:26:27.858 26037-26037/project.e.wifiactivity D/WifiDemo﹕ onCreate()
03-30 04:26:27.936 26037-26059/project.e.wifiactivity W/EGL_emulation﹕ eglSurfaceAttrib not implemented
03-30 04:26:27.936 26037-26059/project.e.wifiactivity W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xf3e840a0, error=EGL_SUCCESS
03-30 04:26:28.130 26037-26037/project.e.wifiactivity D/AndroidRuntime﹕ Shutting down VM
03-30 04:26:28.130 26037-26037/project.e.wifiactivity E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: project.e.wifiactivity, PID: 26037
java.lang.RuntimeException: Unable to start activity ComponentInfo{project.e.wifiactivity/project.e.wifiactivity.WifiConnector}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.wifi.ScanResult.toString()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
**strong text**Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.wifi.ScanResult.toString()' on a null object reference**
at project.e.wifiactivity.WifiScanner.bestReturn(WifiScanner.java:46)
at project.e.wifiactivity.WifiConnector.onCreate(WifiConnector.java:23)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
\;
無線LANスキャナクラス\import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.util.List;
public class MainActivity extends AppCompatActivity implements View.lickListener {
private static final String TAG="WifiDemo";
WifiManager wifi;
BroadcastReceiver receiver;
public Login login = new Login();
TextView text;
Button btn;
Button buttonp;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text=(TextView)findViewById(R.id.text);
btn=(Button)findViewById(R.id.btn);
Button enb = (Button) findViewById(R.id.enb); v
final WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
enb.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!wifiManager.isWifiEnabled()) {
wifiManager.setWifiEnabled(true);
Toast.makeText(MainActivity.this, "Wifi Enabled", Toast.LENGTH_LONG).show();
}
}
});
buttonp = (Button) findViewById(R.id.buttonp);
buttonp.setOnClickListener(this);
Intent l = new Intent(this, WifiConnector.class);
startActivity(l);
btn.setOnClickListener(this);
//get wifi status
wifi=(WifiManager)getSystemService(Context.WIFI_SERVICE);
WifiInfo info=wifi.getConnectionInfo();
String name = info.getSSID();
String macid = info.getMacAddress();
text.append("\n\nWifi Name :"+ name +"\nMac Id :"+ macid);
//list available network
List<WifiConfiguration> configurations= wifi.getConfiguredNetworks();
for(WifiConfiguration configuration : configurations){
text.append("\n\n" +configuration.SSID+"\n"+configuration.BSSID);
}
//register broadcast receiver
if(receiver==null) {
receiver = new WifiScanner();
registerReceiver(receiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
Log.d(TAG, "onCreate()");
}
}
@Override
protected void onStop() {
try {
this.unregisterReceiver(receiver);
super.onStop();
} catch (IllegalArgumentException f) {
f.printStackTrace();
}
}
@Override
protected void onPause() {
try {
super.onPause();
unregisterReceiver(receiver);
} catch (IllegalArgumentException e) {
e.printStackTrace();
}
}
@Override
protected void onResume() {
super.onResume();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
registerReceiver(receiver, intentFilter);
int f = login.resultp();
if (f == 1) {
Intent l = new Intent(this, MainActivity.class);
startActivity(l);
}
}
@Override
public void onClick(View view) {
Toast.makeText(getApplicationContext(), "All Network Searched!!", 0).show();
if (R.id.btn == view.getId()){
Log.d(TAG, "onCreate() wifi.startScan()");
wifi.startScan();
}
}
}
package project.e.wifiactivity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import android.util.Log;
import android.widget.Toast;
import java.util.List;
public class WifiScanner extends BroadcastReceiver {
public ScanResult bestsignal ;
private static final String TAG="WifiScanReceiver";
MainActivity main;
@Override
public void onReceive(Context arg0, Intent arg1) {
List<ScanResult> results = main.wifi.getScanResults();
for(ScanResult result : results) {
if(bestsignal == null || WifiManager.compareSignalLevel(bestsignal.level, result.level)<0)
bestsignal = result;
bestReturn();
}
String message=String.format("%s networks found.%s is the strongest.", results.size(), bestsignal.SSID);
Toast.makeText(main, message, 0).show();
Log.d(TAG, "onReceive() message :"+message);
}
public String bestReturn() {
return bestsignal.toString();
}
}
package project.e.wifiactivity;
import android.app.Activity;
import android.content.Context;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import java.util.List;
public class WifiConnector extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WifiScanner wifiscannner = new WifiScanner();
String bestnetSSID = wifiscannner.bestReturn();
String networkPass = "pass";
WifiConfiguration conf = new WifiConfiguration();
conf.SSID = "\"" + bestnetSSID + "\"";
conf.preSharedKey = "\"" + networkPass + "\"";
WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
wifiManager.addNetwork(conf);
List<WifiConfiguration> list = wifiManager.getConfiguredNetworks();
for (WifiConfiguration i : list) {
if (i.SSID != null && i.SSID.equals("\"" + bestnetSSID + "\"")) {
wifiManager.disconnect();
wifiManager.enableNetwork(i.networkId, true);
wifiManager.reconnect();
break;
}
}
}
}
マニフェスト
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="project.e.wifiactivity" >
<uses-feature android:name="android.hardware.wifi" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.UPDATE_DEVICE_STATS" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<application
android:debuggable="true"
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".Display"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Login"></activity>
<activity android:name=".MainActivity"></activity>
<activity android:name=".WifiConnector"></activity>
</application>
</manifest>
をエラーが原因でnullオブジェクトである...あなたのScanResultが –
nullである私が欲しい、私はそれを理解しますが、何がScanResultを初期化する適切な方法かもしれませんそれを知る。 – user3537196