Question

我写了一个扫描wifi连接的android应用程序。

我使用了以下代码

package com.android.wifitester;

import java.util.List; import android.app.Activity; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.net.wifi.ScanResult; import android.net.wifi.WifiManager; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.widget.TextView;

公共类WifiTester扩展Activity { TextView mainText; WifiManager mainWifi; WifiReceiver receiverWifi; 列表wifiList; StringBuilder sb = new StringBuilder（）;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mainText = (TextView) findViewById(R.id.mainText);
    mainWifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);

    receiverWifi = new WifiReceiver();
    registerReceiver(receiverWifi, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
    mainWifi.startScan();
    mainText.setText("\nStarting Scan...\n");
}

public boolean onCreateOptionsMenu(Menu menu) {
    menu.add(0, 0, 0, "Refresh");
    return super.onCreateOptionsMenu(menu);
}

public boolean onMenuItemSelected(int featureId, MenuItem item) {
    mainWifi.startScan();
    mainText.setText("Starting Scan");
    return super.onMenuItemSelected(featureId, item);
}

protected void onPause() {
    unregisterReceiver(receiverWifi);
    super.onPause();
}

protected void onResume() {
    registerReceiver(receiverWifi, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
    super.onResume();
}

class WifiReceiver extends BroadcastReceiver {
    public void onReceive(Context c, Intent intent) {
        sb = new StringBuilder();
        wifiList = mainWifi.getScanResults();
        for(int i = 0; i < wifiList.size(); i++){
            sb.append(new Integer(i+1).toString() + ".");
            sb.append((wifiList.get(i)).toString());
            sb.append("\n");
        }
        mainText.setText(sb);
    }
}

}

当我在模拟器上运行应用程序时，它崩溃了

清单文件是：

<?xml version="1.0" encoding="utf-8"?>

</application>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

<uses-sdk android:minSdkVersion="8" />

我的问题是为什么它崩溃了，虽然我添加了权限行

Answer 1

简短的回答是：模拟器不做wifi。

在模拟器和其他没有wifi的设备上，行

wifiList = mainWifi.getScanResults();

将导致wifiList为空。您应该检查一下，例如通过这样的try / catch块包围它：

try{ 
    wifiList = mainWifi.getScanResults();
    for(int i = 0; i < wifiList.size(); i++){
        sb.append(new Integer(i+1).toString() + ".");
        sb.append((wifiList.get(i)).toString());
        sb.append("\n");
    }
catch (NullPointerException e) {
    //Add dummy testdata to sb
}

android Wifi应用程序崩溃

1 个答案: