Android自定义载体标签nullpointerexception

Question

我已经将AOKP的自定义载体标签选项添加到我的ROM中，并且一切正常，但在对话框窗口中单击确定时获取设置fc除外...自定义标签文本摘要已正确更新，载体被改变，因为它应该是...

Settings.java：

package com.android.settings.cyanogenmod; 

import android.app.AlertDialog; 
import android.content.ContentResolver; 
import android.content.Context; 
import android.content.pm.PackageManager.NameNotFoundException; 
import android.os.Bundle; 
import android.content.ContentResolver; 
import android.content.Context; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.os.RemoteException; 
import android.os.ServiceManager; 
import android.view.IWindowManager; 
import android.preference.CheckBoxPreference; 
import android.preference.Preference; 
import android.preference.PreferenceScreen; 
import android.provider.Settings; 
import android.preference.CheckBoxPreference; 
import android.preference.ListPreference; 
import android.preference.Preference; 
import android.preference.PreferenceActivity; 
import android.preference.PreferenceGroup; 
import android.preference.PreferenceScreen; 
import android.preference.Preference.OnPreferenceChangeListener; 
import android.provider.Settings; 
import android.text.Spannable; 
import android.util.Log; 
import android.view.IWindowManager; 
import android.view.Display; 
import android.view.LayoutInflater; 
import android.widget.EditText; 

import com.android.settings.R; 
import com.android.settings.SettingsPreferenceFragment; 
import com.android.settings.Utils; 

import java.util.regex.Matcher; 
import java.util.regex.Pattern; 

public class SystemSettings extends SettingsPreferenceFragment implements 
    Preference.OnPreferenceChangeListener{ 

private static final String TAG = "SystemSettings"; 

private static final String KEY_POWER_BUTTON_TORCH = "power_button_torch"; 

private CheckBoxPreference mPowerButtonTorch; 
private static final String KEY_CHRONUS = "chronus"; 
private static final String PREF_FORCE_DUAL_PANEL = "force_dualpanel"; 
private static final String PREF_CUSTOM_CARRIER_LABEL = "custom_carrier_label"; 

Preference mCustomLabel; 

Context mContext; 

String mCustomLabelText = null; 

CheckBoxPreference mDualpane; 
private boolean torchSupported() { 
    return getResources().getBoolean(R.bool.has_led_flash); 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    // Load the preferences from an XML resource 
    addPreferencesFromResource(R.xml.system_settings); 

    mCustomLabel = findPreference(PREF_CUSTOM_CARRIER_LABEL); 
    updateCustomLabelTextSummary(); 

    // Dont display the lock clock preference if its not installed 
    removePreferenceIfPackageNotInstalled(findPreference(KEY_CHRONUS)); 

    mPowerButtonTorch = (CheckBoxPreference) findPreference(KEY_POWER_BUTTON_TORCH); 
    if (torchSupported()) { 
     mPowerButtonTorch.setChecked((Settings.System.getInt(getActivity(). 
       getApplicationContext().getContentResolver(), 
       Settings.System.POWER_BUTTON_TORCH, 0) == 1)); 
    } else { 
     getPreferenceScreen().removePreference(mPowerButtonTorch); 
    } 

    mDualpane = (CheckBoxPreference) findPreference(PREF_FORCE_DUAL_PANEL); 
     mDualpane.setOnPreferenceChangeListener(this); 

} 

@Override 
public void onResume() { 
    super.onResume(); 
} 

@Override 
public void onPause() { 
    super.onPause(); 
} 

@Override 
public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) { 
    if (preference == mPowerButtonTorch) { 
     boolean enabled = mPowerButtonTorch.isChecked(); 
     Settings.System.putInt(getContentResolver(), Settings.System.POWER_BUTTON_TORCH, 
       enabled ? 1 : 0); 
     return true; 
    } else if (preference == mCustomLabel) { 
     AlertDialog.Builder alert = new AlertDialog.Builder(getActivity()); 

     alert.setTitle(R.string.custom_carrier_label_title); 
     alert.setMessage(R.string.custom_carrier_label_explain); 

     // Set an EditText view to get user input 
     final EditText input = new EditText(getActivity()); 
     input.setText(mCustomLabelText != null ? mCustomLabelText : ""); 

     alert.setView(input); 
     alert.setPositiveButton(getResources().getString(R.string.ok), new DialogInterface.OnClickListener() { 

      public void onClick(DialogInterface dialog, int whichButton) { 
       String value = ((Spannable) input.getText()).toString(); 
       Settings.System.putString(getActivity().getContentResolver(), 
         Settings.System.CUSTOM_CARRIER_LABEL, value); 
       updateCustomLabelTextSummary(); 
       Intent i = new Intent(); 
       i.setAction("com.android.settings.LABEL_CHANGED"); 
       mContext.sendBroadcast(i); 
      } 
     }); 

     alert.setNegativeButton(getResources().getString(R.string.cancel), new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int whichButton) { 
       // Canceled. 
      } 
     }); 

     alert.show(); 
    } 
    return super.onPreferenceTreeClick(preferenceScreen, preference); 
} 

public boolean onPreferenceChange(Preference preference, Object objValue) { 
    ContentResolver cr = getActivity().getContentResolver(); 

    if (preference == mDualpane) { 
     Settings.System.putInt(getActivity().getContentResolver(), 
       Settings.System.FORCE_DUAL_PANEL, 
       ((CheckBoxPreference)preference).isChecked() ? 0 : 1); 
     return true; 
    } 
    return false; 
} 

private boolean removePreferenceIfPackageNotInstalled(Preference preference) { 
    String intentUri=((PreferenceScreen) preference).getIntent().toUri(1); 
    Pattern pattern = Pattern.compile("component=([^/]+)/"); 
    Matcher matcher = pattern.matcher(intentUri); 

    String packageName=matcher.find()?matcher.group(1):null; 
    if(packageName != null) { 
     try { 
      getPackageManager().getPackageInfo(packageName, 0); 
     } catch (NameNotFoundException e) { 
      Log.e(TAG,"package "+packageName+" not installed, hiding preference."); 
      getPreferenceScreen().removePreference(preference); 
      return true; 
     } 
    } 
    return false; 
} 

private void updateCustomLabelTextSummary() { 
    mCustomLabelText = Settings.System.getString(getActivity().getContentResolver(), 
      Settings.System.CUSTOM_CARRIER_LABEL); 
    if (mCustomLabelText == null || mCustomLabelText.length() == 0) { 
     mCustomLabel.setSummary(R.string.custom_carrier_label_notset); 
    } else { 
     mCustomLabel.setSummary(mCustomLabelText); 
    } 
} 

}

的logcat：

W/System.err(13551): Removed 2131231241 
W/System.err(13551): Removed 2131231255 
D/dalvikvm(3528): GC_CONCURRENT freed 384K, 16% free 2993K/3552K, paused 2ms+4ms, total 33ms 
D/dalvikvm(13551): GC_CONCURRENT freed 190K, 10% free 3282K/3644K, paused 2ms+8ms, total 37ms 
D/AndroidRuntime(13551): Shutting down VM 
W/dalvikvm(13551): threadid=1: thread exiting with uncaught exception (group=0x40d12600) 
E/AndroidRuntime(13551): FATAL EXCEPTION: main 
E/AndroidRuntime(13551): java.lang.NullPointerException 
E/AndroidRuntime(13551): at com.android.settings.cyanogenmod.SystemSettings$1.onClick(SystemSettings.java:143) 
E/AndroidRuntime(13551): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) 
E/AndroidRuntime(13551): at android.os.Handler.dispatchMessage(Handler.java:99) 
E/AndroidRuntime(13551): at android.os.Looper.loop(Looper.java:137) 
E/AndroidRuntime(13551): at android.app.ActivityThread.main(ActivityThread.java:5191) 
E/AndroidRuntime(13551): at java.lang.reflect.Method.invokeNative(Native Method) 
E/AndroidRuntime(13551): at java.lang.reflect.Method.invoke(Method.java:511) 
E/AndroidRuntime(13551): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795) 
E/AndroidRuntime(13551): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562) 
E/AndroidRuntime(13551): at dalvik.system.NativeStart.main(Native Method) 
W/ActivityManager(1108): Force finishing activity com.android.settings/.SubSettings 
W/ActivityManager(1108): Activity pause timeout for ActivityRecord{40ff74b8 u0 com.android.settings/.SubSettings} 
D/dalvikvm(13124): GC_FOR_ALLOC freed 411K, 22% free 3616K/4608K, paused 28ms, total 34ms 
I/Process (13551): Sending signal. PID: 13551 SIG: 9 
W/InputDispatcher(1108): channel '41188140 com.android.settings/com.android.settings.SubSettings (server)' ~ Consumer closed input channel or an error occurred. events=0x9 
I/WindowState(1108): WIN DEATH: Window{41369d90 u0 com.android.settings/com.android.settings.SubSettings} 
I/ActivityManager(1108): Process com.android.settings (pid 13551) has died. 
E/InputDispatcher(1108): channel '41188140 com.android.settings/com.android.settings.SubSettings (server)' ~ Channel is unrecoverably broken and will be disposed! 
W/InputDispatcher(1108): channel '40ffd998 com.android.settings/com.android.settings.Settings (server)' ~ Consumer closed input channel or an error occurred. events=0x9 
E/InputDispatcher(1108): channel '40ffd998 com.android.settings/com.android.settings.Settings (server)' ~ Channel is unrecoverably broken and will be disposed! 
W/InputDispatcher(1108): Attempted to unregister already unregistered input channel '41188140 com.android.settings/com.android.settings.SubSettings (server)' 
W/InputDispatcher(1108): Attempted to unregister already unregistered input channel '40ffd998 com.android.settings/com.android.settings.Settings (server)' 
I/WindowState(1108): WIN DEATH: Window{41188140 u0 com.android.settings/com.android.settings.SubSettings} 
I/WindowState(1108): WIN DEATH: Window{40ffd998 u0 com.android.settings/com.android.settings.Settings} 
I/ActivityManager(1108): Start proc com.android.settings for activity com.android.settings/.Settings: pid=13575 uid=1000 gids={41000, 1015, 1028, 3002, 3001, 3003, 3007} 
W/WindowManager(1108): Rebuild removed 7 windows but added 6 
W/WindowManager(1108): This window was lost: Window{41369d90 u0 com.android.settings/com.android.settings.SubSettings EXITING} 
W/WindowManager(1108): mDisplayId=0 mSession=Session{41e7d3b0 13551:1000} mClient=android.os.BinderProxy@4108dde8 

线143如下：

mContext.sendBroadcast(i); 

人有一个想法，什么怎么回事？

Answer 1

mContext是null，因为它是在班级的顶部宣布的，但从未给过任何东西。

你很可能getActivity()代替mContext因为这是一个Fragment和Activity是Context子类。

这意味着

mContext.sendBroadcast(i); 

应该

getActivity().sendBroadcast(i);