当我使用NullPointerException
获取布尔值以确定是否将使用BroadcastReceiver
时,我收到ImageButton
。我不知道为什么以及我所看过的所有教程都没有帮助。
这是我的代码调用服务并调用onReceive
//start full day timer service for natural disasters
startService(new Intent(runGraphics.this, NaturalDisaster.class));
//stop full day timer service for natural disasters
stopService(new Intent(runGraphics.this, NaturalDisaster.class));
meteorAndStormStatus = new BroadcastReceiver()
{
@Override
public void onReceive(Context context, Intent intent)
{
meteorExists = intent.getBooleanExtra("meteorStat", false);
Toast.makeText(getApplicationContext(), "Here we are: " + meteorExists, Toast.LENGTH_SHORT).show();
if (meteorExists == true)
{
//on click listener for meteor
meteor = (ImageButton) findViewById(R.id.meteor);
meteor.setVisibility(View.VISIBLE);
meteor.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
if (wasMined == false)
{
meteorRockAmount += 50;
wasMined = true;
}//end if
}//end onClick function
});//end setOnClickListener
}//end if
}//end onReceive function
};//end meteorAndStormStatus BroadcastReceiver
LocalBroadcastManager.getInstance(getApplicationContext()).registerReceiver(meteorAndStormStatus, new IntentFilter("meteorStat"));
这是发送广播的代码
//send broadcast back that a meteor exists
Intent i = new Intent();
i.putExtra("meteorStat", true);
LocalBroadcastManager.getInstance(getApplicationContext()).sendBroadcast(i);
这是我的logcat:
06-06 23:30:22.318: E/AndroidRuntime(21714): FATAL EXCEPTION: main
06-06 23:30:22.318: E/AndroidRuntime(21714): java.lang.NullPointerException
06-06 23:30:22.318: E/AndroidRuntime(21714): at com.project.llb.runGraphics$1.onReceive(runGraphics.java:113)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.support.v4.content.LocalBroadcastManager.executePendingBroadcasts(LocalBroadcastManager.java:297)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.support.v4.content.LocalBroadcastManager.access$000(LocalBroadcastManager.java:46)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.support.v4.content.LocalBroadcastManager$1.handleMessage(LocalBroadcastManager.java:116)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.os.Handler.dispatchMessage(Handler.java:99)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.os.Looper.loop(Looper.java:130)
06-06 23:30:22.318: E/AndroidRuntime(21714): at android.app.ActivityThread.main(ActivityThread.java:3806)
06-06 23:30:22.318: E/AndroidRuntime(21714): at java.lang.reflect.Method.invokeNative(Native Method)
06-06 23:30:22.318: E/AndroidRuntime(21714): at java.lang.reflect.Method.invoke(Method.java:507)
06-06 23:30:22.318: E/AndroidRuntime(21714): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-06 23:30:22.318: E/AndroidRuntime(21714): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-06 23:30:22.318: E/AndroidRuntime(21714): at dalvik.system.NativeStart.main(Native Method)
另外,我使用onReceive在类的onPause()中取消注册接收器。任何帮助,将不胜感激。提前谢谢。
答案 0 :(得分:1)
问题是我有一个if语句if(meteorExists == false)并且在这个语句中我有meteor.setVisibility(View.INVISIBLE)。问题是,如果不首先访问原始if,则会产生NullPointerException。所以为了解决这个问题,我不得不包括一个meteor =(ImageButton)findViewById(R.id.meteor);在我试图将流星设置为隐形之前。谢谢你的帮助。你指出了我正确的方向。