Android应用内结算应用无法运行

Question

I'm attempting to build a simple Android app using In-App Billing. I'm using a Nexus 7 2013 device to run and debug it. I just get the error message, "Unfortunately, your app has stopped." I've tried logging and inserting breakpoints, but it never even seems to get to the beginning of the code. I'm using this tutorial and this one , and have only started working with them. My code:

package com.myknitcards.project;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.myknitcards.project.util.IabHelper;
import com.myknitcards.project.util.IabResult;
import com.myknitcards.project.util.Inventory;
import com.myknitcards.project.util.Purchase;


public class MainActivity extends Activity {
    private Button clickButton = (Button)findViewById(R.id.clickButton);
    private Button buyButton = (Button)findViewById(R.id.buyButton);

    private static final String TAG = "com.myknitcards.project";
    IabHelper mHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main); 

        clickButton.setEnabled(false);

        String base64EncodedPublicKey = 
                "mykeyhere";

        mHelper = new IabHelper(this, base64EncodedPublicKey);

        mHelper.startSetup(new 
                IabHelper.OnIabSetupFinishedListener() {
                     public void onIabSetupFinished(IabResult result) 
                 {
                           if (!result.isSuccess()) {
                             Log.d(TAG, "In-app Billing setup failed: " + 
                        result);
                           } else {             
                             Log.d(TAG, "In-app Billing is set up OK");
                       }
                         }
                });
    }

    public void buttonClicked(View view) {
        clickButton.setEnabled(false);
        buyButton.setEnabled(true);
    }
}

My LogCat reads:

10-14 17:30:07.458: D/AndroidRuntime(10207): Shutting down VM 10-14 17:30:07.458: W/dalvikvm(10207): threadid=1: thread exiting with uncaught exception (group=0x41be2ba8) 10-14 17:30:07.458: E/AndroidRuntime(10207): FATAL EXCEPTION: main 10-14 17:30:07.458: E/AndroidRuntime(10207): Process: com.myknitcards.project, PID: 10207 10-14 17:30:07.458: E/AndroidRuntime(10207): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.myknitcards.project/com.myknitcards.project.MainActivity}: java.lang.NullPointerException 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread.access$800(ActivityThread.java:135) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread$H.handleMessage(ActivityThrea d.java:1196) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.os.Handler.dispatchMessage(Handler.java:102) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.os.Looper.loop(Looper.java:136) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread.main(ActivityThread.java:5001) 10-14 17:30:07.458: E/AndroidRuntime(10207): at java.lang.reflect.Method.invokeNative(Native Method) 10-14 17:30:07.458: E/AndroidRuntime(10207): at java.lang.reflect.Method.invoke(Method.java:515) 10-14 17:30:07.458: E/AndroidRuntime(10207): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 10-14 17:30:07.458: E/AndroidRuntime(10207): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 10-14 17:30:07.458: E/AndroidRuntime(10207): at dalvik.system.NativeStart.main(Native Method) 10-14 17:30:07.458: E/AndroidRuntime(10207): Caused by: java.lang.NullPointerException 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.Activity.findVie wById(Activity.java:1884) 10-14 17:30:07.458: E/AndroidRuntime(10207): at com.myknitcards.project.MainActivity.(MainActivity.java:24) 10-14 17:30:07.458: E/AndroidRuntime(10207): at java.lang.Class.newInstanceImpl(Native Method) 10-14 17:30:07.458: E/AndroidRuntime(10207): at java.lang.Class.newInstance(Class.java:1208) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101) 10-14 17:30:07.458: E/AndroidRuntime(10207): ... 11 more 10-14 17:30:10.701: I/Process(10207): Sending signal. PID: 10207 SIG: 9

I don't know where to even start. Why would it not be able to instantiate the activity? BTW, I have downloaded the TrivialDrive sample from Google's Developer site, and it will run on my tablet, so that's not the issue. Any suggestions are welcome.

Answer 1

Start with the last "Caused by" in the stack trace listing (that is the first exception):

Caused by: java.lang.NullPointerException 10-14 17:30:07.458: E/AndroidRuntime(10207): at android.app.Activity.findViewById(Activity.java:1884)

The doc says findViewById(int id) returns "The view if found or null otherwise." But it's not returning null, it's throwing NPE.

You could look at the source code for Activity.java:1884 or set an exception breakpoint to find out what null it's tripping over.

Perhaps it couldn't load the needed layout resources or manifest or other resources. Or maybe a resource is missing.

Here's a link to the source code for ?? version of Activity.java . It says:

public View findViewById(int id) {
    return getWindow().findViewById(id);
}

So getWindow() must be returning null . The doc says it returns "The current window, or null if the activity is not visual."

Apparently it thinks your main activity is not "visual." Is your main activity declared to be a Service?