Question

这是我的第一个问题，所以请耐心等待。

所以我尝试完成Swipe View，直到我尝试在Fragment中创建了这样的功能。我通过调用Fragment函数成为onClick方法中的NPE。所以这是我的代码

我的主要方法叫做PyramidActivity

import java.util.ArrayList;
import java.util.Locale;
import com.example.testsawa.R;
import com.example.testsawa.R.id;
import com.example.testsawa.R.layout;
import com.example.testsawa.R.menu;
import com.example.testsawa.R.string;
import android.app.ActionBar.Tab;
import android.app.ActionBar.TabListener;
import android.app.Activity;
import android.app.ActionBar;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.graphics.Color;
import android.support.v4.app.FragmentPagerAdapter;
import android.os.Bundle;
import android.os.IBinder;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
import android.support.v4.app.Fragment;



public class PyramidActivity extends FragmentActivity  {

 SectionsPagerAdapter mSectionsPagerAdapter;
 ViewPager mViewPager;
 ActionBar actionBar;
 PiramidFragmentA pirFraA;
 PiramidFragmentB pirFraB;
 PiramidFragmentC pirFraC;
 ImageButton ibOne;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_pyramid);
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    mViewPager.setOnPageChangeListener(new MyPageChangeListener());
    ibOne = (ImageButton) findViewById(R.id.imageButton1);
    ImageButton i = (ImageButton) findViewById(R.id.imageButton2);
}

public void imageClick(View view) { 
    switch (view.getId()) {
    case R.id.imageButton1:
        pirFraA.setIngredient("Test");//this coses a NPE 
        break;
    case R.id.imageButton2:

        break;
    case R.id.imageButton3:

        break;
    case R.id.imageButton4:

        break;
    case R.id.imageButton5:

        break;
    case R.id.imageButton6:

        break;
    case R.id.imageButton7:

        break;
    case R.id.imageButton8:

        break;
    case R.id.imageButton9:

        break;
    case R.id.imageButton10:

        break;
    case R.id.imageButton11:

        break;
    case R.id.imageButton12:

        break;
    default:
        break;
    }

}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    public SectionsPagerAdapter(android.support.v4.app.FragmentManager fm) {
        super(fm);
    }

    @Override
    public android.support.v4.app.Fragment getItem(int position) {
    if (position == 0) {
            return pirFraA = new PiramidFragmentA();
        }
        if (position == 1) {

            return pirFraB = new PiramidFragmentB();

        }
        if (position == 2) {

            return pirFraC = new PiramidFragmentC();
        }
            return null;    
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
        case 0:
            return getString(R.string.title_section1).toUpperCase(l);
        case 1:
            return getString(R.string.title_section2).toUpperCase(l);
        case 2:
            return getString(R.string.title_section3).toUpperCase(l);
        }
        return null;
    }

}

public class MyPageChangeListener implements OnPageChangeListener  {

    @Override
    public void onPageScrollStateChanged(int arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onPageSelected(int arg0) {
        // TODO Auto-generated method stub

    }

}

}

所以我的Fragment类就像这样

import java.util.ArrayList;

import com.example.testsawa.R;
import com.example.testsawa.R.layout;

import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebView.FindListener;
import android.widget.ImageButton;
import android.widget.Toast;

public class PiramidFragmentA extends Fragment {
private ArrayList<String> ingredientsList;
private ImageButton ibOne;
View view;
boolean isPressed = true;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.fragment_piramid_fragment_a,  container,false);
    ibOne =(ImageButton) view.findViewById(R.id.imageButton3);
    return view; 
}

public void setIngredient(String ing){

    ingredientsList.add(ing);

}
public ArrayList<String> getIngredient(){

    return ingredientsList;

}

}

我的Logcat看起来像这样

    08-23 14:51:29.950: E/AndroidRuntime(1794):     FATAL EXCEPTION: main
    08-23 14:51:29.950: E/AndroidRuntime(1794):     java.lang.IllegalStateException: Could not execute method of the activity
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.view.View$1.onClick(View.java:3633)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.view.View.performClick(View.java:4240)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.view.View$PerformClick.run(View.java:17721)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.os.Handler.handleCallback(Handler.java:730)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.os.Handler.dispatchMessage(Handler.java:92)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.os.Looper.loop(Looper.java:137)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.app.ActivityThread.main(ActivityThread.java:5103)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invokeNative(Native Method)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invoke(Method.java:525)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at dalvik.system.NativeStart.main(Native Method)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     Caused by: java.lang.reflect.InvocationTargetException
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invokeNative(Native Method)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invoke(Method.java:525)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at android.view.View$1.onClick(View.java:3628)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     ... 11 more
    08-23 14:51:29.950: E/AndroidRuntime(1794):     Caused by: java.lang.NullPointerException
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at de.piramid.testsawa.PiramidFragmentA.setIngredient(PiramidFragmentA.java:39)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     at de.piramid.testsawa.PyramidActivity.imageClick(PyramidActivity.java:61)
    08-23 14:51:29.950: E/AndroidRuntime(1794):     ... 14 more

我在Fragment类中尝试过onCLik方法，即使它没有用。我希望我能很好地编辑我的问题，你可以帮助我。所以在那之前。

Answer 1

你的ingredientsList变量为null，因此你得到了这个NullPointerException。

08-23 14:51:29.950: E/AndroidRuntime(1794):     Caused by: java.lang.NullPointerException
08-23 14:51:29.950: E/AndroidRuntime(1794):     at de.piramid.testsawa.PiramidFragmentA.setIngredient(PiramidFragmentA.java:39)

你应该初始化这个变量（这只是一个例子）：

public class PiramidFragmentA extends Fragment {

    private ArrayList<String> ingredientsList;

    /** ... */        

    public void setIngredient(String ing){
        if(ingredientsList == null) {
             ingredientsList = new ArrayList<String>();
        }
        ingredientsList.add(ing);

    }
}

Android ViewPager NullPointerException通过调用方法

1 个答案: