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How do I pass the position to my Activity from viewPager?

 原文  2015-07-06 17:20:43  3   1    android/ android-fragments/ android-viewpager

Question

I am trying to get the index/position of the image from my viewPager inside my SelectFragment which I dynamically added in one of my activity and then pass it to my activity using the interface that I have created in my activity to communicate with my SelectFragment class. I can get the toast when I call... 

new SelectFragment().chosenGuitarType(pos);

However, this line throws an error... 

mCallback.onGuitarSelected(position);

Here is my logcat... 

07-07 00:49:05.835    3403-3403/com.example.text.guitar E/InputEventReceiver﹕ Exception dispatching input event.
07-07 00:49:05.835    3403-3403/com.example.text.guitar E/MessageQueue-JNI﹕ Exception in MessageQueue callback: handleReceiveCallback
07-07 00:49:05.855    3403-3403/com.example.text.guitar E/MessageQueue-JNI﹕ java.lang.NullPointerException
        at com.example.text.guitar.SelectFragment.chosenGuitarType(SelectFragment.java:98)
        at com.example.text.guitar.SelectFragment.access$000(SelectFragment.java:24)
        at com.example.text.guitar.SelectFragment$TouchImageAdapter$1.onClick(SelectFragment.java:119)
        at android.view.View.performClick(View.java:4747)
        at com.example.text.guitar.TouchImageView$1.onTouch(TouchImageView.java:91)
        at android.view.View.dispatchTouchEvent(View.java:8186)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2332)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1616)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2665)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2280)
        at android.view.View.dispatchPointerEvent(View.java:8386)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4795)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4646)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4254)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4223)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4334)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4231)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4391)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4254)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4223)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4231)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6610)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6489)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6460)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6425)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6690)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:138)
        at android.os.Looper.loop(Looper.java:131)
        at android.app.ActivityThread.main(ActivityThread.java:5752)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.intern
07-07 00:49:05.855    3403-3403/com.example.text.guitar D/AndroidRuntime﹕ Shutting down VM
07-07 00:49:05.855    3403-3403/com.example.text.guitar W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4175fda0)
07-07 00:49:05.855    3403-3403/com.example.text.guitar E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.text.guitar, PID: 3403
java.lang.NullPointerException
        at com.example.text.guitar.SelectFragment.chosenGuitarType(SelectFragment.java:98)
        at com.example.text.guitar.SelectFragment.access$000(SelectFragment.java:24)
        at com.example.text.guitar.SelectFragment$TouchImageAdapter$1.onClick(SelectFragment.java:119)
        at android.view.View.performClick(View.java:4747)
        at com.example.text.guitar.TouchImageView$1.onTouch(TouchImageView.java:91)
        at android.view.View.dispatchTouchEvent(View.java:8186)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2477)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2209)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2332)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1616)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2665)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2280)
        at android.view.View.dispatchPointerEvent(View.java:8386)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4795)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4646)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4254)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4223)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4334)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4231)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4391)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4254)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4223)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4231)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4200)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6610)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6489)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6460)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6425)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6690)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:138)

And here's my fragment code: 

package com.example.text.guitar;
import android.app.Activity;
import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.Toast;


public class SelectFragment extends Fragment {

    private static final String ARG_SECTION_NUMBER = "section_number";
    private ExtendedViewPager mViewPager;
    static Activity thisActivity = null;
    private onGuitarSelectedListener mCallback;

    public static SelectFragment newInstance() {
        SelectFragment fragment = new SelectFragment();
        return fragment;
    }

    public SelectFragment() {
    }

    public interface onGuitarSelectedListener {
        public void onGuitarSelected(int position);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_select, container, false);
        mViewPager = (ExtendedViewPager) rootView.findViewById(R.id.view_pager);
        TouchImageAdapter touchImageAdapter = new TouchImageAdapter();
        mViewPager.setAdapter(new TouchImageAdapter());
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        thisActivity = activity;
        try {
            mCallback = (onGuitarSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnHeadlineSelectedListener");
        }
    }

    private void chosenGuitarType(int position) {
        Toast.makeText(thisActivity,
                "Your Message " + position, Toast.LENGTH_SHORT).show();
        mCallback.onGuitarSelected(position);

    }

    static class TouchImageAdapter extends PagerAdapter {

        private static int[] images = { R.drawable.guitar1, R.drawable.guitar2 };

        @Override
        public int getCount() {
            return images.length;
        }

        @Override
        public View instantiateItem(final ViewGroup container, int position) {
            final int pos = position;
            TouchImageView img = new TouchImageView(container.getContext());
            img.setImageResource(images[position]);
            img.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    new SelectFragment().chosenGuitarType(pos);
                }
            });
            container.addView(img, LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
            return img;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }
    }
}

My Activity Code: 

package com.example.text.guitar;


import android.app.Activity;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import android.widget.Toast;


public class MainActivity2Activity extends ActionBarActivity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks, SelectFragment.onGuitarSelectedListener {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_activity2);

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {
        // update the main content by replacing fragments
        FragmentManager fragmentManager = getSupportFragmentManager();
        if (position == 0) {
            fragmentManager.beginTransaction()
                    .replace(R.id.container, SelectFragment.newInstance())
                    .commit();
        }
    }

    public void onGuitarSelected(int position) {
        Toast.makeText(thisActivity,
                    "Position: " + position, Toast.LENGTH_SHORT).show();
    }

    public void onSectionAttached(int number) {
        switch (number) {
            case 1:
                mTitle = getString(R.string.title_home);
                break;
            case 2:
                mTitle = getString(R.string.title_primary);
                break;
            case 3:
                mTitle = getString(R.string.title_bookmarks);
                break;
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.main_activity2, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

}

Am I doing this right? I would like to pass the position back to my activity.

1 answers

solution1
 0  2015-07-07 17:39:54

I've managed to solve my own problem.

I changed my click listener to... 

img.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        SelectFragment fragment = (SelectFragment) thisActivity.getFragmentManager().findFragmentById(R.id.container);
        fragment.chosenGuitarType(position);
    }
});

If anyone is curious, this is the library I am using. I implemented an image slider with a click listener so I can click to go to another activity/fragment. https://github.com/MikeOrtiz/TouchImageView

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