java - Android 应用程序因 Fragment 中的 OnClickListener 崩溃

标签 java android android-fragments

我在构建我的第一个应用程序时遇到问题。我正在使用抽屉导航在 fragment 之间切换。但是当我从抽屉导航中选择 OrderFragment 时，应用程序崩溃了。

OrderFragment 只有一个按钮，单击时会显示 toast，但应用程序会在 OrderFragment 加载之前崩溃。

代码是:

MainActivity.java

package com.example.testcocogeek;

import android.app.Activity;
import android.app.Fragment;
import android.app.SearchManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class MainActivity extends Activity {


private String[] mListOptions; 
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;

private CharSequence mDrawerTitle;
private CharSequence mTitle;
private ActionBarDrawerToggle mDrawerToggle;

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

mTitle = mDrawerTitle = getTitle();
mListOptions = getResources().getStringArray(R.array.list_options);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);


// Set adapter for the list view
mDrawerList.setAdapter (new ArrayAdapter<String> (this,
R.layout.drawer_list_item, mListOptions));
// enable ActionBar app icon to behave as action to toggle nav drawer
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// Set the list click listener
mDrawerList.setOnItemClickListener (new DrawerItemClickListener());

// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(
        this,                  /* host Activity */
        mDrawerLayout,         /* DrawerLayout object */
        R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
        R.string.drawer_open,  /* "open drawer" description for accessibility */
        R.string.drawer_close  /* "close drawer" description for accessibility */
        ) {
    public void onDrawerClosed(View view) {
        getActionBar().setTitle(mTitle);
        invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
    }

    public void onDrawerOpened(View drawerView) {
        getActionBar().setTitle(mDrawerTitle);
        invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
    }
};
mDrawerLayout.setDrawerListener(mDrawerToggle);

if (savedInstanceState == null) {
    selectItem(0);
}
}    
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main, menu);
    return super.onCreateOptionsMenu(menu);
} 

/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    // If the nav drawer is open, hide action items related to the content view
    boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
    menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
    return super.onPrepareOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
     // The action bar home/up action should open or close the drawer.
     // ActionBarDrawerToggle will take care of this.
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }
    // Handle action buttons
    switch(item.getItemId()) {
    case R.id.action_websearch:
        // create intent to perform web search for this planet
        Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
        intent.putExtra(SearchManager.QUERY, "Cocogeek");
        // catch event that there's no activity to handle intent
        if (intent.resolveActivity(getPackageManager()) != null) {
            startActivity(intent);
        } else {
            Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
        }
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}

/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selectItem(position);
    }
}

// This method selects correct fragment.

private void selectItem(int position) {
    // update the main content by replacing fragments
    Fragment fragment = null;
    Bundle args = new Bundle();
    switch (position) {
    case 0:
          fragment = new CocogeekFragment();
          break;
    case 1:
          fragment = new OrderFragment();
          break;
    case 2:
          fragment = new LocatorFragment();
          break;
    case 3:
          fragment = new ContactFragment();

          break;
    default:
          break;
    }

    fragment.setArguments(args);
    android.app.FragmentManager frgManager = getFragmentManager();
    frgManager.beginTransaction().replace(R.id.content_frame, fragment)
                .commit();


    mDrawerList.setItemChecked(position, true);
    setTitle(mListOptions[position]);
    mDrawerLayout.closeDrawer(mDrawerList);
}

@Override
public void setTitle(CharSequence title) {
    mTitle = title;
    getActionBar().setTitle(mTitle);
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    // Pass any configuration change to the drawer toggles
    mDrawerToggle.onConfigurationChanged(newConfig);
}
}

OrderFragment.java

package com.example.testcocogeek;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class OrderFragment extends Fragment implements OnClickListener {


public OrderFragment() {
    // Empty constructor required for fragment subclasses
}

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

View mView = (View) inflater.inflate(R.layout.order_fragment, container, false);

// Initialize UI views.
final Button send = (Button) getActivity().findViewById(R.id.send);

//Initialize OnClick listener.
send.setOnClickListener(this);

return mView;

   }

@Override
public void onClick(View v) {

        Toast.makeText(getActivity(), "Clicked" ,Toast.LENGTH_LONG).show();


 }
}

activity_main.xml

<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFF5EE"
>
<!-- The main content view -->
<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
     >
</FrameLayout>
<!-- The navigation drawer -->
<ListView android:id="@+id/left_drawer"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="left"
    android:choiceMode="singleChoice"
    android:divider="@android:color/transparent"
    android:dividerHeight="0dp"
    android:background="#858585"/>
</android.support.v4.widget.DrawerLayout>

order_fragment.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Button
    android:id="@+id/send"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/send" 
    />

</LinearLayout>

logCat:

07-08 12:28:09.332: D/dalvikvm(30471): GC_FOR_ALLOC freed 165K, 2% free 16940K/17136K,     paused 15ms, total 15ms  
07-08 12:28:09.362: I/dalvikvm-heap(30471): Grow heap (frag case) to 35.315MB for 19655120-byte allocation  
07-08 12:28:09.372: D/dalvikvm(30471): GC_FOR_ALLOC freed 2K, 1% free 36132K/36332K, paused 11ms, total 11ms  
07-08 12:28:09.522: I/Adreno-EGL(30471): <qeglDrvAPI_eglInitialize:320>: EGL 1.4 QUALCOMM Build: I0404c4692afb8623f95c43aeb6d5e13ed4b30ddbDate: 11/06/13

07-08 12:28:09.542: D/OpenGLRenderer(30471): Enabling debug mode 0
07-08 12:28:11.852: D/AndroidRuntime(30471): Shutting down VM
07-08 12:28:11.852: W/dalvikvm(30471): threadid=1: thread exiting with uncaught exception (group=0x41625ba8)
07-08 12:28:11.862: E/AndroidRuntime(30471): FATAL EXCEPTION: main
07-08 12:28:11.862: E/AndroidRuntime(30471): Process: com.example.testcocogeek, PID: 30471
07-08 12:28:11.862: E/AndroidRuntime(30471): java.lang.NullPointerException
07-08 12:28:11.862: E/AndroidRuntime(30471): at com.example.testcocogeek.OrderFragment.onCreateView(OrderFragment.java:29)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.Fragment.performCreateView(Fragment.java:1700)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.BackStackRecord.run(BackStackRecord.java:684)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.os.Handler.handleCallback(Handler.java:733)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.os.Handler.dispatchMessage(Handler.java:95)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.os.Looper.loop(Looper.java:136)
07-08 12:28:11.862: E/AndroidRuntime(30471): at android.app.ActivityThread.main(ActivityThread.java:5001)
07-08 12:28:11.862: E/AndroidRuntime(30471): at java.lang.reflect.Method.invokeNative(Native Method)
07-08 12:28:11.862: E/AndroidRuntime(30471): at java.lang.reflect.Method.invoke(Method.java:515)
07-08 12:28:11.862: E/AndroidRuntime(30471): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
07-08 12:28:11.862: E/AndroidRuntime(30471): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
07-08 12:28:11.862: E/AndroidRuntime(30471): at dalvik.system.NativeStart.main(Native Method)
07-08 12:28:13.332: I/Process(30471): Sending signal. PID: 30471 SIG: 9

最佳答案

乍一看你应该替换:

final Button send = (Button) getActivity().findViewById(R.id.send);

与:

final Button send = (Button) mView.findViewById(R.id.send);

R.id.send id 包含在 Fragment View mView 中。

关于java - Android 应用程序因 Fragment 中的 OnClickListener 崩溃，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24629393/

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