void android.support.v4.app.Fragment.setMenuVisibility（boolean）' on a null object reference
2022-09-01 21:59:17
只有在我开始在项目中使用片段后，错误才开始出现
这是我的代码..
public class MainActivity extends AppCompatActivity {
private Toolbar toolbar;
private ViewPager mPager;
private SlidingTabLayout mTabs;
private MyPagerAdapter adapter;
public static final int product_result = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(toolbar);
assert getSupportActionBar() != null;
getSupportActionBar().setDisplayShowHomeEnabled(true);
NavigationDrawerFragment navigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.fragment_nav_drawer);
navigationDrawerFragment.setUp(R.id.fragment_nav_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), toolbar);
mPager = (ViewPager) findViewById(R.id.pager);
adapter = new MyPagerAdapter(getSupportFragmentManager());
mPager.setAdapter(adapter);
mTabs = (SlidingTabLayout) findViewById(R.id.tabs);
mTabs.setDistributeEvenly(true);
mTabs.setCustomTabView(R.layout.custom_tab_view, R.id.tabText);
int bgColor = ContextCompat.getColor(this, R.color.colorPrimary);
mTabs.setBackgroundColor(bgColor);
mTabs.setSelectedIndicatorColors(ContextCompat.getColor(MainActivity.this, R.color.colorAccent));
mTabs.invalidate();
mTabs.setViewPager(mPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
if (id == R.id.navigate) {
startActivity(new Intent(this, SubActivity.class));
}
if (id == R.id.TabActivity) {
startActivity(new Intent(this, ActivityUsingTabLibrary.class));
}
if (id == R.id.VectorTest) {
startActivity(new Intent(this, VectorTestActivity.class));
}
return super.onOptionsItemSelected(item);
}
class MyPagerAdapter extends FragmentStatePagerAdapter {
int icons[] = {R.drawable.home, R.drawable.hot_article, R.drawable.dizzy_person};
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment = null;
switch(position){
case product_result:
fragment = FragmentProduct.newInstance("","");
break;
}
return fragment;
}
@Override
public CharSequence getPageTitle(int position) {
Drawable drawable = ResourcesCompat.getDrawable(getResources(), icons[position], null);
drawable.setBounds(0, 0, 36, 36);
ImageSpan imageSpan = new ImageSpan(drawable);
SpannableString spannableString = new SpannableString(" ");
spannableString.setSpan(imageSpan, 0, spannableString.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
return spannableString;
}
@Override
public int getCount() {
return 3;
}
}
}
这是我的片段.class我传递jsonObject toast的地方。
public class FragmentProduct extends Fragment {
public static final String product_url = "http://oasisgroups.com/oApp/product.php";
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
private VolleySingleton volleySingleton;
private ImageLoader imageLoader;
private RequestQueue requestQueue;
public FragmentProduct() {
// Required empty public constructor
}
public static FragmentProduct newInstance(String param1, String param2) {
FragmentProduct fragment = new FragmentProduct();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public static String getRequestUrl(int limit) {
return product_url + "&limit=" + limit;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
volleySingleton = VolleySingleton.getInstance();
requestQueue = volleySingleton.getmRequestQueue();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, getRequestUrl(10),
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
L.t(getActivity(), response.toString());
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
requestQueue.add(request);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_product, container, false);
}
}
堆栈跟踪
02-29 12:10:01.047 17100-17100/com.mydesign.rockstar.materialdesignexample E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mydesign.rockstar.materialdesignexample, PID: 17100
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference
at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:116)
at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:870)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)
at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
at android.view.View.measure(View.java:18804)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:901)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
at android.view.View.measure(View.java:18804)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2112)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1228)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1464)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
我也在这个链接中看到了同样的问题，我应用了他的解决方案，但它对我不起作用。我仍然卡住了，帮帮我。所以检查我的代码，并建议我在哪里我错过了什么。
