我正在尝试实施DropDownMenu https://github.com/JayFang1993/DropDownMenu
我对此代码有疑问：
MainActivity
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.util.TypedValue;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import com.jayfang.dropdownmenu.DropDownMenu;
import com.jayfang.dropdownmenu.OnMenuSelectedListener;
import com.oguzdev.circularfloatingactionmenu.library.FloatingActionButton;
import com.oguzdev.circularfloatingactionmenu.library.FloatingActionMenu;
import com.oguzdev.circularfloatingactionmenu.library.SubActionButton;
import com.sai.eventee.rss.ServiceStarter;
import com.sai.eventee.util.ScrimInsetsFrameLayout;
import com.sai.eventee.web.WebviewFragment;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements
NavDrawerCallback {
private Toolbar mToolbar;
private NavDrawerFragment mNavigationDrawerFragment;
public static String DATA = "transaction_data";
public static String EMBEDD_DATA = "embedd";
SharedPreferences prefs;
boolean openedByBackPress = false;
//=======================================================
private DropDownMenu mMenu;
private ListView mList;
private int city_index;
private int sex_index;
private int age_index;
private List<String> data;
final String[] arr1=new String[]{"全部城市","北京","上海","广州","深圳"};
final String[] arr2=new String[]{"性别","男","女"};
final String[] arr3=new String[]{"全部年龄","10","20","30","40","50","60","70"};
final String[] strings=new String[]{"选择城市","选择性别","选择年龄"};
private FloatingActionButton mFAB;
private FloatingActionMenu mFABMenu;
//=======================================================
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setupFAB();
boolean newDrawer = getResources().getBoolean(R.bool.newdrawer);
if (newDrawer == true) {
setContentView(R.layout.activity_main_alternate);
} else {
setContentView(R.layout.activity_main);
Helper.setStatusBarColor(MainActivity.this, getResources()
.getColor(R.color.myPrimaryDarkColor));
}
mMenu=(DropDownMenu)findViewById(R.id.menu);
mMenu.setmMenuCount(3);
mMenu.setmShowCount(6);
mMenu.setShowCheck(true);
mMenu.setmMenuTitleTextSize(16);
mMenu.setmMenuTitleTextColor(Color.parseColor("#777777"));
mMenu.setmMenuListTextSize(16);
mMenu.setmMenuListTextColor(Color.BLACK);
mMenu.setmMenuBackColor(Color.parseColor("#eeeeee"));
mMenu.setmMenuPressedBackColor(Color.WHITE);
mMenu.setmMenuPressedTitleTextColor(Color.BLACK);
mMenu.setmCheckIcon(R.drawable.ico_make);
mMenu.setmUpArrow(R.drawable.arrow_up);
mMenu.setmDownArrow(R.drawable.arrow_down);
mMenu.setDefaultMenuTitle(strings);
mMenu.setShowDivider(false);
mMenu.setmMenuListBackColor(getResources().getColor(R.color.white));
mMenu.setmMenuListSelectorRes(R.color.white);
mMenu.setmArrowMarginTitle(20);
mMenu.setMenuSelectedListener(new OnMenuSelectedListener() {
@Override
public void onSelected(View listview, int RowIndex, int ColumnIndex) {
Log.i("MainActivity", "select " + ColumnIndex + " column and " + RowIndex + " row");
if (ColumnIndex == 0) {
city_index = RowIndex;
} else if (ColumnIndex == 1) {
sex_index = RowIndex;
} else {
age_index = RowIndex;
}
//过滤筛选
setFilter();
}
});
List<String[]> items = new ArrayList<>();
items.add(arr1);
items.add(arr2);
items.add(arr3);
mMenu.setmMenuItems(items);
mMenu.setIsDebug(false);
mList=(ListView)findViewById(R.id.lv_list);
data=getData();
mList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, data));
mToolbar = (Toolbar) findViewById(R.id.toolbar_actionbar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
mNavigationDrawerFragment = (NavDrawerFragment) getSupportFragmentManager()
.findFragmentById(R.id.fragment_drawer);
if (newDrawer == true) {
mNavigationDrawerFragment.setup(R.id.scrimInsetsFrameLayout,
(DrawerLayout) findViewById(R.id.drawer), mToolbar);
mNavigationDrawerFragment
.getDrawerLayout()
.setStatusBarBackgroundColor(
getResources().getColor(R.color.myPrimaryDarkColor));
((ScrimInsetsFrameLayout) findViewById(R.id.scrimInsetsFrameLayout)).getLayoutParams().width = getDrawerWidth();
} else {
mNavigationDrawerFragment.setup(R.id.fragment_drawer,
(DrawerLayout) findViewById(R.id.drawer), mToolbar);
DrawerLayout.LayoutParams params = (android.support.v4.widget.DrawerLayout.LayoutParams) mNavigationDrawerFragment.getView().getLayoutParams();
params.width = getDrawerWidth();
mNavigationDrawerFragment.getView().setLayoutParams(params);
}
prefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
// setting push enabled
String push = getString(R.string.rss_push_url);
if (null != push && !push.equals("")) {
// Create object of SharedPreferences.
boolean firstStart = prefs.getBoolean("firstStart", true);
if (firstStart) {
final ServiceStarter alarm = new ServiceStarter();
SharedPreferences.Editor editor = prefs.edit();
alarm.setAlarm(this);
// now, just to be sure, where going to set a value to check if
// notifications is really enabled
editor.putBoolean("firstStart", false);
// commits your edits
editor.commit();
}
}
// Checking if the user would prefer to show the menu on start
boolean checkBox = prefs.getBoolean("menuOpenOnStart", false);
if (checkBox == true) {
mNavigationDrawerFragment.openDrawer();
}
// New imageloader
Helper.initializeImageLoader(this);
}
private void setFilter(){
List<String> temp=new ArrayList<String>();
for (int i=0;i<getData().size();i++){
boolean city=((city_index==0)?true:data.get(i).contains(arr1[city_index]));
boolean sex=((sex_index==0)?true:data.get(i).contains(arr2[sex_index]));
boolean age=((age_index==0)?true:data.get(i).contains(arr3[age_index]));
if(city && sex && age){
temp.add(data.get(i));
}
}
mList.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_expandable_list_item_1,temp));
}
private List<String> getData(){
List<String> data = new ArrayList<String>();
data.add("上海－男－10");
data.add("上海－男－20");
data.add("上海－男－30");
data.add("上海－男－40");
data.add("上海－男－50");
data.add("上海－男－60");
data.add("上海－男－70");
data.add("广州－男－10");
data.add("广州－女－10");
data.add("北京－男－20");
data.add("北京－女－10");
data.add("广州－男－10");
data.add("北京－男－10");
data.add("广州－男－10");
data.add("上海－女－60");
data.add("上海－女－20");
return data;
}
private void setupFAB() {
//define the icon for the main floating action button
ImageView iconFAB = new ImageView(this);
iconFAB.setImageResource(R.drawable.ic_action_new);
//set the appropriate background for the main floating action button along with its icon
mFAB = new FloatingActionButton.Builder(this)
.setContentView(iconFAB)
.setBackgroundDrawable(R.drawable.selector_button_red)
.build();
//define the icons for the sub action buttons
ImageView iconSortName = new ImageView(this);
iconSortName.setImageResource(R.drawable.ic_action_alphabets);
ImageView iconSortDate = new ImageView(this);
iconSortDate.setImageResource(R.drawable.ic_action_calendar);
ImageView iconSortRatings = new ImageView(this);
iconSortRatings.setImageResource(R.drawable.ic_action_important);
//set the background for all the sub buttons
SubActionButton.Builder itemBuilder = new SubActionButton.Builder(this);
itemBuilder.setBackgroundDrawable(getResources().getDrawable(R.drawable.selector_sub_button_gray));
//build the sub buttons
SubActionButton buttonSortName = itemBuilder.setContentView(iconSortName).build();
SubActionButton buttonSortDate = itemBuilder.setContentView(iconSortDate).build();
SubActionButton buttonSortRatings = itemBuilder.setContentView(iconSortRatings).build();
/*
//to determine which button was clicked, set Tags on each button
buttonSortName.setTag(TAG_SORT_NAME);
buttonSortDate.setTag(TAG_SORT_DATE);
buttonSortRatings.setTag(TAG_SORT_RATINGS);
buttonSortName.setOnClickListener(this);
buttonSortDate.setOnClickListener(this);
buttonSortRatings.setOnClickListener(this);
*/
//add the sub buttons to the main floating action button
mFABMenu = new FloatingActionMenu.Builder(this)
.addSubActionView(buttonSortName)
.addSubActionView(buttonSortDate)
.addSubActionView(buttonSortRatings)
.attachTo(mFAB)
.build();
}
//===============================================================================*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// getMenuInflater().inflate(R.menu.rss_menu, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public void onNavigationDrawerItemSelected(int position, NavItem item) {
Fragment fragment;
try {
fragment = item.getFragment().newInstance();
if (fragment != null) {
Bundle bundle = new Bundle();
String extra;
String license = getResources().getString(R.string.google_play_license);
// if item does not require purchase, or app has purchased, or license is null/empty (app has no in app purchases)
if (item.requiresPurchase() == true
&& !SettingsFragment.getIsPurchased(this)
&& null != license && !license.equals("")) {
fragment = new SettingsFragment();
extra = SettingsFragment.SHOW_DIALOG;
} else {
extra = item.getData();
}
bundle.putString(DATA, extra);
fragment.setArguments(bundle);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, fragment).commit();
setTitle(item.getText());
if (null != MainActivity.this.getSupportActionBar()
&& null != MainActivity.this.getSupportActionBar()
.getCustomView()) {
MainActivity.this.getSupportActionBar().setDisplayOptions(
ActionBar.DISPLAY_SHOW_HOME
| ActionBar.DISPLAY_SHOW_TITLE);
}
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Override
public void onBackPressed() {
Fragment webview = getSupportFragmentManager().findFragmentById(
R.id.container);
if (mNavigationDrawerFragment.isDrawerOpen()) {
mNavigationDrawerFragment.closeDrawer();
} else if (webview instanceof WebviewFragment) {
boolean goback = ((WebviewFragment) webview).canGoBack();
if (!goback)
super.onBackPressed();
} else {
super.onBackPressed();
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
List<Fragment> fragments = getSupportFragmentManager().getFragments();
if (fragments != null) {
for (Fragment frag : fragments)
frag.onActivityResult(requestCode, resultCode, data);
}
}
private int getDrawerWidth(){
// Navigation Drawer layout width
int width = getResources().getDisplayMetrics().widthPixels;
TypedValue tv = new TypedValue();
int actionBarHeight;
if (getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true))
{
actionBarHeight = TypedValue.complexToDimensionPixelSize(tv.data,getResources().getDisplayMetrics());
} else {
actionBarHeight = 0;
}
int possibleMinDrawerWidth = width - actionBarHeight;
int maxDrawerWidth = getResources().getDimensionPixelSize(R.dimen.drawer_width);
return Math.min(possibleMinDrawerWidth, maxDrawerWidth);
}
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<include
android:id="@+id/toolbar_actionbar"
layout="@layout/toolbar_default"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<android.support.v4.widget.DrawerLayout
android:id="@+id/drawer"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/toolbar_actionbar">
<FrameLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<com.jayfang.dropdownmenu.DropDownMenu
android:orientation="horizontal"
android:layout_width="fill_parent"
android:id="@+id/menu"
android:background="@color/ripple_material_dark"
android:layout_height="60dp"/>
<ListView
android:layout_width="fill_parent"
android:layout_below="@id/menu"
android:id="@+id/lv_list"
android:background="#ffffff"
android:layout_height="wrap_content"></ListView>
<!-- android:layout_marginTop="?android:attr/actionBarSize"-->
<fragment
android:id="@+id/fragment_drawer"
android:name="com.sai.eventee.NavDrawerFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="start"
app:layout="@layout/drawer_fragment"
tools:layout="@layout/drawer_fragment" />
</android.support.v4.widget.DrawerLayout>
</RelativeLayout>
和Logcat：
10-04 22:48:47.884 27075-27075/com.sai.eventee E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.sai.eventee, PID: 27075
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sai.eventee/com.sai.eventee.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.jayfang.dropdownmenu.DropDownMenu.setmMenuCount(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2493)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2555)
at android.app.ActivityThread.access$800(ActivityThread.java:176)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1437)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5576)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:955)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:750)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.jayfang.dropdownmenu.DropDownMenu.setmMenuCount(int)' on a null object reference
at com.sai.eventee.MainActivity.onCreate(MainActivity.java:90)
at android.app.Activity.performCreate(Activity.java:6005)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2446)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2555)
at android.app.ActivityThread.access$800(ActivityThread.java:176)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1437)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5576)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:955)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:750)
我不知道为什么会出现空指针异常。
答案 0 :(得分：1)
这意味着findViewById（R.id.activity_main_alternate）为mMenu返回null。您的activity_main_alternate.xml是否具有R.id.menu视图？